bluuebunny/crossref_metadata_2025 huggingface dataset:
A physically-based correction for stray light in Brewer spectrophotometer data analysis
Authors: Savastiouk Vladimir , Diémoz Henri , McElroy C. Thomas
Published: July 2023

Abstract. Brewer ozone spectrophotometers have become an integral part of the global ground-based ozone monitoring network collecting data since the early 1980s. The double monochromator Brewer version (MkIII) was introduced in 1992. With the Brewer hardware being so robust, both single and double monochromator instruments are still in use. The main difference between the single Brewers and the double Brewers is the much lower stray light in the double instrument. Laser scans estimate the rejection level of the single Brewers to be 10-4.5 while the doubles improve this to 10-8, virtually eliminating the effects of stray light. For a typical single monochromator Brewer, stray light leads to an underestimation of ozone of approximately 1 % at 1000 DU ozone SCD and can exceed 5 % at 2000 DU, while underestimation of sulphur dioxide reaches 30 DU when no sulphur dioxide is present. This is because even a small additional stray light at shorter wavelengths significantly reduces the slant ozone at large values. An algorithm for stray light correction based on the physics of the instrument response to stray light which adds light from longer wavelengths to shorter ones has been developed. The simple assumption is that count rates measured at any wavelength have a contribution from stray light from longer, and thus brighter, wavelengths because of the ozone cross-section gradient leading to a rapid change in intensity as a function of wavelength. Using the longest measured wavelength (320 nm) as a proxy for the overall brightness provides an estimate of this contribution. The sole parameter, in the order of 0.2 to 0.6 %, that describes the percentage of light at the longest wavelength to be subtracted from all channels is determined by matching ozone calculations from the single and the double monochromator Brewers. Removing this additional count rate from the signal mathematically before deriving ozone corrects for the extra photons scattering within the instrument that produces the stray light effect. Analysing historical data from co-located single and double monochromator Brewers can provide an estimate of how the stray light contribution changes over time in an instrument. The corrected count rates of the measured wavelengths can also be used to improve other calculations: the sulphur dioxide column, the aerosol optical depth, the effective temperature of the ozone layer or any other products. Also presented, is an initial analysis of signs consistent with the stray light effect in the double monochromator Brewers. A multi-platform code to correct the count rates for stray light and saving the corrected values in a new B-file for use with any existing Brewer data analysis software is available to the global Brewer user community at https://zenodo.org/record/8097039 (Savastiouk and Diémoz, 2023).
"NCCS-Impacts” – a new programme of the Swiss National Centre for Climate Services (NCCS)
Authors: Fischer Andreas , Hama Michiko , Möller Andrea , Croci-Maspoli Mischa
Published: July 2023

Switzerland founded its National Centre for Climate Services (NCCS) in late 2015. It is organized as a network of nine Federal Offices and Institutes as well as partners from academia. Since its launch several priority themes have been tackled and published such as new climate change scenarios in 2018 (CH2018) and new hydrological scenarios (Hydro-CH2018). These findings form an indispensable, yet incomplete basis for decision-makers in administration, economy and society. In particular, more information on future climatic impacts is needed. Here, the new programme “NCCS-Impacts” steps in by elaborating a cross-sectoral compilation of climatic impacts in Switzerland as well as a bundle of climate services for decision-support.
The aim of the NCCS programme is to obtain an overview of selected impacts under future climate change in Switzerland and its ensuing central challenges for the environment, economy and society. In addition to the generation of new science-based insights, the programme also has a clear focus on the development and provision of actionable products intended for decision-makers. To this end, the work in the different projects will follow a co-production approach.
In its core, the programme consists of six cross-sectoral and interlinked climate impacts projects that cover the aspects of (1) socio-economic scenarios, (2) human and animal health, (3) ecosystem services, (4) indirect effects, (5) economic costs and (6) critical infrastructures. These topics were identified as priority needs in a comprehensive stakeholder dialogue with representatives from research, administration and the private sector, and by means of a desk review across various sectors.
The programme NCCS-Impacts has been launched in early 2023 and lasts until the end of 2025. In the presentation, we will give an overview of the scope of the programme and present its conceptual framework.
 
Application of the warning value chain in designing a new warning capability for the UK
Authors: Golding Brian
Published: July 2023

Intense convective storms cause many deaths around the world each year from flash floods, landslides, lightning, tornadoes and hail. These are also some of the most difficult to forecast weather hazards and are generally not predictable in a deterministic sense by Numerical Weather Prediction models. In the UK the incidence of such storms has increased significantly in recent years, as a result of climate change, and is projected to increase further with increasing summer temperatures and corresponding increases in absolute humidity. The current UK weather warning service is focused on providing early warnings of six or more hours lead time to enable people to plan ahead for safety. However, the small spatial and temporal scales of convective storms mean that only a very general probabilistic indication can be given of timing and location in these warnings. As a result, most recipients do not prepare for the possibility of severe impacts, even when the accompanying message indicates that they are possible. One option being considered for enhancing the current warning service is to developed a complementary very short range warning focused on storms that present a risk to life. This implies a particular set of responses from warning recipients which make specific demands on the information communicated and the means of communication. On the other hand, current forecasting capabilities for these storms are limited and there are known constraints to forecast improvement. This presentation will demonstrate how a value chain approach has helped to identify the critical components of such a warning system, mapping them on to existing and projected capabilities. Results of a preliminary feasibility study will be shown.
High-resolution modeling of air quality in Hong Kong
Authors: Wang Yuting , Ma Yong-Feng , Li Cathy W. Y. , Wang Tao , Brasseur Guy P.
Published: July 2023

Air quality in urban areas is difficult to simulate due the complex air flows in the cities and the heterogeneous emission sources. Therefore, high model resolution is required to better represent the spatial distributions and temporal variations of the chemical pollutants between the neighborhoods and at the street level. This work exploits the Weather Research and Forecasting (WRF) model coupled with a large-eddy simulation (LES) component and with coupled chemistry to conduct realistic simulations in Hong Kong, a polluted megacity with multi-type pollution sources as well as complex topography. The multi-resolution simulations from mesoscale to LES scales were evaluated by comparing the calculated fields with ozone sounding profiles and with the observations at surface monitoring stations. The evaluation shows that both mesoscale and LES simulations reproduced well the mean concentrations of the chemical species and their diurnal variations at the background sites; however, the mesoscale simulations largely underestimated the NOX concentrations and overestimated O3 near roadside stations due to the coarse representation of the traffic emissions. The LES simulations improved the agreements with the measurements near the road traffic, and the LES with highest spatial resolution (33 m) provided the best results. The LES simulations showed more detailed structures of the spatial distributions of chemical species than the mesoscale simulations, indicating the capability of LES of resolving high-resolution photochemical transformations in urban areas like Hong Kong. The LES simulations showed similar trends with the mesoscale model in the evolution of the profiles of the chemical species with the development of the boundary layer over a diurnal cycle.
Strategies for generating physically consistent realizations from a multi-model blend
Authors: Evans Gavin , Wright Bruce , Moseley Stephen , Ayliffe Benjamin
Published: July 2023

Blending weather forecasts from different sources aims to generate a single forecast which is temporally seamless, spatially consistent and more skilful than the individual inputs. This forecast can capitalise on all available forecast sources throughout the lead time range, such as extrapolation-based nowcasts and convection-permitting ensemble models at shorter lead times, and coarser ensemble models at longer range. Optimising the individual models contributing to the blend using post-processing techniques like neighbourhood processing and calibration helps to optimise overall forecast skill.
A multi-model blend can be created either in physical space or in probability space depending upon the desired output format and the interaction of multi-model blending with other processing steps. The IMPROVER codebase (https://github.com/metoppv/improver) utilises multi-model blending in probability space, which results in spatially and temporally smooth probability and percentile forecasts that are ideal for some use cases. Blending in probability space can avoid artefacts that can be difficult to overcome when blending in physical space. The aim for generating physically consistent realizations from the multi-model blend in IMPROVER is therefore to retain the benefit of the forecast source-specific processing and the relative ease of the probability space blending. Physically consistent realizations are desired by multiple users, including as inputs to hydrological models that require physical consistency including between diagnostics, such as, precipitation and snow melt.
This presentation outlines the requirements for physically consistent realizations, including as input for hydrological models. Prior work focusing on the usage of Ensemble Copula Coupling (ECC) and Schaake Shuffle will be reviewed and challenges with implementing ECC where the choice of dependence template is not obvious will be discussed. Proposals and initial findings will be presented for creating realizations that are self-consistent spatially, across lead times and across diagnostics following multi-model blending in probability space. 
The Human Factor: Increasing the Risk of Weather Extremes in Central Asia
Authors: Fallah Bijan , Russo Emmanuele , Menz Christoph , Hoffmann Peter , Didovets Iulii , Hattermann Fred F.
Published: July 2023

Bias-adjusted and downscaled climate data are essential for regional impact studies. In some cases, a “counterfactual” baseline climate data that isolates the human-induced influences is also required for impact studies that focus on the anthropogenic influence. We examine how human activities have influenced the frequency and intensity of extreme temperature and precipitation events in Central Asia (CA) from 1960 to 2014. We use two sets of simulations from six climate models that are part of the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP) and the Coupled Model Inter-comparison Project phase 6 (CMIP6). One set (labelled as hist-nat) includes only natural factors (solar and volcanic activity) and the other set (labelled as hist) includes both natural and human factors (such as greenhouse gas emissions). We bias-correct and statistically downscale these simulations using the Climatologies at high resolution for the earth’s land surface areas dataset (CHELSA) to a finer spatial resolution (0.25°× 0.25°) to better capture the regional climate variability and impacts. We find that human factors have increased the risk of extreme heat events by four times across most of CA in the hist simulations compared to the hist-nat simulations. We also find that human factors have enhanced the likelihood and magnitude of extreme precipitation events over CA in the hist simulations, especially over Kyrgyzstan and Tajikistan, where landslides and floods are common hazards. Our results suggest that human-induced climate change has contributed to more severe weather extremes over vulnerable regions of CA. Our high-resolution data set is publicly available and can be used for further studies on the causes and consequences of extreme events in CA.
Differences in the shift of phenological phases of field crops and wild plants in the Czech Republic from 1961 to 2022
Authors: Hájková Lenka , Oušková Veronika , Vlach Vojtěch , Musilová Adéla , Možný Martin
Published: July 2023

Global climate change impacts are already monitored in ecosystems and they reveal e.g. earlier onset of spring stages and lengthening plant growing season. However, available results are mainly based on the study of wild plants, whereas only a few studies are devoted to agricultural crops. In this study, phenological data have been used to interpret the influence of climate change on phenological stages of winter wheat, spring barley, Norway maple and lime tree to compare the influence of climate change on field and forest plants and distinguish the influence of farming practices from real climate. So far, not many studies dealt with comparison of phenological shifts between agricultural crops and wild plants. The analyses were focused mainly on subsequent stages: tillering (BBCH 21) in spring barley, heading (BBCH 55) in winter wheat, first leaves (BBCH 11) in Norway maple and beginning of flowering (BBCH 61) in lime tree. The aims of this paper were to calculate the trend in phenological development of winter wheat, spring barley, Norway maple and lime tree in the period 1961–2022 in different climatic zones of the Czech Republic and find out the difference between field crops and wild plants. Mann-Kendall test and Geographic Information system were used. The results showed most significant acceleration of the first leaves in Norway maple up to -28.9 days per period and beginning of flowering in lime tree up to -28.7 days per period. In field crops, the acceleration by heading in winter wheat was up to -13.7 days per period and by tillering in spring barley it was up to -11.6 days per period. A significant trend was found especially in the middle altitudes.
Key words: spring barley, winter wheat, Norway maple, lime tree, BBCH
Analysis of drought stress in the forests of Orava region during period 2015-202
Authors: Krčová Ivana , Turňa Maroš , Rozkošný Jozef , Ivaňáková Gabriela , Labudová Lívia , Ridzoň Jakub , Mikulová Katarína
Published: July 2023

The aim of this work was the analysis of the occurrence of drought, which was determined by the deficit of precipitation and the deficit of soil moisture in the time period 2015 till 2021 in the Orava region, in the comparison with the extent of damage caused by the drought and important biotic pests on the adult forests, which had been registered by the foresters of the Lesy SR, the state corporation. The Orava region was chosen because of the long-term spruce forests decline and the occurrence of more severe drought, which had been rare in the past there. The long-term soil water deficit can expressively weaken the forests, what was finally confirmed in our work. The biotic malign factors Ips typographus L., Pityogenes chalcographus L. and Armilaria sp. were chosen for their high multitudes and for their predisposition to continue in the process of the degradation of woods, as the secondary, respectively the tertiary malign factor beside the drought. The condition of forest vegetation has the long-term feedback to the bad availability of soil moisture, which depends on the specific species resistance to the drought stress. The ascertained results confirm the suitability of the chosen methodology for the drought monitoring, because its outputs are in good agreement with the reports of drought impacts by the end employers. The soil water deficit correlates with deficit of precipitation. It was registered, that the occurrence of important biotic pests in the dry periods is more frequent and the warnings and precautions are inevitable.
Improving the blend of multiple weather forecast sources by Reliability Calibration
Authors: Evans Gavin , Rust Fiona , Ayliffe Benjamin , Hooper Ben
Published: July 2023

Creating a forecast that is seamless across time yet is optimal at each forecast validity time is often achieved by blending forecasts from multiple Numerical Weather Prediction models (or using other forecast sources, such as an extrapolation nowcast). With the increasing usage of convection-permitting ensemble models at shorter lead times, the blending of these forecasts with longer range ensemble models with parameterised convection can lead to a clear transition from one forecast source to another. This is particularly noticeable when visualising the evolution of the gridded forecast. Calibrating the forecast sources with a common truth prior to blending provides a method of improving forecast skill whilst also unifying the characteristics of the forecasts to create a smoother blend throughout the evolution of the forecast.
This presentation aims to describe a non-parametric method, utilising tools from the Met Office’s IMPROVER codebase (https://github.com/metoppv/improver), for calibrating the reliability of the forecast without degrading the forecast resolution. This approach is assessed for its usability for gridded precipitation rate and total cloud amount forecasts. Reliability is markedly improved resulting in similar skill between forecast sources during the blending period and therefore extends the lead time range at which the forecast is more skilful than climatology. This approach is also presented as a step within a series of steps to improve forecast skill therefore highlighting that this approach can be complementary to other techniques without significant tuning. Further refinements to the Reliability Calibration technique removed artefacts in the gridded forecasts. Caveats, including a reduction in sharpness following calibration, are also presented.
Connecting North Atlantic SST Variability to European Heat Events over the Past Decades
Authors: Krüger Julian , Kjellsson Joakim , Pilch Kedzierski Robin , Quinting Julian , Claus Martin
Published: July 2023

The occurrence of European heat events has increased during the last two decades. European heat events are responsible for social, economic and environmental damage and are projected to increase in magnitude, frequency and duration under global warming, strengthening the interest about the contribution of different mechanisms. 
Using the ERA5 reanalysis product, we go beyond case studies relating European heat events with cold North Atlantic sea surface temperatures (SSTs), and perform a systematic approach with a composite analysis to investigate the link between North Atlantic SSTs in a domain south of Greenland and the 2m air temperature (T2m) over central Europe. Composites of different North Atlantic SST states show that events with a negative tendency of North Atlantic SSTs are often followed by positive European T2m anomalies during summers when the North Atlantic SSTs are persistently low for several months. Enhanced lower--tropospheric baroclinicity in the vicinity of a warm conveyor belt over the North Atlantic is followed during these events by a slantwise ascent and an enhanced upper--tropospheric waveguide, promoting a downstream development of an European ridge. 
Convolutional neural network (CNN) models, one for each of the three different stages in a warm conveyor belt (inflow, ascent and outflow), validate the presence of ascending airstreams in the composite of cold North Atlantic SSTs with a negative tendency.  
A wave number decomposition suggests a combination of a wave number 3 pattern and regionally confined Rossby wave activity contributing to a trough--ridge pattern in the North Atlantic--European sector. 
A composite of European heat events further confirms the lagged statistical relationship between cold North Atlantic SSTs with a negative tendency and positive European T2m anomalies. A negative tendency of North Atlantic SSTs precedes 15 of 18 European heat events, and cold North Atlantic SST conditions are present during 14 of 18 European heat events.
An analysis of a extreme wind event in the Basque Country : the 23 october 2022 case
Authors: Egaña Joseba , Munarriz Jaione , Arrillaga Jon Ander , Castaño Antonio , Gaztelumendi Santiago
Published: July 2023

A wind event is analysed during the passage of a depression over the Bay of Biscay. From the northwest of the Iberian Peninsula, it moves in a northeasterly direction until it finally reaches the south of the British Isles. In the upper layers, the flow is strong from the southwest. This configuration generates intense southwesterly winds, especially in central hours and especially in Alava, with Vitoria-Gasteiz being one of the towns most affected. Wind gusts of more than 120 km/h are recorded in exposed areas and more than 100 km/h in non-exposed areas, for example at the Gasteiz station a wind gust of 124 km/h is recorded (third highest record in the Gasteiz station data series). In addition, the high temperatures, the strong wind and the state of the vegetation mean that the risk of forest fires is high and, in fact, a major fire takes place in the Balmaseda area (the most significant fire in Bizkaia in the last 30 years). Due to the wind, there were numerous incidents caused by falling trees, obstacles on the road, falling electricity and telephone poles, flight diversions, etc.
The wind gusts initially forecasted were exceeded. Wind gusts between 80 and 100 km/h were expected in non-exposed areas, but these values are exceeded punctually in many stations. The data from the stations are analysed and compared, and the factors that could have caused the wind to increase over than expected are studied.
The synoptic and mesoscale factors of this episode are analysed. The information from Basque Country Automatic Weather Station Mesonetwork is reviewed, analysing the spatial-temporal evolution of the wind at different locations. After analysing the situation, different conclusions and key factors to be taken into account from the point of view of forecasting are extracted.
Analysis of optical-microwave scintillometric measurements to determine evapotranspiration using RAWLAB’s data boosting and processing software
Authors: van Kesteren Bram , Beyrich Frank
Published: July 2023

Coming from the German automotive industry, RAWLAB has developed a software-based approach that enables non-experts to work with measurement datasets from various sources, make them comparable, and applying complex data-analysis algorithms. Recently, the approach has been extended to include the field of scintillometry. This presentation will introduce the underlying data process and its possibilities resulting from the benefits of combining scintillometry expert knowledge with industry methods. These comprise the use of ASAM's (Association for Standardisation of Automation and Measuring Systems) ODS (Open Data Services) format to store and access any kind of data, as well as the feature to quickly publish any combination of results in automated reports available in e.g. .pdf, .docx, and .pptx formats. Furthermore, novel results and insights concerning the processing of scintillometer data will be discussed, as well as how the software can be used in the operational monitoring of diurnal evapotranspiration. Here we will focus on the use of spectrograms to observe the variation of scintillometer spectra throughout the day, newly derived coefficients for AT and Aq valid for wavelengths between 0.3 - 3 mm, as well as on the preferred algorithms that allow users to get the best estimate for the total evapotranspiration over the course of a day. As an example, we will use two days of operational scintillometer data from the Lindenberg Observatory of the German Meteorological Service (DWD), Lindenberg, Germany, from June 2021 that were obtained during fair weather conditions with typical evapotranspiration summing up to about 3 mm per day.
Real-time extremity assessment of rainfall observations and SINFONY forecasts for small hydrological catchments
Authors: Bondy Jan , Berndt Christian , Schultze Markus , Blahak Ulrich
Published: July 2023

Small-scale, convective heavy rainfall events present a major challenge in flood forecasting, primarily affecting smaller catchments. At such scales, flood forecasts are challenging due to short response times, a lack of stream gauges and limitations of operationally used hydrological models. These models are typically designed for larger catchments, therefore we explore alternative strategies to support the German flood forecasters.
The AREA product (Areal Rainfall Extremity Assessment) aims at complementing the flood forecasters’ workflow based on hydrological modeling by rapidly identifying catchments affected by strong rainfall. We intend to provide a novel post-processing product containing information about the extremity of catchment-specific areal rainfall. First, a nationwide catchment delineation is performed for each pixel of a 50 m x 50 m digital elevation model, selecting only catchments smaller with an area between 10 and 500 km². The catchments and stream network are subsequently upscaled to the operational radar grid with a resolution of 1 km. Finally, areal rainfall is computed for each pixel using the underlying catchment geometry from rain gauge-adjusted radar observations as well as seamless rainfall forecasts resulting from the SINFONY project with lead times of up to 12h.
In order to estimate the extremity of a catchment rainfall event in real-time, we derive return periods based on extreme value statistics. To that end, we consider various accumulation durations and perform a recalculation of areal rainfall for all catchments using a 20-year dataset of radar-derived rainfall. Given the short and limiting observation period of radar data, we attempt to combine the obtained extreme value distributions with existing, regionalized long-term rain gauge statistics (DWD-KOSTRA), in order to estimate longer return periods.
The resulting spatial distribution of areal rainfall with corresponding return periods based on an exhaustive collection of catchments appears to be a useful visualization technique to identify small catchments affected by heavy rainfall. The product will be illustrated based on the analysis of specific case studies.
Recent developments in the provision of wind information for site tenders for German offshore wind farms according to WindSeeG
Authors: Möller Thomas , Spangehl Thomas , Hüttl-Kabus Sabine , Hahn Johannes , Andersson Axel , Kühn Bettina , Grüter Mirko
Published: July 2023

The construction of offshore wind farms in Germany's Exclusive Economic Zone (EEZ) is an important component for the successful implementation of the energy transition. In 2021 the Federal Network Agency started to launch yearly tenders for sites in the North Sea and Baltic Sea which are conducted in cooperation with the Federal Maritime and Hydrographic Agency (BSH) according to the Offshore Wind Energy Act (WindSeeG). The German Meteorological Service (DWD) supports the BSH in compiling the required wind information. This information is made publicly available by the BSH to bidders via the PINTA portal (https://pinta.bsh.de) as part of the tendering procedure.
Detailed information on the wind conditions on the sites is crucial for the bidders' bid calculations. This information is compiled in collaboration by the BSH and the DWD with the participation of external contractors. In detail, corresponding investigations are in-situ measurements on the research platforms in the North Sea and Baltic Sea (FINO1, FINO2 and FINO3, https://www.fino-offshore.de/de/index.html) and one-year LiDAR measurements, which are carried out by external contractors on behalf of the BSH at the sites to be tendered. Furthermore, data and evaluation results of the COSMO-REA6 and ERA5 reanalyses are provided by DWD. These data sets are the basis for the preparation of comprehensive reports on the wind conditions on the sites. The first two tendering processes have successfully completed for three sites in the southeastern North Sea (N-3.7, N-3.8, N-7.2) and for one site in the Baltic Sea (O-1.3) in September 2021 and September 2022, respectively. In 2023, a call for tender for sites N-3.5, N-3.6, N-6.6 and N-6.7, located in the North Sea, has been published.
The reanalysis and measurement data provided allow a detailed investigation of the seasonal variability as well as an in-depth assessment of the current and the historical wind field on each site. The focus of the measurements is on the heights relevant for future wind turbine types. The evaluation of the reanalyses is carried out for the grid points closest to the sites as well as the surrounding grid points and is validated using the existing measurement data. Previous evaluations show a very good correlation, which gives the reanalyses a high significance to determine the wind conditions on the sites. In addition, information on long-term variability is required. Long-term time series of geostrophic wind derived from air pressure data from coastal stations enable an assessment of multi-decadal variations.
Looking ahead, future sites such as N-9 to N-13 and westward of shipping route SN10 in the North Sea are located far offshore increasingly remote from land. This will raise new challenges for the preliminary investigations in all disciplines such as marine environment, geology, subsoil and oceanography, as they are.
Evaluation of CERRA for wind energy applications
Authors: Jourdier Bénédicte , Diaz Carlos , Dubus Laurent
Published: July 2023

The Copernicus European Regional ReAnalysis (CERRA) is a new limited-area reanalysis covering Europe at 5.5 km resolution, produced in the framework of the Copernicus Climate Change Service (C3S) and available in its Climate Data Store (https://cds.climate.copernicus.eu/cdsapp#!/dataset/reanalysis-cerra-height-levels).Near-surface wind speeds are essential variables to simulate wind power production for wind energy applications or prospective studies of the European power system. The purpose of this study is to assess the quality of CERRA’s wind speeds (especially at the height level of 100 m) in respect to these studies and in comparison to other reanalyses such as ERA5.  A first part of the study was to determine which forecast steps to use. CERRA provides an analysis every three hours and hourly forecasts up to 6 hours, therefore forecast streams are overlapping. For example, values at 04 UTC are provided by the step +4h of the 00 UTC analysis and also by the step +1h of the 03 UTC analysis. CERRA documentation leaves the choice to the user. For wind speeds, we recommend not to use the forecast steps close to the analysis as they exhibit too low values. This phenomenon was already observed in AROME NWP model (Jourdier, 2020). This wind deficit is more pronounced in summer, in Northern Europe and offshore. Therefore we chose to use steps +4 to +6h of each analysis.In a second part, average 100 m wind speeds from CERRA were compared to other reanalyses:ERA5, ECMWF’s global 32-km reanalysis, which provides the boundary conditions to the CERRA system.
COSMO-REA6, DWD’s European reanalysis which has a similar horizontal resolution but is based on older ERA-Interim global reanalysis.
Compared to ERA5, CERRA exhibits large differences (up to 6 m/s in average), much higher wind speeds over mountains (especially over the Scandinavian Mountains, the Alps and Dinaric Alps) and higher wind speeds in general over most of Europe either offshore or onshore (except Sweden and Finland). This was expected as ERA5 winds are known to be too low, especially in mountainous areas.Compared to COSMO-REA6, CERRA exhibits smaller differences (up to 3 m/s). CERRA’s wind speeds are higher over Eastern Europe and much higher over some mountains (parts of the Scandinavian Mountains, the Alps). They are lower over the British Isles, most of Scandinavia and most parts of the Mediterranean Sea.Finally, hourly wind power production series were simulated based on CERRA for all wind farms in France. Compared to observed power, CERRA shows less bias than ERA5 and similar hourly correlations. Still some bias remain, mainly positive in Western France and negative in Eastern and Southern France.
Hourly reference evapotranspiration analysis using synoptic meteorological measurements and ERA5 reanalysis data from Kenyan Counties
Authors: Musyimi Peter K. , Mendyl Abderrahmane , Agustiyara Agustiyara , Székely Balázs , Weidinger Tamás
Published: July 2023

Kenya has had five failed rain seasons for the last three years. In this context, there was a mass recurrent crop failure, death of livestock and wildlife, persistent water scarcity, and droughts of varying intensities. There have been a lot of challenges in assessing climate change and variability impacts in Kenya due to limited data sources. Further, assessing the local and regional effects on the hydrological cycle, food security, and available water resources remains a great regional threat. Reference evapotranspiration,  is the evaporative power climatic parameter of the atmosphere, vital for water budgets on the land surface. The study’s main goal was to analyze hourly reference evapotranspiration,  from two climatic regions using single levels ERA5 hourly dataset from 2000 to 2022. The dataset was sought from three stations from, arid, and semi-arid savannah tropical conditions regions (Voi Garissa, and Mombasa) with elevations between 57 m to 579 m, and three (Trans-Nzoia, Nyeri, and Embu) sought from humid Kenya highlands (>1350 m). Reference Evapotranspiration was calculated using Penman-Monteith (FAO56), the standard methodology developed by Food and Agriculture Organization. Results from 5 years (2018 to 2022) in Taita-Taveta County indicated that  ranged from 0.17±0.2 mm/hour in 2020 to 0.22±0.2 mm/hour in 2022. Daily averages were 4.17±1.2 mm./day to 5.2±1.1 mm/day in 2020 and 2022 respectively. The mean monthly and   was highest in March with an estimated value of 159.7±53.7 mm/month while the lowest was 120±15 mm/month in December. This is because March falls at the onset of the long rainy season in Kenya where precipitation is high while December is the last month of the short rainy season when precipitation reduces significantly. These results are vital because they enhance comparisons of the spatial climatological patterns and variability of seasonal precipitation about the evaporative power and demand variation across regions. Further, it will necessitate investigations of uncertainties from the datasets for better decision-making after comparisons with analysis from field meteorological datasets and soil moisture data measurements currently being carried out in Kenya.  Further comparison of the results with reference evapotranspiration from the original station and the Global Land Evaporation Amsterdam Model dataset will also be investigated.
Temperature patterns of the winters in the periods from 1703/04 to 1708/09 in Trenčín, Slovakia
Authors: Melo Marián , Marek Miloš
Published: July 2023

The Diarium of the Jesuit order at Trenčín written in Latin contains systematic daily weather records (with some interruptions) from 8 November 1701 to 10 January 1710. Daily records from this period were kept by two administrators of the Jesuit dormitory (“regens convictus”) Ján Garajský and Juraj Košetič. After the death of Ján Garajský in 1702, the daily weather records are interrupted, so the winter season 1702/03 is without any weather information. With the arrival of his successor Juraj Košetič, such data appear only gradually in the course of 1703. Records related to temperature and precipitation patterns, cloudiness, as well as frequencies of different weather phenomena such as fogs, thunderstorms, strong winds. Information about floods and the occurrence of ice phenomena on the River Váh are also valuable.
In the contribution, we focus on the evaluation of the temperature patterns of individual winter seasons in this period. Winters are defined from December 1 to February 28 (or February 29). For analysis, we selected all daily data describing the temperature state of the weather. Based on this evidence, each day we classified by daily temperature indices (from -3 to +3). Although some winter seasons contain daily weather records for every single day, but not every record specifically relates to a temperature pattern. Out of a total of nine winters during this period, only 6 seasons had more than 70 percent of such daily temperature indices recorded, specifically 1703/04 (73%), 1704/05 (97%), 1705/06 (93%), 1706/07 (86%), 1707/08 (71%) and 1708/09 (81%). From them, the coldest winter season in Trenčín was 1708/09 (with cold temperature pattern), then 1704/05 and 1706/07 (with moderately cold temperature pattern), 1705/06 and 1703/04 (with mild temperature pattern), and the warmest winter season was 1707/08 (with mild temperature pattern). Overall, the coldest month was January 1709, which was also the only very cold month in this ranking. The warmest month was December 1706 with mild temperature pattern.
Like the result of the hard winter of 1708/09 was also the occurrence of ice phenomena (ice cover, ice jam with ice flood later in March) on the River Váh in Trenčín, which are recorded in the Jesuit Diary of this period.
 
Acknowledgment: This work was supported by the Slovak Research and Development Agency under the contract No. APVV-20-0374.
 
Keywords: Jesuit Diary, winter, temperature indices, cold, mild, Trenčín, ice phenomena
Convective Boundary Layer: Some Unresolved Issues
Authors: Kantha Lakshmi , Carniel Sandro , Carniel Cosimo Enrico
Published: July 2023

Given the importance of the atmospheric boundary layer in mediating the transfer of sensible and latent heat from land and ocean surfaces to the lower atmosphere, enormous effort has been expended over the last 60 years to better understand the physical processes therein involved.
Both convective and stable cases have been studied intensively and extensively using theoretical, observational and numerical modelling approaches. The complexities introduced by factors such as inhomogeneous terrain, complex topography, internal boundary layers and secondary circulations have been tackled using dedicated field campaigns and sophisticated theoretical and numerical models.
However, while enormous progress has been made over the years, there still remain significant gaps in our knowledge and unresolved issues. In this work, we focus on the simplest case of a purely convective (shear-free), dry boundary layer (CBL) over a homogeneous surface, to demonstrate the fact that even in this simplest case imaginable, there still emerge some fundamental unresolved issues. Large eddy simulations (LES) are far from perfect, direct numerical simulations (DNS) are beginning to fill in some gaps and could hold the key to resolving at least some of the issues.
Since CBL plays such an important role in the state of the lower atmosphere and a critical one in weather and climate models, we postulate that these grey-areas should be tackled in a more integrated way with a combined observational and modelling approach, benefiting from the support provided by the latest emerging technology. We suggest that the shortcomings highlighted could then be mitigated by well-coordinated observational and LES-DNS modeling campaigns, utilizing modern inexpensive tools such as Unmanned Aerial Vehicles (UAVs) for in-situ sampling and Doppler lidars, wind profiler radars and airborne laser scintillometers for remote sensing.
 
An extratropical driver of evaporation in the tropical and subtropical oceans
Authors: Yaari-Sadeh Tsruya , Raveh-Rubin Shira
Published: July 2023

Ocean evaporation in the subtropics and tropics is the main supplier of moisture to the tropics and is of fundamental importance to the global hydrological cycle, influencing atmospheric and oceanic dynamics and thermodynamics. Ocean evaporation (turbulent latent heat flux) varies on a range of time scales, from the diurnal to longer climatic scales. While previous studies characterize its variability over seasonal-interannual to decadal time scales, here we focus on the subseasonal, and particularly daily-weekly scales, and aim to understand the drivers of this variability. We first show that latent heat flux variability entails transient evaporation hotspots, regionally exceeding 250 W/m2, which build up the long-term climatology. We then show indications for the mechanisms governing this variability, and especially the extreme evaporation hotspots. Namely, it is dry air intrusions from the wake of midlatitude cyclones that reach the low latitudes. The relatively dry and cold airmass over the subtropical and tropical oceans dominates the occurrence and variability of intense latent heat flux in these regions. Our findings suggest, however, that the tropics are not zonally homogeneous, in the sense that such intrusions dominate tropical evaporation in particular regions more than others. For example, in the west of south Africa, southern South America and Mexico, evaporation hotspots co-occur with intrusions from the extratropics 70% of the time and more, while in the western South Pacific and Arabian Sea the co-occurrence reaches values of up to 30%. The fact that the variability and extremes of tropical latent heat flux are governed by extratropical dynamics on this scale, suggest that this mechanism should be viewed as a type of extratropical-tropical interaction, having implications for the predictability of tropical evaporation hotspots. 
Updated and downscaled European winter hardiness maps including Urban Heat Island effects for urban tree species selection.
Authors: Hulsman Lucas , Heusinkveld Bert , Ravesloot Marc , Steeneveld Gert-Jan
Published: July 2023

Trees provide cooling services in urban areas in summer. Which tree species are suitable in cities in a future climate remains an open question. One of the criteria for tree species selection is winter hardiness. Winter hardiness is an indicator of the lowest temperatures that plants typically experience in an area. The United States Department of Agriculture (USDA) defines winter hardiness as the average annual minimum temperature. Hence, it is a straightforward and commonly used indicator to predict the likelihood of certain plants to experience frost damage in winter. The most recent winter hardiness map for Europe was made in 1984, and does not include the climate change from the past decades, and neglects the urban heat island effect (UHI) that causes warmer winters in urban areas, impacting winter hardiness. In this study, we developed an updated and downscaled version of the European winter hardiness maps using minimum temperature from the ECA&D E-OBS dataset version 26.0, and the European Local Climate Zone (LCZ) map with a 100x100m resolution.
The new maps represent the winter hardiness for five standard normal periods between 1951 and 2020, and represent the years 2030, 2050, and 2085 for the Netherlands using four climate scenarios. These maps show how hardiness zones have moved to the north and east over the past decades. They show that roughly 60% of Europe is now in a different hardiness zone compared to the 1951-1980 average, potentially allowing new tree species to flourish here. They also indicate that the Netherlands can move up to three hardiness zones between the present and 2085. Furthermore, these maps show that many urban areas are in different winter hardiness zones compared to the rural surroundings, which has additional consequences for the tree species that are able to flourish in urban environments.
RadClim BSR - Towards a Radar-based Precipitation Climatology for the Baltic Sea Region
Authors: Lowry Blaine , Hoy Andreas , Hashemi Hossein , Karolin Kaarel
Published: July 2023

Project Background: The RadClim BSR project aims to establish the feasibility of developing a radar-based precipitation climatology in the Baltic Sea Region (BSR). The project involves partners in countries across the BSR including Sweden, Estonia and Poland. The status of radar data archiving, utility of the data, and any data harmonisation requirements across the partner countries and the BSR in general are being investigated. Partners in Sweden, Estonia and Poland are acting as country coordinators, reaching out to a large range of actors to thoroughly explore their needs pertaining to radar climatology, utilising a user needs survey (ongoing through spring 2023). Consultations with the national weather services in Germany and Finland, who have already undertaken steps in radar climatology development, are aiding in ensuring best practices are adhered to. This seed project has the intention of laying the framework for the full development of a radar climatology (datasets and visualisations) spanning the BSR, relevant for a large range of actors in the near future.
EMS contribution: At EMS 2023, we will present the results of the user needs survey that was distributed to a wide range of relevant actors in the project partner countries of Sweden, Estonia and Poland. The surveys were translated into each countries official language before being distributed, to maximise participation and ensure all representatives who should offer their perspective could, regardless of English language capacity. The survey results demonstrate user group priorities for the development of such a radar based precipitation dataset and tool, in terms of both content and format. Through to the end of the project in early 2024, the results from this survey will be fully summarised and will then form the basis for the future development of a trans-national radar-based precipitation climatology across the entire BSR.