The site of Els Plans is located since June 2021 in a semiarid area protected for steppe-land birds in the Eastern Ebro Basin, in the term of Preixana (Catalonia), close to a wide irrigated area. Its initial installation was as a reference site in the non-irrigated area of the 2021 LIAISE campaign (Land surface Interactions with the Atmosphere over the Iberian Semi-arid Environment), mainly intended to study the effect of missing irrigation in numerical models. After the end of the campaign in September 2021, some of the teams involved in Els Plans decided to leave the instruments there for some more time. In particular, the UKMO deployment, which included a 50m-high meteorological tower, stayed until July 2022. The resulting 13-month series includes the start of a drought period after a very moist winter in 2021. It allows to inspect the intra-annual evolution of some ABL characteristics at the semi-arid site, including evaporation, dew and frost, soil moisture, local circulations, fog events or mesoscale circulations.

Since July 2022 a Surface Energy Budget station and a weighable lysimeter continue operation allowing to perform the inter-annual monitoring of the aforementioned quantities, including the exceptional drought event in Catalonia that started during 2021 and is still active at the time of writing. The previous long-term drought was in 2008. This information allows to perform an interannual analysis using the three-year period available. The Canal d'Urgell bringing water from the dams in the Pre-Pyrenees was closed for the first time in history in 2023 with a huge impact in the local agriculture and economy. Some substantial rain events have happened since fall 2023, allowing for some greening in the area and the progress of the winter cereals. Long-term observations are necessary to better understand prolonged drought and its impact on terrestrial ecosystem and its feedback mechanism between the different compartments (soil, water, atmosphere, and vegetation).

How to cite: Cuxart, J., Price, J., Martínez-Villagrasa, D., Groh, J., Martí, B., Miró, J. R., Wrenger, B., and Jiménez, M. A.: Intra- and inter-annual monitoring of the Atmospheric Boundary Layer at a semiarid site in the Eastern Ebro basin during the current long-term drought, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-435, https://doi.org/10.5194/ems2024-435, 2024.

A scintillometer is a common instrument to measure path-integrated evaporation and sensible heat fluxes. It consists of a transmitter and a receiver separated along a line of sight of several hundreds of meters to a few kilometers. Turbulent eddies and the associated refractive index fluctuations along the path between transmitter and receiver cause diffraction of the transmitted microwave beam (known as the scintillation effect). Scintillometers have been designed to measure the full spectral range of the signal intensity fluctuations caused by this phenomenon and quantitatively link these fluctuations to the turbulent heat fluxes. Commercial Microwave Links (CMLs), such as used in cellular telecommunication networks, also make use of microwave signals. However, CMLs are obviously not designed to capture scintillation fluctuations. We investigate if and under what conditions CMLs can be used to obtain the structure parameter of the refractive index, C_nn, which would be a first step in computing turbulent heat fluxes with CMLs using conventional scintillation theory. To do so, we use data from three collocated microwave links installed over a 856 m path at the Ruisdael Observatory near Cabauw, the Netherlands. We compare received signal intensity fluctuations sampled at 20 Hz from two 38 GHz CMLs formerly employed in telecom networks in the Netherlands, a Nokia Flexihopper and an Ericsson MiniLink, with measurements from a 160 GHz microwave scintillometer (RPG-MWSC) sampled at 1 kHz and an eddy-covariance system. After comparison of the unprocessed C_nn, we reject the Ericsson MiniLink, because its 0.5 dB power quantization was found to be too coarse. Based on power spectra of the Nokia Flexihopper and the microwave scintillometer, we propose two methods to correct for the white noise present in the signal of the Nokia Flexihopper: 1) we apply a high-pass filter and subtract the noise based on a calibration with the microwave scintillometer; 2) we select parts of the power spectra in which the Nokia Flexihopper behaves similar to the microwave scintillometer and correct for the missed part of the scintillation spectrum based on scintillation theory. Calibration on the microwave scintillometer provides the best possible C_nn estimates for the Nokia Flexihopper, although this is usually not feasible for CMLs. Both of our proposed methods show an improvement of C_nn estimates in comparison to unprocessed estimates, though with a larger uncertainty than the reference instruments. Overall, our study illustrates the potential to use CMLs as scintillometers, especially due to their large global coverage, but also lays out major drawbacks, most of which are related to unfavourable design choices made for commercial microwave links.

How to cite: van der Valk, L., Hartogensis, O., Coenders-Gerrits, M., Hut, R., Walraven, B., and Uijlenhoet, R.: Use of commercial microwave links as scintillometers: potential and limitations towards evaporation estimation, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-86, https://doi.org/10.5194/ems2024-86, 2024.

Rainfall evaporation beneath cloud base level is a potential factor causing sub estimation of weather radar quantitative precipitation estimates (QPE), particularly at mid and long ranges in arid or semi-arid conditions. This effect is studied using observational data from the “Land surface Interactions with the Atmosphere over the Iberian Semi-arid Environment” (LIAISE) field campaign, part of the Global Energy and Water Exchanges (GEWEX) programme, which took place in the Eastern Ebro basin (NE Spain) in 2021. The objective of the study is to assess rainfall evaporation comparing a simple model with field campaign Micro Rain Radar (MRR) observations during LIAISE. The model describes the temporal evolution on a column of a drop size distribution (DSD) considering both sedimentation and evaporation. Ground based automated surface observations collocated with an MRR and a PARSIVEL disdrometer at three sites were used to identify possible events of rainfall evaporation (with precipitation and low relative humidity) and MRR data was processed with the RaProM and RaProM-Pro software (https://doi.org/10.3390/rs12244113, https://doi.org/10.3390/rs13214323) to compute radar reflectivity Z, liquid water content LWC, or precipitation type. Profiles of Z and LWC were examined with Contour Frequency Analysis Diagrams and the simple DSD column model. The case study shows the evolution of observed vs modelled DSDs with and without considering evaporation effects. Results indicated clearly the importance of including the evaporation to describe the evolution of the DSD during the event. This study was supported by Spanish projects WISE-PreP (RTI2018-098693-B-C32), ARTEMIS (PID2021-124253OB-I00) and the Water Research Institute (IdRA) of the University of Barcelona.

How to cite: Bech, J., García-Benadí, A., Udina, M., Polls, F., Peinó, E., Paci, A., and Boudevillain, B.: A case study of rainfall evaporation using a simple drop size distribution column model and Micro Rain Radar observations, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-352, https://doi.org/10.5194/ems2024-352, 2024.

In recent years, the impacts of solar activity on the earth’s surface, atmospheric and orbital environments have become increasingly important. Governments around the world have identified “space weather” as a potentially significant risk to critical infrastructure. However, the monitoring and forecasting capabilities for these events are currently rudimentary compared to terrestrial weather.

A global network of galactic and solar cosmic ray ground level monitors produce data for academic study and Ground Level Enhancement (GLE) event alerting. A GLE is typically characterised by a sudden large increase flux of fast neutrons over a wide area of the Earth’s surface for a period of 15 minutes or longer followed by a relatively gradual drop to the quiescent level. The flux of energetic subatomic particles during these events can degrade solar arrays, damage electronic components or cause single event effects (malfunctions) in semiconductor devices, potentially leading to significant disruption.

However, this network is built primarily using a neutron monitor (NM) design from 1964, named the NM-64. In the intervening years computer driven digital acquisition and processing have been added, but the monitor itself remains the same. Consequently, a new cosmic ray NM has been commissioned, the design for which has been optimised using Monte Carlo N-Particle simulations and experimentally validated. The counting performance of this design matches the NM-64 whilst using alternative non-toxic detectors, and being significantly smaller and lighter.

The new NM-2023, soon to be installed at a UK Meteorological Office site, will send its data to the Met Office Space Weather Operations Centre (MOSWOC) and the Neutron Monitor DataBase (NMDB) for global dissemination. Supporting real-time data processing and transmission to recipients facilitates their integration into operation forecast products, such as the nowcasting of atmospheric radiation exposure for end-users in the aviation sector.

As the accuracy of NM-2023 data is vital, a series of algorithms are applied to perform error checking and correction, along with air pressure correction and data formatting, before the data is disseminated. Two anomaly detection methods are employed, one on the immediate data and the other on the long-term trends. Multiple approaches have been developed for the immediate analysis, one using Principal Component Analysis. Weekly averages of count rates and measurements of neutron multiplicity form some of the long-term analysis. Concurrently with code development, a prototype for the NM-2023 has been gathering cosmic ray data at multiple locations in the UK. The results track trends seen by nearby NM-64s. The presentation will cover a discussion of the anomaly correction algorithms, in combination with a comparison of some data from the current NM-64 network with both the prototype and early results from the NM-2023.

How to cite: Alton, T., Mashao, D., Croft, S., Wild, J., Joyce, M., Packer, L., Bradnam, S., Turner, T., Binnersley, C., and Aspinall, M.: Fault Detection Methods and Early Data in New UK Cosmic Ray Neutron Monitor, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-498, https://doi.org/10.5194/ems2024-498, 2024.

As water is known to be a critical resource for hydrology and water management, with an estimated 2 billion people already affected by water scarcity and a projected 3 billion facing shortages by 2050, it was realized that this was an opportunity for designing and developing a new solution.

Evapotranspiration (ET) plays a vital role in the global water cycle, moving a staggering 500,000 km³ of water annually, with 70,000 km³ occurring over land. However, conventional methods for quantifying ET – such as potential, reference, max, equilibrium, and pan – do not achieve the necessary level of accuracy.

To address these challenges, a new cost-effective solution for direct, automated, and real-time ET measurements has been developed. The LI-710 sensor is a user-friendly device that measures ET, sensible heat, temperature, humidity, and air pressure every 30 minutes. It is significantly more affordable than typical eddy covariance flux stations, costing 5-10 times less, and it consumes 3-15 times less power. Moreover, it can be easily installed and utilized by individuals with limited experience in the field.

Years of field testing alongside traditional research-grade eddy covariance systems have provided excellent results.

Benefits from this innovative sensor have allowed for comprehensive global deployment in locations where infrastructure, funding, and local experience have made it difficult. Applications are extensive across agricultural fields, forests, wetlands, grasslands, water bodies, and many more. Every 30-minutes, fully processed ET values are provided in real-time, including quality flags, to reduce ‘data latency’ for immediate and effective actions.

Within the last year, multiple research agencies have been developing ET networks spanning states, countries, and continents, which this new LI-710 sensor makes possible.

Further innovations include the establishment of a new Internet of the Environment (IoE) platform. The new IoE system connects the Water Node with the Cloud platform. The Water Node includes all hardware necessary for direct, real-time measurement, data collection, and transmission to the Cloud.  The Cloud platform with remote access allows for data storage, analysis, and sharing.

This innovative LI-710 sensor fills needs for both meteorologists and climate change researchers as these two groups work together on new discoveries, interdependencies, and feedback loops. Governments around the world are focusing and funding hydrological-cycle research, and these sensors provide measurements where there were previously gaps in remote field locations. The information from these measurements will help with predicting future weather and climate patterns and with developing solutions for hydrology and water management challenges.

How to cite: Johnson, D., Burba, G., Fratini, G., Griessbaum, F., McCoy, J., Walbridge, R., Frodyma, A., Fuhrman, I., Parr, A., Trutna, D., Thomas, T., Ivans, S., and Xu, L.: New sensor platform for expansion of in-situ measurements for meteorological and climate change measurements, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-721, https://doi.org/10.5194/ems2024-721, 2024.

The research test site WINSENT supports answering questions regarding wind energy technology developments, to align wind energy with nature conservation and to gather a huge amount of open data with respect to the research wind turbines (RWT), environment and to meteorology.
ZSW, as a member of the southern German wind energy research cluster WindForS, has been developed and realized together with further cluster partners the globally unique wind energy research platform WINSENT at a site in mountainous and complex terrain. The research site is characterised by its location on an unwooded, exposed plateau downstream of a steep slope in the Swabian Alb. The steep slope results in higher wind speeds, turbulence and oblique currents. The seasonal change in vegetation on the Albtrauf influences the flow characteristics additionally.
Two RWT, each with a rated output of 750 kilowatts and a hub height of 73 metres have been erected and put into operation. Their rotor diameter is 54 metres, giving a total height of 100 metres. One of the unique selling points of the RWT is that the scientists have unrestricted access to the complete operation and control as well as to the construction data of the turbines in order to analyse their behaviour in detail. In addition to technological tests and investigations on the RWT, special emphasis is placed on the permanent recording of meteorological parameters at the test site and in the surrounding area. In particular, the microclimatic influences of the topography on the wind - and thus ultimately on the wind turbines - is a key focus of research.
Meteorological masts of 100m height are positioned in front of and behind each research turbine to measure the inflow and wake wind field. The top anemometer is as high as the top blade tip position of the turbines and the masts are equipped with various meteorological sensors as well as with bat microphones and bird/insects detection sensors. In addition to the met masts, eddy-covariance systems, ceilometer and rain sensors etc. gather a huge amount of environmental data. The measured data are used amongst others e.g. for the development and validation of a simulation chain, which couples mesoscale and microscale domains using WRF, LES and detailed CFD simulation.
Furthermore three lidar systems installed in the vicinity of the test site also record the wind flow in front of and behind the wind turbines. As a synchronised ensemble, the lidar devices can be designed as a virtual measuring mast and can also measure the wind flow far in front of the escarpment or directly behind the wind turbines.
As a research and development platform, the test site will be available to both natural and engineering scientists in the course of future projects.

How to cite: Rettenmeier, A.: WINSENT – wind energy research in mountainous and complex terrain, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-976, https://doi.org/10.5194/ems2024-976, 2024.

The Korea Meteorological Administration (KMA) has operated atmospheric research aircraft since 2018. The KMA introduced Kingair 350HW that was modified for multiple purpose of atmospheric observations. After modification, 2 pilots, 2 instrument operators and 1 research scientist are on board. Usually duration a flight is about 4.5 hours. The KMA aircraft has 400-hour flight in a year in the purpose of four scientific missions: severe weather monitoring (SW), environmental monitoring (EM), climate change monitoring (CM), and cloud physics and weather modification (CP). For those missions, 27 instruments and devices are installed.

Unlikely usual aircraft observations that intensively carry out during specific period, the KMA aircraft has routine observation about 400 hours an every year. In addition, as long as without any risk of damage for instruments, all of those are turn-on during observation. This gives us a merit of integrated insights and comprehensive understandings. The KMA aircraft observations are only carried out in flight information restriction of South Korea. From 2018 to 2023, total flight time (frequency) of SW, EM, CM, and CP are 299(43.3%), 85(12.3%), 85(12.3%), and 130(18.9%), respectively.

SW is focusing on weather events such as heavy rainfall, snowfall and typhoon. Most of those events are populated during summer season. EM is related to a study on something like Asian dust, aerosols, particles and reactive gases. Aerosol events are usually concentrated on spring season. CM is interested in the variability of greenhouse gases and is carried out every month. Most CP activities are experiments of weather modification. Approximately 250 species of atmospheric variables are observed and estimated a single flight with full operation of instruments.

How to cite: Goo, T., Jung, S., Kim, M., Kang, D., Han, S., Lee, G., Kang, M., and Shin, J.: Introduction of the KMA/NIMS atmospheric research aircraft observations for 6 years and scientific missions., EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-388, https://doi.org/10.5194/ems2024-388, 2024.

The utilization of multi-rotor UAS aircraft for atmospheric data collection is an expanding field, and one method employed for measuring atmospheric wind speed is the so called tilt angle method. This method correlates the tilt angle assumed by the multi-copter during hovering to compensate for aerodynamic drag forces due to the atmospheric wind.
At the Umweltphysik Group of the Eberhard Karls Universität Tübingen, a cost-effective and easily replicable calibration method has been devised and tested. However, this approach overlooks the crucial vertical component of the wind, essential for calculating vertical turbulent fluxes.
To address this limitation, a follow-up study proposes an analytical approach that involves calibrating relationships between wind speed and tilt angle, motor RPM and tilt angle, as well as vertical wind speed and RPM. The necessary data for this calibration can be obtained through telemetry from an open-source flight controller's log files and proper electronic speed controllers.
Accurate calibration of these relationships is ensured through real-world flight testing to maintain high precision. Indoor tests or wind tunnel experiments might yield biased results due to interactions with walls, failing to accurately represent the aircraft's outdoor aerodynamic behavior.
Considering environmental parameters such as air density is vital, as evidenced by notable differences between calibrations conducted in winter and summer. These variations underscore the necessity of accounting for environmental influences to avoid constant biases in the wind retrieval.
Subsequently, the method will undergo further validation by flying the aircraft in close proximity to a sonic anemometer to assess its accuracy in measuring atmospheric parameters.

How to cite: Bramati, M., Schoen, M., Savvakis, V., Wang, Y., Bange, J., and Platis, A.: Horizontal and vertical wind speed sampling using multirotor UAS aircraft, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-638, https://doi.org/10.5194/ems2024-638, 2024.

Currently, the WMO UAS-DC, which “aims at demonstrating the potential capability of UAS to play a role as an operational component of the WMO Integrated Global Observing System (WIGOS) under the Global Basic Observing Network (GBON).” [WMO, 2024] is running since March 2024, with Special Observing Periods in April, August, and September 2024.

Around 50 operators of uncrewed aircraft systems, including private entities, NHMS, and research institutions, plan to contribute atmospheric measurements worldwide. Beyond the operator group, the data user group is expected to utilize the obtained data, assess their quality, and potentially guide observational and simulation experiments to explore their impact, distinct from traditional sources like radiosondes or the TAMDAR/AMDAR system. Initial results are anticipated in 2024, providing insights into system capabilities, deployed types, robustness, and operational modes.

The presentation aims to provide a comprehensive overview of global activities and common challenges faced. As most of the uncrewed measurement systems are deployed beyond visual line of sight, specific rules for granting permissions have to be applied. In addition to regulatory and safety concerns, hurdles related to adverse weather conditions such as high wind speed, precipitation, and in-flight icing are significant and will be discussed from the point of view of the operations by the Institute of Flight Guidance, Technische Universität Braunschweig, Germany. Considering these aspects when projecting the future use of uncrewed aircraft systems in operational meteorology is crucial. A detailed examination of observational data and operation records will allow for an assessment of the progress demonstrated during the WMO UAS-DC.

How to cite: Bärfuss, K. and Gallia, M.: Update on the Use of Uncrewed Aircraft Systems for Operational Meteorology and Atmospheric Research, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-825, https://doi.org/10.5194/ems2024-825, 2024.

Wind energy is one of the key technologies in the transition to cleaner energy. WINSENT ("Wind Science and Engineering Test Site in Complex Terrain"), a project funded by the German Federal Ministry for Economic Affairs and Climate Protection (BMWK) and the Baden-Württemberg Ministry of the Environment, has established a wind energy test site in complex terrain, providing invaluable insights into the dynamics of wind energy in such environments.

Located on the Swabian Alb near Stuttgart, Germany, the site has unique features, including its proximity to a steep afforested edge and specialised equipment such as research wind turbines (RWTs) and meteorological measurement masts, which allow the study of the turbulent overflow of the seasonally changing slope and the behaviour of wind turbines in complex terrain.

The University of Tübingen is contributing to the project by carrying out in-situ measurements using fixed-wing and multi-copter uncrewed aircraft systems (UAS) at the test site. These UAS are deployed in different positions, including the inflow, the slope, above and behind the test site, and resolve turbulent fluctuations down to the sub-metre range. Previous measurement campaigns (Intensive Operation Period, IOP) were carried out in the previous WINSENT project. In the followup WINSENTvalid project, additional IOPs will be carried out to collect in-situ measurement data to validate the numerical models developed by WINSENT. Furthermore, the impact of the newly constructed RWT on the airflow is being investigated by comparing it with pre-construction data.

The presentation will include a description of the test site, the IOPs carried out and a presentation of the first measurement data.

How to cite: Gruchot, L., Bramati, M., Schön, M., Zum Berge, K., and Bange, J.: UAS measurements as part of the project WINSENT ("Wind Science and Engineering Test Site in Complex Terrain"), EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-801, https://doi.org/10.5194/ems2024-801, 2024.

WindBorne Systems has developed a novel balloon-based observation system, enabling constellations of balloons to be flown throughout the troposphere for extended periods of time. Each balloon, known as a Global Sounding Balloon (GSB), can fly for weeks at a time while being remotely directed to ascend and descend from a few hundred meters above the earth surface to the lower stratosphere, collecting up to 50 vertical profiles of wind speed and direction, pressure, temperature, and humidity per flight. Data collected by GSBs is available in real-time and can be used as a data source for numerical weather prediction initialization and verification, validation of parameterizations, and climate reanalyses.

Over the past 5 years, over 1250 GSBs have been flown and have collected atmospheric data throughout much of the world. During the first 4 years of operations, the GSB was developed, demonstrated and refined during large-scale intermittent field campaigns. In early 2023 WindBorne began operating a persistent constellation of GSBs and by early 2024, the constellation averaged 15 GSBs aloft at any given time with an expected increase to 100 aloft, supporting collection of over 300 vertical profiles of data per day, by the end of 2024.

WindBorne has partnered with the United States National Oceanic and Atmospheric Administration to optimize the assimilation of GSB observations for use in numerical weather prediction, and to further assess the impact of the observations on forecasts. During summer and autumn of 2022, 169 GSBs were flown in the tropical Atlantic and the Arctic, collecting observations throughout large parts of the northern hemisphere during a 3 month period. The observations were assimilated into retrospective runs of the NOAA National Center for Environmental Prediction Global Forecast System (GFS) and reduced both average geopotential height errors in the tropics by 2-3% and tropical cyclone forecast track errors by up to 18%. Experiments are currently underway to assimilate GSB data into AI-driven weather prediction models.

How to cite: Hutchinson, T., Sushko, A., Creus-Costa, J., Tallapragada, V., Wu, X., Mueller, M., and Cucurull, L.: WindBorne Global Sounding Balloons: Observations and Forecast Impacts, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-888, https://doi.org/10.5194/ems2024-888, 2024.

In 2023, Centre for Maritime Research and Experimentation (CMRE) kick-started a new scientific programme, which aims at studying the effects of climate change on the security sphere. Being the Arctic region one of the most threatened areas but also an important geopolitical hotspot, in June-July 2023 CMRE deployed three deep moorings for monitoring the acoustic-oceanographic conditions in the long term. These moorings constitute the NATO Arctic underwater Climate Observatory (NACO), and they build upon CMRE’s previous effort in 2021-2023 to study underwater acoustic noise and physical oceanographic properties in the Arctic under the Environmental and Operational Effectiveness Programme. In fact, the Arctic is undergoing a process of “Atlantification”, which is affecting not only its oceanographic characteristics, but also its acoustical ones. Wider areas currently covered by compact sea ice are expected to progressively become marginal ice zone. The moorings are equipped with passive acoustic recorders and oceanographic sensors. Although data did not show a clear relation between sea-ice concentration and noise levels in the marginal ice zone, they indicate the presence of transmissions ducts that increase the noise in the high frequencies in the subsurface area. The overall soundscape recorded in Fram Strait will be discussed, including anthropogenic activities. The biological soundscape showed seasonality evidenced by the presence of whale singing. CMRE is currently working at assessing the soundscape components with the aims of monitoring in the long term how they change in consequence of climate change, going from the physical environment (rain, wind, waves) to ecosystem and human activities.

How to cite: Giorli, G., Russo, A., Real, G., and Carniel, S.: NATO Arctic Climate Observatory and recent observations on acoustical ambient noise in the Arctic, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-1037, https://doi.org/10.5194/ems2024-1037, 2024.

Observational data of thunderstorm hazards, such as hail reports in the European Severe Weather Database, suggest that severe convective storms are especially frequent over the surrounding slopes of mountain ranges. The same geographic regions are also projected to experience the strongest increases in severe weather occurrence as a result of global warming. Given the potential high impact of intensifying severe convection in these densely populated parts of Europe (and other regions of the world), it is critical to better understand where and why these storms become more severe. While a number of field campaigns has investigated either terrain effects on the atmospheric boundary layer or severe storm dynamics away from terrain, their topical overlap, severe convection dynamics near terrain, is less researched.
For these reasons, ESSL is currently coordinating efforts to plan an international field campaign on severe convective storms surrounding the Alps and lower mountain ranges in central Europe from the Pyrenees to the West to the Tatras mountains to the East. A network of over 20 partner institutions across these countries has already been engaged. The research focus is on high-resolution data collection of the pre-convective environment and within individual severe storms. However, the field campaign will also provide wider opportunities to validate recent innovations in forecasting, nowcasting, and measurements, such as new instruments on the Meteosat Third Generation satellite, numerical model parametrizations of terrain-related processes, drone-based surveys and profiling, and polarimetric radar algorithms. This presentation will give a short review of the scientific literature on the topic of severe convective storms near complex terrain and summarize the most important research questions. Based on that, the current plans for the TIM field campaign are presented to invite collaborations from the EMS community.

How to cite: Fischer, J., Groenemeijer, P., Holzer, A., Eisenbach, S., and Partners, C.: Thunderstorm Intensification from Mountains to Plains: The TIM Campaign, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-194, https://doi.org/10.5194/ems2024-194, 2024.

Scanning Doppler Wind Lidars are used in a variety of applications, thanks to the versatility brought by their scanning head. Their principal output is the wind speed along the lidar beam, termed the radial wind speed. When used for vertical profiling, the horizontal wind speed and wind direction are obtained from a wind field reconstruction algorithm (DBS or VAD) applied to the radial wind speed along several high-elevation lines of sight.

However, for other scanning strategies (i.e., with low elevation or horizontal scans), the use of such algorithms is not common, making the radial wind speed the sole output of the Doppler Wind Lidar. The radial wind speed is more difficult to interpret visually for a human user, harder to compare with numerical models, and requires more work to be used into advanced algorithms.

Thus, we showcase the Volume Wind wind field reconstruction algorithm, capable of reconstructing the horizontal wind speed and wind direction from measurement points taken at the same elevation and varying azimuth.

We present data taken from the PANAME2022 campaign, in which a Doppler Wind Lidar (WindCube Scan 400S) was set up on an 88m-high tower in Paris city. The lidar performs scans at 0° elevation above the urban area of Paris, measuring radial wind speed from within the Urban Boundary Layer.  Then, we create maps of horizontal wind speed and direction, spanning a large part of the Paris urban area, using the Volume Wind wind field reconstruction algorithm.

This allows us to study the influence of the topography on the wind field at the height of the urban canopy. The effect of the bed of the Seine river is of particular interest, as it is thought to be an important ventilation corridor in periods of extreme heat. These results highlight the potential of remote sensors for studying the Urban Boundary Layer, and the added value of advanced processing algorithms. 

How to cite: Toupoint, C., Cespedes, J., Kotthaus, S., Preissler, J., Thobois, L., and Haeffelin, M.: Mapping horizontal wind speed using a single Doppler Wind Lidar scanning horizontally: a test case over Paris, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-419, https://doi.org/10.5194/ems2024-419, 2024.

Improving understanding of urban atmospheric boundary layer (ABL) processes and dynamics is central to improving the modelling and forecasting of weather, air quality, and thermal comfort, in particular in densely populated urban areas. The ERC (European Research Council) urbisphere-Paris measurement campaign generated extensive in-situ and remotely sensed observations of the ABL from a network of concurrently operated automated lidars and ceilometers (ALC), doppler wind lidars, radiometers, and automatic weather stations to explore surface-atmosphere feedbacks focusing on ABL dynamics upwind, over, and downwind of a metropolitan area.

Paris, one of the densest metropolitan areas in Europe, is located ~130 km from the coast in relatively flat orography, making it well-suited to study urban modifications of atmospheric boundary layer dynamics. urbisphere-Paris aims to gather consistent and coherent datasets on the magnitude and interplay of surface heat fluxes, radiation fluxes, aerosol load, and boundary layer dynamics to evaluate and improve next generation numerical weather and air quality modelling approaches.

From March 2023 to March 2024 a transect along the predominant wind direction had seven Vaisala CL61 Ceilometers operating. As the transect extended both upwind and downwind of the city centre by 60 km to include the rural periphery, modifications of the ABL aerosol profile, cloud properties, and mixed layer dynamics could be observed as air moves into, across, and beyond the metropolitan area.

The transect provides continuous profiles of attenuated backscatter and linear depolarisation ratio, with very high vertical (4.8 m up to 15.4 km) and temporal (every 5 s) resolution. From this other variables are derived, such as mixed layer height (MLH), cloud cover of boundary layer clouds (CC), and cloud base height (CBH). This contribution will present selected cases of spatiotemporal differences in ABL processes along the urban-rural continuum. Wind direction changes the upwind/ downwind effects such as the urban plume. Differences in temporal evolution of the ABL are also explored, including MLH, CC and CBH. These results will help identify both typical and unusual patterns to explore further with high resolution numerical weather prediction models.

How to cite: Looschelders, D., Morrison, W., Carrera, M., Christen, A., Fenner, D., Grimmond, S., Haeffelin, M., Hilland, R., Kotthaus, S., Legain, D., Masson, V., and Zeeman, M.: Urban modification of the atmospheric boundary layer over Paris – insights from intensive ALC profiling observations along a rural-urban transect, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-594, https://doi.org/10.5194/ems2024-594, 2024.

The European Partnership on Metrology (EPM) joint research project BIOSPHERE aims to develop the necessary instrumentation, methods, and measurement infrastructure to assess how the increasing ionization of the atmosphere, caused by extraterrestrial radiation fields (cosmic rays and solar UV radiation) and amplified by anthropogenic emissions, affects the human and ecological health of our planet.

Both electron precipitations of extraterrestrial origin and energetic bursts of protons released from the sun during solar flares or coronal mass ejections have the potential to affect lower stratosphere ionization and interfere with catalytic ozone depletion reactions. This can lead to an increase of the biologically active UV radiation flux, with significant implication for ecosystems, plants and human health, like cancers and cellular dysfunctions. 

To estimate the impact of these extraterrestrial radiation fields on the biosphere, the EPM project BIOSPHERE will provide traceable metrological data on cosmic ray fluxes, UV solar radiation at the earth surface, and the total ozone column which are key to assessing the role of cosmic rays in the atmospheric dynamics. For this purpose, dedicated instrumentation for determining the dependence of secondary cosmic rays (SCRs) on primary cosmic rays (galactic cosmic rays, solar particle events) and atmospheric parameters (e.g., temperature, density and aerosol concentration) has been developed and characterized. This instrumentation measures the SCR flux rate during measurement campaigns, side-by-side with spectra of UV solar radiation at ground level and total atmospheric ozone, with the aim of identifying and correlating changes of extraterrestrial cosmic radiation (revealed with SCR fluxes increased) with changes in atmospheric parameters (ground-based UV radiation, total ozone column). As the cosmic ray flux measured at ground level is influenced by the overlying atmosphere, a metrological methodology is currently being developed to correlate SCR flux rates with temperature and pressure. This method will also help to quantify the rates of ionizing particles in the lower stratosphere that can interfere with catalytic ozone depletion reactions. Traceable measurements of cosmic ray fluxes, UV radiation spectrum and ozone column are being carried out in measurement campaigns at four European sites. We will present here the instrumentation developed, the instrumental methodologies and the results of the first two campaigns.

How to cite: Doppler, L., Bolsée, D., Van Laeken, L., Rapp, B., Al-Qaaod, A., and Faton, K.: The project EURAMET BIOSPHERE, instrumentation development and atmospheric measurements, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-585, https://doi.org/10.5194/ems2024-585, 2024.

The Finnish Meteorological Institute (FMI) ceilometer network now has about 45 ceilometer stations across Finland that report the full vertical profile of attenuated backscatter profiles, which are processed and displayed in real time on a dedicated website (ceilometer.fmi.fi). This data is also forwarded to E-PROFILE, part of the surface observation network in Europe coordinated by EUMETNET.

The primary objective of ceilometers is for measuring cloud base, but, with the improvements in the sensitivity of the ceilometers now available, it also possible to diagnose the presence of aerosol, precipitation, and differentiate between liquid and ice clouds. For Finland, one important achievement of the ceilometer network is the reliable identification of supercooled liquid layers. This has led to the development of an 'icing' product which highlights the likelihood of icing (e.g. for trees, masts, aircraft) and has been used to evaluate the icing forecast generated by FMI in conjunction with in-situ measurements of ice accretion. Other products are also being developed (such as fog forecasts) for real time generation and display.

Recently, the FMI ceilometer network has been augmented with 5 ceilometers having depolarisation capability (Vaisala CL61). The performance is such that episodes of dust, pollen and smoke are readily identifiable at the nominal instrument resolution without further averaging. In addition, it is also possible to distinguish between solid precipitation (ice and snow) and freezing rain, which has proved extremely useful for aviation forecasters. In this presentation we will demonstrate both the characterisation and quality control applied to the depolarisation instruments to ensure reliable measurements, particularly close to the surface, and compare remote sensing with surface-based identification of freezing rain events.

How to cite: O'Connor, E., Le, V., Filioglu, M., Shang, X., Vakkari, V., and Moisseev, D.: Enhancing Finland's ceilometer network, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-832, https://doi.org/10.5194/ems2024-832, 2024.

Ground-based microwave radiometers (MWR) provide valuable information on thermodynamic profiles and cloud liquid water by measuring the thermal emission, expressed as brightness temperatures (TB), of atmospheric gases and hydrometeors in several channels, and have thus become a widely used tool in atmospheric remote sensing. MWR are being deployed for process studies of boundary layer structure and development, as well as for operational data assimilation in numerical weather prediction models (NWP). Due to their robustness and ability to operate unattended in long-term deployments, MWR are currently implemented into two observation networks in Europe. EUMETNET's profiling network E-PROFILE and the European Research Infrastructure ACTRIS are both establishing centralized near-real-time processing and provision of MWR data at about 30 stations, covering different climate zones.

Assessing the quality of long-term data sets in a network configuration is a crucial part for ensuring continuous operation and detecting instrument malfunctions. Near-real-time monitoring of data streams can be utilized to help station operators with instrument maintenance and statistical analysis of critical instrument parameters can unveil degradation and resulting drifts. In ACTRIS, a centralized monitoring is being developed with an online graphical interface and instrument specific alerting system, allowing for quick responses and initiation of mitigation strategies to avoid a prolonged impact of instrument failures on data quality. For MWR the stability of all receiver components, which can be prone to the environmental temperature, is an important factor in the quality assessment and needs to be monitored together with the spectral behavior of observed TB for automated data flagging. In addition, parameters of regularly performed relative calibrations (automated procedure) and absolute calibrations (with a liquid nitrogen cooled target) should be considered in any long-term operation for a better evaluation of the system status.

Another tool for judging the instrument performance is the detection of systematic errors by comparing the observations to a model background (O-B). During scenes with no liquid water clouds present, TB are simulated by a radiative transfer model with input from a NWP model. The resulting differences to the observations are exploited in a statistical way to detect drifts, erroneous absolute calibrations, and for TB bias corrections. A similar approach of simulating TB will also be used to serve as training data set for developing a statistical retrieval, which is based on a common data input, needed to ensure homogeneous MWR data streams throughout the network. The performance of the retrieval method will be evaluated in an inter-comparison study, involving different retrieval algorithms, based on observations during the “PAris region urbaN Atmospheric observations and models for Multidisciplinary rEsearch” (PANAME) campaign.

How to cite: Marke, T., Pospichal, B., Böck, T., Martinet, P., and Löhnert, U.: Microwave radiometer data quality monitoring and retrieval development framework for network operation, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-871, https://doi.org/10.5194/ems2024-871, 2024.

The present work aims to describe the main objectives and activities of the research project “Cyprus GNSS Meteorology Enhancement” (CYGMEN) funded (€1.500.000) by the Cyprus Research Innovation Foundation (RIF) in the frames of "Strategic Research Infrastructures" Call for Proposals. CYGMEN was initiated at December 2023 with the aim to establish a Meteorological cluster (CyMETEO) in Cyprus that will strategically augment existing Frederick Research Center and Department of Meteorology infrastructure, through the introduction of: a) a Lighting detection network, b) a dense GNSS network for atmospheric water vapor estimation (supported by Cloudwater Ltd and Nicosia Development Agency, c) a Radar Wind Profiler (RWP) and d) a Microwave Radiometer (MWR). Within this framework, preliminary activities for the establishment of CyMETEO infrastructure will be presented here. The CyMETEO infrastructure will be also accompanied by an advanced CyMETEO service that will be developed in order to: a) process and provide in near real-time all different types of data generated by CyMETEO infrastructure (CyMETEO Observational Analysis Component) and b) provide advanced short-term weather forecasting through the assimilation of CyMETEO data into the state-of-the-art Weather Research and Forecasting (WRF) model currently employed operationally by the Cyprus DoM without, however, performing any Data Assimilation (CyMETEO Simulation Analysis Component). Thus, preliminary results from the CyMETEO service design and development will be also shown. Furthermore, another aim of this study is to evaluate the performance of the GNSS tropospheric analysis component of the CyMETEO system over Nicosia district, prior to its deployment. For this purpose, GNSS tropospheric product (IWV) as deriving from the hyper-dense CYGMEN GNSS station network will be validated by being compared with respective IWV values obtained from Nicosia Radiosonde station, as well as from ERA5 Reanalysis datasets.

How to cite: Oikonomou, C., Haralambous, H., Tymvios, F., Charalambous, D., Satraki, M., Kotroni, V., Lagouvardos, K., and Loizou, E.: Cyprus GNSS (Global Navigation Satellite System) Meteorology Enhancement , EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-887, https://doi.org/10.5194/ems2024-887, 2024.

The real-time measurement of ionospheric (geometry-free) combinations, of transmitter-receiver Global Navigation Satellite Systems (GNSS) multifrequency carrier phase measurements, constitute the input of a unique all-time all-weather global detector of the distribution and changes of electron content in the Earth ionosphere (see for instance Hernández-Pajares et al. 2011).

The resulting area of research, GNSS Ionosphere (see definition in Hernández-Pajares et al. 2022), and the corresponding Space Weather monitoring capabilities with unprecedented spatial and time resolution, will be summarized in this presentation. In particular, the performance of the real-time 24/7 detection and measurement of solar flares during more than one solar cycle (Hernández-Pajares et al. 2023) will be illustrated and commented. The system relies on continuous tracking of the intensity of expected global patterns in the Earth’s ionosphere’s free electron distribution, which are associated with solar flares. A summary of the corresponding validation will be provided, comparing it to external and direct solar EUV flux measurements obtained from space missions, like the SOHO-SEM. In particular we will show how GNSS Ionosphere can provide better solar flare detection and solar EUV flux rate tracking performance than such a conventional orbital EUV photometers, under events involving relativistic electrons.

References:

Hernández-Pajares, M., Juan, J.M., Sanz, J., et al., 2011. The ionosphere: effects, GPS modeling and the benefits for space geodetic techniques. J.Geodesy 85 (12), 887–907. https://doi.org/10.1007/s00190-011-0508-5.

Hernández-Pajares, M., 2022. GNSS ionosphere. In: Sideris, Michael G.  (Ed.), Encyclopedia of Geodesy. Springer International Publishing, New York City, pp. 1–7. https://doi.org/10.1007/978-3-319-02370-0_172-1.

Hernández-Pajares, A. García-Rigo, E. Monte-Moreno et al., GNSS Solar Astronomy in real-time during more than one solar cycle, Advances in Space Research, https://doi.org/10.1016/j.asr.2023.12.016

How to cite: Hernández-Pajares, M., García-Rigo, A., and Monte-Moreno, E.: GNSS Ionosphere application to Space Weather monitoring, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-1041, https://doi.org/10.5194/ems2024-1041, 2024.

Nitrous oxide (N₂O) is stratospheric ozone depleting, long-lived green-house trace gas with a 100-year global warming potential 298 times greater than carbon dioxide, (IPCC, 2013). Microbial production processes in agricultural soils contribute significant portion of the total N₂O emissions. Nitrogen fertilization and manure management are the main drivers for the N₂O fluxes at the soil-atmosphere interface, which are highly variable in space and time. The eddy covariance (EC) technique provides a continuous landscape-scale flux estimates with high temporal resolution. The availability of mid-infrared tunable diode lasers (TDL) operating at room temperature allowed the development of high precision fast response gas analyzers suitable for the EC method. In this study we describe the design and evaluate the performance of a novel, field-deployable low-power N₂O EC system. The system consists of compact closed-path TDL absorption spectrometer with a 1 m single-pass, small volume optical cell which allows the use of low power DC pump. It features a cyclone-based inertial particle separator acting as a non-barrier filter to prevent contamination of the optical components with minimal attenuation of N₂O fluctuations. The effects of absorption line broadening and dilution due to water vapor are minimized using sulfonated tetrafluoroethylene ionomer intake tube acting as water vapor permeable membrane to dry the air sample. The new N₂O EC system was deployed in manure fertilized agricultural cornfield 3 m above the canopy and was collocated with an open-path CO₂ and H₂O infrared gas analyzer and ultrasonic anemometer (IRGASON). Spectral analysis and Ogive functions demonstrated that the new EC system achieves adequate performance and excellent frequency response to measure N₂O fluxes under a wide range of meteorological conditions. Further refinements for stable and prolonged unattended operation are described.

How to cite: Bogoev, I.: Advancements in atmospheric nitrous oxide eddy covariance flux measurements, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-15, https://doi.org/10.5194/ems2024-15, 2024.

The Global Navigation Satellite System (GNSS) Radio Occultation (RO) technique sounds the atmosphere providing high quality vertical profiles of the thermodynamics on a global scale. The Polarimetric RO (PRO) technique is an extension of traditional RO that retrieves precipitation information in addition to the standard thermodynamic products. The technique has been demonstrated aboard the Spanish Low Earth Orbiter (LEO) PAZ, as part of the Radio Occultation and Heavy Precipitation (ROHP) experiment led by the Institut de Ciències de l’Espai (ICE-CSIC/IEEC) in collaboration with NOAA, UCAR, and NASA/Jet Propulsion Laboratory. This mission enables the investigation of intense precipitation events and their associated meteorological conditions by retrieving atmospheric thermodynamic variables and offering insights into the vertical structure of precipitation.

The determination of the vertical structure is accomplished through the observable differential phase shift (ΔΦ), defined as the difference in the accumulated phase delay between the two linear polarizations (H-V) as function of the tangent point of the PRO rays. During intense precipitation events certain challenges arise in obtaining high-quality measurements of thermodynamic parameters due to signal attenuation. However, the PRO technique is less affected by attenuation, presenting an opportunity to obtain high-resolution thermodynamic profiles and information about the vertical structure of hydrometeors, simultaneously.

Validation of the PRO technique with two-dimensional data has been successfully conducted using the Global Precipitation Measurement (GPM) mission gridded products (like Integrated Multi-satellitE Retrievals for GPM, IMERG). In this analysis, vertical structure validation has been performed using data from the Next Generation Weather Radars (NEXRAD), a network of dual-polarized Doppler radars operating at the S-band, covering the entire United States territory. By exploiting the dual-polarization capabilities of NEXRAD, a comparison of the specific differential phase shift (K_dp) structures with the PRO observable ΔΦ aids in examining similarities and differences in the detection of precipitation between the two instruments.

Furthermore, to explore the sensitivity of the PRO technique to various types of hydrometeors, the Weather Research and Forecasting-Advanced Research Weather Model (WRF-ARW) is employed for a comparative analysis, focusing on hydrometeor water contents. The variation of the model’s microphysics parametrizations allows for the study of the PRO technique’s sensitivity based on different assumptions about hydrometeors. Changes in these parametrizations impact total precipitation, vertical structure of hydrometeors, cloud properties, energy budget, spatial structure, among others. The validation and sensitivity study of the PRO technique will contribute to an enhanced understanding of the observables obtained and will offer insights into the phenomena characterizing intense precipitation situations.

How to cite: Paz, A., Padullés, R., and Cardellach, E.: Sensitivity to the vertical structure of hydrometeors using Polarimetric RO, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-1009, https://doi.org/10.5194/ems2024-1009, 2024.

Thermodynamic profiles in the atmospheric boundary layer can be retrieved from ground-based passive remote sensing instruments with an optimal estimation physical retrieval such as Tropospheric Remotely Observed Profiling via Optimal Estimation (TROPoe). The retrieval combines measurements, prior information, and corresponding uncertainties to find an optimal solution of the atmospheric state. TROPoe permits combining passively sensed radiances from infrared spectrometers and microwave radiometers with thermodynamic profiles from Raman lidars, Differential Absorption lidars, Radio Acoustic Sounding Systems, radio soundings, or numerical weather prediction models. After more than 10 years of development, the TROPoe retrieval code was recently converted to Python and put into a Docker container to facilitate its usage for both operations and research. It is currently used operationally by the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) program and by the Swiss weather service MeteoSwiss as part of the EUMETNET. With a high temporal resolution on the order of minutes, the retrieved thermodynamic profiles are a powerful tool to study the temporal evolution of the boundary layer.

Since each profile is retrieved independently from the previous one, the time series of thermodynamic variables contain random uncorrelated noise, which may hinder the study of diurnal cycles and temporal tendencies. In this work, we investigate how the temporal consistency of thermodynamic profiles retrieved with TROPoe can be improved by including information from a previous retrieved profile as input to the retrieval. We demonstrate that this method works well in mid-latitudes, polar and tropical sites and for retrievals based on measurements from infrared spectrometers and microwave radiometers. We further present methods to enhance the availability of valid profiles retrieved from infrared spectrometers by preventing overfitting and by adding information from an additional infrared band in high moisture environments when the typically used spectral bands are saturated.

How to cite: Adler, B., Turner, D. D., Bianco, L., Wilczak, J., Djalalova, I., and Myers, T.: Retrieving thermodynamic profiles in the atmospheric boundary layer from ground-based passive remote sensing instruments using an optimal estimation physical retrieval , EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-195, https://doi.org/10.5194/ems2024-195, 2024.

We investigate the relationship between the CNR and the mean horizontal wind speed estimated by a Doppler lidar. Intuitively, high values of CNR represent high concentration of particles that backscatter the light beam and therefore denote observations with high accuracy, while decreasing values of the CNR gradually give rise to a higher uncertainty. For a Leosphere V2 Doppler wind lidar that was operated in DBS mode in the high Arctic, we observed three distinct ranges of the normalized mean wind speed along the range of CNR values. In the CNR range from ≈ -14 dB to -22 dB there is a decrease of about 5% in the observed mean horizontal wind speed. It is very fortunate that the decrease is followed by a flat plateau of the wind speed for CNR values between -22 dB and -26 dB in which the estimate of the wind speed is not sensitive to the choice of the CNR threshold value. An abrupt increase in the normalized wind speed for CNR values < -26 dB signifies that the backscattered signal becomes weak due to low aerosol concentrations and noise starts to corrupt the estimation of the mean wind speed. This characteristic pattern was also found in observations at the Meteorological Observatory Lindenberg using a WindCube 200s and a Stream Line XR system, both operating in VAD mode. But the specific CNR values separating the three distinct ranges are not quite the same. Generally, the flat plateau and the subsequent rapid increase as CNR values decrease further are well known and are a consequence of the detector sensitivity with respect to the noise level; this feature can help operators to identify a filter threshold suitable for their particular instrument. However, the decrease of the wind speed for CNR values between -14 dB and -22 dB deserves further investigation.

Based on the two data sets of Doppler wind lidar observations, the decrease in the wind speed for CNR values, as well as the flat plateau will be presented and discussed. The CNR dependence on the observed wind speed is likely instrument dependent but can also have a sensitivity to height as well as meteorological conditions.

How to cite: Gryning, S.-E., Kayser, M., O’Connor, E., and Batchvarova, E.: Relationship between Doppler wind lidar observed wind speed and Carrier-to-Noise ratio, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-218, https://doi.org/10.5194/ems2024-218, 2024.

The meteorological community, and in particular the wind energy community, have been trying to establish a methodology to correct/convert turbulence measures derived from measurements performed with Doppler wind lidars. The idea with these corrections is that lidar-based turbulence measures become equivalent or comparable to those turbulence measures that we normally retrieve using traditional in-situ instrumentation such as cup anemometers on masts. Part of the reason of this quest is the ability of Doppler wind lidars to be both versatile and affordable, apart from the most important characteristic of these instruments, which is their high accuracy and precision in measuring winds within and beyond the limits of meteorological masts. Particularly, for offshore applications, floating Doppler wind lidars are nowadays the standard for wind resource assessment, since deploying and maintaining instruments on tall meteorological towers offshore is currently too expensive. With regards to versatility, Doppler wind lidars are used for different applications ranging from, e.g., atmospheric modeling, wind turbine wake studies, and wind turbine control, among others. The wind energy community in particular is therefore making efforts in the development of recommended practices and standards to enhance the adoption of measurements from lidars. Corrections for lidar-based turbulence measures have been however investigated for decades. The major difficulties for establishing a turbulence correction are related to two main points: turbulence contamination and turbulence filtering due to probe-volume averaging. These two points lead to what we here refer to as the lidar-turbulence paradox, which basically means that in order to determine the ratio between the lidar turbulence measure to that of a cup anemometer, we need to know the characteristics of atmospheric turbulence; but these characteristics of turbulence are the ones we want to measure with our lidars.

We circumvent the paradox using a physics-based lidar-turbulence model, which serves for the training of a number of neural networks. The measurements we study are from continuous-wave Doppler lidar wind profilers, which were deployed besides a tall 250-m meteorological mast at the Østerild test station for wind turbines in northern Denmark. Metek USA-1 sonic anemometers on the masts match four lidar measurement levels and are used as reference for the turbulence measures. The prediction of the neural networks, which has the lidar measures as inputs, are compared with the measurements from independent Doppler wind lidars.

How to cite: Peña, A., Yankova, G., and Malini, V.: Unraveling the lidar-turbulence paradox, EMS Annual Meeting 2024, Barcelona, Spain, 1–6 Sep 2024, EMS2024-255, https://doi.org/10.5194/ems2024-255, 2024.