AS2.4 | Air-Land Interactions (General Session)
EDI
Air-Land Interactions (General Session)
Co-organized by BG3/HS13/SSS11, co-sponsored by iLEAPS and ICOS
Convener: Anne Klosterhalfen | Co-conveners: Nurit Agam, Jan Cermak, Natascha Kljun, Dilia Kool, Matthias Mauder, Christoph Thomas
Orals
| Tue, 16 Apr, 08:30–12:30 (CEST)
 
Room 1.85/86
Posters on site
| Attendance Mon, 15 Apr, 10:45–12:30 (CEST) | Display Mon, 15 Apr, 08:30–12:30
 
Hall X5
Orals |
Tue, 08:30
Mon, 10:45
The session is addressed to experimentalists and modelers working on air-land interactions from local to regional scales including urban and natural terrestrial ecosystems. The programme is open to a wide range of new studies in micrometeorology and related atmospheric and remote sensing disciplines. The topics include the development of new devices, measurement techniques, experimental design, data analysis methods, as well as novel findings on surface layer theory and parametrization, including local and non-local processes. The theoretical parts encompass soil-vegetation-atmosphere transport, internal boundary-layer theories and flux footprint analyses. Of special interest are synergistic studies employing experimental data, parametrizations and models. This includes energy and trace gas fluxes (inert and reactive) as well as water, carbon dioxide and other GHG fluxes, and processes related to fog, dew, and water vapour adsorption. Specific focus is given to outstanding problems in land surface boundary layer descriptions such as complex terrain, effects of horizontal heterogeneity on sub-meso-scale transport processes, energy balance closure, stable stratification and night time fluxes, dynamic interactions with atmosphere, plants (in canopy and above canopy) and soils, and biophysical effects.

Orals: Tue, 16 Apr | Room 1.85/86

Chairpersons: Anne Klosterhalfen, Matthias Mauder
08:30–08:35
1) Land-atmosphere interactions and biophysical effects
08:35–08:55
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EGU24-6114
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solicited
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On-site presentation
Alexander Graf, Georg Wohlfahrt, Ankur Desai, and the FLUXNET ALBEDO team

In considerations about land management and global climate, biophysical effects like those of albedo are known to modify biochemical effects of greenhouse gas release or uptake. In particular, the cooling effect of afforestation via creation of carbon sinks has been shown to be partly offset by the low albedo and snow-masking effect of tree canopies.

In this presentation, we give a global overview on the relationship between albedo and CO2 uptake (net ecosystem productivity NEP and net biome productivity NBP). We focus on a recent study (Graf et al. 2023, https://doi.org/10.1038/s43247-023-00958-4) and the questions:

(i) Do ecosystems sequestering more CO2 have a lower albedo as a rule?

(ii) How close would such a relation be and how much room does it leave for climate-smart land use?

(iii) Given the different immediacy of albedo and NBP based radiative forcing, are there different mitigation policies to be preferred at different points in time?

To empirically investigate these questions with direct in-situ measurements, we identified 176 FLUXNET stations with sufficient coverage of NEP, incoming and outgoing shortwave radiation and ancillary data. A method to fill gaps in outgoing shortwave radiation and identify snow cover periods was developed and validated against available data and PI-provided snow statistics. 

We found a hyperbola-like decrease in maximum achievable effective (flux-weighted) long-term albedo as NEP increases, and vice versa. Apart from this joint limit, which also applied to non-forest and snow-free sites, the relation scattered strongly, indicating some room for climate-smart land use considering both albedo and carbon sequestration.

A conceptual model based on a paired-site permutation approach showed that maximizing each site’s NEP without considering albedo, leads to albedo-based positive radiative forcing (warming) during the first approximately 20 years, before being offset by an even stronger NBP-based cooling. However, the fact that most sites are currently far below their possible maximum albedo-NEP combination also allows for a balanced scenario in which both parameters are improved simultaneously. It avoids warming on all timescales, but provides less cooling than pure NEP maximization in the long term. We discuss how these timelines would interact with current emission reduction policies, the reasons underlying the relationship and real-world examples of joint NEP and albedo change.

How to cite: Graf, A., Wohlfahrt, G., Desai, A., and team, T. F. A.: Reflect sunlight or use it to store carbon?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6114, https://doi.org/10.5194/egusphere-egu24-6114, 2024.

08:55–09:05
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EGU24-9231
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ECS
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On-site presentation
Vincent de Feiter, Sebastiaan de Haas, Jordi Vilà-Guerau de Arellano, Raquel González Armas, Daniël Rikkers, Guido Haytzmann, Martin Janssens, Oscar Hartogensis, Imme Benedict, Luiz Machado, and Cléo Quaresma

The Amazonian hydrological and carbon cycle are controlled by a complex, interconnected and interdependent myriad of surface and atmospheric processes. Improving our understanding and numerical representation of these cycles under a changing climate requires a deeper exploration of the biospheric-atmospheric coupling and the processes governing the formation and deepening of shallow cumulus clouds. Utilising a comprehensive set of surface and upper-air atmospheric measurements from the CloudRoots-Amazon22 campaign alongside an integrated hierarchy of models, we construct a numerical experiment to systematically study these processes throughout the dry season of 2022. The model hierarchy consists of a large eddy simulation resolving turbulence and shallow cumulus formation, a coupled rainforest-atmosphere mixed-layer model to map the sensitivity to surface and atmospheric observations and a moisture tracking model to identify and quantify moisture sources, sinks, and long-range transport. Individual days of observations were characterised into representative shallow convective and shallow-to-deep convective regimes. We accurately replicated the evolution of radiation and the asymmetrical exchange fluxes of energy, momentum, moisture, and carbon during the shallow convective regime. By analysing the diurnal variability of the state variables, we can determine how turbulent mixing controls the morning transition, from strong gradients to well-mixed conditions above the forest. Ongoing work involves improving the representation of in-canopy processes and simulating the shallow-to-deep convective regime by introducing thermodynamic forcings, such as moist air intrusion or increased wind sheared conditions, on the shallow convective experiment.  

How to cite: de Feiter, V., de Haas, S., Vilà-Guerau de Arellano, J., González Armas, R., Rikkers, D., Haytzmann, G., Janssens, M., Hartogensis, O., Benedict, I., Machado, L., and Quaresma, C.: Constructing a comprehensive numerical experiment to study biospheric-atmospheric feedbacks driving dry season cloud formation over the Amazon Basin , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9231, https://doi.org/10.5194/egusphere-egu24-9231, 2024.

09:05–09:15
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EGU24-5597
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ECS
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On-site presentation
Bo Huang, Yan Li, Xia Zhang, Chunping Tan, Xiangping Hu, and Francesco Cherubini

The forest plays a crucial role in the land ecosystem, impacting local climates through various biophysical mechanisms. While numerous observational and modeling studies have explored the distinctions between forested and non-forested areas, the impact of forest management on surface temperature has been relatively understudied. This limited attention is attributed to the inherent challenges associated with adapting climate models to effectively account for the complexities of forest structure parameters. Employing a combination of machine learning-based statistical analysis and a regional climate model, along with high-resolution maps detailing various forest compositions and structures, we explore the connection between specific forest management strategies and local temperature variations. The findings reveal a tendency for more developed forests to contribute to higher land surface temperatures compared to younger or less developed ones. Relative to the present state of Fennoscandian forests, an ideal scenario with fully developed forests is found to an annual mean warming of 0.26 ℃ in statistical models, with a range of 0.03 to 0.69 ℃ (5th to 95th percentile). However, the dynamical model indicates an annual average cooling effect of -0.25 °C, ranging from -0.42 to -0.10 °C (5th to 95th percentiles), attributing this difference to the dynamical model's inability to accurately simulate winter warming. Both models project a cooling effect in summer, with statistical and dynamical models showing -0.03 ± 0.22 ℃ and -0.53 ± 0.20 ℃, respectively. Conversely, scenarios involving undeveloped forests result in an annual average cooling of -0.29 ℃ in statistical models, with a range of -0.61 to -0.01 ℃, a slight summer warming of 0.03 ± 0.16 ℃, and a winter cooling of -0.69 ± 0.47 ℃. The dynamical model, however, predicts an annual average warming of 0.28 ± 0.18 °C, a summer warming of 0.53 ± 0.15 °C (mainly driven by increased sensible heat fluxes), and a winter cooling of -0.29 ± 0.25 °C. This study deepens our understanding of how alterations in vegetation impact climate patterns. While our findings shed light on the intricate connections between forest composition and surface temperatures, there's a clear need to refine how regional climate models capture the intricate biophysical mechanisms within forest dynamics. Enhancements in this representation will be crucial for establishing a comprehensive understanding of how forest management practices specifically influence local climate regulation services.

How to cite: Huang, B., Li, Y., Zhang, X., Tan, C., Hu, X., and Cherubini, F.: Investigating forest management's impact on local climate in Fennoscandia through statistical and dynamical modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5597, https://doi.org/10.5194/egusphere-egu24-5597, 2024.

09:15–09:25
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EGU24-13667
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On-site presentation
Sonia Wharton, Matteo Puccioni, Holly Oldroyd, Matthew Miksch, Matthias Falk, Stephan de Wekker, Robert Arthur, and Jerome Fast

The atmospheric boundary layer above forest canopies is difficult to measure in practice, and our understanding of its flow physics usually is still limited to tall tower measurements which have limited reach above the canopy, or vertically-profiling remote sensing measurements which are usually taken outside of the canopy. We present a recent 5-month study of wind flow measurements taken above a 50-m tall forest in Washington state, USA, using two Doppler lidars. One vertical-profiling lidar was placed directly on top of the 70-m tall Wind River National Ecological Observatory Network (NEON) tower and took measurements of wind velocity, direction and turbulence up to 220 m above ground level. A scanning lidar was placed in a nearby clearing and programmed to scan the wind field over the forest canopy, including overlapping its scans with the profiling lidar on top of the tower. The scanning lidar also captured terrain induced flows across the surrounding mountain-valley terrain. Both lidars captured wind jets and periods of intermittent turbulence over the forest canopy. How and when these mechanically-forced turbulence events penetrate the high leaf area index (LAI) forest canopy are studied using NEON’s eddy covariance flux exchange measurements and the tower profile measurements of air temperature, pressure, moisture, and wind velocity within the forest.

 

Applications of studying wind flow over the forest canopy are broad and vary from a better characterization of the wind profile for wind energy resource assessment to improving our understanding of vertical exchange processes by studying how “top-down” forced turbulence events influence mass and energy fluxes between the forest canopy and atmosphere. Special consideration of how above canopy processes influence canopy coupling/decoupling, including top-down turbulent sweep events, will be presented for the tall Wind River forest. We will also discuss upcoming experiments including 1) the deployment of 3-d sonic anemometers in the Wind River subcanopy (as part of a larger Integrated Carbon Observation System (ICOS) below-canopy study) to advance our understanding of canopy mixing processes and 2) a new campaign planned for the deciduous Mountain Lake Biological Station NEON tower in the mountains of Virginia, USA. The latter study is designed to observe changes in the above-canopy wind profile and its interactions with below-canopy flows and vertical flux exchanges across a summer-to-winter LAI transition.

 

How to cite: Wharton, S., Puccioni, M., Oldroyd, H., Miksch, M., Falk, M., de Wekker, S., Arthur, R., and Fast, J.: Deployment of Doppler lidar within forests: Advancing our understanding of canopy-atmospheric boundary layer processes , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13667, https://doi.org/10.5194/egusphere-egu24-13667, 2024.

09:25–09:35
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EGU24-10102
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On-site presentation
Volker Wulfmeyer and the The LAFI Team

The quality of weather forecasts, seasonal simulations, and climate projections depends critically on the adequate representation of land-atmosphere (L-A) feedbacks. These feedbacks are the result of a highly complex network of processes and variables related to the exchange of momentum, energy, and mass. Significant challenges persist in understanding processes and feedbacks, which this initiative will address.

The Land-Atmosphere Feedback Initiative (LAFI) is an interdisciplinary consortium of researchers from atmospheric, agricultural, and soil sciences as well as from bio-geophysics, hydrology, and neuroinformatics proposing a novel combination of advanced research methods. The overarching goal of LAFI is to understand and quantify L-A feedbacks via unique synergistic observations and model simulations from the micro-gamma (» 2 m) to the meso-gamma (» 2 km) scales across diurnal to seasonal time scales.

LAFI consists of a network of closely intertwined projects addressing six research challenges formulated as objectives and hypotheses on 1) alternative similarity theories, 2) the impact of land-surface heterogeneity, 3) partitioning evapotranspiration, 4) understanding entrainment, 5) synergistic characterization of L-A feedback, and 6) droughts or heatwaves potentially investigated by ad-hoc field observations. Collaboration across the twelve projects will be fostered by three Cross Cutting Working Groups on Deep Learning, Sensor Synergy and Upscaling, as well as the LAFI Multi-model Experiment.

In this presentation, an overview of the LAFI research approach is given with particularly emphasis of the synergy of observations and modeling efforts substantiated by first results from the Land-Atmosphere Feedback Observatory (LAFO) at the University of Hohenheim in Stuttgart, Germany.

How to cite: Wulfmeyer, V. and the The LAFI Team: The Land-Atmosphere Feedback Initiative, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10102, https://doi.org/10.5194/egusphere-egu24-10102, 2024.

2) Turbulence - observational and modelling studies
09:35–09:45
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EGU24-3967
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On-site presentation
Patricia Glocke, Christopher C. Holst, Basit A. Khan, and Susanne A. Benz

The impact of underground heat (or cold) sources such as man-made infrastructures or geothermal systems have been extensively studied in geosciences. Soil temperatures near underground parking garages may be up to 10 K warmer than their surroundings. However, the coupling between these temperature anomalies in the soil and the atmosphere as a bottom-up scheme has been neglected so far. We investigated how this scenario can be modeled in the turbulence and building resolving large eddy simulation urban climate model PALM-4U and assessed the impact of modified soil temperatures on air temperatures in an idealized domain. Hereby, the soil temperatures at 2-meter depth were increased and decreased by 5 K, respectively. Multiple scenarios were considered, differentiating between cyclic and Dirichlet/radiation boundary conditions along the x-axis. Further, we ran the simulations under summer and winter conditions, day and night, and three land cover types which are bare soil, short grass, and tall grass. After three days of simulation time, cyclic boundary conditions induced air temperature anomalies due to changes in the subsurface temperature. However, Dirichlet/radiation boundary conditions did not show alterations. Analyzing the cyclic scenarios, although the absolute air temperature was significantly influenced by the landcover, the magnitude of the air temperature anomaly shows little variation. Daytime and seasonality exerted a greater influence on the magnitude. The greatest positive near-surface air temperature anomaly when increasing the soil temperature was 0.38 K for all land cover types and develops during winter between 09:00 and 10:00 CET. Smallest influence was found during summer at 09:00 CET, where increased soil temperatures resulted in a 0.02 K rise over short- and tall grass, and 0.18 K over bare soil. Conversely, decreasing soil temperatures showed predominantly inverse patterns.

The findings contribute to the general comprehension of the coupling of soil- and atmospheric temperatures, inferring also insights of simulating idealized but reality-oriented scenarios in PALM-4U.

How to cite: Glocke, P., Holst, C. C., Khan, B. A., and Benz, S. A.: Impact of Subsurface Thermal Anomalies on Air Temperatures in Idealized Scenarios Using PALM-4U, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3967, https://doi.org/10.5194/egusphere-egu24-3967, 2024.

09:45–09:55
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EGU24-17604
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ECS
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On-site presentation
William Antolin, Mélanie Rochoux, and Patrick Le Moigne

 

Session: AS2.4: Air-Land Interactions

 

Abstract:

Experimental fires provide insights into the behavior of wildland fires and their interactions with the atmosphere. They help modelers build simulations capable of accurately describing fire dynamics, and which can help identify the key processes driving fire development. In particular, the FireFlux I case (a tall grass fire covering 30 hectares) was the first experimental fire to provide in situ measurements of atmospheric dynamics near the fire, highlighting the complexity of fire-induced flows and the importance of fire-induced upward vertical motion (Clements et al. 2007). Despite much theoretical work on forest canopy turbulence, its interactions with fire dynamics are still poorly understood, while they could play an important role (Heilman et al. 2021).

One of the difficulties in wildland fire simulations stems from the disparity between scales. Highly detailed models based on computational fluid dynamics (CFD) tend to represent chemical, radiation, and turbulence processes at the cost of reduced domain size. Conversely, meteorological models tend to provide a better representation of ambient wind over a larger domain size, but this is at the expense of parameterization choices. An intermediate modeling scale is needed to represent the geographical and micrometeorological scales involved in a wildland fire, especially in the development of the fire plume and the induced air entrainment. In recent years, we have therefore worked on designing and validating a coupled atmosphere-fire model, Meso-NH/BLAZE (Costes et al. 2021), where BLAZE represents the fire as a propagating flaming front and Meso-NH is run in large-eddy simulation (LES) mode at high resolution (10-100 m). This preliminary work has highlighted the predominant influence of surface wind on fire behavior and thus the critical need to make it more representative.

In this study, we show that accounting for interactions between forest canopy, surface wind and fire can be done by adding a drag term in the Meso-NH momentum and TKE equations (Aumond et al. 2013), and by running coupled atmosphere-fire simulations at very high resolution (10m and finer). We also assess for the FireFlux I case, the impact of the forest canopy on fire spread through several original data analyses, including wavelet transforms, fire-canopy interaction statistics, and sensitivity to atmospheric turbulence.

 

References

Clements, C. B., et al. (2007) Observing the Dynamics of Wildland Grass Fires: FireFlux – A Field Validation Experiment. Bull. Amer. Meteor. Soc., 88, 1369–1382. doi: 10.1175/BAMS-88-9-1369

 E.Heilman WE, et al. (2021) Observations of Sweep–Ejection Dynamics for Heat and Momentum Fluxes during Wildland Fires in Forested and Grassland Environments. Journal of Applied Meteorology and Climatology 60(2), 185–199. doi:10.1175/jamc-d-20-0086.1

Costes, A., et al. (2021) Subgrid-scale fire front reconstruction for ensemble coupled atmosphere-fire simulations of the FireFlux I experiment. Fire Safety Journal, 126, 103475, doi: 10.1016/j.firesaf.2021.103475

Aumond, P., et al. (2013) Including the drag effects of canopies: Real case large-eddy simulation studies. Boundary-Layer Meteorology, 146, 65–80, doi: 10.1007/s10546-012-9758-x

How to cite: Antolin, W., Rochoux, M., and Le Moigne, P.: The role of forest canopy-wind interactions on experimental fire behavior using coupled atmosphere-fire modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17604, https://doi.org/10.5194/egusphere-egu24-17604, 2024.

09:55–10:05
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EGU24-10016
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ECS
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On-site presentation
Jonathan Kostelecky and Cedrick Ansorge

Atmospheric flows virtually always occur over rough surfaces, which enhances the drag, mixing and vertical transport of pollutants and moisture in the atmospheric boundary layer (ABL). During nighttime, when the absence of solar radiation leads to surface cooling, a stratified surface layer forms, and turbulence decreases in intensity and spatial extent, giving rise to large-scale intermittency. Roughness is known to counteract the buoyancy-induced reduction of turbulence in the stable regime by an increase of mixing, but the effects are lumped together in surface-layer similarity. To investigate the interaction of surface roughness and stable density stratification in the ABL at the process level, direct numerical simulation (DNS) of rough turbulent Ekman flow at Reynolds numbers well within the turbulent regime and for large domains is performed. Roughness is represented by an array of 56×56 roughness elements with a uniform width and height distribution on the lower wall. This small-scale three-dimensional surface roughness is fully resolved with an immersed boundary method (IBM) and has a packing density of 10%. For neutral stratification, we have obtained data in the transitionally rough regime and at the verge of the fully rough regime. Starting from the roughest neutral case with z0+≈2, stable stratification is gradually increased with a constant-temperature (Dirichlet) boundary condition. The focus of this study is the direct effect of roughness on the stability regime, the rough-wall scaling in the logarithmic layer and the scaling for the roughness parameters z-nought for momentum and temperature, which is crucial for the Monin–Obukhov similarity theory.


* This work is funded by the ERC Starting Grant ”Turbulence-Resolving Approaches of the Intermittently Turbulent Atmospheric Boundary Layer [trainABL]” of the European Research Council (funding ID 851347). Simulations were performed on the resources of the High-Performance Computing Center Stuttgart (HLRS) on the Hawk cluster. The computing time and storage facilities were provided by the project trainABL with the project number 44187.

How to cite: Kostelecky, J. and Ansorge, C.: Simulation and scaling analysis of small-scale roughness in neutrally and stably stratified turbulent Ekman flow, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10016, https://doi.org/10.5194/egusphere-egu24-10016, 2024.

10:05–10:15
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EGU24-1358
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ECS
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On-site presentation
Zhengtai Zhang

The observed surface wind speed (SWS) over China has declined in the past four decades, and recently, the trend has reversed, which is known as SWS stilling and recovery. The observed SWS is vulnerable to changes in nonclimatic factors, i.e., inhomogeneity. Unfortunately, most of the existing studies on the long-term trend of SWS were based on raw datasets without homogenization. In this study, by means of geostrophic wind speed and penalized maximal T test, we conduct a systematic homogeneity test and exploration of the homogenization impact for SWS at over 2,000 stations in China from 1970 to 2017. The results show that the inhomogeneity in the observed SWS over China is detectable at 59% of national weather stations. The breakpoint years are mainly concentrated in the late 1970s, mid-1990s and early 2000s. Overall, 18% of breakpoints are caused by station relocations, and the remaining breakpoints are likely related to anemometer replacement and measurement environment changes that occurred during the mid-1990s and early 2000s. After homogenization, the decreasing trend in SWS during 1970-2017 decreased from -0.15 m/s decade-1 to -0.05 m/s decade-1. The homogenized SWS recovery period advanced from the early 21st century to the early 1990s, which is consistent with the SWS variations, excluding the impact of urbanization around weather stations. The phase change in the Western Hemisphere warm pool (WHWP) might be one of the causes of homogenized SWS recovery.

How to cite: Zhang, Z.: Homogenization of observed surface wind speed based on geostrophic wind theory over China from 1970 to 2017, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1358, https://doi.org/10.5194/egusphere-egu24-1358, 2024.

Coffee break
Chairpersons: Natascha Kljun, Nurit Agam, Dilia Kool
3) Micrometeorologic methods
10:45–11:05
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EGU24-11109
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ECS
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solicited
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On-site presentation
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Gabriel Destouet, Nikola Besic, Emilie Joetzjer, and Matthias Cuntz

Flux estimation from eddy-covariance flux tower measurements faces the problem of integrating fluxes only in the case of fully developed turbulence and in non-stationary environments with advective components. The standard eddy-covariance method operates on fixed-length signals, requiring the knowledge of a maximum correlation time-length as well as post-processing steps assessing the suitability and quality of the data. Statistical tests are carried out to assess if flux estimates were performed during sufficiently developed turbulence and if they were corrupted by advective components. Tests with friction velocity u* or σw, steady-state tests, and flux variance similarity are now standard during and after flux calculations. More elaborate methods such as ogive optimisation are used to deal with advection. An important disadvantage of all these statistical tests is that they discard the whole time interval such as half an hour if they detect failure.

Time-scale (time-frequency) analyses have been used as an alternative to the standard time-analysis approach to estimate ecosystem fluxes. In particular, wavelet analysis, which is well adapted to the study of non-stationary and scale invariant processes such as turbulence, has been used in previous works. It presents the ability of separating the different components of the flux in time-scale space and as such could be an efficient alternative for flux estimation avoiding the above statistical tests.

To address this problem, we propose a general framework for analysing fluxes in time-scale space, and propose a new method for identifying and extracting turbulent transport that avoids advective components and does not need statistical tests after the flux calculations. The new method is based on the analysis in time-scale domain of the amplitude of the vertical component of the Reynold stress tensor and can be seen as a time-scale transposition of standard tests mentioned above. As a direct consequence, we are able to estimate fluxes at high time resolution over times and scales with sufficiently developed turbulence. We show application of the framework at the beech forest site FR-Hes and demonstrate its relation with standard eddy covariance calculations. Our methodology is implemented in the Julia package TurbulenceFlux.jl and is readily available. The proposed framework and its code implementation is fully differentiable and hints to further investigations, such as the study of flux ecosystem response times, or sensitivity analysis against wavelet and averaging window parameters.

How to cite: Destouet, G., Besic, N., Joetzjer, E., and Cuntz, M.: Time-scale turbulent transport extraction and high time resolution flux estimation using wavelet analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11109, https://doi.org/10.5194/egusphere-egu24-11109, 2024.

11:05–11:15
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EGU24-22211
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On-site presentation
Andreas Ibrom, Konstantinos Kissas, Anastasia Gorlenko, and Charlotte Scheutz

Tall tower eddy covariance (EC) measurements can be used to narrow down the gap between the ecosystem and the continental scale observations by capturing greenhouse gas (GHG) fluxes in a landscape scale (>10 km2). Because of the large footprint, tall tower platforms enable monitoring of greenhouse gas net fluxes, integrating over a multitude of diverse GHG sources and sinks within anthropogenic ecosystems. Yet, the temporal variability of atmospheric stability and atmospheric boundary layer affects the size of the flux footprint and the quality of EC flux estimates, respectively, thereby complicating the interpretation of surface flux estimates. The objective of this study is to determine an optimal sampling scheme alternating between different measuring heights (zm) in order to maximise the number of valid flux measurements as well as mitigating the effect of weather fluctuations on the longitudinal position of the footprint.

We used a six months’ data set of continuous turbulence data measured from a recently deployed prototype flux observation station in a rural area close to the Danish Capital of Copenhagen, Zealand. The system is mounted on a 200 m telecommunication tower equipped with 3D ultrasonic anemometers in three different heights (70m, 90m, 115m) and with a TILDAS GHG analyser capable of switching between three sampling lines corresponding to the specified heights.

We define an optimal sampling strategy based on the peak location of the individual, crosswind-integrated footprints from valid samples. As valid, we characterized those flux measurements, when the zm was within the constant flux layer, as estimated from ceilometer measurement. For each of the half hours, we selected the zm with the footprint’s peak location closest to a target position.

In this presentation, we demonstrate the ability to constrain the flux footprint within a target landscape area by establishing a sampling schedule across the three sampling heights. The results showed that designing a sampling strategy that combines multiple heights has the potential to bring the aggregated footprint for the entire period (footprint climatology) closer to the targeted area. A similar outcome can be attained when sampling from a single height and excluding the instances where the footprint significantly deviates from the target area. Nevertheless, this comes with the trade-off of discarding valid data. Moreover, the weather effect on the variability of the crosswind-integrated footprints was reduced by setting an optimal, multi-height strategy in comparison to the aggregated footprints from the individual heights.

How to cite: Ibrom, A., Kissas, K., Gorlenko, A., and Scheutz, C.: Optimising the sampling strategy in tall tower eddy covariance flux measurements, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22211, https://doi.org/10.5194/egusphere-egu24-22211, 2024.

11:15–11:25
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EGU24-14868
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On-site presentation
Sinikka Paulus, Rene Orth, Sung-Ching Lee, Jacob A. Nelson, Anke Hildebrandt, Ngoc Nguyen, Markus Reichstein, and Mirco Migliavacca

Soils take up water vapor from the atmosphere through processes that involve vapor diffusion and water retention. This can theoretically occur in any ecosystem under the preconditions of a humid atmosphere and dry soil pores. It can play a critical role in dry ecosystems because it can provide a substantial proportion of the total water inputs at the daily timescale. However, it remains insufficiently investigated in many regions, partly due to the absence of continuous, dedicated measurements.

In this study, we use a recently developed algorithm to detect and filter Eddy Covariance (EC) derived negative latent heat flux data collected at semi-arid and arid sites to identify soil water vapor adsorption. In a previous study, we successfully used EC data to detect soil water vapor adsorption for a Mediterranean ecosystem. 

Our findings indicate that these negative latent heat fluxes exhibit a correlation with soil water content and relative humidity at various sites suggesting that a part of the negative latent heat flux is related to soil water vapor adsorption. Building on these findings, we demonstrate that soil water vapor adsorption occurs during the dry season in various ecosystems, including woody savannas, grasslands, shrublands, and even some forests. The flux magnitude reaches values comparable to daily evaporation, which is in line with existing literature on the few previously measured ecosystems.

Furthermore, we analyze the drivers of the occurrence and dynamics of soil water vapor across sites. Thereby we study the influence of e.g. soil texture or vegetation height. This way, our study expands our knowledge of the spatial extent and inter-annual dynamics of soil water vapor adsorption in natural ecosystems and, more generally, sheds light on a mostly overlooked aspect of land-atmosphere interaction.

How to cite: Paulus, S., Orth, R., Lee, S.-C., Nelson, J. A., Hildebrandt, A., Nguyen, N., Reichstein, M., and Migliavacca, M.: Mapping soil moisture uptake by dry soils across Eddy covariance measurement sites, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14868, https://doi.org/10.5194/egusphere-egu24-14868, 2024.

4) New technologies
11:25–11:35
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EGU24-9627
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ECS
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On-site presentation
José Ángel Callejas Rodelas, Alexander Knohl, Ivan Mammarella, Timo Vesala, Olli Peltola, and Christian Markwitz

Eddy covariance (EC) studies typically involve the use of one or maximum two measuring towers, which leads to a low level of spatial replication, compromising the statistical representativity of EC measurements, especially above highly heterogeneous ecosystems, such as agroforestry systems. Lower-cost eddy covariance setups (LC-EC) represent a potential solution to this problem, since their affordability allows for the installation of multiple EC towers to study heterogeneity at the landscape scale. In the last years, several LC-EC setups have been successfully validated against conventional EC setups (CON-EC), with the main difference being the use of slower gas analyzers. These introduce a higher uncertainty due to the enhanced high-frequency spectral attenuation in the turbulent energy spectrum.

In this study, we analyzed turbulent fluxes of CO2 and H2O and turbulence characteristics measured by three flux towers equipped with LC-EC setups above one agroforestry system located in Wendhausen, Germany. The agroforestry system was a Short Rotation Alley Cropping (SRAC) system, consisting of alternating rows of trees and crops. The three flux towers were installed at different North-South aligned tree stripes. Additionally, we compared the results of the three LC-EC setups above the SRAC with another LC-EC setup installed at an adjacent monocropping (MC) field.

The objectives of the study were: (i) to evaluate the spatial variability of EC fluxes from the three flux towers above the SRAC system; (ii) to compare the variability of fluxes within the SRAC to the variability of fluxes between SRAC and MC; (iii) to quantify whether the use of several LC-EC setups counteracts the higher uncertainty associated to LC-EC, due to the increased statistical robustness of the measurement network compared to the hypothetical use of just one EC station.

The highest spatial variability across the SRAC was measured for CO2 fluxes, followed by latent heat (LE) flux, with coefficients of variation, calculated following Oren et al. (2006) (https://doi.org/10.1111/j.1365-2486.2006.01131.x), of 2.3 and 1.4 (dimensionless), respectively. The spatial variability in CO2 and LE fluxes within the SRAC was similar to the variability between MC and SRAC, and was attributed to the different land cover types around the towers. On the other hand, the spatial variability in sensible heat flux (H), momentum flux and turbulence characteristics (such as friction velocity and variance of vertical wind speed), within the SRAC, was smaller than the variability between SRAC and MC, likely explained by the development of an internal boundary layer (IBL) above the SRAC.

Our results show that the heterogeneity of the SRAC, despite not affecting significantly the turbulence characteristics across the site, leads to a large spatial variation in CO2 and LE fluxes. Therefore, a distributed network of several EC systems is necessary to properly quantify patterns and drivers of CO2 and latent heat fluxes above such heterogeneous land-use systems.

How to cite: Callejas Rodelas, J. Á., Knohl, A., Mammarella, I., Vesala, T., Peltola, O., and Markwitz, C.: Increased spatial replication above heterogeneous agroforestry improves the representativity of eddy covariance measurements, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9627, https://doi.org/10.5194/egusphere-egu24-9627, 2024.

11:35–11:45
|
EGU24-6590
|
ECS
|
Virtual presentation
Thi Thuc Nguyen, Ariel Altman, Nadav Bekin, Nurit Agam, and Elad Levintal

Soil respiration (Fs) datasets often exhibit low temporal-spatial resolution and spatial bias, particularly lacking observations in arid/semi-arid regions. This limitation significantly constrains our understanding of the mechanisms governing soil carbon dynamics and hinders the correct estimation of CO2 emissions at regional to global scales. Challenges in Fs estimation arise mainly from logistical constraints in manual data collection and the high costs of commercial measuring devices. To address this, we developed a low-cost, open-source, autonomous soil CO2 sensor system. The system design emphasized easy adoption and customization for non-engineer end-users, enabling the collection of high-frequency, long-term soil CO2 concentration data, and consequently, Fs estimates. A system including six low-cost CO2 sensors distributed at two soil depths (5 and 10cm) was deployed in the Negev Desert since May 2023. Fs estimates were determined from CO2 concentration gradient using Fick's law (FG) and cross-validated with Fs measured by automated chambers (FC). We found a good agreement between FG and FC both in the short term (i.e., sub-daily fluctuation) and long term (i.e., annual net CO2 emission). Our data also revealed daily and seasonal Fs patterns correlating with environmental factors like temperature and precipitation. The results demonstrate that our system, despite costing less than 10% of automated chamber systems, offers equivalent accuracy in Fs estimates, higher temporal resolution, and potential for enhanced spatial resolution if widely adopted.

How to cite: Nguyen, T. T., Altman, A., Bekin, N., Agam, N., and Levintal, E.: Continuous, long-term monitoring of soil CO2 concentration and CO2 flux using a novel, low-cost CO2 sensor system, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6590, https://doi.org/10.5194/egusphere-egu24-6590, 2024.

11:45–11:55
|
EGU24-9193
|
On-site presentation
Jan Wozniak

Automated Solution for Discrete Gas Sample Analyses with
Picarro G2508 and SAM Autosampler
Jan Woźniak1, Joyeeta Bhattacharya2, Magdalena E. G. Hofmann1, Frank Krijnen3, Guillermo Hernandez
Ramirez4
1Picarro B.V., Eindhoven, The Netherlands, 2Picarro Inc., Santa Clara, USA; 3University of Saskatchewan; 4University of Alberta

Abstract
Greenhouse gas research community has witnessed an ever-increasing need for automated
solutions for measuring greenhouse gas concentrations in small discrete gas samples. However,
traditional solutions like gas chromatographs often incur high initial and maintenance costs or are
complicated to deploy and maintain, and almost impossible to work with in the field. There has
been a rising interest in the SAM autosampler (www.openautosampler.com) which so far has
been utilized mostly for isotopic measurements of greenhouse gases (e.g., isotopic CO2/CH4), in
conjunction with low flow Picarro analyzers (<50 mL/min). In this report, we demonstrate the
compatibility, efficiency, and advantages of the SAM autosampler with Picarro Greenhouse Gas
(GHG) Concentration analyzers like the G2508 multi species gas analyzer, with much higher flow
rates (>200 mL/min). The results of our experiments show excellent precision and accuracy for
discrete CH4, CO2 and N2O gas measurements. Also, we have been able to determine linearity in
dilution factors and characterized memory effects and its variability in different gas species (e.g.,
comparing CO2 vs N2O). This report also provides recommendations on the methods and best
practices for discrete gas sample measurements. In summary, the Picarro G2508 (or other GHG
analyzers) in conjunction with SAM Autosampler offers an attractive, cost-effective, and simpler
alternative to gas chromatograph or similar available solutions

How to cite: Wozniak, J.: Automated Solution for Discrete Gas Sample Analyses withPicarro G2508 and SAM Autosampler, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9193, https://doi.org/10.5194/egusphere-egu24-9193, 2024.

5) Fog, dew, NRWI
11:55–12:05
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EGU24-9320
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ECS
|
On-site presentation
Nadav Bekin, Dennis Ashilenje, Abdelghani Chehbouni, Lhoussaine Bouchaou, Lamfeddal Kouisni, Dilia Kool, and Nurit Agam

Soil CO2 efflux is primarily attributed to the metabolic activity of soil organisms and is a major component of the global carbon balance. The carbon balance of deserts, such as the Sahara Desert, the largest desert on Earth, is considered neutral as low soil moisture inhibits biological activity and reduces the soil CO2 efflux to its lower limit. Studies in the last decades challenge this paradigm, reporting a mysterious nocturnal CO2 uptake by desert soils, which in some cases leads to a net gain of carbon by the soil. While the factors controlling this phenomenon are still under debate, it is clear that the presence of water is essential. How, then, can nocturnal CO2 uptake occur in the driest soil conditions when no apparent water is available to drive the process? We embarked on a field expedition in the Sahara Desert, southwest Morocco, during the summer of 2022 to explore the dynamics of water and carbon in this presumably “stagnant” ecosystem. We discovered nocturnal water vapor adsorption, driven by atmospheric water vapor transported from the Atlantic Ocean and penetrating hundreds of kilometers inland where the vapor is captured in the soil’s top layer. Changes in soil water content were determined from soil relative humidity (measured using a profile of relative humidity sensors) and soil-specific vapor sorption isotherms (measured using a vapor sorption analyzer). With this novel method, we were able to detect a daily increase of 0.3 mm of water even at a distance of 250 km from the Ocean. Concurrent measurements of CO2 fluxes (measured using manual and automatic flux chamber systems), confirmed that small atmosphere-to-soil CO2 fluxes occurred during the night, coinciding with downward water vapor fluxes. This indicates that the atmosphere provides a consistent water source and may initiate soil CO2 uptake. Simultaneous measurements of water vapor and CO2 fluxes at a second site suggested that the quality of the correlation between the two fluxes depends on soil properties. Overall, the daily CO2 cycle was unbalanced (net uptake of 0.08 g m-2) implying that the soil acted as a carbon sink. This sink is small, but considering its occurrence even in inland desert ecosystems and the fact that arid and hyper-arid regions occupy 26% of Earth’s terrestrial surface, the effect of atmospheric water capture by desert soils on CO2 exchange may play a significantly larger role in the global carbon balance than previously thought. 

How to cite: Bekin, N., Ashilenje, D., Chehbouni, A., Bouchaou, L., Kouisni, L., Kool, D., and Agam, N.: Water and Carbon Dioxide Interactions in the most unlikely places: The hidden dynamics of the Sahara Desert soils, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9320, https://doi.org/10.5194/egusphere-egu24-9320, 2024.

12:05–12:15
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EGU24-1084
|
ECS
|
On-site presentation
Eleonora Forzini, Giulio Castelli, Aida Cuni-Sanchez, and Elena Bresci

In the Namib Desert, along the South-Western African coast, fog represents the main water input for local flora and fauna. During the last years, changes in the timing of fog occurrence and in the quantity of water that can be harvested from it, have been observed in several areas of the world, including the Namib Desert. A deeper insight into fog presence and fog water yield changes can help to understand to what extent Namib Desert’s ecosystem is being and will be affected in future by climate change. This information can also contribute to local environmental protection and carbon dioxide sequestration strategies, as fog water can be used for reforestation and land restoration. An 8-year-long dataset of harvested fog water rates recorded daily in 13 ground stations along the Namib Desert was statistically analysed to inspect advection fog occurrence evolution. The results show a noticeable intra-annual and inter-annual variability in rates and seasonality of harvested fog water. On the other hand, observed trends in collected fog water time series are generally decreasing, but longer time series are required to confirm the trend since El Niño Southern Oscillation (ENSO) phenomenon presence in the analysed period might have had an impact. The main hypothesis is that changes in fog occurrence and its characteristics are due to climate modifications, given that no extensive human activities are present in the area. However, further analyses on fog-related climatic and meteorological factors, possibly including remote sensing or reanalysis datasets aiming to increase the available data timespan, are envisioned to understand to what extent fog collection in the Namib Desert will be affected in future by climate change.

How to cite: Forzini, E., Castelli, G., Cuni-Sanchez, A., and Bresci, E.: Analysis of fog occurrence changes in the Namib Desert across time and space and impacts on natural and artificial fog collection, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1084, https://doi.org/10.5194/egusphere-egu24-1084, 2024.

12:15–12:25
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EGU24-16214
|
ECS
|
On-site presentation
|
Narendra Reddy Nelli, Diana Francis, Ricardo Fonseca, Olivier Masson, Mamadou Sow, Rachid Abida, and Emmanuel Bosc

Fog is a prevalent weather phenomenon in several arid regions, including the Empty Quarter desert in the United Arab Emirates (UAE), located on the northeastern side of the Arabian Peninsula. Despite being primarily an arid country with desert landscapes dominating its terrain, most events causing visibility to drop below 1 km in the UAE are attributed to condensation processes rather than dust occurrences. We present in-situ measurements of fog microphysics from the Barakah Nuclear Power Plant (BNPP, a coastal site located at 23.968052°N, 52.267309°E) and atmospheric electric field measurements obtained during the Wind-blown Sand Experiment (WISE)-UAE field campaign conducted at Madinat Zayed (23.5761° N, 53.7242° E; elevation: 119 m).

Measurements of fog microphysics were conducted during the winter season of 2021 -2022 at the BNPP, located in the Western coastal region of the United Arab Emirates. Twelve fog events were observed during this period. The primary objective of this study is to detail the microphysical characteristics of these events and refine current visibility parameterization schemes based on in-situ measurements of fog microphysical properties. All observed fog events are found to share a common feature: a bimodal distribution in droplet number concentration (Nc), with modes at 4.5 µm and 23.2 µm . Despite the high proportion of fog smaller droplets associated with the fine mode, the greatest contribution to the liquid water content (LWC) comes essentially from medium to large droplets between 10 µm and 35 µm. The recalibration of existing visibility parameterization schemes revealed that the decrease (increase) in horizontal visibility with increasing (decreasing) LWC (FI, fog index) tends to be more gradual for the studied cases compared to standard visibility parameterization schemes. Additionally, the fog sedimentation velocity, estimated to be at a maximum of 1.85 cm s-1, occurs predominantly in the LWC range of 100 - 200 mg m3, corresponding to a median volume diameter 24.8 µm. Our findings shed new light on the complexity of fog microphysics and its impact on visibility, underscoring their importance in refining weather models for accurate fog forecasting.

For the first time, the changes in the atmospheric electric field (Ez) during foggy conditions is studied in a hyper-arid region; the United Arab Emirates (UAE), using comprehensive measurements during the Wind-blown Sand Experiment (WISE)-UAE. The longer the fog persists, the more variable Ez becomes, primarily due to the fog's ability to absorb and redistribute the charges of the atmospheric small ions. This absorption alters the ion balance, affecting electrical conductivity within the atmosphere, which in turn leads to sustained alterations in Ez. A record high Ez value of 2571 V m-1 was measured during a long-lasting fog event. Ez values returned to normal during the fog dissipation phase. The results of this work can be applied to develop techniques for fog harvesting and to improve fog forecasting by accounting for the effect of the electric field on fog lifetime and characteristics.

How to cite: Nelli, N. R., Francis, D., Fonseca, R., Masson, O., Sow, M., Abida, R., and Bosc, E.: Microphysical and Electrical Characteristics of Fog in the United Arab Emirates, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16214, https://doi.org/10.5194/egusphere-egu24-16214, 2024.

12:25–12:30

Posters on site: Mon, 15 Apr, 10:45–12:30 | Hall X5

Display time: Mon, 15 Apr 08:30–Mon, 15 Apr 12:30
Chairpersons: Jan Cermak, Anne Klosterhalfen, Christoph Thomas
X5.32
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EGU24-592
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ECS
|
Izabela Pawlak and Małgorzata Kleniewska

The impact of increasing CO2 on global temperature and strengthening of the greenhouse effect makes the measurements of gas exchange between the Earth’s surface and the atmosphere particularly important. Observational data on greenhouse gases exchange between different types of ecosystem and the atmosphere are crucial in thorough understanding the global climate mechanisms. Fruit tree ecosystems constitute an important kind of land use in Central Europe and apple is very extensively cultivated fruit tree crop in the world. Because intensively used apple orchards have a potential for carbon (C) sequestration and to be an important sink of atmospheric CO2 the continuous measurements of processes of ecosystem-atmosphere exchange are necessary for properly determining of global carbon (C) budget.

This work presents the results of continuous closed-path EC measurements of carbon dioxide (CO2) fluxes in the apple orchard located near Grójec in the Masovian voivodeship on the largest orchard area in Poland. These are the results of the first and the only measurements of the net CO2 fluxes (started in February 2023) carried out in the apple orchard ecosystem in Poland. The main goal of the work is to present variations of CO2 flux at different time scales at different stages of fruit tree growth and during different climatic conditions. The turbulent fluxes of CO2 were calculated on a 30-min basis. The raw data were computed using the EddyPro -7.0.9 software taking into account the necessary corrections and procedures to correct the obtained results. CO2 fluxes were characterized by clear daily variability with negative values during the day (CO2 uptake in the photosynthesis process) and positive at night (CO2 release in plants respiration processes). The most intensive CO2 absorption took place between May and September (phases of flowering and fruit development and ripening) the with a maximum in June. Negative 30 min mean CO2 flux value reached for this month was around 12 µmol ּ m-2 ּ s-1 around noon. In the remaining months the CO2 absorption processes were lower and ranged around a few µmol ּ m-2 ּ s-1

How to cite: Pawlak, I. and Kleniewska, M.: Variability of turbulent carbon dioxide flux netto at different time scales in an apple orchard ecosystem in Central Poland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-592, https://doi.org/10.5194/egusphere-egu24-592, 2024.

X5.33
|
EGU24-22465
Eric Rappin

The Kentucky Mesonet is a great asset for the Commonwealth of Kentucky, from realtime storm monitoring to building a detailed climate record. A detailed climate record is essential as causality between observations and extreme weather can be identified. The climate record being developed at the 80+ Kentucky Mesonet observation stations consists of approximately 75 indices. The indices include frequency, extremes, range, duration, and trends of precipitation, droughts, and temperature. For example, calculations of Warm/Dry days (daily mean temperature > 75th percentile of daily mean temperature and daily mean rainfall < 25th percentile of daily precipitation sum where the percentiles are based on a climatology taken from reanalysis between 1961 and 1990) are done for daily, monthly, seasonal, bi-annual, and annual aggregation periods. Particular attention will given to soil moisture - precipitation feedbacks as Kentucky has a karst geology which generates soil moisture gradients. Soil Moisture-precipitation feedbacks, the beginning and ending of land-atmosphere interactions in general, are highly dependent on the wind flow regime and atmospheric stability, so these relationships will elucidated in the presentation.  Tools will be developed based on interactions with policymakers and stakeholders as they will be making decisions today that impact the region’s main economic sectors (e.g. water, energy, transportation, etc.) as infrastructure erected today will likely be in place when the climate is different than at present. Examples will be provided that sample the different climate zones of the state, relative elevations of site locations, as well as different land cover and land uses.

How to cite: Rappin, E.: Land-Atmosphere Interactions as Observed by a Statewide in-situ Surface Observation Network, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22465, https://doi.org/10.5194/egusphere-egu24-22465, 2024.

X5.34
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EGU24-579
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ECS
Peter K. Musyimi, Balázs Székely, Hellen W. Kamiri, Tom Ouna, and Tamás Weidinger

The optimal solution for solving many uncertainties associated with weather and climate data is accurate field measurement. This enhances various climate services that can be offered to different sectoral case studies and solve societal weather-related challenges by ensuring the obstacles are overcome amicably, for instance, climate adaptation barriers in the face of climate variability. The main goal of our study was to make long-term meteorological measurements in Mount Kenya region rainforest biome at an elevation of 1998 m above sea level (Karatina University weather station) and 3055 m above sea level (Mount Kenya field station) used at various scales from 2022. We are using Temperature-Moisture-Sensor (TMS) burial (1 m) and TMS Long (45 cm) soil sensors as well as temperature/relative humidity data loggers. These devices provide us with crucial data and reshape field measurement campaigns in data-scarce regions of Kenya. The soil moisture sensors also measure soil temperature, surface, and air temperature. The soil moisture data and temperature at various scales is acquired at an interval of 10 minutes while the data logger records data at an interval of 30 minutes.  Another key goal was to acquire soil moisture data at tropical rainforest biome which is scarce as well as relative humidity and temperature. The objectives of the study are to analyze reference evapotranspiration and estimation of real evapotranspiration in humid Mount Kenya climatic region, Nyeri County; compare climate parameters in two different elevations; to understand microclimatic changes associated with varying elevations and ensure data quality control in analysis by checking uncertainties and sensitivities associated with ERA5 reanalysis, synoptic (GFS/ECMWF) and station datasets. Therefore, to narrow the gap between missing data, uncertainties, and quality control of data, meteorological field measurements cannot be misconstrued.

Keywords: data loggers, field measurement, soil moisture, quality control, Kenya,

How to cite: Musyimi, P. K., Székely, B., Kamiri, H. W., Ouna, T., and Weidinger, T.: Meteorological and Soil Moisture Measurements in Mount Kenya Region at Various Scales, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-579, https://doi.org/10.5194/egusphere-egu24-579, 2024.

X5.35
|
EGU24-16949
|
ECS
Khue Vu Hoang Ngoc, Georg Jocher, Vu Le D. A., Son Le T., An Bui T., Bang Ho Q., and Huong Pham Q.

Agriculture is an important economic sector of Vietnam, the most common is wet rice cultivation. Wet rice cultivation is known as the main contributor to national greenhouse gas emissions. To better understand greenhouse gas exchange in wet rice cultivations and to investigate the factors influencing carbon cycling and sequestration in these types of ecosystems, since 2019, the first eddy covariance station has been installed in a paddy field in Long An province, Mekong Delta, Vietnam. The station is equipped with state-of-the-art equipment for CO2 and CH4 gas exchange and meteorological ancillary measurements. Data from the station are processed following the ICOS recommendations (Integrated Carbon Observation System) for CO2. For CH4, data are separately processed and gap-filled using a random forest model from methane-gap fill-ml, a machine learning package, as there is no standard method for CH4 flux gap-filling yet. Finally, the CO2 equivalent (CO2eq) based on CO2 and CH4 fluxes was estimated. The study area implemented a new water management practice called alternate wetting and drying, which helps to save water and reduce methane emissions. This practice resulted in the minor release of 0.8 kg CH4 per hectare in 2020 and 0.67 kg CH4 per hectare in 2021. However, CO2eq from the rice fields was negative, indicating that the rice fields acted as a sink for CO2eq, with -5.54 kg CO2eq per hectare in 2020 and -7.03 kg CO2eq per hectare in 2021. On a provincial level, rice cultivation activities in Long An, with a total area of 498293 ha, resulted in a CO2eq uptake of 2760 and 3503 tons in 2020 and 2021, respectively. This result is in contrast to the initial hypothesis that rice fields are a source of greenhouse gases. However, N2O was not investigated in this study, which is also known as a strong greenhouse gas.

How to cite: Vu Hoang Ngoc, K., Jocher, G., Le D. A., V., Le T., S., Bui T., A., Ho Q., B., and Pham Q., H.: Measuring Greenhouse Gas Exchange from Paddy Field Using Eddy Covariance Method in Mekong Delta, Vietnam, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16949, https://doi.org/10.5194/egusphere-egu24-16949, 2024.

X5.36
|
EGU24-5207
Anna Lindenberger, Magdalena von der Thannen, and Hans Peter Rauch

Although occupying only 7% of the earth's surface, wetlands store 33% of the world's terrestrial carbon. When these ecosystems are drained to be converted into agricultural, forestry or mining exploitations, they release greenhouse gases contributing to climate change. While bringing together 18 partners from 9 countries, the REWET (REstoration of WETlands to minimise emissions and maximise carbon uptake – a strategy for long term climate mitigation) project focuses on determining how the restoration and management of wetlands can be optimised to maximise their carbon uptake while in balance with type-specific natural processes and biodiversity.

The REWET project draws upon a network of seven Open Labs (OLs) located in different geographical areas of Europe and covers different types of terrestrial wetlands: freshwater wetlands, peatlands and floodplains. The heterogeneity of the Open labs allows the application of different restoration methodologies while following the same monitoring plan to provide replicable knowledge.

This paper presents the measurements and the first result of the OL in Austria within the REWET project. The site is a restored and now protected floodplain area at the Morava River. EC measurements are used to calculate the CO2 and CH4 fluxes and the seasonal as well as annual carbon balance of the ecosystem. Furthermore, the effect of floodplain water levels and grazing in this area is investigated. The EC instruments have been set up on a floating platform to allow measurements also during flood events, when understudied, critical transition of GHG fluxes may occur. The CO2/H2O analyser started collecting the first data in the middle of October 2023 whereas the CH4 analyser was added in end of December 2023. Since the CO2 analyser was put on site first flood events occurred end of December, which is the first data to be processed and analysed. Additional to the results the challenges in setting up an EC tower in a floodplain area will be presented.

 

 

 

Funded by the European Union. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them.

How to cite: Lindenberger, A., von der Thannen, M., and Rauch, H. P.: Eddy Covariance (EC) measurements in a restored floodplain area at the Morava River in Austria within the EU funded REWET project, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5207, https://doi.org/10.5194/egusphere-egu24-5207, 2024.

X5.37
|
EGU24-19705
Influence of surface inhomogeneity on the formation of turbulent fluxes above the swamp surface
(withdrawn)
Ilya Drozd, Arseny Artamonov, Dmitriy Chechin, Artem Pashkin, Irina Repina, Victor Stepanenko, Alexander Varentsov, and Michael Varentsov
X5.38
|
EGU24-13971
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ECS
Observations of diurnal and seasonal variation of heat fluxes and an evaluation of bulk Richardson parameterizations in the East River Watershed, Colorado
(withdrawn)
Sreenath Paleri, Tilden Meyers, Temple Lee, and Mark Heuer
X5.39
|
EGU24-22205
Anastasia Gorlenko, Konstantinos Kissas, Charlotte Scheutz, and Andreas Ibrom

Eddy covariance (EC) flux measurements are relevant for the study of global change biology when integrated over long-term periods (Baldocchi, 2019). This could lead to researchers being reluctant to adopt state-of-the-art correction methods, especially for sites that have collected continuous data and trends for the last 20 years. The storage change (SC) correction has often been overlooked and simplified and is generally under-investigated in the literature. The present study highlights the dynamics of the storage change term in two different landscapes and proposes a simple correction factor that can be applied backwards to historical data in a forested ecosystem.

The first studied site is a mixed deciduous forest in Denmark (DK-Sor), where a sequential vertical profile system (12 heights) has been installed in 2021 to characterize the vertical component of the storage change more accurately. We compare the often-used 1 point method with the results from the profile system for CO2 and H2O. We study the SC component in terms of its diurnal course, its impact on the annual carbon budget, and its relation to atmospheric stability parameters.

The second site is a Danish rural area (DK-Hove), where four different greenhouse gas fluxes are measured with EC sensors installed at 3 heights on a 200 m tall telecommunication tower. The SC profile system here consists of 5 levels and needs to adapt to the dynamic eddy covariance measurement height of the landscape-scale GHG monitoring system. We present 6 months of SC data from the tall tower for CO2, CH4, N2O and CO, their diurnal courses and relation to meteorological variables.

Overall, this work aims at bringing an additional contribution to shed light on the often-neglected SC term.

 

Reference:

Baldocchi, Dennis D. How eddy covariance flux measurements have contributed to our understanding of Global Change Biology. United Kingdom: N. p., 2019. Web. doi:10.1111/gcb.14807.

How to cite: Gorlenko, A., Kissas, K., Scheutz, C., and Ibrom, A.: Quantification of storage change at two contrasting eddy covariance sites, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22205, https://doi.org/10.5194/egusphere-egu24-22205, 2024.

X5.40
|
EGU24-5340
|
ECS
Alexander Platter, Katharina Scholz, Albin Hammerle, Mathias W. Rotach, and Georg Wohlfahrt

The assessment of net ecosystem CO2 exchange often relies on eddy covariance systems. However, this method overlooks CO2 advection, even if it is often non-negligible. This is especially the case under stable, low-turbulence nighttime conditions. Hence, there is a need to filter nighttime eddy covariance data for periods when advection can be expected to be non-negligible. This study evaluates both well-established and novel filtering methods at a mountain forest site in Tyrol, Austria (Forest-Atmosphere-Interaction-Research (FAIR) site, AT-Mmg). Established methods, including friction velocity (u*) filtering, its counterpart using the standard deviation of vertical velocity  fluctuations (σw) and an after-sunset flux maxima approach (commonly referred to as van Gorsel method) are applied. Additionally we use a more recent approach with a physically-derived measure of flow decoupling for filtering. With this method also stability information is taken into account, not only a turbulence scale, as in the commonly used u* filtering. As often seen in literature, the uncorrected CO2 flux underestimates the nighttime respiration, as it appears for all the filtering methods. Despite being based on widely differing assumptions, the various filtering approaches yielded relatively similar carbon budget estimates over 14 months of measurements (-252 to -290 g C/m2). in contrast to the uncorrected budget of -521 g C/m2.

Furthermore, we introduce a novel K-means clustering approach that groups flow situations into clusters based on vertical profiles of temperature, σw and wind speed. These clusters need then to be evaluated to determine whether they represent a flow situation in which CO2 advection is expected to be irrelevant. Such scenarios are often Foehn periods or early-night situations with high turbulence and low stability. This approach is relatively straightforward to implement, works with an unlimited number of input variables and has the advantage that the identified periods are easy to interpret. This method results in a 14-month budget of -232 g C/m2 for our study site. 

The universality of the clustering method allows not only for an unlimited number of input variables, it can be also easily extended for the entire day. There is no a priori reason not to filter eddy covariance data during the daytime when low-turbulence situations with persistent in-canopy flows may lead to non-negligible advection, especially in complex terrain. We made an attempt of daytime filtering in this study with the clustering method, but also with some adapted versions of the benchmark methods. All of these daytime filtering methods suggest that there is an underestimation of the CO2 uptake in the morning for the uncorrected measurements. Filtering for both nighttime and daytime leads to a range of 14-month budgets of -451 to -359 g C/m².

Further analysis, incorporating different established sites, direct advection measurements or numerical simulations, could be used in future to explore the full potential of the novel clustering approach, especially with its application to daytime flux data.

How to cite: Platter, A., Scholz, K., Hammerle, A., Rotach, M. W., and Wohlfahrt, G.: Uncertainty of eddy covariance-derived net ecosystem CO2 exchange over a mountain forest reduced by multiple nighttime filtering approaches, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5340, https://doi.org/10.5194/egusphere-egu24-5340, 2024.

X5.41
|
EGU24-10295
|
ECS
Yi Fan Li, Kuo Fong Ma, Chin Jen Lin, Yen Jen Lai, Po Hsiung Lin, and Taro Nakai

Nocturnal advection significantly influences the accurate estimation of net ecosystem exchange (NEE). This phenomenon is prevalent in Taiwan's subtropical montane forests, introducing a potential bias when relying solely on eddy covariance data for carbon budget calculations. From the preliminary analysis, the wind speed can be well estimated through the temperature difference between the heated and unheated fiber optical.The derived five-minute average wind speed exhibits a high coefficient of determination (R^2) of up to 0.94.

In the current study, a fiber observational setup consisting of a 40m vertical section and a 90m horizontal section has been implemented to investigate temperature dynamics and airflow in complex terrain. The wind speed profile can be well reflected from the preliminary data analysis. Insights gained through this approach contribute to a better understanding of the nocturnal canopy advection model, offering valuable corrections to NEE estimates.

How to cite: Li, Y. F., Ma, K. F., Lin, C. J., Lai, Y. J., Lin, P. H., and Nakai, T.: Exploring Nocturnal Canopy Advection in Complex Terrain Through Active Heating Fiber Optics: Unraveling Temperature Dynamics and Airflow Patterns, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10295, https://doi.org/10.5194/egusphere-egu24-10295, 2024.

X5.42
|
EGU24-8926
|
ECS
|
Anas Emad

Atmospheric fluxes near the surface are key metrics for understanding the interactions between the biosphere and the atmosphere. There is an increasing demand for highly accurate flux measurements for species where fast-response analytical techniques are not available. This includes, among others, stable isotopes, oxygen, ammonia, nitrogen compounds, and bio-aerosols.

Here we introduce quantized eddy accumulation with error diffusion, a new easy-to-implement, high-accuracy eddy accumulation method that is compatible with slow-response analytical techniques. Similar to relaxed eddy accumulation, this method involves sampling air at a constant flow rate and directing it into one of two containers, depending on the vertical wind velocity. The flux is then calculated based on accumulated concentration averages over the flux averaging interval. However, unlike relaxed eddy accumulation, the new method is a direct method that does not require the empirical coefficient β. These developments were made possible by developing a new representation of conditional sampling at a constant flow rate as a quantization process of vertical wind velocity. Fluxes estimated with relaxed eddy accumulation were found to be biased due to sub-optimal quantization. To account for these errors, an error diffusion algorithm was developed, which made it possible to minimize the biases inherent in the quantization process, thereby allowing for accurate and direct flux estimates.

Quantized eddy accumulation with error diffusion is shown to achieve direct flux measurements with errors smaller than 0.1% of the reference eddy covariance flux. Additionally, this method enables an increase in the concentration difference in accumulated samples between updrafts and downdrafts without compromising accuracy, making it especially suitable for detecting smaller fluxes. It also provides improved accumulation volume dynamics, flexible accumulation intervals, and is less prone to errors from non-zero vertical wind velocities.

These new developments are especially useful for measuring small fluxes of elusive atmospheric constituents, particularly in the presence of measurement challenges such as instrument drift or frequency attenuation. A notable application is the accurate measurement of water stable isotopes, which enables the tracing of biological processes and the accurate partitioning of measured fluxes.

How to cite: Emad, A.: Quantized eddy accumulation with error diffusion: a new direct micrometeorological technique with minimal requirements, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8926, https://doi.org/10.5194/egusphere-egu24-8926, 2024.

X5.43
|
EGU24-6604
Ivan Bogoev

The eddy covariance (EC) method has been widely used to capture the temporal and spatial patterns of nitrous oxide (N2O) emissions from a wide variety of agricultural ecosystems. Technological advancements in the recent years have brought new tunable infrared laser-based closed-path gas analyzers suitable for EC measurements. To achieve high sensitivity and low measurement noise, these analyzers use multi-pass optical cells with long sensing path. A drawback of these cells is the relatively large internal volume requiring high-flow rate, high-power pumps to attain fast response to changes in gas concentration.  Additionally, these cells are prone to contamination and require in-line filters. In this study we evaluate the frequency response of a novel, low-power, field deployable N2O closed-path EC system consisting of: (1) a gas analyzer with a small volume single-pass optical cell, (2) a 3 m sulfonated tetrafluoroethylene ionomer intake tube acting as water vapor permeable membrane to dry the air sample, (3) a cyclone type, non-barrier inertial particle separator (IPS) to mitigate the effects of particulates contamination of the optical sample cell, and (4) a small, low-power pump module with an automatic pressure and flow control. The performance of the new N2O EC system is evaluated in-situ 3 m above a fertilized agricultural wheat field and compared to a co-located fast-response H2O and CO2 open-path gas analyzer and sonic anemometer (IRGASON). Tube delays, determined by cross-covariance of N2O with vertical wind, were consistent over time and varied between 0.2 and 0.5 s. Spectral and co-spectral analysis of vertical wind, temperature, H2O, CO2 and N2O showed good agreement. Ogive functions demonstrated that the new system has adequate frequency response to capture >90% of the N2O fluxes for a wide range of wind speeds and atmospheric stabilities and is suitable for deployment in remote areas.

How to cite: Bogoev, I.: Frequency Response Evaluation of a Low-power Closed-path Eddy Covariance System for Measuring Nitrous Oxide Fluxes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6604, https://doi.org/10.5194/egusphere-egu24-6604, 2024.

X5.44
|
EGU24-7892
Morten Hundt, Marco Brunner, Jonas Bruckhuisen, and Oleg Aseev

Monitoring of trace and greenhouse gas fluxes is key to understand the interaction between atmosphere, plants, and soil and therefore to improving our understanding of the climate system in general.

Complex flux systems, in environments where both biogenic and anthropogenic sources and sinks play a role, require measurement of many different inert and reactive trace gases and greenhouse gases simultaneously to obtain a complete budget.

Until recently, however, the monitoring was usually limited to only a few gases per measurement device making the technique complex and expensive but providing only a limited picture. MIRO Analytical has developed a novel multicompound gas analyzer that can monitor up to 10 air pollutants (CO, NO, NO2, O3, SO2 and NH3), greenhouse gases (CO2, N2O, H2O and CH4) and other atmospheric trace gases such as (OCS, HONO, CH2O) simultaneously at ppb level.

The eddy covariance (eddy flux) technique is often used to measure fluxes of trace gases but requires a high time resolution. Our compact instrument, combing several mid-infrared lasers (QCLs), offers 10 Hz sampling rate, outstanding precision, selectivity and accuracy and an automatic water vapor correction, which makes it ideal for eddy covariance flux measurements.

In our contribution, we will introduce the measurement technique and will demonstrate application examples of this all-in-one atmospheric flux monitor. The system will be compared to alternative devices in parallel measurements and results of long-term observations and shorter campaigns will be presented.

How to cite: Hundt, M., Brunner, M., Bruckhuisen, J., and Aseev, O.: Simultaneous trace gas flux monitoring of 10 greenhouse gases and air pollutants with a single instrument, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7892, https://doi.org/10.5194/egusphere-egu24-7892, 2024.

X5.45
|
EGU24-956
|
ECS
|
Joseph Gaudard, Richard Telford, Vigdis Vandvik, and Aud Helen Halbritter

Measurements of gas fluxes are widely used when assessing the impact of global-change drivers on key aspects of ecosystem dynamics, especially carbon. It shows whether an ecosystem is a source or a sink of atmospheric carbon, and how the storage dynamics could change in the future. Ecosystem gas fluxes are typically calculated from field-measured gas concentrations over time, using a linear or exponential model and manually selecting good quality data. This approach is highly time consuming and prone to potential bias that might be amplified in further steps, as well as having major reproducibility issues. The lack of a reproducible and bias-free approach creates challenges when combining global-change studies to make biome and landscape scale comparisons.

The Fluxible R package aims to fill this critical gap by providing a workflow that removes individual evaluation of each flux, reducing risk of bias, and making it reproducible. Users set specific data quality standards and selection parameters as function arguments that are applied to the entire dataset. The package runs the calculations automatically, without prompting the user to take decisions mid-way, and provides quality flags and graphs at the end of the process for a visual check. This makes it easier to use with large flux datasets and to integrate into a reproducible workflow. Using the Fluxible R package makes the workflow reproducible, increases compatibility across studies, and is more time efficient.

How to cite: Gaudard, J., Telford, R., Vandvik, V., and Halbritter, A. H.: Fluxible: an R package to calculate ecosystem gas fluxes in a reproducible and automated workflow., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-956, https://doi.org/10.5194/egusphere-egu24-956, 2024.

X5.46
|
EGU24-2407
|
ECS
Impact of deforestation on global monsoon precipitation   
(withdrawn after no-show)
Yue Liang, Xiyan Xu, and Gensuo Jia
X5.47
|
EGU24-9790
|
ECS
Shreyas Deshpande and Cedrick Ansorge

Slope flows, resulting from the interplay between buoyancy and gravitational forces, are well-known to govern a plethora of local weather phenomena. In particular, orographic features and the associated surface roughness can induce turbulent mixing in the planetary boundary layer. While orographic drag models have been proposed to understand the effects of turbulence and waves due to orography, numerical simulations locally rely on closures based on the Monin-Obukhov Similarity Theory. The validity of these models and their interaction regarding turbulence production due to orography at unresolved scales is questionable. We study the turbulence generation by small-scale orography under the influence of stable stratification and weak mixing. To bypass the common complications with surface modeling, we use direct numerical simulation featuring a shallow valley to study the problem at a reduced scale. To imitate the intricate boundary conditions, an Immersed Boundary Method is used that features fully resolved three-dimensional roughness elements in the form of a local valley. However, modeling such flows also poses challenges due to the numerous parameters governing the triggering of turbulence. In this presentation, we introduce a scaling framework orographic for the problem and a viable numerical set-up along with the first results from preliminary studies at intermediate scale separation.

* This work is funded by the ERC Starting Grant ”Turbulence-Resolving Approaches of the Intermittently Turbulent Atmospheric Boundary Layer [trainABL]” of the European Research Council (funding ID 851347).

How to cite: Deshpande, S. and Ansorge, C.: Turbulence generation by unresolved orography, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9790, https://doi.org/10.5194/egusphere-egu24-9790, 2024.

X5.48
|
EGU24-18634
|
ECS
Mayank Gupta, Ajinkya Khandare, and Subimal Ghosh

At the local scale, energy exchange shapes microclimates and ecosystems crucial for human health and well-being. For urban areas, the effect, such as Urban Heat Island, is directly manifested in these surface energy fluxes with contrasting responses in values between urban and rural areas. Although progress has been achieved in modeling the land surface energy balance, challenges arise from complex, variable parameterizations linked to surface and climate characteristics, introducing uncertainties. In this work, we utilized the thermodynamic theory that considers the land-atmosphere as a radiative-convective system to analytically estimate total turbulent heat flux and land surface heat storage flux for 20 Urban sites and compared them with Eddy covariance observations. The heat fluxes are determined only from four primary parameters: incoming and outgoing longwave and shortwave radiations at the terrestrial surface. Using the monthly averages derived from the total turbulent flux estimates at the eddy covariance sites, we observed root-mean-square error (RMSE) of 29.16 ± 11.3 Wm−2, a mean bias error (MBE) of -7.09 ± 19.6 Wm−2 and R2 value of 0.82 ± 0.16. We further tested the analytical estimates with land use land cover of Urban sites. Our findings illustrate the distribution of land surface heat storage flux estimates following land use land cover characteristics. The analytical estimates of heat fluxes for urban areas offer several advantages, such as ease of implementation and inexpensive computation, facilitating the evaluation of urban land use feedback for informed urban planning.

How to cite: Gupta, M., Khandare, A., and Ghosh, S.: Urban Surface Energy Flux Estimations Utilizing a Thermodynamic Analytical Framework, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18634, https://doi.org/10.5194/egusphere-egu24-18634, 2024.

X5.49
|
EGU24-15005
Claudio Cassardo, Valentina Andreoli, Davide Bertoni, Sujeong Lim, Massimiliano Manfrin, and Seon K. Park

While there are several series of daily observations of temperature, precipitation and few other parameters available in many locations in the world, sometimes lasting more than a century, there are much less series of other variables related to the surfae atmospheric layer or underground soil, such as sensible and latent heat fluxes, soil heat flux, soil temperature and moisture in the root layer and below it. This work aims to propose a method to evaluate such parameters at a climatic time scale using a trusted land surface model, taking the variables from the outputs of the simulation and creating a database. In this work, the selected model is the UTOPIA (University of TOrino land surface Process Interaction model in Atmosphere). This technique can be applied in general to each site in which hourly observations of the seven parameters needed for the simulation are available (temperature, humidity, pressure, the two components of the horizontal wind velocity, precipitation and solar radiation or cloudiness). In a preliminary phase, the database will be created on the period 1992-2023, on which we have the availability of hourly measurements carried out at the Department of Physics of the Turin University. In a second phase, we plan to develop a methodology to derive hourly observtions from the existing series of data gathered in the city of Turin, using peculiar methods to interpolate or extrapolate the missing observations of required inputs and to downscale hourly observations from daily observations. This methodology could be tested using the eisting data in the recent climate period.

How to cite: Cassardo, C., Andreoli, V., Bertoni, D., Lim, S., Manfrin, M., and Park, S. K.: Climatology of surface parameters for the city of Turin using UTOPIA (Italy) land surface model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15005, https://doi.org/10.5194/egusphere-egu24-15005, 2024.

X5.50
|
EGU24-12447
Land-Atmosphere interactions in urban areas
(withdrawn after no-show)
Lahouari Bounoua, Noura Ed-Dahmany, and Kurtis Thome
X5.51
|
EGU24-7308
|
ECS
Jannis Groh, Thomas Pütz, Daniel Beysens, Harry Vereecken, and Wulf Amelung

Precipitation (i.e. rain, snow, hail) is the main form of water input to our ecosystem. However, depending on local climatic conditions, a significant amount of water can also be produced by various fractions of non-rainfall water inputs (NRWIs), namely dew, hoar-frost, rime, fog, and adsorption of water vapour in the soil. Such NRWIs are often neglected because they are typically small compared to daily rainfall. However, these NRWIs provide our ecosystems with additional water, which is important for the survival of the fauna and flora in the ecosystem, especially during drier periods.

Although NRWIs are understood in principle, much remains to be learnt about their precise determination at the ecosystem level, their spatial and temporal distribution, and their ecological function for the ecosystem. We present a conceptual measurement setup that allows us to determine each non-rainfall water component for natural and extensive grasslands as well as for agricultural ecosystems. Our results for the experimental site Selhausen (Germany, TERENO-SOILCan) show that i) the main part of NRWI comes from dew formation, ii) the rate and frequency of dew formation differs significantly between vegetation types under similar atmospheric boundary conditions, and iii) the drivers of dew formation during a dry down period differ between ecosystems (grassland and arable land). A better understanding of these vegetation and soil-dependent effects will help us to better predict dew formation processes in our ecosystems in the future.

How to cite: Groh, J., Pütz, T., Beysens, D., Vereecken, H., and Amelung, W.: Role of vegetation and soil-induced effects of microclimate on non-rainfall water inputs, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7308, https://doi.org/10.5194/egusphere-egu24-7308, 2024.

X5.52
|
EGU24-12298
Pedro Berliner, Mercy Ama Boadi Manu, Dillia Kool, and Nurit Agam

Water vapor adsorption (WVA), a non-rainfall water input, is a poorly documented phenomenon despite its role in regulating water and energy fluxes in soils of coastal deserts. Water vapor movement towards the soil surface and its absorption by the soil occurs whenever the atmospheric water potential is higher than that of the air-filled soil pores. The latter is influenced by soil characteristics, in particular the soil surface area and pore connectivity. Thus, it is expected that under similar atmospheric conditions,  absorption of water vapor will be determined by soil characteristics. We carried out a detailed field trial in which we compared two loamy soils with different salt content.

Water vapor absorption was measured using micro-lysimeters (MLs) instrumented with relative humidity (RH) and temperature sensors at depths 0.5cm, 2cm, 5cm, 10cm, and 45cm in both MLs during the 2022 and 2023 summers. Total absorption was determined as the increase in mass from a minimum (obtained during late afternoon) to a peak observed on the next day before sunrise. Concurrent changes in soil water potential at each depth were computed by applying the Kelvin equation.

Relative humidity in both soils was low during the entire season with the average computed water potential values being lower in the high salt content soil. The total daily water vapor absorption was lower in the low salt content soil, and the rate of absorption was different . The temperature and RH distribution patterns with depth also differed consistently throughout the measuring season for both soils. The effect of salt on water vapor absorption will be highlighted.

How to cite: Berliner, P., Boadi Manu, M. A., Kool, D., and Agam, N.: The dynamics of water vapor  absorption by soils typical of arid lands, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12298, https://doi.org/10.5194/egusphere-egu24-12298, 2024.

X5.53
|
EGU24-2642
Nurit Agam and Dilia Kool

Drylands are 57% of the terrestrial area of the world, and are disproportionally affected by climate change. This is particularly pertinent in so-called “climate-change hotspots” such as the Mediterranean, where temperature increases at a rate of up to 0.45 oC/decade and precipitation is expected to decline. Given the sparsity of studies in drylands and the consequent lack of understanding of the unique processes in drylands, the degree to which these projections are accurate for drylands is questionable. The fact that drylands, by definition, are classified according to the aridity index, exposes the inherent assumption that desert hydrology is primarily governed by precipitation and potential evapotranspiration (ET0). There is increasing evidence, however, that non-rainfall water inputs (NRWIs; fog, dew, and water vapor adsorption) are a substantial source of water in multiple desert environments. In arid and hyper-arid drylands, water vapor adsorption is not only the least studied of the three NRWIs, but also likely the most common. In the Negev desert, Israel, the projected decrease in rainfall and increase in temperature, and therefore increase in ET0, is expected to result in drier soils. This potentially will increase the amount of water vapor adsorption. Here we present the actual rate of warming and the corresponding changes in ET0 in the Negev desert. We then elucidate, for the first time, the contribution of water vapor adsorption to desert hydrology and how it might be affected by climate change based on changes observed in the last 20 years.

How to cite: Agam, N. and Kool, D.: Can dry get wetter even if rainfall declines?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2642, https://doi.org/10.5194/egusphere-egu24-2642, 2024.

X5.54
|
EGU24-6150
|
ECS
Deepanshu Malik, Hendrik Andersen, and Jan Cermak

This study comprehensively investigates the vertical geometry of low-level clouds in the Namib desert. Using ceilometer measurements and meteorological station observations, a precise determination of cloud-base height and the separation of low-level stratus and fog is performed.
The Namib Desert, known for hyper-arid conditions and frequent cloudiness, presents an intriguing environment for the study of low-level clouds and their vertical geometry. Fog (ground-touching low-level clouds), a common atmospheric phenomenon in the Namib Desert, is influenced by the interplay of coastal upwelling and spatial temperature differences. Differentiation of fog from other low-level clouds and understanding cloud dynamics are crucial, as fog impacts the water balance in this arid region. Here, ceilometer measurements of cloud base altitude are analyzed and combined with local station measurements with the aim of developing a statistical model to robustly predict cloud base altitude.
Initial results suggest a robust correlation between the cloud base height and surface relative humidity, as well as other meteorological variables. This finding proves beneficial for utilizing meteorological parameters such as the lifted condensation level as a surrogate for cloud-base height. The outcomes of this study hold significance for modeling of satellite-based fog probability product and ecological studies.

How to cite: Malik, D., Andersen, H., and Cermak, J.: Investigation of the Vertical Geometry of Low Level Clouds in the Namib Desert, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6150, https://doi.org/10.5194/egusphere-egu24-6150, 2024.

X5.55
|
EGU24-15582
|
ECS
|
Eva Pauli, Jan Cermak, Hendrik Andersen, and Michaela Schütz

A better understanding of fog and low stratus (FLS) life cycle processes can help traffic safety, improve solar power planning and enhance the understanding of ecosystem processes in fog-prone regions. Nevertheless, large-scale analyses of FLS life cycle processes are challenging due to the high spatial variability of FLS and complex interactions between the land surface and the atmosphere.

Here, we use a satellite-based FLS formation and dissipation time data set, as well as reanalysis data to investigate regional variations in the FLS life cycle in the Po valley region in northern Italy. With its large spatial extent, relatively low topographic variability and high FLS occurrence, the Po valley is an ideal area to study FLS life cycle processes in central Europe. In a case study approach, we analyze FLS life cycle processes pertaining to variations in land surface characteristics and atmospheric drivers. First results reveal the importance of the temporal development of temperature, specific humidity and boundary layer height for FLS formation during radiation-driven FLS events. These effects are further modified by the local topography and the synoptic situation.

This analysis provides a basis to set up further process-oriented sensitivity studies using explainable machine learning, which has shown to be an ideal tool to gain a deeper understanding of the effect of non-linear land-atmosphere interactions on the FLS life cycle.

How to cite: Pauli, E., Cermak, J., Andersen, H., and Schütz, M.: A satellite-based analysis of fog and low stratus life cycle processes in the Po valley, Italy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15582, https://doi.org/10.5194/egusphere-egu24-15582, 2024.

X5.56
|
EGU24-16368
|
ECS
Alex Vlad, Gabriela Iorga, Nicu Barbu, and Sabina Stefan

Fog forecasting and fog nowcasting events are challenging issues especially when the fog phenomenon appears in the vicinity of airports because the reduced visibility associated with fog represent a high risk for air traffic events. Bucharest Henri Coandă International Airport (OTP, 44.57°N, 26.1°E, 95 m above sea level) is the largest airport in Romania and is located about 16 km north of Bucharest, the capital and most developed city of Romania. Its surroundings are comprised partly of residential and natural protected areas, and partly have agricultural use. Due to its geographic position, the airport is an important air traffic hub on the routes between western and eastern world destinations. In terms of numbers of flights, during the observation period analyzed here, the air traffic at OTP was significantly lowered during the spring of 2020 due to COVID-19 pandemic but soon after the restrictions were lifted and due to redirection of the flights over Ukraine after 2022, the air traffic is significantly increased in present.

Data and analyses reported here cover a period of 2 decades from the beginning of 2003 to the end of 2023. Meteorological data, including fog events, relative humidity, wind speed and direction, were measured by the weather station of Romanian Air Traffic Services Administration ROMATSA R.A. Data about boundary layer and solar radiation was extracted from the public available database from the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA5.

Present study reports the analysis of the evolution of the frequency of fog events and the relationships between fog events and speed and direction of the wind, and between fog events and the relative humidity. The correlations between the boundary layer height, solar radiation and the fog events were also investigated. Bivariate polar plots revealed fog appears with higher frequency (about 32%) during cold season, from October to March, and during early morning hours. Overview of the entire data set shows in some years mono-modal distributions of the fog frequency of occurrence with respect to the local time with peaks during the night and in the early morning hours and mono-modal flat distributions in other years. We observed the fog events are correlated with dominant wind directions of east-nord-east (ENE) and west-south-west (WSW). Statistical analysis of the data also showed a prevalence of the radiation fog over the advection fog.

Acknowledgement: AV was supported by the University of Bucharest, PhD research grant. AV acknowledges the partial funding from the NO Grants 2014-2021, under Project contract no. 31/2020, EEA-RO-NO-2019-0423 project. Data regarding boundary layer and solar radiation was extracted from the public available database from the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA5. We thank ROMATSA R.A. for access to the database.

How to cite: Vlad, A., Iorga, G., Barbu, N., and Stefan, S.: Examining the fog occurrence over the Bucharest Henri Coandă International Airport and its adjacent area, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16368, https://doi.org/10.5194/egusphere-egu24-16368, 2024.

X5.57
|
EGU24-3683
Chuntan Han, Rensheng Chen, and Hongyuan Li

Based on the understanding of long-term field observations, we monitored the amount of precipitation and dew/frost with field experimental studying in mountainous catchment, using the precipitation observation network in alpine mountainous regions and independently designed observation methods for dew and frost. The purposes of field experiments were to quantitatively identify the distribution pattern of precipitation and dew/frost, characterize the vertical water inputs in catchment scale, and further analyze the formation and transformation law of water resources in inland river source regions.  This dissertation also aimed to rationally develop and utilize precipitation and dew/frost resources, and identify the relationship between precipitation and dew/frost in alpine ecosystems, which will provide the perspective and knowledge of cold region hydrology for promoting regional sustainable development. The main conclusions of the dissertation are as follows:

(1) the relationships between dew/frost and precipitation, and dew/frost and evaporation in the alpine steppe of Hulu catchment.

The interannual ranges in the alpine steppe of Hulu catchment was from 32.36 to 59.68 mm for dew/frost formation, from 404.1 to 557.9 mm for the precipitation and from 343.9 to 372.0 mm for the evaporation.  Therefore, the amount of dew/frost accounts for 5.7% to 12.7% of the precipitation and 7.2% to 17.4% of the evaporation in the same period.

(2) Dew/frost had a significant impact on eco-hydrological system in dry season and comparatively high percentage of frost.

In the dry season, averaged amount of multi-year dew/frost accounted for 54.5% and 40.9% of the multi-year mean precipitation and multi-year mean evapotranspiration, respectively.  Therefore, dew/frost mostly occurred in the dry season.  The annual mean dew amount was 5.90 mm, and the annual mean amount in the dew proportion of dew/frost was 15.26%, while the annual mean frost amount was 31.33 mm, and the frost proportion in dew/frost was 84.74%.  On the monthly scale, frost was mainly generated from March to May and from September to November, which corresponded to the stages of freezing-thawing and thawing-freezing, respectively.

(3) dew/frost events highly depending on precipitation events based on isotope results.

Stable isotope of atmospheric precipitation in the Hulu catchment changed between each season which was noticeable from May to September; not obvious from October to April of the following year.  The spatial and temporal distribution patterns of δ18O and δD isotopes were mainly influenced by the sources of water vapor and small-scale environment.  The occurrence of dew/frost often occurred a few days after a precipitation event, and its stable isotope composition and its variation law were consistent with that of precipitation.  The results showed that the formation and source of dew/frost water are highly dependent on the occurrence of precipitation.  Dew had similar characteristics of precipitation occurred earlier.  However, frost mainly happened in the freezing-thawing process of soil, and is closely related to the isotope value of soil vegetation, which needed further analysis of soil and vegetation isotope samples.

How to cite: Han, C., Chen, R., and Li, H.: Comparative observation and estimation of precipitation and dew/frost on the Northeastern Tibetan Plateau, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3683, https://doi.org/10.5194/egusphere-egu24-3683, 2024.

X5.58
|
EGU24-16844
Carlos M. Regalado, Omar Garcia-Tejera, and Axel Ritter

Interception of fog droplets in cloud forests leads to wetting of the canopy, hampering transpiration and affecting the energy dynamics of the vegetation due to evaporation of the leaf water lamina and the reduction in the incoming solar radiation. We carried out continuous concurrent measurements of the canopy temperature (through infrared thermometers), artificial leaf wetness (LWS) and the micrometeorology of a cloud forest in the Anaga Biosphere Reserve (Tenerife, Canary Islands) during a 4-month period. Fog presence at the site, characterized by visibility measurements (Ω), was coincidental with variations in LWS and a decline in net solar radiation, Rn, i.e. 62.2 W m-2 during foggy conditions (Ω < 1 km) versus 245.0 W m-2 for fog-free conditions (Ω ≥ 1 km). Infrared readings during foggy conditions of one of the representative species of the cloud forest stand, the perennial tree Erica platycodon, showed that differences between canopy and ambient temperatures were primarily driven by Rn. After a fog event, E. platycodon was estimated to remain wet for at least 30 minutes up to 2.25 hours. This study provides information about the consequences of fog in the wetting/drying dynamics of cloud forests of the Canary Islands and their leaf thermoregulation.

How to cite: Regalado, C. M., Garcia-Tejera, O., and Ritter, A.: Leaf thermoregulation and fog wetting dynamics of Erica platycodon in a Macaronesian cloud forest, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16844, https://doi.org/10.5194/egusphere-egu24-16844, 2024.

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EGU24-20860
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ECS
Maria Giovanna Di Bitonto, Carol Monticelli, Salvatore Viscuso, and Alessandra Zanelli

Fog harvesting, an ancient water extraction technique, has gained renewed attention in recent years with the introduction of the Fog Water Collector. Comprising a mesh and supporting structure, this collector has proven effective in extracting water from atmospheric moist air. The Raschel mesh, initially designed for agricultural purposes, has become the predominant choice due to its affordability and widespread availability. Current research endeavors aim to enhance fog water yield by optimizing both collector design and mesh properties.

While Raschel mesh coatings have traditionally been explored to improve efficiency, recent findings suggest that alternative meshes may outperform the conventional Raschel mesh. However, challenges persist in understanding the resistance, lifespan, and maintenance requirements of these newer materials.

Our research takes a systematic approach to address this gap by assessing the durability of various fog harvesting meshes under laboratory conditions. A series of standardized tests are conducted to evaluate their efficiency, providing insights into the intricate relationship between cost, water collection efficiency, duration, and environmental impact. The study aims to inform decision-making processes surrounding fog harvesting mesh selection, considering factors such as initial investment, operational efficiency, and long-term sustainability.

By conducting these analyses in a controlled laboratory environment, we aim to provide valuable insights without the logistical challenges associated with field studies. This approach allows for a thorough examination of fog harvesting mesh performance, contributing to the broader understanding of NRWIs and their potential applications at different scales.

How to cite: Di Bitonto, M. G., Monticelli, C., Viscuso, S., and Zanelli, A.: Laboratory analysis on fog harvesting meshes employing durability tests, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20860, https://doi.org/10.5194/egusphere-egu24-20860, 2024.