Chairpersons: Frank Beyrich, Fred C. Bosveld
The latest generation of active and passive ground-based remote sensing instruments, often called “profilers”, has shown its potential for continuous and high-resolution measurements of thermodynamic and kinematic vertical profiles as well as particle-related profiles. It is precisely these observations of the atmospheric boundary layer that are increasingly needed to improve the forecast quality of high-resolution numerical weather prediction (NWP) and nowcasting.
For this purpose, the DWD has initiated the project “Pilotstation” to evaluate options for a qualitative network expansion with suitable surface remote sensing profilers. Currently, we assess the following profilers in a dedicated testbed at Lindenberg Observatory: Doppler lidar, microwave radiometer, water vapor broadband-DIAL, and cloud radar. Furthermore, we plan to evaluate a compact Raman lidar in the future. At DWD, the assessment of candidate systems takes place holistically focusing on all aspects of instrument reliability, operational sustainability, data quality, and on the potential benefit for the NWP using assimilation experiments. This implies efforts to standardize data processing steps and data formats, the development of software tools to support network operations and the proper integration of the observations in the data assimilation system. After the initial testing and evaluation at the Lindenberg Observatory, a suite of instruments will be installed at the weather station in Aachen-Orsbach to enable an end-to-end testing in an operational framework.
We give an overview of the ongoing project and present results regarding the various aspects: operations and sustainability, data quality and assimilation tests for the different testbed instruments and observations. This contribution complements the efforts of network development for future operational use within the frame of the EUMETNET's E-PROFILE observations program and the COST action PROBE.
How to cite: Knist, C., Kayser, M., Löffler, M., Vural, J., Schomburg, A., Görsdorf, U., Lauermann, F., Leinweber, R., Klink, S., and Lehmann, V.: DWD Pilotstation – Evaluating ground-based remote sensing systems for future observing networks, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-119, https://doi.org/10.5194/ems2022-119, 2022.
EUMETNET's E-PROFILE programme aims to gather, centrally process and deliver profiles of wind, temperature, humidity and aerosols including volcanic ash in near real-time. It consists of a data hub to collect process and distribute data while the instruments are owned and operated by EUMETNET members as well as partners from academia and industry. As of today, E-PROFILE integrates operationally 30 radar wind profilers and more than 400 automatic lidars and ceilometers (ALC) producing profiles of wind speed and direction and attenuated backscatter coefficient, respectively. Most radar wind profilers are assimilated into ECMWF's Integrated Forecasting System (IFS) and an extensive analysis of Forecast Sensitivity to Observation (FSO) data from ECMWF confirms the positive impact of those data on the forecast quality. ALC data are calibrated centrally by E-PROFILE using natural atmospheric targets and provide a basic yet quantitative information of aerosols including volcanic ash and durst, which are considered airborne hazards for aviation. With more than 400 operational sites, E-PROFILE's ALC network is a valuable complement to satellite observations and surface based research lidar networks. In the current programme phase (2019 - 2023) we are working on an advanced processing chain to retrieve aerosol extinction coefficients and aerosol mass concentration from ALCs to better meet the user requirements. Finally, E-PROFILE has been tasked to integrate microwave radiometers and Doppler lidars and to collect, process and distribute temperature, humidity and wind measurements from these instruments. This new component of the E-PROFILE programme aims at filling the observational gap in the atmospheric boundary layer. We present briefly the operational components of E-PROFILE, give a detailed update on the ongoing developments and highlight how E-PROFILE serves NWP and informs about airborne hazards.
How to cite: Haefele, A., Bircher-Adrot, S., Rüfenacht, R., Lehmann, V., Mattis, I., Mortier, A., Cimini, D., and Turp, M.: EUMETNET's E-PROFILE network for thermodynamic profiling and the detection of airborne hazards, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-623, https://doi.org/10.5194/ems2022-623, 2022.
The depth of the aerosol layer at the Villum Research Station at Station Nord in the high Arctic is analyzed based on eight years of observations from a ceilometer. The depth of the aerosol layer is assigned to the inflection point in the attenuated backscatter profile by two methods; one is based on polynomial approximation of the profile and the other is direct numeric differentiation. The analysis is based on two types of hourly profiles; one consists of averaging the attenuated backscatter observations and the other by computing the median. It is noted that the depth of the aerosol layer in the Arctic might be different from the depth of the turbulent layer near the ground.
Near the ground, the observed backscatter exhibits a pronounced seasonal variation, having low values during the summer and high values during the winter. The strength of the seasonal variability decreases with height and is virtually absent at 1 km.
Due to sporadic occurrence of outliers in the range between 50 m and 80 m in the ceilometer observations, this part of the profile is not used in this study. Restricting the observations to heights above100 m, the depths of the aerosol layer are found to be typically 230-250 m. It varies little between winter and summer, but the spread in the depth was larger during the winter as compared to summer.
To extend the profile of the attenuated backscatter below 100 m, the ceilometer measurements were combined with Carrier-To-Noise-Ratio observations from a Doppler wind Lidar. Thus, hourly profiles of attenuated backscatter starting at 40 m, are obtained. The results are available for 2018 only and they show aerosol-layer depths below 100 m as well as depths around 230-250 m and they show few observations of aerosol-layer depths between 100 m and 230 m.
Acknowledgement: This article is based upon work from COST Action CA18235 PROBE, supported by COST (European Cooperation in Science and Technology). www.cost.eu.
How to cite: Gryning, S.-E., Batchvarova, E., Floors, R., Münkel, C., Sørensen, L. L., and Skov, H.: Long-term ceilometer/wind-lidar observations of aerosol-layer depth in the Arctic, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-234, https://doi.org/10.5194/ems2022-234, 2022.
Air quality and meteorology in urban environments are strongly affected by dynamical processes occurring in the atmospheric boundary layer. Vertical ventilation, horizontal advection, and atmospheric stratification, largely driven by surface-atmosphere exchanges influence the transport of momentum, heat, moisture, gases, and aerosols.
To improve the understanding of these exchange processes in the urban atmosphere and the implications of spatial variations in topography, surface roughness, and surface cover; the 3-dimensional wind field is studied. In this work, we are reporting results of the novel “volume wind processing (VW)” software to retrieve horizontal wind information on a 3D spatial grid from observations of a single scanning Doppler wind lidar (Vaisala Windcube 400s). In the framework of the PANAME initiative (PAris region urbaN Atmospheric observations and models for Multidisciplinary rEsearch), the Doppler wind lidar is deployed on the rooftop of a tall building in central Paris, France, for the duration of two years. It is set to perform a series of scan strategies to monitor the vertical and horizontal variations of the mean wind field across the city center.
In addition to classical vertical wind profiling at the location of the lidar in Doppler Beam Swinging mode (DBS), 2D maps of horizontal wind speed are obtained from zero-elevation Plan Position Indicator (PPI) scans to assess spatial heterogeneity of the wind field. Further, the VW provides vertical profiles of horizontal wind to be derived at large distances (up to 7km) from the sensor using sector PPI scans at multiple elevation angles. It is the objective of this work to quantify the uncertainties in the VW products, to optimize the scan strategies considering spatial and temporal variations of the wind field, and to finally demonstrate their potential for a variety of applications.
Observations describing the horizontal and vertical variations in wind speed and direction, at high spatial resolution and continuous temporal coverage, are expected to greatly advance the process of understanding the urban atmosphere dynamics. These new generation data are also valuable for the evaluation of numerical simulations (weather and air quality), the quantification of wind energy resources, air traffic (e.g., drones) and sustainable urban design.
How to cite: Cespedes, J., Kotthaus, S., Thobois, L., and Haeffelin, M.: Deriving 3D wind fields in the Paris urban atmosphere from scanning Doppler lidar observations, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-676, https://doi.org/10.5194/ems2022-676, 2022.
The energy reaching the earth surface in form of solar radiation during the daytime is partly reflected as outgoing radiation, partly conducted into the ground and partly trans- ported into the atmosphere by turbulent eddies of various scales forming the convective boundary layer (CBL) during the daytime. The latter energy flux partitions into sensible heat flux H and latent heat flux L. The understanding of H and L profiles is decisive for correct atmospheric simulations with models since these profiles rule the heat and water budgets, the distribution of humidity and temperature, and thus the atmospheric stability and furthermore the formation of clouds and precipitation (Behrendt et al. 2020).
In recent years, it has been demonstrated that lidar, is capable of not only determining mean profiles and gradients in the daytime CBL, the interfacial layer, and the lower free troposphere above but also higher-order-moment profiles of turbulent fluctuations for more and more variables, like vertical wind, moisture, temperature, aerosol backscatter, horizontal wind and dissipation rate, taking advantage of the synergy between a Raman lidar (temperature, moisture and aerosol backscatter) and Doppler lidars (vertical and horizontal wind) (Wulfmeyer, et al. 2016).
In this regard, the Institute of Physics and Meteorology of the University of Hohenheim has developed a thermodynamic profiler based on the Raman lidar technique, namely the Atmospheric Raman Temperature and Humidity Sounder (ARTHUS) (Lange et al. 2019). ARTHUS can be operated on ground-based, ship-borne and airborne platforms.
Stable 24/7 operations over long periods were achieved during several field campaigns and at the Land Atmosphere Feedback Observatory (LAFO) at the University of Hohenheim accumulating almost a year of data until now and covering a huge variety of weather conditions. Two collocated Doppler lidars (one in vertically staring mode and a second one in a 6-beam scanning mode) give the horizontal and vertical wind components, needed for H and L calculations, as well as dissipation rate.
ARTHUS has been also deployed during the EUREC4A field campaign (Stevens et al, 2020), on board RV Maria S Merian, to study ocean-atmosphere interaction, (18 Jan to 18 Feb 2020), along with two Doppler lidars.
Between 15th July and 20th September 2021, ARTHUS was deployed at Lindenberg Observatory from the German Weather Service (DWD).
At the conference, L, H and dissipation rate case examples from these campaigns will be presented.
References
Behrendt et al. 2020, https://doi.org/10.5194/amt-13-3221-2020
Lange et al. 2019, https://doi.org/10.1029/2019GL085774
Stevens et al. 2021, https://doi.org/10.5194/essd-2021-18
Wulfmeyer et al. 2016, https://doi.org/10.1175/JAS-D-14-0392.1
How to cite: Lange Vega, D., Späth, F., Abbas, S., Behrendt, A., and Wulfmeyer, V.: Observation of turbulence profiles with lidar synergy, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-439, https://doi.org/10.5194/ems2022-439, 2022.
Chairpersons: Jens Bange, Frank Beyrich
The overall objective of the Land surface Interactions with the Atmosphere over the Iberian Semi-arid Environment (LIAISE) project is to improve the understanding of land-atmosphere and hydrology interactions in a semi-arid region characterized by strong surface heterogeneity owing to contrasts between the natural landscape and intensive, irrigated agriculture. It is known that irrigation can potentially impact the local atmospheric boundary layer (ABL) characteristics, thereby modifying near surface atmospheric conditions within and downwind of irrigated areas (e.g., Lawston et al., 2020) and potentially the recycling of precipitation. The understanding of the impact of anthropization and its representation in models have been inhibited due to a lack of consistent and extensive observations. In recent years, land surface and atmospheric observation capabilities have advanced while irrigated surfaces have been increasing, leading to a renewed need for dedicated field campaigns over contrasting (climate) regions.
We present a summary of the LIAISE field campaign intensive phase between July 15–29 2021, which took place over the Catalan counties of Urgell and Pla d'Urgell within the Ebro basin in north-eastern Spain. LIAISE is located in a semi-arid hot, dry Mediterranean climate, with a very sharp delineation between a vast, nearly continuous intensively-irrigated region and the generally much more dry rain-fed zone to the east of the study domain. Intensive, spatially distributed surface-based and airborne measurements of the atmospheric boundary layer were made, along with intensive eco-physiological observations and remotely-sensed high spatial resolution mesoscale measures of surface variables from aircraft and unmanned aerial vehicles (UAVs). Two energy budget sites were extended with a network of soil moisture sensors since they were used to evaluate remote sensing data from aircraft. More than 30 institutions took part in the campaign covering a wide range of expertise and spatiotemporal scales in the methods involved, be it through modelling or measurements.
In this contribution we will elaborate on the spatial and temporal scales involved in the processes of evapotranspiration. We will make a strong case for integrated approaches combining observation and modelling techniques to further develop our understanding of evapotranspiration. This will be illustrated with a case study using a mixed layer column model heavily guided and constrained by measurements.
How to cite: Hartogensis, O., Boone, A., Mangan, M.-R., Bellvert, J., Best, M., Brooke, J., Canut-Rocafot, G., Cuxart, J., Le Moigne, P., Miro, J. R., Polcher, J., Price, J., and Quintana Segui, P.: LIAISE campaign: Measuring and Modelling Evapotranspiration over Irrigated Terrain in a Semi-Arid Environment, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-616, https://doi.org/10.5194/ems2022-616, 2022.
Urban meteorological networks in Europe: A review
Assessment of climate in urban environments strongly relies on the quality and resolution of meteorological data. Intensive urbanization processes in urban environments affect and modify local climates so the traditional weather stations located on the outskirts of the urban areas can hardly be considered in the analysis of local climate. Technological progress led to major improvements in sensor development, which increases the number and density of urban meteorological networks. This article presents a review of urban meteorological networks in Europe, including an assessment of their spatial distribution and density, type and density of the sensors, data resolution, and main barriers and challenges in their development and maintenance. The analysis includes urban meteorological networks whose characteristics or data are reported in scientific journals referred in the Web of Science database. Also, the networks reported during the data collection of urban and rural networks from partners participating in the COST Action project entitled FAIRNESS “FAIR NEtwork of micrometeorological measurements” (CA20108) are included in this review. This COST Action aims to develop synergy between stakeholders, researchers, and civil society to promote open data and enhance data visibility and usage. In conclusion, recommendations for future urban meteorological networks development emerged from identified gaps and challenges in measurement logistics, methods, and data assimilation of the existing networks, along with the discussion regarding the possibility of establishing an open data platform for long-term data availability.
Acknowledgment: This research is supported by the COST Action project entitled “FAIR NEtwork of micrometeorological measurements”, no. CA20108.
How to cite: Dunjic, J., Savic, S., Milosevic, D., and Secerov, I.: Urban meteorological networks in Europe: A review, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-267, https://doi.org/10.5194/ems2022-267, 2022.
Cold pools are crucial for understanding the organization of atmospheric convection. However, basic properties like their size, shape and temperature structure remain obscured by the insufficient resolution of operational station networks. In summer 2021 the FESSTVaL field experiment aimed to address this observational gap and shed light on the structure and life cycle of cold pools on the sub-mesoscale (100 m to 10 km). The experiment took place in the rural surrounding of the Meteorological Observatory Lindenberg (south-east of Berlin, Germany) and featured a dense network of custom-designed low-cost measurement stations covering an area of 30-km diameter. The instrumental setup included 80 novel APOLLO stations sampling air temperature and pressure at 1-s resolution and 19 supplementary weather stations. A X-band rain radar also provided highly resolved information on rainfall.
The FESSTVaL network recorded 42 cold pool events of different strength and size during the three-month measurement phase. Based on the spatial interpolation of the network observations, morphological properties of more than 1200 identified cold pool objects are derived. The analysis reveals a median cold pool diameter of 8.4 km. According to average aspect ratios between 1.5 and 1.6, the sampled cold pools are not round, independent of their size and strength. Moreover, large cold pools tend to be stronger and more heterogeneous than small ones. As FESSTVaL is especially suited to study young cold pools, we further analyse the growth phase of selected events initiated inside the station network. Remarkably, their area scales very linearly with the accumulated rainfall amount suggesting that rainfall is the main driver for the growth of cold pools, both directly by evaporative cooling and indirectly by downward transport of upper air masses.
How to cite: Kirsch, B., Hohenegger, C., and Ament, F.: The morphology of convective cold pools in a dense station network during FESSTVaL, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-462, https://doi.org/10.5194/ems2022-462, 2022.
Accurate monitoring of the wind field is highly relevant in many fields of meteorology. Modern, surface-based in-situ measurement devices are capable of detecting highly, temporally fluctuating wind patterns such as gusts. However, more and more applications (e.g. air traffic, wind energy, high-resolution modelling, etc.) require temporally highly resolved wind observations throughout the whole atmospheric boundary layer. Doppler wind lidars (DWLs) have the potential to provide these wind observations. Steinheuer et al. 2022 introduce a quick continuous measuring mode (CSM) in combination with a new flexible retrieval, which can be used to produce such high-resolution wind observations. In the framework of the Field Experiment on Sub-Mesoscale Spatio-Temporal Variability in Lindenberg (FESSTVaL) in summer 2021, three boundary layer profiling sites were established at a distance of about 6 km to each other in the area of the Meteorlogical Observatory Lindenberg, specifically at the sites Lindenberg, Falkenberg, and Birkholz. DWLs were placed at these sites and operated in the CSM from May to August 2021. With this setup, one goal was to investigate whether individual gust observations can be considered representative of their surroundings or whether significant differences are already evident on the meso-gamma scale (2-20 km). In addition, the spatial-temporal development of gusts can be observed and weather conditions leading to strong gusts can be investigated. Other measurement instruments have also been deployed at the sites and provide additional parameters to investigate specific processes. These instruments include, for example, ceilometers to determine the cloud base height or microwave radiometers that allow the determination of thermodynamic profiles. We will present different case studies demonstrating the benefits of simultaneously applying the CSM to the DWL and highlighting the differences between the sites. In particular, for small-scale weather phenomena such as cold pools, these are striking and the profiling of the wind, temperature and humidity gives insight about the vertical build up and horizontal variability of the cold pool.
Steinheuer et al. 2022: “A new scanning scheme and flexible retrieval for mean winds and gusts from Doppler lidar measurements”. In: doi: 10.5194/amt-2021-426.
How to cite: Steinheuer, J. and Löhnert, U.: High-resolution observation of extreme winds at the Sub-Mesoscale with Doppler wind lidars during FESSTVaL, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-214, https://doi.org/10.5194/ems2022-214, 2022.
The variability of vertical profiles of the normalized vertical velocity variance was examined to characterize turbulence and to investigate its dependence on meteorological parameters in the convective boundary layer. The vertical profiles of the vertical velocity variance were calculated using the Doppler lidar dataset from the FESSTVaL measurement campaign collected during two consecutive summer periods. The measurements took place around the Lindenberg meteorological observatory (MOL-RAO), near Berlin, Germany, representative of a flat-terrain covered with crops and patches of forest. The variability of a daily average of the normalized variance was analyzed during a period of a well-developed boundary layer. We classified the dataset into three main categories based on the presence of clouds and extracting only the periods without precipitation: clear-sky, cloud-topped, and rainy days. The mean profile of the normalized variance of the vertical velocity systematically increases from the rainy, cloud-topped to clear-sky days categories. The magnitude of the mean profile during the clear-sky and cloud-topped days is similar to the reference profile of Lenschow et al. (1980), although the variability among the days is large. The dependence of this variability of the normalized variance on the meteorological parameters was examined. We found that the relative humidity, Bowen ratio, surface latent heat flux, and cloud fraction relate to the variability of the normalized variance. A closer look at the cloud fraction during the cloud-topped days shows an increment of the normalized variance with a decrease of humidity in the boundary layer similar to the increment from rainy to cloudy and clear-sky days.
How to cite: Dewani, N., Sakradzija, M., Schmidli, J., and Schlemmer, L.: Vertical velocity variance and its dependency on meteorological parameters in the convective boundary layer, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-581, https://doi.org/10.5194/ems2022-581, 2022.
Cosmic-ray neutron albedo sensing (CRNS) is a modern technology that can be used to continuously measure the average water content in the environment (i.e., in soil, snow, or vegetation). The sensor footprint encompasses an area of 10-15 hectares and extends to 20-50 decimeters deep into the soil. This method might be an alternative to conventional in-situ sensors or to expensive sampling of soil or snow. It also has the potential to bridge the scale gap between point-scale measurements and remote-sensing data in both, the horizontal and the vertical domain.
Currently, more than 200 sensors are operated in the growing networks of national and continental observatories. CRNS stations are continuously monitoring the local water dynamics at various field sites worldwide. They require almost no maintenance over the years due to a solar module, battery and telemetry. Since the method works non-invasively, the soil is left undisturbed. The passive sensing technique measures natural cosmogenic background radiation which interacts with hydrogen in the ground independent of temperature, frost, or wind effects. CRNS can also be used on mobile platforms for on-demand soil moisture mapping at the field- or regional scale. The sensors are rapidly operational on any ground- or airborne vehicle.
In this presentation we will show various examples of stationary CRNS and their performance compared to traditional sensors at various sites in Germany, Europe, and beyond. We will discuss applications for hydrological modeling and new spatial mapping approaches. The data is particularly useful to study hydrological extreme events, droughts, heatwaves, floods, snow melt/accumulation, and it can be applied as a lower boundary condition in atmospheric models, in hydrological models, or agricultural irrigation management.
How to cite: Schrön, M., Zacharias, S., Beyrich, F., Böttcher, F., Boeing, F., Marx, A., Fatima, E., Kumar, R., Kaluza, M., Samaniego, L., Attinger, S., and Dietrich, P.: Autonomous Monitoring of Soil Moisture & Snow Water Equivalent with Stationary and Mobile Cosmic-Ray Neutron Sensors, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-577, https://doi.org/10.5194/ems2022-577, 2022.
The Multipurpose Airborne Sensor Carrier (MASC) is a fixed-wing unmanned aircraft system (UAS) that has been continuously developed and used for in-situ, high-resolution flight measurements of atmospheric variables such as wind, temperature, humidity as well as trace gas and particle concentrations by the Environmental Physics group at University of Tübingen. The most recent innovation in the MASC-series is the MASC-V type vertical takeoff and landing UAS. It has been designed in cooperation with ElevonX d.o.o.. Compared to its predecessor, MASC-3, it can automatically takeoff and land on small patches of land while carrying an identical atmospheric measurement payload. This capability, complemented by an enhanced safety and operational concept, allows for deployment in offshore applications. Particularily, MASC-V has demonstrated safe operation beyond visual line of sight (BVLOS) from the remote safety pilot in offshore applications within the EUs new legal framework introduced in 2020.
Before its first offshore mission, MASC-V underwent a system validation against a meteorological tower at the German Weather Service (DWD) Observatory site at Falkenberg, Germany. Offshore measurements were conducted from the German offshore island Heligoland at the Testfield for Maritime Technologies in cooperation with the Fraunhofer Institute for Applied Material Science in September 2021. The goal of the Heligoland campaign was to validate the remote sensing of sea surface wind measurements by Synthetic Aperture Radar (SAR) satellites of the Sentinel-1 formation at low flight altitudes (20 m - 30 m). SAR satellites can deliver detailed wind data over large areas such as the German Bight including for example wind farm wake effects. Direct validation of these results is difficult with other in-situ techniques. Buoys and measurement towers or platforms can provide stationary data. Aerial measurements with manned aircraft are only possible at higher altitudes. The new UAS data provide the first aerial in-situ SAR validation measurement at low altitude. Additionally, we have demonstrated the capabilities of VTOL fixed-wing UAS for vertical profiling as well as to operate tens of kilometers away from ground personell over open water.
How to cite: Weber, I., Platis, A., zum Berge, K., Schön, M., Boventer, J., Bamati, M., Savvakis, V., Miranda Garcia, G., Sajidi, M., Wang, Y., and Bange, J.: The Unmanned Multipurpose Airborne Sensor Carrier MASC-V for Offshore Wind Energy Research, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-371, https://doi.org/10.5194/ems2022-371, 2022.
Chairpersons: Fred C. Bosveld, Jens Bange
Exchange and transport processes in the atmospheric boundary layer (ABL) are driven by turbulence on a wide range of scales. In heterogenous and complex terrain, the common simplification of turbulence to one-dimensional statistical models does not necessarily hold. Coherent structures such as convective cells, secondary circulations, gusts, slope and valley flows can be summarized to sub-mesoscale structures which are not well represented in models. Part of the reason for the lack of understanding of these flow features is the challenge to adequately sample their three-dimensional, spatio-temporal structure and their contribution to the energy budget of the ABL.
We present a system to achieve simultaneous spatial measurements with a fleet of multirotor unmanned aircraft systems (UAS). The major benefit of this approach is, that true simultaneous measurements can be obtained without the need of expensive infrastructure such as masts or lidar instruments. The SWUF-3D (Simultaneous Wind measurement with Unmanned Flight systems in 3D) fleet was first deployed at the Meteorological Observatory Lindenberg - Richard Aßmann-Observatory (MOL-RAO) of DWD in association to the FESSTVaL campaign. With more than 1000 single flights, the system was validated against sonic anemometers at the 99-m mast in 2020 and 2021 and was able to provide reliable measurements of the wind vector with a RMSE below 0.3 m/s. We showed that turbulent eddies can be resolved with a time resolution of up to 2~Hz, unless the overall TKE level is below the noise threshold of the UAS measurements, which can be the case in stable ABL conditions. We show that fluctuations of the vertical wind component can be captured with the system, if calibrated motor thrust data is used for the estimation. This allows to calculate TKE, momentum fluxes and friction velocity in neutral and convective atmospheric stratification. Additionally to the wind vector estimation, which is done with avionic data of the autopilot, pressure, temperature and humidity sensors are carried by each UAS.
The highlights of the two-week long campaign during FESSTVaL were spatial measurements of a gust front associated to a thunderstorm and a 4.5-hour long continuous vertical profiling of the atmosphere during a convective boundary layer morning transition period. Results of these measurements will be presented.
Within the project ESTABLIS-UAS (Exposing Spatio-temporal structures of Turbulence in the ABL with In-Situe Measurements by UAS, funded by the European Union), the SWUF-3D fleet will be enhanced to allow operation in larger areas and in complex terrain. A fleet of up to 100 UAS shall be deployed during TEAMx (Multi-scale transport and exchange processes in the atmosphere over mountains – programme and experiment) in 2024.
How to cite: Wildmann, N. and Wetz, T.: Towards spatio-temporal turbulence measurements in the atmospheric boundary layer with a fleet of UAS, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-133, https://doi.org/10.5194/ems2022-133, 2022.
Doppler wind lidar systems are an indispensable tool for the observation of the atmospheric boundary layer. With varying atmospheric conditions in the boundary layer the performance and availability of these systems varies. In order to ensure their quality measurements are needed to validate the lidar measurements.
During the FESSTVaL field measurement campaign in summer 2021 airborne meteorological measurements in the atmospheric boundary layer above the measuring field Falkenberg of the German Weather Service measurements were recorded for this purpose.
The focus was on the validation of Doppler lidar measurements of the wind speed, wind direction and turbulence kinetic energy in the altitude range from 90 m to 600 m above ground. The obtained data will be used to show in how far the lidar data quality is depending on the altitude the measurements have been taken from.
The validation data were collected with an unmanned aerial system (UAS) of type MASC-3 (Multipurpose Airborne SensorCarrier 3) operated by the University of tuebingen.
The UAS MASC-3 is used for in-situ meteorological measurements of turbulent variables (three-dimensional wind vector, temperature, humidity and turbulence) as well as aerosol particles in the lower atmosphere. [1]
With the help of our UAS measurements, the quality, spatial resolution, and significance of lidar data is investigated and will be assessed in different measurement configurations and under different atmospheric conditions, such as thermal stratification, water vapor content, concentration of aerosol particles and aerosol particle size distribution.
Suitable scanning strategies for the lidar systems can thus be determined, characterized, and the measurement error as well as the representativeness and availability of the lidar wind and turbulence data will be quantified.
The result of the assessment will help to determine the initially mentioned performance and availability of lidar more accurately, as well as to better integrate remote sensing instrumentation into an operational measurement network.
[1] A. Rautenberg et al., MDPI Sensors doi:10.3390/s19102292 (2019)
How to cite: Boventer, J., Weber, I., Schön, M., zum Berge, K., Platis, A., Bange, J., Beyrich, F., Detring, C., and Päschke, E.: Validation of Doppler wind LiDARs of the German Weather Service (DWD) using small unmanned aerial systems ( UAS ), EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-237, https://doi.org/10.5194/ems2022-237, 2022.
Ground-based microwave radiometers (MWRs) which operate within the K-band and V-band (22 – 32 GHz and 51 – 58 GHz) are used to obtain temperature profiles (T) and rather coarse humidity profiles (H) of the troposphere. MWRs measure microwave radiances, expressed as brightness temperatures (TB), in zenith and other angles over an area of ~10 km radius. The brightness temperatures can be used to retrieve the T-profiles and H-profiles. Ground-based MWRs are also among the best instruments to measure path integrated values like IWV (Integrated Water Vapor) and LWP (Liquid Water Path), with excellent uncertainties below 0.5 kg/m2 and 20 g/m2, respectively. Besides zenith observations which provide these variables with a high temporal resolution (up to 1 second), elevation scans are used to retrieve more precise temperature profiles close to the ground, as well as to assess horizontal water vapor and cloud inhomogeneities.
Driven by the E-PROFILE program, a business case proposal was accepted by EUMETNET last year to continuously provide MWR data to the European meteorological services for boundary layer monitoring and assimilation to numerical weather prediction (NWP) models. Also, the European Research Infrastructure for the observation of Aerosol, Clouds, and Trace gases ACTRIS and the European COST action PROBE (PROfiling the atmospheric Boundary layer at European scale) currently focus on establishing continent-wide quality and observation standards for MWR networks for research as well as for NWP applications.
When installing a MWR, it has to be kept in mind that external error sources like physical obstacles and radio frequency interference (RFI) can have an impact on observations and the quality of the obtained atmospheric profiles when they are within the range of the MWR. Therefore, identifying and coping with these kinds of errors is one important part of the quality control, especially while searching for a suitable measurement location with low disturbances. If physical obstacles like trees, towers, masts and walls are too close to the MWR they can have significant repercussions in elevation scans which are necessary for deriving accurate T-profiles. That is why it is crucial to pinpoint the exact location of these obstacles and to determine a minimum distance at which they do not interfere with the MWR anymore. We will present a sensitivity study which uses a line-by-line (LBL) radiative transfer (RT) model and in which obstacles at any distance from the profiler can be simulated. Output comparisons with and without these simulated obstacles provide a theoretical atmospheric penetration depth per frequency channel and elevation.
How to cite: Böck, T., Pospichal, B., and Löhnert, U.: Characterizing the influence of obstacles on scanning microwave profilers, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-682, https://doi.org/10.5194/ems2022-682, 2022.
The size, shape and ground-impact location of each hailstone is characterised by its trajectory through the parent hailstorm. This trajectory determines whether the hailstone passes through regions of the storm that are more favorable for growth or even miss out entirely. Recent simulation-based studies have demonstrated the diversity of trajectories and how certain pathways exist in response to storm processes. Hail trajectories can also be simulated from radar observations, and this has been shown to significantly improve the accuracy of the estimated ground hail swath for case studies. Operational hail analysis techniques currently do not consider trajectories, leaving a degree of uncertainty when estimating ground impact. The lack of robust observational datasets to verify trajectories is one factor that limits the transition of this new science into operations.
This talk will introduce an innovative approach to measuring trajectories within a hailstorm using hailstone-shaped probes called “HailSondes”. Improvements in low-energy radio, energy storage and electronics miniaturization are combined to make this new sensor possible, which, until recently, was the realm of fantasy for meteorologists. HailSonde measurements will provide critical validation for the practical application radar-derived trajectories for hailstorm analysis and nowcasting, supporting the transition to future hail services and benefiting a wide range of sectors from aviation, risk management, transport and public safety. The design challenges, simulations, prototype development and deployment of HailSondes within field experiments are discussed.
How to cite: Soderholm, J., Kumjian, M., Peterson, A., Brook, J., and Protat, A.: Measuring Hailstone Trajectories with the HailSonde, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-511, https://doi.org/10.5194/ems2022-511, 2022.
As the production of the current solar radiation sensor systems ceased and changes due to automation of the measuring network were necessary, a new concept of solar radiation measurements in Germany was established by Deutscher Wetterdienst (DWD). Aiming at an efficient network with high-quality data, it was decided to enhance the coverage of high-quality pyranometers that measure global and diffuse solar radiation, herewith also allowing the calculation of sunshine duration via the pyranometric method. The use of low to moderate quality instruments to measure solar radiation and sunshine duration will be discontinued in the future. To compensate for the reduction of the number of in-situ measurements and with solar radiation products from satellite data continuously improving in quality, the integration of both data sources was planned within the project DUETT at DWD.
The project DUETT focuses on the development of merging algorithms for the parameters global radiation and sunshine duration and therefore uses data from the (future) 42 pyranometer stations as well as near-real-time satellite data based on measurements of the METEOSAT SEVIRI instrument with a latency of only a few minutes. Preoperational, merged DUETT products are processed on an hourly basis with a spatial resolution of 2x2 km for Germany and a time delay of 15 minutes after each full (synoptic) hour for both parameters. Here, validation results of the latest version of the merging procedure, based on independent in-situ data, are presented for both parameters for a validation period of one full year; possible future improvements are also discussed.
How to cite: Klameth, A., Brinckmann, S., and Trentmann, J.: Towards the combination of in-situ and satellite-based solar radiation data in near-realtime – the project DUETT at DWD, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-154, https://doi.org/10.5194/ems2022-154, 2022.
Chairpersons: Frank Beyrich, Fred C. Bosveld
Doppler Lidar is a powerful measuring technique for observing particularly vertical wind profiles in the atmospheric boundary layer. It is well known that the performance of such long-range wind lidars depends to some extent on the atmospheric conditions, which causes a variable upper limit of the accessible measuring heights. Another, more fundamental constraint of long-range lidars refers to the lower height limit which is typically > 50 m. Furthermore, useful profiling in these height ranges requires range resolution much finer than the height range itself. An adequate range resolution causes broad Doppler spectra which result for typical Lidar wavelengths (1 – 1.5 um) in an unacceptable poor velocity resolution.
The height range below 50 m plays a key role for the interaction between surface and atmosphere and can show sharp and sometimes complex gradients as for example in nocturnal stable layers. The diurnal evolution of the profile of mean wind and turbulence close to the surface can be quite different from higher layers and cannot be inferred from upper height observations.
A combination of Lidar techniques has been developed to overcome the above-mentioned lower range limitation and to extend the lower height range down to < 10 m while preserving the long-range capability.
Field data from such recently developed Lidar system will be presented in comparison with composite profiles from simultaneous measurements with a conventional long-range pulsed Doppler Lidar, a short-range FM-CW-Lidar and a 15 m mast with sonic instrumentation. The analysis will include profiles of mean wind as well as of turbulence parameters.
How to cite: Kirtzel, H.-J. and Peters, G.: A Doppler Lidar technique for monitoring the „whole“ boundary layer, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-629, https://doi.org/10.5194/ems2022-629, 2022.
Continuous water vapor profiling within the atmospheric boundary layer is a major unmet measurement requirement for real-time monitoring of humidity profiles and improving numerical weather prediction. Water vapor mixing ratio profile information can be used in mesoscale numerical models for severe weather prediction, flash flood prediction, energy management, and other applications. Vaisala has been developing broadband Water Vapor Differential Absorption Lidar (DIAL) to meet with the need of lacking humidity profile observations. Vaisala broadband DIAL not only reports water vapor mixing ratio in the boundary layer, but also serves as an atmospheric profiler offering attenuated backscatter profile to obtain information on scatterers in the atmosphere including clouds, precipitation, and aerosols.
In this presentation, the latest hardware and software improvements on our broadband DIAL are presented with case examples. In recent years, we have been continuously testing our prototypes with different scientific partners in different climates as well as on our test field. Based on the vital feedback from our scientific partners we have been able to focus and develop solutions to improve the prototype performance incrementally. We have been developing features based on the user feedback, as well as improving data format and data visualization. Most importantly, the performance of the instrument has been improved, including the reduction of instrument-related biases in various situations. Our target is to meet the needs of the community to better serve the field of numerical weather prediction and use of broadband DIAL in networks.
In addition, we will present our vision of the finalized product that can help with meteorological applications from numerical weather prediction improvements to atmospheric boundary layer research and unattended operation in all-weather situations.
How to cite: Tuononen, M., Lehtinen, R., Tuominen, P., and Roininen, R.: Latest developments on Vaisala broadband DIAL with examples, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-559, https://doi.org/10.5194/ems2022-559, 2022.
For many applications, such as ensuring efficiency of future wind farms and characterizing wind hazards at ports, airports, or industrial plants, measuring accurate and precise wind is critical. Scanning Wind Lidars provide a solution to deliver demanding wind measurements, measuring in full hemisphere at multiple ranges around its location with multiple scanning patterns (azimuthal scans, elevation scans, etc.). Since their implementation, user feedbacks called for more flexibility in measurement modes, limitation of range ambiguities, and longer acquisition distances. For these reasons, a new version of the Windcube Scan was designed to overcome these limitations. An internal and external validation was performed over the last year to ensure acceptable behaviors and measurement performances of hardware/software components of outdoor/indoor measurements for established regulations.
The internal validation conducted within Vaisala France site near Paris consists of both an indoor and outdoor validation protocol. The indoor verification test, characterized as a patented indoor bench, aims at testing radial wind speed precision with intrinsic lidar parameters such as pulse shape, energy, etc. The outdoor validation follows guidelines set by the ISO 28902-2 as the lidar wind speed was compared to an ultrasonic anemometer on a meteorological tower 2.5km away. The instantaneous wind speed measurements from both devices are then compared for precision and accuracy with proper filtering of unsuitable weather conditions.
External validation prompted collaboration with MeteoSwiss and DWD, both pioneers in the PROBE European project for large-scale remote-sensing deployment and data-sharing. Both organizations received the new version of WindCube Scan for a beta test. They gathered wind data at their sites and compared radial data to other remote sensing devices. All scanning patterns (PPI, RHI, DBS, VAD, fixed) were tested to verify the performances of different resolutions, data retrieval, and wind speed precision.
The results of this validation thus far show positive performance and noticeable improvements of the new version of the Windcube Scan. Additionally, the external validation collaboration with other PROBE members highlights the importance of fortifying and understanding remote sensing device precision and data collection methods for large-scale observational network integration.
How to cite: Benzo, C. and Thobois, L.: Validation of the New Version of the WindCube Scan Lidar, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-633, https://doi.org/10.5194/ems2022-633, 2022.
Open-path eddy covariance systems, based on broad-band non-dispersive infrared (NDIR) gas analyzers, are widely used for CO2 and H2O flux measurements in remote locations around the world, because of their low power consumption, fast response, and reliable operation. Nevertheless, agreement between open- and closed-path CO2 fluxes has limited inter-site comparability, especially in cold or non-growing seasons and low-flux environments, where physiologically unreasonable CO2 uptake is often observed by the open-path systems. A possible explanation is sensor-surface heating from internal-electronics power dissipation and solar radiation, which causes unaccounted gas density changes in the optical path. Fast-response thermometers, co-located with the gas analyzer, have been used to correct these effects. However, the fragility of the thermometers has prevented the wide adoption of this approach. A challenge for the open-path sensor design is that in-situ air temperature affects not only the gas density but also the broadened half-width and intensity of the spectral absorption lines. We hypothesize that fast air temperature fluctuations in the optical path of the gas analyzer can change the amount of absorbed light and cause errors in the CO2 concentration measurement. Because of the natural covariance of sensible and CO2 fluxes, such errors are well correlated with the vertical wind and can potentially propagate into flux calculations. We used spectral-line parameters, obtained from the high-resolution transmission molecular spectroscopic database (HITRAN), to evaluate the temperature effects on the integrated absorption spectra of CO2-air-mixtures across the 4.2 to 4.3 μm infrared active region utilized by NDIR analyzers. Results show that air temperature strongly influences absorption, and if not properly corrected, potentially introduces biases in the CO2 concentration measurements. Strong lines exhibit Doppler broadening, where the line peak and width decline with increasing temperatures, causing underestimation of CO2 concentration. Weak lines exhibit the opposite behavior. Based on our simulations, optimizing the optical filter passband can balance these opposing effects and greatly reduce the temperature dependence. In practice, manufacturing tolerances, shifts in the center wavelength, and the temperature sensitivity of the optical filters prevent complete elimination of the temperature-line broadening. A 13-nanometer shift in the filter pass band can introduce a 0.008 mmol m-3 K-1 underestimation in the CO2 concentration, which is a 0.67 μmol m-2 s-1 systematic error in CO2 flux per 100 watts of sensible heat flux.
How to cite: Bogoev, I.: Quantifying biases in open-path eddy covariance CO2 flux measurements caused by spectroscopic effects in broadband non-dispersive infrared gas analyzers, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-130, https://doi.org/10.5194/ems2022-130, 2022.
Most of the world’s population now lives in urban areas that have different urban climates and environmental characteristics with elevated temperatures, frequent heat stress, and air pollution due to urbanization and climate change. These processes affect the daily lives of citizens worldwide, however, detailed spatial and temporal meteorological and environmental data in cities are often lacking. In order to address this problem, the Novi Sad Urban Climate Research Team (NSUCRT) has developed a Mobile Micrometeorological Carts (MMCs) to enable detailed spatial and temporal measurements in urban and non-urban areas. MMCs consist of sensors that measure air temperature, relative humidity, wind speed and direction, globe temperature, global radiation, and six-directional short- and long-wave radiation. The measurement time resolution is two minutes. In addition, a desktop application was created for the transfer of data from MMCs to a computer. This type of detailed and precise equipment will enable researchers and practitioners to obtain micrometeorological data in diverse urban (and non-urban) areas, such as urban squares, streets, parks, river quays, forests, etc. Based on the obtained micrometeorological data, hot and cool spots in the city can be identified, which can be used for the development of climate-friendly planning and design guidelines tackling heat-health issues in cities. In addition, the obtained micrometeorological data can be used for the calculation of mean radiant temperature and outdoor thermal comfort indices, which are important for assessing the comfort and health of citizens in diverse urban environments. Finally, MMCs measurements can be applied for the validation of microclimate models, such as ENVI-met, PALM-4U, SOLWEIG, and RayMan.
Acknowledgment: The research was supported by a project (number 142-451-2557/2021-01) financed by the Autonomous Province of Vojvodina (regional government).
How to cite: Milošević, D., Savić, S., Šećerov, I., and Dunjić, J.: Introducing Mobile Micrometeorological Carts (MMCs) for urban and non-urban micrometeorological measurements, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-59, https://doi.org/10.5194/ems2022-59, 2022.
The Ruisdael Observatory is a long-term initiative designed to improve the measurement and modeling of atmospheric processes under the umbrella of the National Roadmap for Large-Scale Research Facilities in the Netherlands. The observatory is run by a consortium of eight institutes and universities, each of which operate unique, state-of-the-art equipment and facilities for characterizing the state of the atmosphere, its radiative properties and the interaction with the land surface.
As part of Ruisdael, TU Delft is responsible for operating a large number of in-situ and remote sensing instruments for measuring precipitation, clouds, aerosols, wind and temperature. Currently, our network consists of 3 cloud radars, 6 micro-rain radars, 8 optical disdrometers, 3 radiometers and a mobile facility. Initial deployment started in Cabauw in 2020, followed by a rapid expansion of the network to Delft, Rotterdam and Lutjewad in 2021-2022.
At each site, high-resolution observations of precipitation, clouds, aerosols and wind at multiple-frequencies, polarizations are collected. A wide spectrum of parameters is covered, with special emphasis on sensor synergy and co-location. All data are free and open to the general public. Higher level data are stored in NetCDF format and distributed via the KNMI Data Platform (KDP) and ACTRIS data platform, together with all relevant information and metadata. Raw data are stored locally at TU Delft and can be accessed upon request to the authors. In addition to providing high-quality research data, the testing facilities at the Green Village in Delft also provide unique opportunities for education and training within the new MSc programs in Applied Earth Sciences and Environmental Engineering.
How to cite: Schleiss, M., Unal, C., Mackenzie, R., Guzzo, S., and Russchenberg, H.: Simultaneous measurements of rain, clouds, and aerosols within the Ruisdael Observatory, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-562, https://doi.org/10.5194/ems2022-562, 2022.
Numerical Weather Prediction (NWP) models with a horizontal grid of 2 km or finer need detailed information for estimating the initial state of the atmosphere. Ground-based remote-sensing instruments like Sodars, Doppler lidars and Profilers provide already meteorological information of the Atmospheric Boundary Layer (ABL). Although observational networks have been extended over the years, there are still gaps in data gathering particular on the finer scales. Therefore we have commenced research to investigate data from third parties. Here we focus on wind-information in the ABL from recreational Hot-air Balloon (HaB) flights. In the basic equipment of a HaB pilot there is a professional navigation device, which is compulsory for safety reasons. Similarly to routinely launched weather balloons, the Global Navigation Satellite System (GNSS)-data from consecutive positions and the elapsed time are the basis of the calculation of the horizontal wind vector. On a yearly basis about 6000 flights are taken place in the Netherlands, mainly during the morning- and evening transition. As soon as the surface is covered with snow and when convection is strongly reduced, flights may also take place during the day. The HaB data are validated with observations from the meteorological site of Cabauw and we compare the HaB winds with mast data and other available observations like a RASS wind profiler and a wind lidar. We also compare the HaB data with the results of an NWP model and we will report about a first attempt to assimilate the HaB data in a NWP model. To explore the possibilities of this new type of wind observations in more complex terrain, we will present also the results of an intriguing HaB flight in Austria showing a typical mountain-valley circulation.
How to cite: de Bruijn, C., de Haan, S., Bosveld, F., Marseille, G.-J., and Holtslag, B.: Sensing the Wind with Hot-air Balloons and their Application in NWP Models, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-390, https://doi.org/10.5194/ems2022-390, 2022.
The planetary boundary layer (PBL) is the lowest part of the atmosphere and it is directly influenced by its contact with a planetary surface and the PBL height (PBLH) varies with time, season and topography. In this study, PBLH is estimated from atmospheric profiles utilizing the parcel method, the bulk Richardson method and the temperature inversion method using the potential temperature, turbulence and temperature gradients, respectively. Additionally, the theta gradient profile and the mixing ratio gradient profile are used to estimate PBL discontinuity in the previous methods. The ERA5 reanalysis is used as reference data in order to develop the PBLH estimation algorithm. During the day, the PBLH is first estimated by the parcel method. If the estimated PBLH is less than 3000 m, it is final PBLH. If not, secondly, calculate the bulk Richardson number to find the height below criteria (0.25) as the final PBLH. When these conditions are not satisfied, finally, the height of the maximum theta gradient subtracts the difference between the height obtained from the bulk Richardson number and the height of the maximum theta gradient. These differences are hourly averaged over the duration of the study. During the nighttime (from evening to morning), PBLH is estimated by the temperature inversion method, and if it greater than 1500 m or not calculated, PBLH is calculated using the theta gradient method and the mixing ratio gradient method. The algorithm is applied to Ground-based microwave radiometer (MWR) profiles, the one-dimensional variational (1D-VAR) retrieval profiles based on the optimal estimation by combining MWR brightness temperatures and a priori information from Local Data Assimilation and Prediction System model. The PBLH difference between MWR and ERA5 shows a large correlation coefficient (0.59) than between 1D-VAR and ERA5. On contrary, the statistical error of 1D-VAR is lower than MWR. Compared to MWR, The RMSE is reduced to 12 % and bias is reduced to 82.5 %. Detailed methods and results in this study will be presented at the conference.
How to cite: Song, Y., Ahn, M. H., and Lee, S. J.: Estimation of planetary boundary layer height (PBLH) from profile data at Bosung site, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-329, https://doi.org/10.5194/ems2022-329, 2022.
The marine Atmospheric Boundary Layer (ABL) over the southern Bulgarian Black Sea coast is studied based on remote sensing measurements with a monostatic Doppler sodar system located about 400 m inland. The accumulated long-term acoustic data (August 2008 – October 2016) with high spatial (10 m) and temporal (20 minutes running averages at every 10 min) resolution was used by applying statistical approaches to the wind and turbulent profiles to reveal the complex vertical structure of the coastal boundary layer when marine airflow comes over the land. Тhe processes observed in air masses transformation due to the sharp change in physical characteristics of the surface are related to Internal Boundary Layer (IBL) formation. Its spatial scales as a sublayer of the coastal ABL are studied by a height dependent on the distance from the shore. In the absence of temperature and humidity profiles measurements, an approach through the turbulent profiles’ characteristics representative for different lengths of the marine air masses run (400 to 2500 m) was used to examine whether the formation of IBL over land can be observed in sodar data. The different length distances passed by the marine airflow are fixed by a selection of intervals of geographical directions of the wind in the study region. Analysis of the observed changes in the values of the averaged profiles and their dispersions reveals IBL heights up to 150 m depending on the lengths of the marine air masses run.
This study of long-term remote sensing data is a pioneer for the Black Sea basin region and was conducted in a coastal area with modest observation networks in Bulgaria. The work is inspired by the activities of its authors within COST Action CA18235 PROBE (PROfiling the atmospheric Boundary layer at European scale), supported by COST (European Cooperation in Science and Technology) and the National Science Fund of Bulgaria, Contract KP-06-N34/1 "Natural and anthropogenic factors of climate change – analyzes of global and local periodical components and long-term forecasts".
How to cite: Barantiev, D. and Batchvarova, E.: Internal boundary layer characteristics at the southern Bulgarian Black Sea coast, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-598, https://doi.org/10.5194/ems2022-598, 2022.
The value of permanent, multi-sensor surface-based observatories that collect continuous long-term observations for satellite L2 data products has grown significantly the last 10-15 years. Examples of such established surface-based networks include: The Aerosol, Clouds and Trace Gases Research Infrastructure (ACTRIS) network, the US Department of Energy Atmospheric Radiation Measurements (ARM) observatories and the recently established 94-GHz Miniature Network for EarthCARE Reference Measurements (FRM4Radar). At the same time, there is a significant increase in the availability of airborne platforms (e.g., DLR Halo, French Falcon and the NASA airborne program) with comprehensive instrument payloads that mimic the satellite primary measurements.
Here, a simple L1 transformational operator that can convert L1 suborbital (surface-based or airborne) measurements to the EarthCARE CPR L1 observations is described. The L1 transformational operator ensures that the orbital-suborbital comparison accounts for differences in the sampling geometry, measurement uncertainty, and instrument sensitivity. Furthermore, the operator account for the impact of the surface echo on satellite-based radar observations. Examples of the application of the operator on surface-based observations measurement from the ESA FMR4Radar network are presented. Such long-time data sets are the optimal foundation for a statistical analysis of the CPR performance. The analysis will emphasis on clouds and precipitation processes near ground. In addition, it is show how important ground-based networks are that they can play an important role in the evaluation of future CPR satellite missions. The L1 transformational operator can be easily expanded other spaceborne radar systems. Our plans include the application of the L1 transformation operator to high resolution cloud resolving model output.
How to cite: Pfitzenmaier, L., Kollias, P., Puigdomènech, B., Lamer, K., Battaglia, A., and Löhnert, U.: A L1 transformational operator for the objective evaluation of the EarthCARE Cloud Profiling Radar data products, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-669, https://doi.org/10.5194/ems2022-669, 2022.
Compared to conventional weather radars, dual-polarimetric radar systems can provide more precise information about precipitation amounts, types, shapes, concentration, drop size distributions, and precipitation processes. The wealth of information is exploited to improve our understanding on precipitation generating processes, to evaluate and improve numerical weather prediction models and provide more accurate (short-term) forecasts and severe weather warnings. As support for this research we provide and describe a five years (2014 - 2019) open-access dataset measured with the dual-pol Doppler X-band (9.3 GHz) weather radar in Bonn (BoXPol), western Germany. The BoXPol data set is archived by the German Climate Computing Centre (DKRZ) as daily NetCDF files consisting of all important polarimetric variables for each of the ten plan position indicator scans. Furthermore, supporting notebooks for processing and visualization of the polarimetric data are provided with the data set. The radar scanning strategy, the technical radar information and the best practice for radar data processing, like e.g. differential phase processing, derivation of specific differential phase, partial beam blockage detection and attenuation correction, are described as well. We compare the ground-based radar reflectivity measurements with the satellite observations of the Dual- frequency Precipitation Radar, operating on the core satellite of the Global Precipitation Mission, to provide absolute calibration offsets with the data set. Stable calibration periods are identified with the Relative Calibration Adjustment technique using reflectivity statistics generated from local stable clutter. Absolute calibration for the differential reflectivity measurements is determined using the vertically pointing scan (birdbath scan) and provided as well.
How to cite: Pejcic, V., Soderholm, J., Mühlbauer, K., Louf, V., and Trömel, S.: Open Access to Five Years of Calibrated Measurements of the Polarimetric X-band Weather Radar in Bonn (BoXPol), EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-363, https://doi.org/10.5194/ems2022-363, 2022.
Polarimetric microphysical retrievals are of great value for data assimilation, numerical model evaluation and improvement. However, the accuracy of ice microphysical retrievals remains poorly explored. In order to evaluate these retrievals and assess their accuracy, polarimetric radar measurements are spatially and temporally collocated with in-situ aircraft measurements conducted during the Olympic Mountain Experiment (OLYMPEX) campaign. Retrievals for ice water content, total number concentration, and mean volume diameter of ice particles derived from the polarimetric X-band Doppler on Wheels (DOW) measurements are evaluated utilizing an in-situ data set of the University of Dakota (UND) Citation aircraft. Vertical profiles of microphysical retrievals are derived from sector-averaged RHI scans. The comparison of these estimates with in-situ data from ten flight missions provides insights into strengths, weaknesses, and accuracy of the retrievals, and quantifies the improvements of polarimetry-informed retrievals compared to non-polarimetric, conventional ones. Especially the recently introduced hybrid IWC retrieval exploiting reflectivity ZH, differential reflectivity ZDR and specific differential phase KDP outperforms other retrievals based on either (ZH, ZDR) or (ZH, KDP) or non-polarimetric retrievals in terms of root mean square error and correlations with in-situ measurements. Only IWC retrievals derived via optimal fitting parameters from the High Altitude Ice Crystal – High Ice Water Content (HAIC-HIWC) field campaign data using either KDP or ZDR and KDP achieve comparable correlations, but exhibit a higher root mean square error. ZH-based retrievals for the mean volume diameter partly exhibit significant deviations from airborne in-situ measurements, while polarimetric retrievals show good agreement. For the latter, however, a discrepancy can be observed for large particles at warmer temperatures near the melting layer. On the basis of our evaluation study, the most accurate ice microphysical retrievals are now used to evaluate the ICON numerical weather prediction model to reveal potential biases and deficiencies as a first step towards model improvements.
How to cite: Blanke, A., Heymsfield, A., Moser, M., Voigt, C., and Trömel, S.: Evaluation of radar polarimetric ice microphysical retrievals using in-situ aircraft measurements from the OLYMPEX campaign, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-430, https://doi.org/10.5194/ems2022-430, 2022.
Fibre-optic based Doppler wind lidars (DL) are able to retrieve vertical profiles of kinematic quantities across the lower atmosphere with high spatio-temporal resolution. Especially short-term forecasting would benefit from assimilating their data which renders these compact systems promising candidates for operational use in future observing networks of meteorological and environmental services. Therefore, DWD includes the assessment of DLs in the effort to evaluate ground-based remote sensing systems for their operational readiness, called “Pilotstation”. Besides tests focusing on aspects such as technical reliability, uncertainty characterization, scanning strategies, and the verification of the retrieved mean wind speed and direction with the help of independent reference data from a 482 MHz radar wind profiler (RWP) and 6-hourly radiosonde (RS) ascents, DWD developed a standardized retrieval assuring a high-quality Level-2 product.
However, a prerequisite for operational applications is the robust detection of atmospheric return signals in the presence of instrumental noise. While the most common approach filters data via a fixed signal-to-noise ratio (SNR) threshold, we find the non-linear consensus method (CNS), already operational in the data processing chain of radar wind profilers, to be more efficient in the weak signal regime where it increases data availability without reducing data quality.
Here, we present results from a long-term assessment at the Lindenberg Meteorological Observatory using the RWP and RS as references and from a side-by-side comparison of eight Halo Photonics “Streamline” DLs during the FESSTVaL 2021 field experiment. We focus on the characterization of the instrumental noise and show its impact on the derived winds and the data availability.
How to cite: Kayser, M., Lehmann, V., Päschke, E., Detring, C., Knist, C., Leinweber, R., and Beyrich, F.: Instrumental noise and its impact on mean wind measurements, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-408, https://doi.org/10.5194/ems2022-408, 2022.
Turbulence kinetic energy (TKE) is an important process variable to characterize the atmospheric boundary layer. State-of-the-art numerical weather prediction (NWP) models solve a prognostic TKE equation, this generates the interest in measurement data of this variable for verification of the NWP model output. Operational TKE measurements are typically performed using 3D ultrasonic anemometers; this limits their availability to near-surface levels (up to about 200 m above ground at a few tower sites). Alternatively, TKE may be derived from measurements with ground-based remote sensing instruments, such as Doppler lidars.
At the Meteorological Observatory Lindenberg – Richard-Aßmann-Observatory (MOL-RAO) of the German Meteorological Service (DWD) we have implemented an algorithm suggested by Smalikho und Banakh (2017, Atmos. Meas. Tech. 10, 4191–4208) to derive TKE profiles from Doppler lidar measurements. In addition, this algorithm allows to derive profiles of momentum flux, eddy dissipation rate and the integral length scale of turbulence. Thus, a consistent data set to characterize turbulent processes in the atmospheric boundary layer can be obtained. The method includes a correction for an underestimation of TKE due to pulse volume averaging effects. It is based on a special Doppler lidar scan regime - a continuous scan mode (CSM) with very high azimuthal resolution (< 2 deg). This implies using a small number of lidar pulses per ray such that classical data filtering approaches cannot be applied.
We briefly introduce the scan configuration and the methodology for TKE derivation and discuss an alternative data filtering approach which has been realized and tested at MOL-RAO. The methodology has been applied to a data set covering one year of quasi-operational measurements with a Halo Photonics Streamline Doppler lidar at MOL-RAOs boundary-layer field site (GM) Falkenberg. Here, the intercomparison of the derived TKE values versus sonic measurements at a height of 90m at the GM Falkenberg tower shows good agreement. Case studies illustrate the potential to characterize enhanced turbulence associated with cold pools affiliated to thunderstorms or in the shear zone below the axis of a nocturnal low-level jet. Finally, the Doppler lidar TKE values have been compared to the output of DWD’s NWP models.
How to cite: Päschke, E., Beyrich, F., Detring, C., Kayser, M., Leinweber, R., and Becker, C.: Profiles of turbulence kinetic energy derived from Doppler lidar measurements, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-97, https://doi.org/10.5194/ems2022-97, 2022.
The ability to reduce CO2 and other gas emissions to meet global emission targets and air quality standards also requires measuring gas sources and sinks and gas transport mechanisms with the highest possible spatial and temporal resolution.
For a higher spatially resolution of gas distributions and concentrations in the sub-atmosphere unmanned aerial systems (UAS) can be used for in-situ measurements in conjunction with stationary ground measurements. In particular, the use of fixed-wing UAS due to their inability to flight longer times and ranges with only a minor disturbance to the measured volume compared to widely used multicopter UASs.
This study presents a lightweight, small, cost-effective nondispersive infrared CO2 gas sensor system for universal use on board fixed wing UASs. The gas sensor is integrated into an aerodynamic 3D-printed housing, so-called "EGG-Pod". This housing is designed as a gas measurement system that acts as a passive pump which maintains and measures a constant volumetric flow that feeds a gas measurement chamber during flight. This cost-effective approach can be transferred to other mobile platforms, especially due to its simple structure, and its scalability to fit other gas sensors.
To characterize this measurement system, the nocturnal CO2 stratification effect was measured. The ground-level build-up effect of CO2 is caused by ground cooling in radiant and anticyclonic weather conditions. The resulting CO2 vertical gradient was used to define the resolution of the system. For this purpose, flight measurements were compared with the CO2 measurements from the ICOS-Tower (Integrated Carbon Observation System) near Lindenberg Meteorological Observatory - Richard Aßmann Observatory (German Weather Service DWD).
How to cite: Mashni, H., Buechau, Y.-G., Boventer, J., Platis, A., and Bange, J.: Small and Lightweight Gas Measurement System for Unmanned Fixed-Wing Research Aircrafts, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-210, https://doi.org/10.5194/ems2022-210, 2022.
In recent years, air quality in cities has increasingly become the focus of social, media and political attention. Studies classify particulate matter and nitrogen oxides in particular as harmful to health, which are caused, for example, by private motorised transport or energy and heat generation. In order to ensure the health and quality of life of the population, various measures have been designed on the basis of EU directives (e.g. driving bans, speed limits, moss areas). In most cities, however, the assessment of pollution is based on selective measurements at a few stations. Their informative value for entire cities - especially for the legitimisation of strict measures - is publicly and scientifically highly disputed (Hooftman et al. 2018; BMU 2021). An area-wide network of sensors, on the other hand, is expensive, maintenance intensive and leads to competition for use in public spaces. In order to increase the public acceptance of air pollution control measures and at the same time increase the resilience of local measurements with regard to traffic policy decisions, a concept is to be developed in UnLuBW (funded by the Federal Ministry for Digital and Transport) in cooperation with selected municipalities with which particulate matter and nitrogen oxides can be measured flexibly and meaningfully by small and cost-effective unmanned aircraft systems (UAS) (Lambey and Prasad 2021). The use of UAS in the field of pollutant dispersion is also described in a new VDI guideline (Foken and Bange, 2020).
During measurement campaigns before and after measures to reduce the emission of particular matter and nitrogen oxides, the small UAS are going to measure particles, nitrogen gases and meteorological data at different locations within a municipalities simultaneously. These results are compared and evaluated.
How to cite: zum Berge, K., Platis, A., Schön, M., Bramati, M., Savvakis, V., Bange, J., Hochschild, V., Braun, A., Warth, G., Hager, K., Geske, F., Schlettig, C., and Anger, M.: UnLuBW - Pollutant monitoring through technological development of UAS applications, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-589, https://doi.org/10.5194/ems2022-589, 2022.
A precise estimation of the surface energy budget is a challenge to better understand, model and forecast both weather and climate, and their dependence on external constraints. However, in the micrometeorology community, it is already well known that the energy balance closure is an issue over many surfaces (Foken, 2008). Previous studies often focused on turbulent fluxes, effects of advection or time averaging for the flux calculation. This study is dedicated to evaluating the accuracy of the ground heat flux, thanks to a field experiment carried out on the ICOS site of Lamasquère (FR-Lam). Both the soil heat flux and storage are often difficult to precisely measure because thermal conductivity and heat capacity are strongly dependent on the very local soil texture (% clay, % sand, % organic matter) and water content.
The experimental campaign is conducted over a wheat field from autumn 2021 to summer 2022, and heat pulse sensors are installed in various pits to measure thermal parameters (conductivity and heat capacity) at different depths within the ploughing crust. This device currently complements the operational measurements of temperature and soil water content profiles (sensors at 5, 10, 30, 50 and 100 cm), meteorological measurements and turbulent fluxes from an Eddy Covariance set-up.
In a first step, we will present the results of the sensor measurements for the soil thermal parameters, their local dynamics in relation to the soil parameters, the vegetation development and the weather. Then, using these measurements and the temperature profiles in the soil, we will evaluate the accuracy of the ground heat flux in order to estimate its impact on the closure of the energy balance of vegetated surfaces. These results will be also compared to measurements from self-calibrated heat flux plate and the heat storage in the soil layer above the plate.
How to cite: Brut, A., De La Rue Du Can, O., Granouillac, F., Zawilski, B., Boone, A., Canut, G., Lothon, M., and Lohou, F.: Measurement and evaluation of the soil thermal parameters on the surface energy balance in an agricultural plot, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-123, https://doi.org/10.5194/ems2022-123, 2022.
