bluuebunny/crossref_metadata_2025 huggingface dataset:
The new Italia – Deutschland science-4-services network in weather and climate (IDEA-S4S) 
Authors: Navarra Antonio , Jones Sarah , Bassini Sanzio , Cacciamani Carlo , Crewell Susanne , Ditas Jeannine , Facchini Maria Cristina , Gualdi Silvio , Hinkelmann Reinhard , Jung Thomas , Kiendler-Scharr Astrid , Kusche Jürgen , Masbou Matthieu , Seuffert Gisela , Volosciuk Claudia
Published: June 2022

Italy and Germany are establishing a new bilateral cooperation in meteorology, climatology and related disciplines that will create a hub of excellence for cutting edge research and translate the findings into improving operational services and university education. The joint research and education network IDEA-S4S will harness expertise of universities, research institutes and operational services in both countries and foster scientific exchange and collaboration to improve weather, climate and environmental services.

Within the new programme, the core areas of scientific expertise of both countries will be systematically brought together, activities will be streamlined and extended beyond basic research collaboration to form a holistic IDEA-S4S network of weather and climate science and education, extending from qualification of graduates to support for early career researchers to networking of senior scientists. The programme will cooperate with WMO and the European Meteorological Infrastructure (ECMWF, EUMETSAT, EUMETNET) and strengthen the scientific environment for the ECMWF sites in Bonn and Bologna. A Joint Steering Committee will oversee the cooperation and guide the overall scientific and strategic direction of the programme.

Through four-year funding periods, the network aims to make substantial progress in seamless high-resolution probabilistic Earth system prediction, employing state-of-the-art observing systems and Earth system models. This requires improved understanding and application of coupled processes between the components of the Earth system (including atmosphere-ocean-ice-land-vegetation-rivers) as well as between the impacts of human activities and the Earth system. Such complex weather and climate prediction systems place high demands on high-performance computing infrastructure, generate extremely large data volumes and need to integrate observations seamlessly into the models.

In this contribution, we will present the concept and roadmap of the IDEA-S4S network, which will focus on improving seamless weather and climate forecasts, in particular for high impact events such as floods and droughts. Both countries have experienced devastating impacts of such extreme events with unusual rainfall intensities, some of which even lead to the destruction of entire regions. Better understanding the complex structure and the numerous feedback processes in such events will improve the prediction of future events in support of a better prepared and resilient society.
Simultaneous measurements of rain, clouds, and aerosols within the Ruisdael Observatory
Authors: Schleiss Marc , Unal Christine , Mackenzie Robert , Guzzo Saverio , Russchenberg Herman
Published: June 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. 
Impacts of the coupling of the wave and the ocean model to the atmospheric model on the predictability of extreme events
Authors: Wiese Anne , Ho-Hagemann Ha Thi Minh , Grayek Sebastian , Koch Wolfgang , Staneva Joanna
Published: June 2022

Two-way coupling between atmosphere and ocean models has already been widely used to improve the results of atmosphere models during extreme events, as well as long-term simulations. Also the coupling of an ocean surface wave model to an atmosphere model has already been shown to have a positive impact on the atmosphere model enhancing the agreement with observations, especially during extreme wind events. The results of many previous studies by different groups showing an improvement of the simulations with coupled atmosphere – ocean or atmosphere – wave models now leads to the question, whether the inclusion of a wave model into an atmosphere – ocean model system can improve the results of the atmosphere model further. In this study the atmospheric model COSMO-CLM, the wave model WAM and the ocean model NEMO are used. To evaluate the impacts of coupling all three models with respect to two-way coupling on the lower atmosphere during extreme events but also during the year, three experiments are carried out. In one experiment the full exchange between the three models is enabled, whereas in the other two either the wave model is not giving any feedback to the atmosphere and the ocean or the ocean model is disconnected from the atmosphere and wave model. In order to analyse the added value of the inclusion of the wave model, the analysis is split into evaluating the impact on the lower atmosphere throughout the year but also during specific events. These specific events are either where the impact of the wave model is particularly high or extreme events. One focus of this study is on the simulation of storms, since both the wave model and the ocean model have an impact on the atmosphere model during those events. Moreover, it is analysed whether the effect of the wave model opposes or enhances the effect of the ocean model on the lower atmosphere during extreme events as well as throughout the year. Furthermore, to assess the skill of the fully coupled system with respect to the two-way coupled systems the simulation results are compared to observations of wind speed, temperature and pressure in general but especially during extreme events.
Assimilation of ground-based remote sensing profiler data at MeteoSwiss
Authors: Crezee Bas , Merker Claire , Regenass Daniel , Leuenberger Daniel , Vural Jasmin , Haefele Alexander , Hervo Maxime , Martucci Giovanni , Bättig Philipp , Arpagaus Marco
Published: June 2022

Conventional atmospheric measurement systems fail to provide observations of the essential variables characterizing the planetary boundary layer (PBL) with satisfactory spatial and temporal resolutions. Moreover, the available profile observations are very sparsely distributed. Due to this observational gap the thermodynamic structure of the PBL in the initial conditions for NWP is prone to errors, just as the representation of winds in the lower atmosphere. This affects the accuracy of forecasts of high-impact phenomena such as convective storms or winter fog and low stratus, and is relevant for the quality of downstream applications, warnings, and emergency responses.

Humidity and wind exhibit a very high variability in space and time and, together with temperature, determines the atmospheric stability. It is therefore of major interest to investigate the potential benefit of assimilating additional profile observations of humidity, temperature, and wind into the NWP system. In this contribution, we give an overview of our efforts to include novel, ground-based remote sensing profiler observations into the 1km mesh-size, LETKF-based, ensemble data assimilation system COSMO/KENDA-1.

We present the assimilation of brightness temperatures from three microwave radiometers installed on the Swiss Plateau using the RTTOV-gb forward operator, as well as experiments assimilating water vapor mixing ratio and temperature profiles from a Raman lidar located in Payerne. Additionally, we show an assimilation case study with wind lidars focusing on a local wind system in Basel.
The assimilation of Raman lidar observations leads to improved humidity analyses and precipitation forecasts, particularly for high intensities. It is further shown that state-dependent observation errors lead to more skillful results than constant observation errors.
Autonomous Monitoring of Soil Moisture & Snow Water Equivalent with Stationary and Mobile Cosmic-Ray Neutron Sensors
Authors: Schrön Martin , Zacharias Steffen , Beyrich Frank , Böttcher Falk , Boeing Friedrich , Marx Andreas , Fatima Eshrat , Kumar Rohini , Kaluza Maren , Samaniego Luis , Attinger Sabine , Dietrich Peter
Published: June 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.
Lessons in climate service development from Klimaatlas, the Danish National Climate Atlas
Authors: Payne Mark R. , Sørensen Alan , Christiansen Bo , Andree Elin , Boberg Frederik , Su Jian , Madsen Kristine S. , Madsen Marianne S. , Olesen Martin , Christensen Ole B. , Pedersen Rasmus A. , Thejll Peter , Langen Peter L. , Olsen Steffen M. , Schmith Torben
Published: June 2022

Responding to the challenges of a changing climate requires information that is relevant and actionable at the local scale where adaptation actions take place. Here we describe the development of Klimaatlas, the Danish National Climate Atlas, a tool to provide information to ministries, regional authorities, businesses and citizens about climate change in Denmark.  We focus in particular on the key decisions that needed to be made during development and the lessons learnt from doing so that are relevant to the development of similar tools in other jurisdictions. We describe the user groups that we involved in the development of the atlas, how their interactions shaped the final product, and the ongoing role of the user in the project. Communication and dissemination of results was approached on three different levels simultaneously, and we describe this approach, and its benefits, in detail. We detail some of the major technical challenges faced, particularly around the choice of bias-correction methods, and how these issues were overcome. The approach to quantifying and communicating uncertainty, and its importance, also receives particular attention. We assess the impact of Klimaatlas, and the challenges around quantifying its usefulness, together with the results of a recent user survey identifying the strengths and weaknesses. We also place Klimaatlas in the context of other comparable products, and particularly the recently developed IPCC Interactive Atlas. Finally, we discuss issues around future maintenance and possible expansions of Klimaatlas, including the use of convection permitting simulations, incorporation of compound events, updates between IPCC cycles and extensions to new sectors.
Unpacking the logics of physical climate storylines
Authors: Baldissera Pacchetti Marina , Coulter Liese , Dessai Suraje , Shepherd Theodore , Sillmann Jana , Van Den Hurk Bart
Published: June 2022

The Physical Climate Storyline (PCS) approach is increasingly recognized by the research community as a tool to produce and communicate decision-relevant climate risk information. While PCS is generally understood as a single concept, different methodologies are applied according to the aims and purposes of the approach. To unpack this diversity of detail, this paper gives an overview of the key methodological practices and assumptions, i.e. the “logics” that are associated with variants of the PCS approach. We analyze physical climate storylines as both a product and a process and recognize that (i) those who build the storylines (e.g. physical climate scientists, interdisciplinary groups of scientists, or transdisciplinary groups of scientists and societal stakeholders) and (ii) the purpose for which these storylines are built (e.g. improving scientific understanding or communicating information) influence key features of the methodology (process) and hence key features of the storyline (product). We note that PCS can have cognitive aims, i.e. aims related to the pursuit of knowledge and hence promote cognitive values, and non-cognitive aims, i.e. the practical, social and ethical aims of the knowledge that is produced, and hence promote non-cognitive values. We then examine how value judgements are implicitly or explicitly included in the aims and construction of PCS. We conclude the discussion by suggesting that the PCS approach can further mature (i) in the way it incorporates the narrative element, in particular in trans- and multi-disciplinary contexts, (ii) in the way it incorporates value judgments, and (iii) in the way that the evidence chosen to build PCS constrains what is considered plausible.
UnLuBW - Pollutant monitoring through technological development of UAS applications
Authors: zum Berge Kjell , Platis Andreas , Schön Martin , Bramati Matteo , Savvakis Vasileios , Bange Jens , Hochschild Volker , Braun Andreas , Warth Gebhard , Hager Karsten , Geske Franziska , Schlettig Christoph , Anger Michael
Published: June 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.
Internal boundary layer characteristics at the southern Bulgarian Black Sea coast
Authors: Barantiev Damyan , Batchvarova Ekaterina
Published: June 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".
Measuring meso-scale gradients in the Arctic during HALO-(AC)3
Authors: Paulus Fiona , Neggers Roel
Published: June 2022

Moisture and aerosol exchange between the Arctic and the mid-latitudes plays a crucial role in the ongoing rapid warming of the Arctic climate. In particular the downward longwave radiation associated with liquid clouds as embedded in warm-air intrusions has been found to contribute significantly to enhanced melting of the ice sheet. The observed persistence of liquid clouds at high latitudes is not yet fully understood, but the transitions between cloud and cloud-free states are likely to be linked to large-scale dynamics. Recent Lagrangian Large-Eddy-Simulations (LES) following air masses into the Arctic have shown that the evolution of the mixed-layer depth is predominantly controlled by large-scale subsidence, and that relatively abrupt changes in subsidence rates can cause cloud collapse. This subsequently causes a drastic change in the surface energy budget. In order to support this modeling result with observations, simultaneous measurements of the large-scale subsidence and the mixed-phase cloud properties are necessary.

During the recent HALO-(AC)3 field campaign in Spring 2022, we used dropsonde patterns to measure divergence and other gradients across meso-scale areas. This approach has already been tested in the subtropics during the during the NARVAL and EUREC4A field experiments and has now been performed in the Arctic for the first time. Given the considerable differences in atmospheric dynamics between the subtropics and the Arctic, it is not clear a priori if this method can be equally successful. To find out, we present a comparison of independent measurements obtained during different flights and by two airplanes sampling the same area. Preliminary results show for the first time that the dropsonde method yields reliable estimates of mesoscale gradients in the Arctic, including subsidence and vorticity. Ongoing efforts to combine the wealth of HALO-(AC)3 data with targeted Lagrangian high resolution simulations will be briefly discussed.
Vegetation and climate: initial concepts about the relation between the sun-induced chlorophyll fluorescence (SIF) and the soil water content (SWC)
Authors: Quiros Juan , Siegmann Bastian , Damm Alexander , Rascher Uwe
Published: June 2022

Climate conditions directly impact on vegetation growth, this is quite clear; yet, “how vegetation functioning alters climate?” is an open query rising many questions. Understanding the impact of vegetation functioning on climate is important to better comprehend climatological processes and thus to improve models, due to the influence of plants on the carbon and water cycles. For decades it was impossible to have information about plant functioning in the (regional to global) scale of climatological models, nevertheless, the advent of satellite-based remote sensing (RS) methods for the retrieval of sun-induced chlorophyll fluorescence (SIF, as a proxy of photosynthesis) made it feasible. For instance, using satellite SIF and precipitation data, Green et al. (2017; DOI 10.1038/ngeo2957) recently provided one of the first contributions in such direction. The authors reported that regional biosphere-atmosphere feedbacks can explain up to 30% of precipitation variance, mainly because of the role of plants in the regulation of the water flux from the soil towards the atmosphere. As a complement to such studies with focus on the vegetation-atmosphere link, in two recent studies we analyzed the relation that SIF has with the soil water content (SWC) at airborne and satellite scales. At airborne scale we found that (i) the SIF-SWC relation is crop- and growth stage-dependent, and that (ii) SIF showed a faster response to water limitations compared to conventional (reflectance-based) RS products. On the satellite level we found a strong impact of the SIF-SWC relation on the gross primary productivity (GPP) during a heat wave at European scale. With these contributions from the RS area, we aim to provide novel information that can help the meteorological research community to better understand how vegetation functioning can alter climatological processes, with potential applications in the improvement of climate models.
Beyond Monin-Obukhov Similarity Theory and the Hockey-Stick Transition
Authors: Urbancic Gabin
Published: June 2022

Monin-Obukhov Similarity Theory (MOST) is the canonical theory of boundary layer meteorology and describes the structure of the Atmospheric Surface Layer (ASL). The theory results in the stability functions which relate the non-dimensional local gradient to the Monin-Obukhov stability parameter. In the near-neutral limit MOST converges to the logarithmic wind profile of von Karman and Prandtl. Although MOST is still widely used, limitations have been clear for decades. In the very stable conditions, the surface scaling regime of MOST is replaced by the local scaling regime of Nieuwstadt (1984). More recently, it has been clear that non-local, finite-sized eddies have a large influence on the surface fluxes, even during near-neutral and stably stratified conditions. A local theory, which uses the local gradients, cannot describe all the properties of the ASL. The most significant work on the topic comes from the Hockey-Stick Transition (HOST), developed by Sun et al. (2012). HOST demonstrates two regimes where turbulence first scales with the local gradient until a threshold wind speed is reached, after which the turbulence scales with the wind speed. These features cannot be derived from MOST. Multiple studies have considered how to merge MOST and HOST with some success (e.g. Sun et al. 2020; Grisogono et al. 2020)

In this talk, I will develop the regimes of validity of MOST and HOST using a multitude of datasets measuring the ASL from near-neutral to very stable conditions. I will describe how the different theories differ and in which way they are consistent. The role of bulk shear and finite eddies are discussed illustrating the non-local structure of the ASL and its influence on the associated surface fluxes. I will consider for which scales a finite eddy is active or inactive in the surface fluxes and how it relates to Townsends attached-eddy hypothesis. The talk will end with a prognostic of where improvements and progress is likely to occur.
The effects of orientation and dimensions of outdoor shading devices on thermal comfort
Authors: Ou Hsing-Yu , Lin Tzu-Ping
Published: June 2022

In recent years, climate change and the urban heat island effect have caused extreme heat and thermal discomfort in the city. To adapt to this extreme condition, shading is one of the adaptation strategies. Effective shade can protect people from excessive solar radiation, improve outdoor thermal comfort and encourage people to engage in outdoor activities. Therefore, several countries have developed shading policies including constructing shading devices such as shaded walkways and increasing tree shades. For shading facilities, the orientation and dimensions are key factors affecting thermal comfort beneath them. However, it is rarely discussed in past studies and isn’t particularly specified in the government policies. Therefore, the objective of this research is to understand the relationship between the orientation and dimensions of outdoor shading devices and thermal comfort to provide references for policy-making and design.

This research applies the Ladybug tool to calculate the physical equivalent temperature (PET) under various dimensions and orientations of two basic types of outdoor shading devices, the independent and the attached, during summer days. The effect of the dimensions on thermal comfort is evaluated with the effective aspect ratio.

The results show that the lower the effective aspect ratio, the higher the average PET and the discomfort rate (the percentage of time with PET over 34℃) during summer days. The discomfort rate can be reduced to less than 5% when the effective ratio of shading devices is above 1.8. The orientation of shading devices also affects PET. For independent shading devices, the average PET and discomfort ratio in the N-S orientation is the highest and the E-W orientation is the lowest, while the attached type is the highest in the west and the lowest in the north. In addition, this study finds regression equations for the average PET of shading devices in summer with the effective aspect ratio as a parameter. Moreover, this study organizes the results into a reference table so users can easily understand the PET discomfort rate of shading devices in different dimensions and orientations.

This research provides valuable information for the government to develop shading policies, assist designers to design comfort shading devices, and predicts thermal comfort levels under shading devices in various dimensions and orientation.
Comparison of UTCI between the ERA5 reanalysis and the ALADIN model for Czechia
Authors: Novak Martin , Hynčica Martin
Published: June 2022

The UTCI (Universal Thermal Climate Index) combines selected meteorological elements (air temperature, wind, humidity, and radiation) into a single value (in °C) describing level of thermal stress on humans. Computation of UTCI is implemented in several datasets, comparison of two of which is presented here. The ALADIN is NWP (numerical weather prediction) model commonly used for forecasting; operational calculation of UTCI has started in 2019. In contrast, the ERA5 reanalysis is based on observed data spanning period from 1979 to 2021. Therefore, the aim here is a comparison of datasets different in their nature: meteorological model with reanalysis. Results can also be interpreted as a verification of UTCI in ALADIN. The analysis is conducted for years 2019 and 2020 due to the availability of data. After interpolation of both datasets on the same regular grid (resolution is 7.1 km) covering the Czech Republic, datasets are compared from both temporal and spatial perspectives. Subtraction of UTCI between ERA5 and ALADIN is made at every gridpoint in hourly step. Hourly differences are consequently aggregated in daily, monthly, and seasonally step. Considering seasonally and monthly differences, no substantial changes are evident; interesting results emerge when analyzing single hourly data (00-24): it is shown that the UTCI in ALADIN is overestimated in the morning (1-2 °C) whereas the opposite is found for the afternoon and early evening (1-3 °C) in all seasons.. Spatial differences are, however, mostly small at majority of gridpoints, although underestimation of UTCI in ALADIN is detected in higher altitudes (above 500/600 m), where differences at some gridpoints reach up to 6.5 °C. Differences are inherent to orography, owing to coarse grid resolution of ERA5 (30 km) compared to ALADIN (2.3 km). Flattened orography mask in ERA5 reflects in larger differences in higher altitudes.
Estimation of precipitation preceding precipitation extremes of different lengths
Authors: Müller Miloslav , Crhová Lenka , Kašpar Marek , Laco Martin
Published: June 2022

For water management purposes, the design rainfall intensities with different durations are an essential data basis. However, the actual runoff response of such a rainfall event is substantially influenced by other factors, including the time structure of the rainfall event and the previous saturation of the landscape. In our paper, we focus on the latter of these factors because the design of small-scale water management structures is usually based on the assumption that the saturation of the catchment at the beginning of a rainfall event of a given duration is on average. The aim of our research is to test the validity of this assumption in different parts of the country and to trace any general patterns of the relation between precipitation extremes and antecedent precipitation totals in relation to relief.

We use data from 60 Czech rain-gauge stations for which short-term rainfall intensity data for several decades are at our disposal. At each station, we select annual maximum rainfall totals for time windows ranging from half an hour to one day. We estimate the magnitude of antecedent saturation using the antecedent precipitation index over a 30-day period (API30); for sub-daily extreme totals, we also consider any precipitation on that day from the morning to the start of the precipitation episode. Because the index exhibits almost the same seasonal distribution as the daily precipitation totals, we express the magnitude of API30 relative to the normal for a given calendar day. For each station, we calculate relative saturation values before each annual maximum rainfall episode of a given length. Considering the episodes with decreasing weight according to rainfall magnitude, we evaluate average relative saturation values. We find that already before episodes with a length of 150 minutes we have to take into account slightly increased saturation, especially in mountainous regions in the east of the Czech Republic.
Understanding processes leading to surface gusts by modeling windstorms at very high resolution
Authors: Pantillon Florian , Lfarh Wahiba , Chaboureau Jean-Pierre
Published: June 2022

Windstorms associated with extratropical cyclones are destructive natural hazards due to the resulting surface gusts mostly. Processes governing the formation of gusts are thus crucial for the societal impact of windstorms but are not well understood and too small scale to be explicitly represented in numerical weather prediction models. The ANR project WINDGUST aims to better understand the formation of wind gusts through innovative numerical simulations with the Meso-NH atmospheric model. Accurately modeling windstorms requires high resolution over a large domain to represent both fine-scale structures and mesoscale dynamics, as well as advanced physical parameterizations and coupling with surface models to capture complex interactions. Running such simulations is a computational challenge, as is the analysis of the resulting deluge of data.

First results are presented for the intense Mediterranean cyclone Adrian that hit Corsica on 29 October 2018 with gusts above 50 m/s and extended damages. While state-of-the-art meteorological simulations with kilometer-scale resolution are able to develop strong mesoscale winds associated with the cold conveyor belt of the cyclone, large-eddy simulations with hectometer-scale resolution are necessary to explicitly represent their boundary-layer organization. The latter reveal the presence of coherent structures as convective rolls align with the main wind direction over the warm Mediterranean sea. Lagrangian tracers computed online during the model integration highlight their crucial role in the downward transport of momentum to the surface. The characteristics of convective rolls depend on the horizontal grid spacing but are also strongly sensitive to the representation of surface fluxes over sea, which are poorly constrained under winds above 20–25 m/s. These results suggest a large uncertainty in numerical weather predictions of surface gusts using kilometer-scale models.

Future work will extend the methodology to Atlantic cyclones involving different mesoscale features and using full atmosphere-wave-ocean coupling in order to accurately represent air-sea interactions under windstorm conditions.
Unraveling cross-equatorial dry intrusion influence on Indian summer monsoon rainfall
Authors: Rai Deepika , Raveh-Rubin Shira
Published: June 2022

The summer monsoon provides most of the rain in India. Any variability in rainfall, particularly on the daily-to-weekly scale, strongly impacts the environmental systems and socioeconomic activity. This study focuses on cross-equatorial dry intrusions (DIs) in which dry air masses descend slantwise from the southern midlatitudes upper troposphere towards lower levels in the Arabian Sea during monsoon season. The presence of dry air masses in the Arabian Sea, a hot spot for such DIs, has great potential to modify the moisture availability and rainfall over India.

Using the Lagrangian analysis tool, LAGRANTO, forced by ERA-interim reanalysis data for 40 monsoon seasons (1979-2018), we identify 130 DI events. We show that 95% of DI air masses reach below 800 hPa in the central Indian Ocean within two days of their initiation in the southern hemisphere. Though rare (<1% frequency in time), their presence in the marine boundary layer triggers intense ocean evaporation due to enhanced moisture gradient in the lower levels. These DIs enhance low-level flow that facilitates more moisture transport from the central Indian ocean towards India. Depending on the wind pattern, increased moisture transport changes rain over land: 60% of the DI events are associated with more than 25% enhancement, whereas 40% with about 10% decrease in the rain compared to climatology. In summary, cross-equatorial dry air masses reaching the marine boundary layer over the tropical Indian Ocean during the summer monsoon season are responsible for developing anomalously moist air and heavy precipitation over the Indian region downstream and thus crucial for summer monsoon rainfall predictability, especially its extremes.
Surface Solar Radiation based on Satellite Observations – the new SARAH-3 Climate Data Record
Authors: Pfeifroth Uwe , Drücke Jaqueline , Trentmann Jörg , Hollmann Rainer
Published: June 2022

The EUMETSAT Satellite Application Facility on Climate Monitoring (CM SAF) generates and distributes high quality long-term climate data records (CDR) of energy and water cycle parameters, which are freely available.

In 2022, a new version of the “Surface Solar Radiation data set – Heliosat” will be released: SARAH-3. As the previous editions, the SARAH-3 climate data record is based on satellite observations from the first and second METEOSAT generations and provides various surface radiation parameters, including global radiation, direct radiation, sunshine duration, photosynthetic active radiation and others. SARAH-3 covers the time period 1983 to 2020 and offers 30-minute instantaneous data as well as daily and monthly means on a regular 0.05° x 0.05° lon/ lat grid. Compared to previous versions, the data quality of SARAH-3 has been substantially improved over snow-covered surfaces, e.g, in the Alpine region, by the use of an internally derived snow mask. SARAH-3 will be accompanied by a near-realtime data processing, which enables operational applications, e.g., climate monitoring

In this presentation, an overview of the SARAH climate data record and example applications will be given. A focus will be on the SARAH-3 developments and validation with surface observations. Further, SARAH-3 will be used for the analysis of climate variability and potential trends in Europe during the last decades. The data record reveals that there is a positive trend of surface solar radiation in Europe during the last decades, which is superimposed by decadal and regional variability. The most significant brightening during the last decades is estimated for spring.
Deriving 3D wind fields in the Paris urban atmosphere from scanning Doppler lidar observations
Authors: Cespedes Jonnathan , Kotthaus Simone , Thobois Ludovic , Haeffelin Martial
Published: June 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.
Communicating uncertainties for flood warning in small catchments using ensemble hydrological forecasting
Authors: Grundmann Jens , Six Achim , Philipp Andy
Published: June 2022

Reliable warnings and forecasts of extreme precipitation and resulting floods are important for disaster mangers to initiate flood defence measures. Thus, disaster managers are interested in extended lead times, which can be obtained by employing forecast of numerical weather models as driving data for hydrological models. Especially for small catchments, warning and forecasting systems are challenging due to the short response time of the catchments and the uncertainty of meteorological forecasts. To portray the inherent uncertainty of weather model output, ensemble hydro-meteorological forecasts can be used.

By this contribution, we present our operational web-based demonstration platform for ensemble hydrological forecasting in small catchments of Saxony, Germany (http://howa-innovativ.hydro.tu-dresden.de/WebDemoLive/). We use the ICON/COSMO-D2-EPS product of the German Weather Service (DWD), which provides an ensemble of 20 members each three hours.

Each member is evaluated regarding specific extreme precipitation thresholds for predefined hydrological warning regions. If these thresholds are exceeded in a specific region, rainfall-runoff models for the associated catchments are started to propagate the meteorological uncertainty into the resulting runoff, followed by statistical post processing and visualization. Forecasts are updated each hour if new precipitation observations by the radar product RADOLAN-RW of the DWD is available and they are processed for lead times up to 27 hours.

Different options for the visualization of the uncertainty information in precipitation and resulting runoff were discussed and evaluated by a series of workshops with locally responsible civil protection forces and water authorities. This leads to the current design of the web-based demonstration platform in an iterative process.  

The web-based demonstration platform is established for three pilot regions with different hydrological settings in Saxony, Germany. Besides layout and technical issues, results and experiences with the demonstration platform are presented for observed extreme events in the small pilot regions in 2018 and 2021.
Contributions of DWD’s Data Centres to the Improvement of Climate Data Availability and Quality for Africa
Authors: Kaspar Frank , Andersson Axel , Ziese Markus , Hollmann Rainer
Published: June 2022

Reliable weather observations are an important basis for climate change assessments and climate services. Compared to other regions of the world, long time series of weather observations are sparse in many African countries. Various activities at national or international level are ongoing to improve the availability and quality of climate databases. In this presentation, we will provide examples from international data centers hosted at Germany's national meteorological service DWD (Deutscher Wetterdienst). The international exchange of monthly climate reports (CLIMAT) is monitored within the Monitoring Centre of the GCOS Surface Network (Global Climate Observing System). In that context the data is also quality controlled and made publicly available.

Such recent climate observations can be complemented by digitization of historical hand-written weather observations which are available in distributed archives. DWD houses huge archives of historical handwritten journals of weather observations originating also from the activities of his predecessor organizations. These archives do not only comprise observations from Germany, but also of the oceans and land stations in many parts of the world. International observations are part of the marine archive (located in DWD's branch office in Hamburg) which contains (among others) the collections of the German Naval Observatory, “Deutsche Seewarte,” a predecessor of DWD that existed from 1868 to 1945 in Hamburg. It includes meteorological data records from ships, as well as from land stations in many parts of the world (e.g., from former German colonies).

International data centers, such as the Global Precipitation Climatology Centre (GPCC), collect international data. They perform quality-control of these observations and provide derived products in support of global and regional climate assessments. These activities can also contribute to the improvement of national climate databases, as e.g., demonstrated in a cooperation among selected countries with the SASSCAL initiative (Southern African Science Service Centre for Climate Change and Adaptive Land Management). Satellite-based observations are an additional source that can provide climatological information for selected parameters. In particular, the METEOSAT satellite series provides valuable data for the African continent. The Satellite Application Facility on Climate Monitoring (CM SAF) provides high resolution climate data covering the last decades derived from observations of such meteorological satellites.

Reference:

Kaspar, F., Andersson, A., Ziese, M., Hollmann, R. (2022). Contributions to the Improvement of Climate Data Availability and Quality for Sub-Saharan Africa. Front. Clim. 3: 815043. https://doi.org/10.3389/fclim.2021.815043