bluuebunny/crossref_metadata_2025 huggingface dataset:
New convective guidance at the Australian Bureau of Meteorology
Authors: Warren Robert , Richter Harald , Blockley Ivor , Sgarbossa Dean
Published: July 2023

Operational guidance for thunderstorms and severe convective hazards at the Australian Bureau of Meteorology has undergone a major uplift in recent years, with the introduction of new NWP models, post-processing systems, and convection diagnostics. The latest guidance is based on the third generation of the Australian Community Climate and Earth-System Simulator (ACCESS) suite, which includes global and convection-allowing models run in both deterministic and ensemble configurations. In this presentation, we will introduce the ACCESS suite and discuss three sources of convective guidance based on its outputs. The first is the new ConvParams post-processing suite, which ingests model-level data from the ACCESS Global and Global Ensemble models and computes a wide array of convective parameters for use in ingredients-based forecasting of thunderstorms and associated hazards. The second is the Bureau’s lightning prediction system, Calibrated Thunder, which combines ACCESS Global Ensemble forecasts and recent lightning observations to produce calibrated probabilistic forecasts of lightning within a 10-km radius across Australia and surrounding coastal waters. The third comprises storm attributes from the convection-allowing ACCESS City and ACCESS City Ensemble models, including simulated reflectivity, updraft helicity, and parameterised lightning flash rates. For the ensemble, these diagnostics are post-processed to obtain the ensemble maximum and neighbourhood-maximum ensemble probabilities (NMEPs), and interrogated using a variety of novel visualisation strategies. Our presentation will provide an overview of each of these guidance streams, describe how they are used in operations, and assess their strengths and limitations. We will also highlight promising avenues for future guidance developments at the Bureau of Meteorology.
Deep learning model for six hour rainfall prediction
Authors: Na Inchae , An Sojung , Oh Taejin , Jang Jiyeon , Park Wooyeon
Published: July 2023

This study utilized a convolutional neural network (CNN) architecture based on Convlstm and Trajgru models with CBAM method to predict rainfall. The radar and satellite data collected and preprocessed during summer seasons from 2019 to 2022 were used along with additional auxiliary data including longitude, latitude, and terrain information to perform deep learning-based rainfall prediction.CBAM method is used to focus attention on specific spatial and channel relationships. Convlstm and Trajgru are neural network architectures designed to process spatiotemporal data.Assuming that atmospheric flows move at a maximum speed of 72 km/hour, to predict based on information six hours ahead of time, a spatial context of 432 km in all directions, which includes a 512 km X 512 km domain, was used for training.In order to train and validate the deep neural network, the produced radar data from the Korean Meteorological Administration was compared and evaluated. The model was trained to predict rainfall for the next 0-360 minutes using a combination of continuous GK2A satellite data and radar images captured every 30 minutes starting from 2 hours before the current time.The predictive models trained with different loss functions, including Huber loss, Cosh loss, and a combination of MSE and MAE with adjustable ratios, were compared based on their performance in predicting the thresholded rainfall intensities of 0.1, 1, 4, and 9 mm/hr, as evaluated by the critical success index (CSI). In addition, the rainfall intensities were classified into eight categories using a segmentation technique, and the performance of the models was analyzed accordingly.
Current status and future plan for KIM operational system
Authors: lee youngsu
Published: July 2023

Korea Institute of Atmospheric Prediction Systems(KIAPS) is currently developing a numerical weather prediction model, including a data assimilation system, to replace the Unified Model(UM). The KIAPS Integrated Model(KIM) consists of a spectral element-based non-hydrostatic dynamical core using a finite-volume method and physics packages. The data assimilation system adopted a hybrid 4D-EnVAR. 4D-EnVAR means that combined KIM VARiational data assimilation system(KVAR) and Local Ensemble Transform Kalman Filter(LETKF) data assimilation technique. Ensemble members currently uses 50 members. To evaluate the performance of the KIM, it is one of the important factors to understand the performance of system by operating and combining the individually developed systems. KIM Operational System(KOS) constructed a cycle experiments using the cylc meta-scheduler, which is widely used by various operational agencies and research laboratories. The cyclical experiments involves a data assimilation process every 6 hours, including KIM Package for Observation Processing(KPOP). The cyclical experiments were performed DA systems at 4 times a day, and 10-day forecasts are execute at 00 and 12 UTC due to model verification. Each task was written by python scripts and was configured to efficiently parallelize by using the cylc meta scheduler. Each task was configured pre- and post-processing progress and can be executed independently. Post processing contains visualization and remap from cubed-sphere grid to lat/lon grid. In addition, the grid remapped lat/lon grid data is used for visualization and displayed on the monitoring system for performance verification and stable operation of the numerical forecasting system. All of procedure are carried out automatically without any operation by user.
Introduction the status of Technology Development to Improve Drought Prediction on the Korean Peninsula
Authors: Park Hye-Sook , Jeong Jee-Hoon
Published: July 2023

Due to global warming and climate change, unusual weather phenomena are occurring frequently in various parts of the world, causing significant damage. For example, in 2022, Seoul on the Korean Peninsula recorded 381.5 mm of daily rainfall on August 8, breaking the record for the highest hourly and daily rainfall in 115 years since meteorological observations began in 1907. In addition, the heavy rainfall was concentrated in a small area for a short period of time, causing strong regional variations and making it very difficult to predict. Meanwhile, the winter of 2022 recorded the lowest January-February precipitation (6.1 mm) since 1973, and the southern region experienced the worst drought in more than 50 years, causing difficulties in agriculture and limited water supply, while the early tropical night and heat wave that began in June brought many socioeconomic damages.If extreme heat events persist due to global warming, they will lead to meteorological drought, which in turn will lead to agricultural drought, hydrological drought, and socioeconomic drought. In Korea, a joint task force team of the Korea Meteorological Administration, the Ministry of Environment, and the Ministry of Agriculture, Food, and Rural Affairs has been operating since 2015 to discuss and issue drought forecasts and warnings for each sector in order to systematically manage water at the national level and strengthen preemptive disaster response.   The Korea Meteorological Administration (KMA) has been conducting long-term research and development by establishing the Extreme Weather Research Center (Heat waves, Meteorological Droughts, and Chang ma (which is a component of East Asian Monsoon) since 2017 to secure core technologies and foster future human resources to recognize the seriousness of severe weather phenomena on the Korean Peninsula due to climate change and to prepare for them. The technologies developed at the Center are applied to the operational forecasts at KMAIn this study, we introduce the fundamental mechanisms of the meteorological drought occurrence on the Korean Peninsula, flash droughts prediction, droughts outlook techniques, and the current status of 3-6 month long-range forecasting techniques derived from the Droughts Center.
Causal drivers of Recurrent Rossby Wave Packets
Authors: Ali Mubashshir , Martius Olivia , Röthlisberger Matthias , Methven John , Zscheischler Jakob
Published: July 2023

The recurrence of upper-level synoptic-scale Rossby wave packets (RRWPs) at a location over a short period can lead to persistent surface weather that may drive extreme weather events. RRWPs were observed during several extreme weather events, for example, the 2010 heatwave over Russia, the 2004 and 2009 south-eastern Australian heatwaves, and the anomalous western European precipitation of 1983. RRWPs have been shown to lengthen hot, cold, dry and wet spells across the globe.
Motivated by the importance of RRWPs, this work investigates the causal drivers of RRWPs in the North Atlantic basin for summer and winter in a two-step approach. First, composite maps of top-30 RRWP events during 1979 – 2018 are used to study the characteristics of RRWP events and identify potential drivers using ERA-5 reanalysis data. The potential drivers are shortlisted following statistical significance in a bootstrapping approach. Subsequently, the causality of the shortlisted drivers is assessed using a Bayesian causal network (CN) framework for time series.
Composite maps reveal that RRWP events have a preferred seasonal phase configuration despite not having an explicit condition for phasing in the event selection. In winter, wavenumbers 3, 4 and 5 dominate with a hemisphere-wide wave pattern, whereas wavenumbers 5, 6 and 7 dominate in summer without a hemisphere-wide wave pattern. The causal networks reveal that local changes in atmospheric blocking and low wavenumber flow, termed background flow, are major drivers of RRWPs. RRWPs also have a feedback effect on background flow and blocks. The tropical-extratropical causal link only exists in winter and is indirect, mediated by the changes in the background flow over the Pacific. The causal drivers outlined in this study help to further the understanding of RRWPs.
Where are the coexisting parallel climates? Large ensemble climate projections from the point of view of chaos theory
Authors: Herein Matyas , Tel Tamas , Haszpra Timea
Published: July 2023

We review recent results of large ensemble climate projections considering them to be simulations of chaotic systems. The quick spread of an initially localized ensemble in the first weeks after initialization is an appearance of the butterfly effect, illustrating the unpredictability of the dynamics. We show that the growth rate of uncertainty (an analogue of the Lyapunov exponent) can be determined right after the initialization. The next phase corresponds to a convergence of the no longer localized ensemble to the time-dependent climate attractor, and requires a much longer time. After convergence takes place, the ensemble faithfully represents the climate dynamics. Concerning a credible simulation, the observed signal should wander within the spread of the converged ensemble all the time, i.e. to behave just as any of the ensemble members. As a manifestation of the chaos-like climate dynamics, one can imagine that beyond the single, observed time-dependent climate, a plethora of parallel climate realizations exist. Converged climate ensembles also define the probability distribution by which the different climate realizations occur. Large ensemble simulations were shown earlier to be credible in the sense formulated. Here in addition, an extended credibility condition is given which requires the ensemble to be a converged ensemble, valid also for low-dimensional models. Interestingly, to the best of our knowledge, no low-order physical or engineering systems subjected to time-dependent forcings are known for which a comparison between simulation and experiment would be available. As illustrative examples, the CESM1-LE (Community Earth System Model Large Ensemble) climate model and a chaotic pendulum are taken.
The impact of serial cyclone clustering on extremely high sea levels in the Baltic Sea
Authors: Rantanen Mika , Sinclair Victoria , Särkkä Jani , Johansson Milla , Laurila Terhi , Jylhä Kirsti
Published: July 2023

Extremely high sea levels in the Baltic Sea and the resulting coastal flooding events are typically caused by the passage of extratropical cyclones (ETCs). ETCs raise the sea level by their strong winds and low atmospheric pressure. The role of individual ETCs for the extreme sea levels in the Baltic Sea has been studied in some case studies, but less attention has been paid to the serial clustering of ETCs (SCC, the passage of multiple cyclones within a short period of time). In particular, little research has been done on whether extremely high sea level events in the Baltic Sea are typically caused by just one extreme ETC or by the combined effect of several consecutive ETCs. In this study, the role of SCC for the extreme sea levels in the Baltic Sea is investigated. 
We use objectively determined cyclone tracks from ERA5 reanalysis and sea level observations from four tide gauges: Kemi (Finland), Helsinki (Finland), Pärnu (Estonia) and Riga (Latvia). All ETCs from the October-March period in 1980-2019 that pass within 700 km of the tide gauge are included in the analysis. Clustering and non-clustering days are defined as days when the 7-day running sum of ETCs is ≥ 3 and 1, respectively. Then, SCC and single cyclone periods are defined by adding ±1 day to the dates of the first and last ETC around the clustering and non-clustering days.
We find that SCC periods tend to produce on average 30 cm higher sea level than the climatology at the tide gauges, and about six days after the SCC onset dates. In addition, the daily maximum sea level peaks about 40 cm higher during SCC periods than during single cyclone periods. Thus, this result implies that the SCC periods are typically associated with higher sea level than the periods when only one intense ETC passes the tide gauge. However, when we look at the extreme sea level events at the tide gauges, we find that in Helsinki, Pärnu and Riga about 40 % of the events can be attributed to the SCC periods and about 15 % to the periods when only single ETC passes the tide gauge.
Our results demonstrate that serial cyclone clustering is an important phenomenon for the occurrence of extreme sea levels in the Baltic Sea, and in fact relatively few extreme sea levels and the associated coastal flooding events in the Baltic Sea are caused by only one single ETC.
On the Relationship between Atmospheric Blocking and Heatwaves in Germany
Authors: Lohmann Richard , Ahrens Bodo
Published: July 2023

Atmospheric blocking describes a quasi-stationary weather pattern in midlatitudes which is characterised by a disruption of the westerly flow. Within the blocking anticyclone, large-scale subsidence of air effects dissipation of clouds. Intensive solar radiation during summer leads to a positive radiation balance causing heatwaves which are intensified by adiabatic warming of subsiding air. In case of longer persistence of the anticyclone, dry episodes can extend to droughts which intensifies the heat due to reduced latent heat flux. In this study, we investigate the relationship between blocking and heatwaves in Germany in reanalyses and a subset of selected CMIP6-Simulations. Using the heatwave definition and heatwave magnitude index by Russo et al. (2014), we find that heatwaves are related to the occurrence of blocking in Central Europe. The probability of heatwave occurrence is round about the factor 10 higher with blocking than without blocking. To quantify the value of blocking as predictor for heatwaves, the Heidke Skill Score (HSS) is calculated. The HSS shows that blocking gives an additional value on predicting heatwaves. Strong heatwaves (with a magnitude > 1.5 following Russo) have even a higher relationship to blocking. However, the HSS gives lower values compared to the consideration of all heatwaves. This is related to the low number of days with strong heatwaves compared to the high numbers of blocking days leading to a high number of false alarms. Comparing the relationship of blocking and heatwaves between reanalyses and historical CMIP6-Simulations yields that the models can reproduce the results of the reanalyses in general for all heatwaves. For strong heatwaves, some models underestimate the influence of blocking. Furthermore, we show that no model is simulating such a strong heatwave as 2003 occurred in Central Europe.
Evaluation of the urban climate model PALM-4U with conventional and non-conventional monitoring data for a case study Vienna, Austria
Authors: Zuvela-Aloise Maja , Hahn Claudia , Hollosi Brigitta
Published: July 2023

The newly developed Parallelized Large-Eddy Simulation Model for Urban Applications (PALM-4U) has been applied for the city of Vienna to simulate thermal conditions in urban environment and to evaluate its performance using different modelling configurations as well as variable spatial scales.
Model simulations were carried out for a representative clear-sky heat day in August 2022 for the entire city of Vienna with a spatial resolution of 20 m and for a selected residential area in the city with a spatial resolution varying between 1 and 10 m. The data related to geographical information and urban structures are based on high-resolution GIS data provided by the city of Vienna, including multi-purpose area map, street tree cadastre, digital elevation and surface model, which were combined with the national land cover data (Land Information System Austria - LISA) to account for the unresolved vegetation and Open Street Map to include building properties in surrounding areas of the city. Selected model configurations enable evaluation of model performance both on micro-scale taking into account variable building types, resolved vegetation and detailed surface properties as well as on city-scale including interaction with regional weather conditions and complex terrain.
The results for hourly air temperature were compared with the conventional weather stations of the national weather service and the city of Vienna. In addition, quality-controlled data from more than 1000 citizen weather stations from the company Netatmo available in Vienna were used to compare differences in temperature variability and spatial patterns. The results show high intra-urban variability during daytime, but distinct spatial pattern during the night.
In order to evaluate the temperature variations on micro-scale, a measurement campaign at the headquarter of the Austrian weather service using 25 low-cost weather stations equipped with LoRaWAN Dragino LHT65 sensors was conducted. The stations were positioned in the vicinity of different artificial and natural surfaces (e.g. grass, parking lot, street) and structures (e.g. concrete and green roof) and the retrieved data were used to evaluate temperature variations in the high-resolution model setup. Both, measurements and the model results, show high variability in air temperature during daytime and higher temperatures near building structures than vegetation. Due to extremely dry conditions, natural surfaces, such as free soil or low grass show high daytime temperatures as well.    
Tailored AGROmeteorological FORECAST for improving resilience and sustainability of Austrian farming systems under changing climate
Authors: Eitzinger Josef , Thaler Sabina , Atencia Aitor , Hann Patrick , Kubu Gerhard , Manschadi Ahmad M. , Lalic Branislava , Palka Marlene , Schneider Stefan , Sremac Ana Firanj , Trnka Miroslav , Trska Claus
Published: July 2023

Optimization of agricultural inputs in all relevant spatial and time scales by means of smart and precision farming options is considered in the project of AGROFORECAST as crucial for ensuring sustainable and resilient production in agriculture, protecting ecosystem services, enhancing biodiversity and food security as well as socio-economic conditions for the farmers. Despite increasing appreciation of the potential value of weather forecasts for agriculture, there is still a gap between what scientists consider as “useful” information and what users (e.g. farmers, advisory services, policy makers) recognize as “usable” in their decision-making processes. 
The main objective of this project was to combine stakeholder-tailored agrometeorological tools/indicators and weather forecasting of different lead times that can be used for optimizing agricultural decision-making in the face of changing climate and climate variability. A focus is laid on efficient use of inputs for crop production (water, fertilizer, agricultural chemicals) needed for smart and precision farming options while protecting (agro-) ecosystem resources and functions in order to identify suitable and, from a stakeholder perspective, acceptable adaptation and mitigation options. Beside the optimization/downscaling of seasonal forecasts, software applications (crop model and GIS-based spatial tool) for forecasting agrometeorological conditions by indicators were further developed and tested (incl. stakeholder involvement) against performance strengths and weaknesses/limitations at various locations and farmers field site. The results show that the performance of the applied tools and indicators depend mainly on a) weather forecast lead time b) regional climate conditions and c) type of impact indicators. Applications for crop management are promising in order to mitigate climate change impacts, cropping risks and negative environmental impacts in crop production (e.g. through reduced N-fertilization). Additionally, results of applications under ÖKS15 climate scenarios for selected case study sites were achieved.
North American Cold Spells Modulate North Atlantic Extratropical Cyclones and Extreme Weather in Europe
Authors: Leeding Richard , Riboldi Jacopo , Messori Gabriele
Published: July 2023

Recent research has established a statistical link between North American cold spells (CS) and concurrent wet or windy extremes in Europe. Here, we investigate whether such a link can be related to changes in the characteristics of north Atlantic extratropical cyclones (hereafter cyclones). Despite large regions of anomalous baroclinicity during periods of North American CS, the number of cyclones across the north Atlantic as a whole is comparable to climatology. We however find that CS over different North American regions are associated with different large-scale atmospheric configurations, that enhance the jet stream in the vicinity of the CS but result in different upper level wind anomalies in the east Atlantic. These in turn modulate the regional distributions and characteristics of cyclones in the north Atlantic and Europe. For eastern Canada CS, the north Atlantic jet extends over northern Europe, with the Atlantic storm track as a whole experiencing more intense cyclones which then affect France, the British Isles and Northern Europe. For eastern United States CS, the jet is displaced equatorward and extends over southern Europe, with a significantly heightened number of cyclones affecting Iberia, France and Southern Europe. For central Canada CS, the jet is displaced north of climatology and only partly extends over Europe, resulting in an anomalously high cyclone density in the eastern Atlantic and a higher number of cyclones affecting Iberia only. For eastern Canada and eastern United States CS, we observe a significantly heightened occurrence of cyclones undergoing explosive deepening. Our results provide a dynamical explanation for previous statistical findings on the concurrence of north American CS and wet or windy extremes over Europe.
Scanning Doppler lidar at Cabauw: study of the convective boundary layer in the summer of 2022
Authors: Knoop Steven , Theeuwes Natalie , Apituley Arnoud
Published: July 2023

A scanning Doppler lidar, the  Windcube200S (Vaisala/Leosphere), has been operating at our research site Cabauw since April 2021, to provide detailed measurements of the wind field, aerosols and clouds, in the framework of Ruisdael Observatory [1]. First measurements mainly focused on operational wind profiling (based on DBS scans). The phenomenon of the triplet storm in February 2022 (Dudley, Eunice, Franklin) was nicely captured by the Doppler lidar. Synergy with a Doppler cloud radar was demonstrated, providing wind profiles up and within clouds [2]. Doppler lidar wind profiles can also be combined with the in situ wind measurements in the tall mast up to 200m, for instance for low-level jet studies and climatology.
In this presentation we focus on a measurement campaign we performed in the summer of 2022 (June 21 to August 21), which was aimed to study the convective boundary layer. For this the Doppler lidar continuously performed vertical stare scans with an accumulation time of 1 s, interrupted each hour with 10 minutes of wind profiling (DBS scans) and a low-elevation azimuth scan (PPI) of 3 minutes. The vertical stare data nicely show the up- and downdrafts, together with the formation and presence of (shallow cumulus) clouds. We show a direct comparison between the vertical velocity data and high resolution large eddy simulations and numerical weather prediction model simulations, and discuss the possibilities in model development and validation. 
From the vertical stare data also turbulence characteristics, such as the variance and dissipation rate, can be extracted. From the variance the mixing height can be derived. We will apply a retrieval method of the vertical wind speed variance and dissipation rate including the effect of probe volume of the Doppler lidar [3], which we will validate by sonic measurements in the tall mast.
[1] https://ruisdael-observatory.nl/
[2] José Dias Neto, Louise Nuijens, Christine Unal, and Steven Knoop, Combined wind lidar and cloud radar for high-resolution wind profiling, Earth Syst. Sci. Data 15, 769, 2023, https://doi.org/10.5194/essd-15-769-2023
[3] Banakh, Smalikho, Falits, Sherstobitov, Estimating the Parameters of Wind Turbulence from Spectra of Radial Velocity Measured by a Pulsed Doppler Lidar, Remote Sens. 13, 2071, 2021, https://doi.org/10.3390/rs1311207
Meteorological forcing of unusually high glacier melt on James Ross Island, Antarctic Peninsula in summer 2022/2023: in-situ observations and WRF model simulations
Authors: Matějka Michael , Láska Kamil , Zdeněk Stachoň
Published: July 2023

Antarctic Peninsula (AP) glaciers experiencing mean summer air temperature near the melting point are highly sensitive to both long‑term climate variability and short-term but intense warm air advection events. Large scale flow during these events could be further modified by interaction with topography, e.g., by foehn development at the eastern coast of 1000 – 2000 m high AP mountain range. Foehn effect on glacier melt was extensively studied at the Larsen C Ice Shelf region. However, less attention was given to ablation events occurring at the northeastern coast, where AP mountains are less prominent, and where flow interacts also with complex topography of western Weddell Sea islands. In this contribution, we present an analysis of three pronounced melt events in summer 2022/2023 observed on the Davies Dome glacier (514 m a.s.l.) and a cirque-based Triangular Glacier (180 m a.s.l.), both located on Ulu Peninsula, northern James Ross Island. Melt events were identified and their intensity was quantified with an ultrasonic depth sensor data supplemented by snow and ice density observations. The selected events induced total snow/ice melt of ~1.19 m water equivalent (Triangular Glacier) and ~0.28 m water equivalent (Davies Dome) and significantly contributed to an anomalous ablation season 2022/2023 in this region. In-situ air temperature, wind speed, albedo, and net radiation observations allowed identification of crucial meteorological factors leading to snow and ice melt. Differences in melt regime of studied glaciers were further discussed. In addition to in-situ measurements, the Weather Research and Forecasting (WRF) model was run in a very high resolution for investigated events. The model output allowed analysis of synoptic-scale advection patterns leading to enhanced glacier ablation. An attention was given also to the effects of AP mountains and James Ross Island topography on incoming flow characteristics and possible foehn development.
„Klimaszenarien.AT“ - a strategy to new national climate scenarios in Austria
Authors: Schellander-Gorgas Theresa ,   ÖKS Steering Committee
Published: July 2023

Klimaszenarien.AT is an initiative started by 8 scientific and climate service partners in Austria with the aim of developing new national climate scenarios for Austria until 2026 („ÖKS26“).  The main goal is to consider both, a sound scientific basis at the latest state of research and users’ specific requirements concerning climate data and information. Activities of the initiative are, to a large part, carried out in funded research projects.
The workplan of Klimaszenarien.AT roughly defines two stages: The first phase (2021-2025) focuses on the generation of the regional climate scenario data , while the second phase (2023-2026) is dedicated to distillation and communication of climate information for stakeholders and users.
Stage one uses multiple sources of climate projection and reference data from global to regional scales and addresses specific research topics, such as the understanding of atmospheric processes or the linkage of large- and regional-scale impacts of climate change, with a special focus on mountainous areas.
Stage two focuses on the construction of climate information for various user contexts, in terms of main statements and on applicable formats for visualization and provision of the climate information. The initiative aims at serving the principle of use: The derived climate information shall not only be „useful“, i.e. reliable and relevant, but also „useable“, i.e. findable and accessible and, finally, „used“ by public, media, decision-makers and advanced users.  Hence, also the experiences of users with the predecessor, the Austrian „ÖKS15“ scenarios, are gathered within the framework of a comprehensive stakeholder process.
The two phases are closely related to each other and overlap in time. The goal of this concept is that the final outputs, i.e. the generic scenario data as well as the information and products derived therefrom, are understood as the fruit of collaborative efforts by the various actors.
The process of generating „ÖKS26“ is further related to a number of international activities, such as the (EURO-)CORDEX project and the D-A-CH-scenario project. The latter is a cooperation of the national weather services DWD (D), GeoSphere Austria (A) and MeteoSwiss (CH) with the aim to harmonize the new generations of national climate scenarios to the greatest possible extent and to avoid transborder inconsistencies.
A new guidance on measuring, modelling and monitoring the canopy layer urban heat island
Authors: Schlünzen K. Heinke , Grimmond Sue , Baklanov Alexander , Martilli Alberto , Masson Valéry , Miao Shiguang , Ren Chao , Roth Matthias , Stewart Iain
Published: July 2023

Urbanization influences the local climate by changing the natural surface energy balance affecting the regional temperature field. One of the best-known and widely studied phenomenon is the canopy layer urban heat island (CL-UHI) which is found in cities of all sizes. Specifically, night-time temperatures are often higher in urban areas than in the surrounding rural areas. The CL-UHI characteristics differ between cities, within a city and with time of the day and the season. Climate change induced warming in cities is similar to that experienced in rural areas, but modified by the CL-UHI.
The CL-UHI is an additional heat burden on top of background anthropogenic warming, and therefore an increasing focus of urban planners. Given this development, and in response to the request of the 18th World Meteorological Congress (Resolutions 32 and 61), experts from WMO GAW (Global Atmosphere Watch) Urban Research Meteorology and Environment (GURME) initiated in 2020 an expert team inviting more than 30 world-wide experts to contribute to a guidance on measuring, modelling and monitoring the CL-UHI [1]. Topics include a clear definition of the CL-UHI and clarifications of what it is not, causes of the CL-UHI (e.g. meteorological and morphological influences), methods to assess the CL-UHI intensity (measurements, modelling approaches) as well as CL-UHI application examples. The guidance also explains why the CL-UHI mitigation is only part of an answer to reduce urban heat problems. The guidance will serve as a useful reference for meteorologists, climatologists, meteorological administrative staff, and others interested in the CL-UHI.
[1] WMO (2023): Guidance on Measuring, Modelling and Monitoring the Canopy Layer Urban Heat Island (CL-UHI).
K.H. Schlünzen, S. Grimmond, A. Baklanov (edts.), World Meteorological Organisation, WEATHER CLIMATE WATER. 2023 edition. WMO-No. 1292, pp.88. https://library.wmo.int/doc_num.php?explnum_id=11537 last used 11.04.2023
Sensitivity analysis of the 2D VAR retrieval method in the application to the wind turbine wakes
Authors: Krutova Maria , Bakhoday-Paskyabi Mostafa , Reuder Joachim
Published: July 2023

Scanning lidars measure a wind field over a large area with a higher resolution than numerous anemometer installations would allow. The drawback is that a scanning lidar measures only the radial velocity – the projection of the actual velocity to the lidar's line of sight. Reconstructing the original wind field requires a retrieval procedure. Most of the retrieval algorithms were developed for homogeneous wind fields. While those algorithms estimate the free flow well, they do not preserve non-homogeneous structures such as wind turbine wakes.    A recently developed 2D-VAR algorithm [1]  utilizes the property of conventional retrieval methods to estimate the homogeneous flow and uses it as an input to the cost-optimization function. The cost-optimization retrieves the wake structures more accurately. While the solution for a homogeneous flow is stable, the result of the cost optimization is affected by the initial guess field, e.g., a uniform wind field based on the FINO1 or SCADA time series.   We perform a sensitivity analysis of the 2D VAR retrieval algorithm for lidar scans of the Alpha Ventus wind farm taken from the FINO1 platform during the OBLEX-F1 campaign. Partially covering September 2016, the dataset provides a range of wind speeds and directions to test the algorithm's performance under various conditions. The algorithm's sensitivity is evaluated for different initial guess fields. The retrieval algorithm is evaluated based on the agreement with the reference data: FINO1 cup anemometer or SCADA time series. The retrieval accuracy is described by comparing the radial velocity calculated from the retrieved field to the original lidar scan. The results show that the retrieved field near the wind turbine tends to agree with the SCADA series better than with the FINO1 series. The agreement to the SCADA data is the best when the initial guess is based on the corresponding turbine series. The radial velocity residuals are slightly biased and are primarily localized in the near wake. Whether it is a positive or negative bias depends on the intensity of the wakes.
 

[1] Cherukuru, N. W., Calhoun, R., Krishnamurthy, R., Benny, S., Reuder, J. and Flügge, M.: 2D VAR single Doppler lidar vector retrieval and its application in offshore wind energy, Energy Procedia, 137, 497–504, doi:10.1016/j.egypro.2017.10.378, 2017. 
Hydro-meteorological and impact characterization of floods in the Basque Country
Authors: Gaztelumendi Santiago , Egaña Joseba , Otxoa de Alda Kepa , Solsona Fernando , Santos Alonso Ruben , Stocker Christian
Published: July 2023

Severe weather phenomena affect the Basque society in many ways, from disruption in various sectors and substantial damages in infrastructure to human and economic losses. Flooding is, among others, one of the natural event that causes a relatively high impact in Basque Country, usually as a consequence of intense and persistent precipitation.
In this study, we focus on the analysis of flood impacts produced in our territory and their meteorological characterization, during the period 1996-2021. The final objective is to contribute to knowledge of impact processes, increasing awareness and preparedness during flood events.
Impact from meteo-climatic hazards depend on the nature of the meteo-climatic severe event and on the vulnerability of exposed human assets to this particular hazard. In this work we use, as a proxy for flood impact, damages data paid by Spanish Insurance Compensation Consortium in the Basque territory during a twenty five years period (1996-2020). Such data are conveniently prepared with different aggregation level in order to facilitate its analysis at basin level and to draw conclusions. Results are presented grouped per date, period, amount, damage type, location and other relevant characteristics from each analyzed area in combination with some meteorological aspects.
A meteorological analysis of main impact events is performed using synoptic classification, and other weather types classifications (type of precipitation, cloud systems and severe weather categorization).Hydro-meteorological parameters are analyzed mainly based on data coming from the Basque mesonetwork and other data acquisition system available in the area (Radar, Meteosat, etc..). In the Basque Country, rivers flows in two main watersheds, the Cantabrian and the Mediterranean. In the Cantabrian basins high precipitations rates and steep slopes promotes river flooding with certain regularity in a relatively high populated and industrial area promoting more than 90% of total economic losses. The rivers of the Mediterranean side have less flood incidence due to lower precipitation rates, relatively softer slopes and less population densities causing less than 10% of total impact.
A new bias-corrected EURO-CORDEX dataset for Hungary based on the HuClim database
Authors: Simon Csilla , Torma Csaba Zsolt , Kis Anna
Published: July 2023

Climate change is one of the greatest challenges we face today. Beside higher temperature values, an increase in the frequency and intensity of extreme weather events are likely to occur in the future, which is also highlighted by the latest IPCC report. Global and regional climate models (GCMs and RCMs, respectively) have become indispensable tools for climate research, but these model simulations are encumbered with uncertainty from a variety of sources. These uncertainties can be quantified and reduced by evaluating several RCMs together, as members of an ensemble, or by applying bias-adjusted results. In our research we focus on the signal of changes in climate extremes related to temperature and precipitation over Hungary based on raw and bias-adjusted data. An ongoing international initiative called CORDEX (COordinated Regional Downscaling Experiments) provides a large number of RCM simulations for 14 domains of the world. EURO-CORDEX is a sub-programme of CORDEX, covering the European domain and providing regional climate projections at a horizontal resolutions of 0.11° (about 12.5 km) and 0.44° (about 50 km). In our study 5 high-resolution RCMs (CCLM, HIRHAM, RACMO, RCA, REMO) are investigated from the framework of EURO-CORDEX. The simulations follow the radiative forcing scenario RCP8.5 and cover the period 1976–2099. The most important step of the research is the bias-correction of the raw RCM simulations by using the most accurate, measurement-based, high-resolution, homogenized and quality controlled HUCLIM dataset currently available for Hungary, which has not been used yet to produce an available bias-corrected database. The internationally accepted percentile-based quantile mapping method was chosen for the bias-adjustment and was performed on a monthly basis. As part of the study, the evaluation of the new database is presented here for two variables (daily precipitation and daily mean temperature).
Assessing Best Practices of Impact-Based Alerting in Europe and Asia: A Case Study Approach
Authors: Lowry Blaine , Ghimire Uttam , Bössner Stefan , Hoy Andreas
Published: July 2023

Project Background: The project ‘Assessing Best Practices of Impact Based Alerting’ takes a case study approach to assessing the progress that is being made towards implementation of an impact-based paradigm for hydrometeorological warnings in both Europe and Asia. National Meteorological and Hydrological Service (NMHS) agencies around the world have been strongly encouraged by the World Meteorological Organization (WMO) to transition their alerting programs from hazard-based to impact-based warnings (IBW). This is happening in the context of the Sendai Framework 2015-2030. Currently, at roughly the halfway point to the conclusion of the Sendai Framework, this project performs a ‘check-in’ on the progress of this transition at NMHSs and affiliated partners in both Europe and Asia. This investigation also comes in the wake of recent, high-profile flooding and extreme heat events in both Europe and Asia. The increasing frequency of extreme weather events due to climate change increases the need for a clear understanding of the requirements and obstacles for NMHS agencies as they transition to an IBW approach.
EMS presentation: At EMS 2023, we will present the findings of interviews conducted at NMHSs and associated key stakeholders, investigating the transition process to IBW in the UK, Sweden and Belgium in Europe and also Bhutan and Nepal in Asia. These findings contribute to a final project report (currently being developed as of April 2023). This report will be operationally relevant, speaking directly to NMHS agencies, key stakeholders (utilities, transport operators, health care practitioners, emergency management officers, etc.) and engaged members of the public alike. The focus will be on lessons learned and best practices from agencies who have already made the transition, while identifying concerns or roadblocks that may be holding back organisations who have yet to make the transition to IBW from doing so. The report will function as a tangible, relevant ‘handbook’ helping all NMHS agencies take the necessary steps, in their own national contexts, towards meeting the WMO recommendation.
Wind speed maps for Austria: An artificial-intelligence approach
Authors: Tilg Anna-Maria , Schicker Irene , Lexer Annemarie , Andre Konrad , Heidenhofer Martina
Published: July 2023

The crucial role of wind power in the future energy generation demands to investigate the influence of climate change on wind speed and the associated consequences for wind power. Especially in areas with complex terrain, there are still open research needs for wind energy in future climate (Clifton et al., 2022). To assess future wind climate, one requirement is the availability of a climatological dataset of wind speed with high spatial and temporal resolution to downscale wind speed from global and regional climate models (GCMs, RCMs). So far, no such dataset has been available for Austria. To fill this gap, a wind speed atlas for the past 30 years (1991 – 2020) is compiled for the diverse landscape of Austria, having flat and mountainous terrain, using a set of artificial intelligence (AI) methods.
A comparison of gridded wind speed data considering three baseline methodologies will be presented: The ‘Integrated Nowcasting through Comprehensive Analysis’ (INCA) model combining ERA5 and station observations, a generalized additive regression model (GAM) and a deep neural network (DNN) model with adapted loss function. All approaches are used to create a wind speed analysis for the years 1991 to 2020 with a spatial resolution of 1 km to 1 km for the territory of Austria. Furthermore, they consider the same station-observation dataset of 10-m wind speed measurements of the national weather service in Austria. Preliminary results from the validation against wind speed observations not used in the observation dataset will be shown as well. First results of the GAM and DNN baselines are promising. The uncertainty in interpolation given through the methodologies is, so far, within the expected range.
The availability of a wind atlas for Austria allows downscaling of climate projections and thereby the investigation of the climate change impact on future wind speeds and future wind power potential in Austria.
Reference
Clifton, A., Barber, S., Stökl, A., Frank, H., and Karlsson, T.: Research challenges and needs for the deployment of wind energy in hilly and mountainous regions, Wind Energ. Sci., 7, 2231–2254, https://doi.org/10.5194/wes-7-2231-2022, 2022.
Storylines simulations suggest intensification of recent European droughts in warmer climates.
Authors: Sánchez Benítez Antonio , Athanase Marylou , Jung Thomas , Goessling Helge
Published: July 2023

According to the latest IPCC report, under the ongoing climate change, extreme weather events in Western Continental Europe, including heatwaves and droughts, are becoming more prolonged, intense, and frequent, and are set to strengthen in a progressively warmer climate. Total changes observed in these extreme events can be discriminated between the relative contributions of dynamical changes – change in likelihood of weather patterns  – and of thermodynamic changes. While the former remains uncertain in future climate projections, the latter is more certain, with a robust and ubiquitous rise in future land-surface temperatures.
To separate and analyze both contributions, we employ the nudged storyline approach, in which our CMIP6 coupled climate model (AWI-CM1) is nudged towards the observed large-scale free-troposphere dynamics using different climate background conditions and initial states. As a result, the same weather conditions, including jet stream and blockings, are simulated in different climates (pre-industrial, present and future 2, 3 and 4 ºC warmer climates). This methodology provides a very efficient manner of making the consequences of climate change more comprehensible to non-experts and experts alike, as extreme events fresh in people's memory are simulated in different climates with just moderate computational resources.
This configuration reproduces recent extreme events, like the 2019 or 2022 European heatwaves and the ongoing European drought. Our simulations reveal an intensification of these hot and dry extreme events both from preindustrial to present (attribution) and from present to warmer (projection) climates. Moreover, taking advantage of our methodology, observed and projected changes can mainly be attributed to thermodynamic changes, with dynamical changes playing a minor role.