Global surface temperatures continue to rise, with projections indicating over 2°C warming by 2100, primarily attributed to anthropogenic greenhouse gas emissions. Urban areas, responsible for 70% of global emissions, are focal points for climate change mitigation. The PAUL Cities project aims to monitor emissions reduction in megapoles. Current monitoring infrastructures like ICOS focus on atmospheric, oceanic, and ecosystem measurements. This study explores the potential of using slow-response analyzers on tall atmospheric towers for Eddy Covariance flux computations, addressing technical challenges and height-induced complexities. Additionally, a novel wavelet-based method is proposed for attributing fluxes to biogenic and anthropogenic sources, using carbon monoxide as a distinctive tracer. Results from sites near Paris demonstrate the feasibility and versatility of these approaches, offering valuable insights for urban emission monitoring strategies worldwide.

How to cite: Herig Coimbra, P. H., Loubet, B., Laurent, O., Bignotti, L., Lozano, M., Mauder, M., Heinesch, B., Bitton, J., and Ramonet, M.: Advances in Urban Greenhouse Gas Monitoring: Integrating Slow-Response Atmospheric Towers and Wavelet-Based Techniques for Flux Measurements and Attribution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6214, https://doi.org/10.5194/egusphere-egu24-6214, 2024.

The eddy covariance (EC) method is the standard technique for determining forest ecosystem-atmosphere turbulent exchange, however, it encounters a significant challenge: the air masses below the canopy often become decoupled from the air masses above it. Consequently, the EC measurements of scalar fluxes (e.g. H₂O and particularly CO₂) above the canopy can be biased due to missing signals from below-canopy processes. This decoupling is strongly site dependent and influenced by atmospheric conditions, canopy properties and tower-surrounding topography. Multiple approaches have been developed in the recent decades to address decoupling (e.g. u_* filtering, quality flags for flux measurements, storage change evaluations, direct advection measurements), however, all of them appeared to be insufficient to fully tackle the problem. A promising additional approach is based on subsequent EC measurements below and above the canopy. Specifically, examining the correlation of the standard deviation of vertical wind (obtained via sonic anemometers) below and above the canopy provides insight into the coupling state, as this correlation remains linear during fully coupled periods.

To date, there is no standardized approach to address decoupling yet, hence, it is commonly not explicitly considered in EC measurement networks and infrastructures such as FLUXNET or ICOS (Integrated Carbon Observation System). A specialized working group within ICOS strives for addressing this by initiating an extensive multi-site experiment. This multi-site experiment aims to i) evaluate the performance of different types of sonic anemometers below canopy for decoupling investigations, ii) explore the spatial heterogeneity of below canopy processes in relation to decoupling, iii) develop a robust procedure to integrate decoupling investigations in the standard processing of EC measurement networks.

The anticipated experimental design involves three testing sites chosen to represent a broad range of canopy characteristics. These sites consist of a deciduous broadleaf forest in flat terrain (Lanžhot, Czech Republic), a coniferous forest in mountainous terrain (Renon, Italy), and a tall evergreen needleleaf forest in moderately complex mountain-valley terrain (Wind River, USA). The working group, in collaboration with industry partners, plans to deploy approximately 30 sonic anemometers across these sites. While around 10 sonic anemometers of the same type will be installed at the Wind River site, the rest, comprising different types, will be set up at Lanžhot and Renon. Installations, arranged in an array below the canopy around the primary EC measurement tower, are scheduled to commence in spring 2024, with the goal of year-long data collection to cover all seasons.

This presentation will set the proposed experiment on a solid theoretical background, introduce the measurement design and discuss the experiment aims.

How to cite: Jocher, G., Kowalska, N., Liu, H., Wharton, S., Montagnani, L., and Papale, D.: Addressing forest canopy decoupling in eddy covariance flux measurement networks, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7413, https://doi.org/10.5194/egusphere-egu24-7413, 2024.

The continuous observation of ecosystems fluxes between the biosphere and atmosphere provides a much-needed foundation for effective real-world management of our geo-ecological life support systems. Over a thousand flux measurement sites globally use sophisticated eddy-covariance (EC) instruments and are organized in international monitoring networks, e.g. FLUXNET, NEON, ICOS. The integration of automated spectrometers measuring irradiance, reflectance and sun-induced chlorophyll fluorescence (SIF) adds valuable optical proxies for photosynthesis and carbon fixation at top-of-canopy level:  field spectroscopy provides  a powerful tool for understanding measurements of plant carbon uptake, thus providing a link between fluxes and satellite remote sensing and enabling local information to be scaled up to the globe. In the last years many efforts have been made for merging these two types of measurements. Nevertheless, when combining these two sources of information one major limitation is to match the different areas seen by the EC flux measurements and field spectroscopy. Typically the proximal sensing instruments have a fixed field of view (FOV) which limits the measured area to a portion of the underlying canopy. The FOV depends on the set up defined and can vary between a few degrees and 180 degrees, and, alongside the mounting height, determines the size of the monitored area. On the contrary, classical EC flux measurements provide data that typically refer to a larger and variable FOV, also referred to as footprint. The footprint of EC data varies spatially according to meteorological conditions, so – unless a site is perfectly homogenous – the comparison between proximal sensing and EC is always flawed by the footprint mismatch. Additionally, the results of a classical EC time series are difficult to attribute to individual sources and sinks within an upwind source area due to spatial aggregation. Recently the FluxMapper EC approach has been shown to transcribe high-frequency temporal information onto half-hourly Flux Maps around the tower which resolve fluxes spatially through signal disaggregation. Analogous to the proximal sensing techniques, the spatial resolution of the Flux Map depends on the sensor distance from the canopy. In this contribution, for the first time, we provide preliminary results of combining field spectroscopy techniques and Flux Mapper EC, and evaluate spatial heterogeneity effects on the interpretability relative to classical EC. Broader impacts include cost-effective measurement, reporting, and verification of nature-based and technological climate solutions in support of the Glasgow Climate Pact and the Dubai Climate Summit net-zero commitments.

How to cite: Julitta, T., Burkart, A., Bower, S., and Metzger, S.: Accounting for spatial variability when combining fluxes and proximal sensing techniques., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16121, https://doi.org/10.5194/egusphere-egu24-16121, 2024.

Despite the influence of drought on ecosystem functions and human well-being, there are significant uncertainties in our understanding of the impacts of drought for ecosystems and humanity. Over the past decade, large Environmental Research Infrastructures (ERIs) have been implemented around the world to advance our understanding in the responses of the biosphere to environmental change. These emergent ERIs now provide a unique opportunity to advance our understanding of ecological processes, such as drought, across continents, decades, and disciplinary boundaries. Against this backdrop, 6 ERIs (SAEON/South Africa, TERN/Australia, CERN/China, NEON/USA, ICOS/Europe, eLTER/Europe) have established an international network-to-network collaboration – the Global Ecosystem Research Infrastructure (GERI). To date, GERI activities have focused on garnering support, establishing baseline pathways for communications across continents and cultures and an initial mapping of each ERI’s data availability to facilitate future research. 

With recent funding from a U.S. National Science Foundation AccelNet award, GERI is poised to begin harmonizing key drought-related data. Working with stakeholder partners in the The Drought-Net Research Coordination Network’s and International Drought Experiment, we have identified key baseline data products for harmonization capable of driving new discoveries across continents. These data include soil moisture, precipitation, soil texture, and aboveground biomass, water balance, etc. As we advance this project, these harmonized data will be open, findable, searchable, and accessible, and made available to the broader community for research and discovery and stakeholder networks including the International Drought- Network to test and model. Data contributions from these new and emerging networks will be encouraged and streamlined through accessible metadata and standards. Lessons learned from the intersection of global drought data will be applied to the expanding set of environmental data collected by research networks around the world.

How to cite: Loescher, H. W., SanClements, M., Bäck, J., Borman, T., Feig, G., Grant, M., Kutsch, W. L., Laney, C., Mabee, P., Mirtl, M., Morris, B., Ohlert, T., Ruddell, B., Siggers, A., Smith, M., Sullivan, P., Yu, X., and Zacharias, S.: Harmonizing Data Across Continents and Networks to Address Ecological Drought, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2039, https://doi.org/10.5194/egusphere-egu24-2039, 2024.

Climate change is having a global impact through the increased frequency, magnitude and duration of droughts, fires, floods and other extreme climatic events. The societal solutions to this crisis depend on the ability of policy makers, private enterprise, and society at large to access and utilise scientific research into climatic variables and carbon/greenhouse gas dynamics across scientific domains. This will also require connecting, exchange and collaboration between these stakeholders. One of the most suitable approaches that supports the needs of all parties is the development of standardised observations in sustainable research infrastructures (RIs), that can facilitate both basic and applied scientific analyses and produce the data products needed.

The Horizon Europe funded KADI project (Knowledge and climate services from an African observation and Data research Infrastructure) aims to provide the conceptual framework for the future implementation of a pan-African RI that delivers the science-based services to fully address the requirements of the Paris agreement and the UN SDGs. The project aims to  have direct societal benefit through facilitating inter-disciplinary cooperation between African and European Partners and conceptualising the requirements for climate change observations in Africa.

The project  works towards the development of a comprehensive design for a pan-African climate observation system using the climate services identified and required by key stakeholders as a guiding design principle, and further building on the knowledge compiled and gaps identified through the SEACRIFOG collaborative inventory tool, the OSCAR/Surface, OSCAR/Space and OSCAR/Requirements tools. The project  connects scientists, data and knowledge users at local, national and global levels, to develop a community of practice in climate services. These networking and knowledge exchange activities allow for the development of an RI design study and the identification of the key players who can implement the conceptual design as sustainable funding for long-term observations becomes available.

The main activities in the project  utilise a co-design approach to identify the climate services required by key stakeholders and  explore these through a series of climate service pilot projects that  focus on the impacts of climate change on terrestrial ecosystems, coastal areas, urban developments and national GHG budgets. The outputs from this will inform the strategic design of the long-term observational and data infrastructures required. A knowledge exchange platform will facilitate pan-African and European innovation, linking the science-based concept design and the policy cooperation required to develop a functional and collaborative RI, and provide long-term sustainable support for the integration of African climate-services into global observation systems.

How to cite: Ozolina, K., Bilola, T., Saunders, M., Salmon, E., Skjelvan, I., Bornman, T., Klausen, J., Feig, G., Merbold, L., and Kutsch, W.: Designing a pan-African climate observation system to deliver societal benefit through climate action: The KADI project, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18742, https://doi.org/10.5194/egusphere-egu24-18742, 2024.

Climate, potential biota, topography, geological parent material, and time. The state factor-interactive-controls hypothesis is a pervasive concept in ecosystem ecology that could explain long term controls of eddy covariance estimates of gross primary productivity. The hypothesis is adopted by ecologists whenever a gradient analysis is used (a chrono-sequence or a climate gradient). In this framework the state factors of climate, potential biota, topography, geological parent material, and time control ecosystem processes but are not themselves influenced by ecosystem processes at local scales. Interactive controls like realized plant functional types, soil resources, microclimate and disturbance frequency influence and are influenced by ecosystem processes. Flux networks represent whole ecosystem process measurements and while much has been learned from analyzing short term controls, longer term controls have been investigated less often. The last two decades have seen the growth of the Ameriflux network in North America; similar measurements of ecosystem carbon, water and energy exchange made across a wide range of ecosystem types. We tested whether gross primary productivity, estimated using the eddy covariance method across more than 40 ecosystems in North America conformed to the State-Factor-Interactive-Controls hypothesis. To estimate state factors we combined satellite observations, digital elevation models, geological and soil maps and climate re-analysis. By limiting our analysis to sites with more than 10 years of data we were able to remove the effect of short-term direct controls (light, temperature, moisture etc) on gross primary productivity. We found significant interactive effects of climate and geological substrate and a strong direct effect of climate on average gross primary productivity. We also found a strong effect of biota on the variation that was not explained by state factors. Comparing these patterns to predictions from an Earth System Model we found contrasting results. These findings provide support for the state factors-interactive-controls hypothesis and suggest new opportunities for ecological synthesis using networks of ecological data.

How to cite: Moore, D., Zhang, W., Abarzua, A., and Devine, C.: Using flux networks to discover long term controls of ecosystem productivity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13492, https://doi.org/10.5194/egusphere-egu24-13492, 2024.

Livestock grazing contributes to greenhouse gas (GHG) emissions, soil degradation and erosion, and loss of biodiversity. Regenerative pasture management includes improvements such as sowing high-diversity seed mixtures with legumes and other deep-rooted forbs in addition to C3 and C4 grasses, alternating intensive grazing with rest periods, bio-based fertilizers, etc. These improvements may alleviate degradation and restore multiple ecosystem services, including soil carbon sequestration and heat wave mitigation. Predictive understanding of management impacts requires process-based models that accurately simulate herbaceous growth and allocation in response to grazing and irrigation events. Moreover, accurate and timely model forecasts depend on well-validated data collected at appropriate temporal and spatial scales, delivered with low latency.

We used four years of eddy covariance data in combination with vegetation indices and a process-based model to improve estimates of Net Ecosystem Production (NEP) and energy balance in response to livestock and wildlife grazing in an area with fluctuating soil moisture availability. The enhanced vegetation index (EVI) for the degraded pasture, grazed mainly by native wildlife (kangaroos), demonstrated wide seasonal variations of 0.2 to 0.6, whereas EVI was maintained more consistently close to 0.5 for an improved pasture, grazed intermittently by cattle or sheep. Across three wet years, NEP for the improved pasture averaged 12% higher compared to the degraded one (153 vs. 137 g C m-2 y-1), associated with average 20% greater gross primary production (GPP; 1822 vs. 1521 g C m-2 y-1). However, NEP on the improved pasture was lower than on the degraded pasture in two of those three years, possibly due to grazing-related differences in biomass removal. Sensible heat fluxes were higher from the degraded pasture, especially during hot/dry periods. Ongoing analyses are evaluating soil C storage for benchmarking flux data. Model predictions are also being improved by validating representation of productivity by C3 and C4 species and carbon allocation to roots and crowns. This work contributes to enhancing environmental sustainability in managed grasslands with near-real-time forecasting ability for grazing and irrigation management.

How to cite: Pendall, E., Knauer, J., Wright-Osment, N., Macdonald, C., Barton, C., Chandregowda, M., Power, S., and Medlyn, B.: Progress in forecasting carbon, water and energy fluxes in improved and degraded pastures: data-model comparison near Sydney Australia , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1551, https://doi.org/10.5194/egusphere-egu24-1551, 2024.

Coastal redwood forests are among California’s most productive and largest carbon-storing natural ecosystems. However, there is a gap in knowledge on their water and carbon fluxes due to the lack of direct flux measurements. We received funding and advisory support from the State of California in order to address the water and carbon fluxes from redwood forest under declining fog conditions, different forest floor management, increasing droughts and other climate change threats during the period when the State is preparing for carbon neutrality goals (to be accomplished by 2045). Two tall eddy covariance towers will be installed in summer of 2024 to continuously monitor forest health at early and mid-seral growth stages (91 % of the coastal redwood forest ). Due to the complexity of terrain, we will equip the towers with the additional profile measurements throughout the canopy and downslope from the main towers to address the advection and  flux drainage. Occasional ancillary forest inventory surveys will be conducted within the flux footprint for improved data interpretation.  The study results will be uploaded to AmeriFlux and FLUXNET data repositories, and regularly communicated to the State agencies, advisory board and local communities through meetings and cooperative extension events. We invite suggestions for collaboration for continuing this project beyond the current timeline for long-term study and broader impact.  

How to cite: Suvocarev, K., Chu, H., Klinek, L., Miksch, M., Oldroyd, H., Magney, T., Chan, S., Biraud, S., and Paw U, K. T.: An Integrated Observatory for Redwood Forest Health and California Carbon Neutrality , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14226, https://doi.org/10.5194/egusphere-egu24-14226, 2024.

According to the IPCC and the Paris Agreement, the imperative to limit global warming to 1.5°C, or well below 2°C, compared to the pre-industrial era, necessitates achieving a balance between anthropogenic emissions by sources and removals by sinks (net-zero anthropogenic CO₂ emissions) by the second half of this century. In this context, a prerequisite for credible climate action is an accurate estimation of both these large fluxes. Recent initiatives have focused on improving the quantification of the land sector mitigation potential and reducing the discrepancies between models and observations at a global level. However, the implementation of climate mitigation policies often takes place at the local level, where entities like local authorities (e.g., cities and regions) often wield more impactful roles in the transition to a sustainable economy than higher-level bodies such as Nations. Conversely, the assessment of CO₂ removals from forests and other land uses is traditionally lacking at the local compared to the national level. 

Following a support request from the local administration for the definition of a long-term climate mitigation plan, we tested a data-driven method relying on eddy covariance (EC) data to quantify the carbon sink of the Aosta Valley Region in northwestern Italy for the period 2010-2022. Our model integrates various approaches, incorporating eddy covariance measurements of CO₂ fluxes, MODIS NDVI data, daily gridded meteorological variables, and a 250m spatial resolution land cover map to calculate the net carbon uptake of the regional ecosystems. A Random Forest model was used to up-scale the eddy covariance data to the regional level, by testing different sets of drivers (air temperature, VPD, Snow (presence/absence), NDVI, solar radiation,...). Furthermore, global models developed in the framework of the FLUXCOM initiative were fine-tuned with the local predictors and applied at a regional scale. Finally, we compared our findings with independent data derived from the National Greenhouse Gas Inventory.

Preliminary results revealed that forests and other ecosystems in the region currently offset on average nearly 70% of anthropogenic emissions in the region, also depending on the interannual variation of air temperature and the occurrence of extreme events. We will delve into the discrepancies among various methods, exploring their respective advantages, limitations, and spatiotemporal variability. This evaluation of the regional carbon budget and associated uncertainties represents an important step toward the benefit of using flux observations for implementing climate-smart land management—a pivotal component in meeting carbon neutrality targets.

How to cite: Galvagno, M., Filippa, G., Tuzzi, L., Cremonese, E., Collalti, A., Colombo, R., Dalmonech, D., Grassi, G., Migliavacca, M., Tomelleri, E., and Nelson, J.: Empowering local Climate Change mitigation policies through Eddy Covariance flux measurements, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12677, https://doi.org/10.5194/egusphere-egu24-12677, 2024.