bluuebunny/crossref_metadata_2025 huggingface dataset:
How well have CMIP3, CMIP5 and CMIP6 future climate projections portrayed the recently observed warming?
Authors: Carvalho David , El Akkraoui Amal , Errico Ronald M. , Bosilovich Michael , Privé Nikki C.
Published: July 2023

Despite the dire conclusions of the Intergovernmental Panel on Climate Change (IPCC) Assessment Reports in terms of global warming and its impacts on Earth’s climate, ecosystems and human society, a skepticism claiming that the projected global warming is alarmist or, at least, overestimated, still persists. Given the years passed since the future climate projections that served as basis for the IPCC 4th, 5th and the upcoming 6th Assessment Reports were released, it is now possible to answer this fundamental question if the projected global warming has been over or underestimated.This work presents a comparison between CMIP3, CMIP5 and CMIP6 future surface temperature projections and observations, by comparing 21 years of CMIP3, 15 years of CMIP5 and 6 years of CMIP6 future temperature projections with observations. It should be highlighted that only the future temperature projections from the CMIP scenarios are under evaluation in this study, not the scenarios per se.The results show that global temperature increase over land areas projected by all CMIPs and future climate scenarios here analyzed are well in line with the observations, being noticeable that the observed warming is closer to the upper level of the projected ones. Moreover, CMIPs project a global warming slightly lower than the one shown by  observations, and CMIPs climate projections that consider future climate scenarios with higher GHG concentrations appear to be the more realistic ones.These results show that CMIPs future warming projections have been slightly conservative up to 2020, which can suggest a similar cold bias in their warming projections up to the end of the current century. However, given the short future periods here analyzed, inferences about warming at longer timescales cannot be done with confidence, since the models internal variability can play a relevant role on timescales of 20 years and less.
User adapted climate projections
Authors: Hygen Hans Olav , Dyrrdal Anita Verpe
Published: July 2023

There is a distinct need for climate information and climate projections in society. These needs cover a wide range of use from key information on expected changes to the full range of projections in terms of data.
In climate research the realization that one needs a wide range of projections based on combinations of different models (e.g. combinations ofGCM and RCM) to create a wide ensemble of futures is necessary. This leads to enormous streams of data. In Norway, the new set of national projections will include about 550 simulations with various combinations of emission scenarios, variables, model combinations, bias adjustments methods, hydrological models etc.
As stated above there is a wide range of needs from simple requests to complex impact modelers capable of using the full model output. The Norwegian Centre for Climate Services (NCCS) today serves either end of this spectrum fairly well. NCCS produce Climate fact sheets on a county level, which serve the simpler needs, but also provide the full model ensemble. But the interim users that need more than simple summaries and are incapable of using the full ensemble are not served sufficiently. The result can be, as was shown at EMS 2022, basically to use a single realization for future climate in impact research, despite the access to large ensembles.
Climate services, as e.g. provided by NCCS, should provide user-adapted pre-selection of climate projections; so-called representative projections. To do this in the right way, user needs should be better understood and appropriately grouped. At this stage NCCS do not provide such representative projections, but we would like to raise the discussion on how to go forward.
Effective Use of Meteorological Illustration in Communicating with the Public
Authors: Steelman Diana , Maruri Mercedes
Published: July 2023

The adverse phenomena of ocean-meteorology can be complicated and difficult for people not from a meteorological background to understand. Scientific illustrations create a base knowledge in meteorological concepts so that in adverse situations, the public can evaluate the risks and how to act in order to reduce the socioeconomic impacts. 
In collaboration with the Universidad del País Vasco(UPV/EHU) and the basque meteorological service(Euskalmet), the principle objective of this project is to investigate which are the best technical methods of scientific illustration to explain and advise about the risks of different adverse phenomena. The work will center around the phenomena most frequent in the Basque Country and the highest priorities for Euskalmet, the regional meteorological service who publish the results. This project will create a collection of illustrations for Euskalmet for their different communication channels. Such illustrations may consist within scientific articles, books, information pamphlets, social media, diagrams, or posters. The objective within each work is to explain the content of the phenomena in an attractive and accessible way to any potential audience. In order to achieve this objective, the communication between the illustrator and environmental engineer must be fluid. The experience of this collaboration will enhance the learnings from past meteorological illustrations and how they have evolved over time, which is the first and crucial start to this work. 
In this historical study, we will analyze the evolution of meteorological understanding alongside the graphic techniques used within their context (scientific, informative, educational) up to what is being used in the present day. This work aims to follow this year’s motto of the World Meteorological Organization “the future of weather, climate, and water across generations”, learning from the past to project into the future, using the most effective and modern techniques to make the population more aware of meteorology in general, climate change, and the socio-economic influence the weather has on our lives.
Evaluation of Cold Wave Impact-based Forecasts in South Korea
Authors: Park Bo-Geum , Youn Min-Jeong , Park Byoung-Kwon , An Yong-Jun , Park Eun-Ju , Kim Eun-Jin , Lee Hyun-Sook , Park Seong-Chan
Published: July 2023

In recent years, cold waves have caused the increase in the number of patients, hospitalizations and deaths during the wintertime in South Korea. To mitigate these damages, the cold wave impact-based forecasting can be a measure to alleviate the victims by alarming the warnings to public before it happens.
Since 2020, the Korea Meteorological Administration has been providing operational cold wave impact-based forecasts, categorizing four levels of impact (attention(blue), caution(yellow), warning(amber), and danger(red)) and offering different actions. Thresholds for impact levels are determined by two criteria: when the daily minimum temperature drops sharply from the previous day or when it remains below a certain threshold for more two consecutive days. In addition, these thresholds are classified by region to provide cold wave warnings that considers local climate characteristics.
Through the case studies of winter in 2020(’20-’21) and 2021(’21-’22), we have examined the correlation between cold-related illnesses and levels of impact. The results show a correlation coefficient of 0.51 between the forecasts and cold-related illnesses above the amber. To study the lagged effect of cold waves, we also calculated the correlation coefficient for the lag of 0 to 3 days. The results show that the correlation coefficient for the one-day lag was 0.56 in the red, which is higher by 0.27 than that with 0-day lag(0.29) for the year of 2020 case. The coefficient for 1-day lag is 0.73 in the red, which is also higher by 0.08 than the coefficient(0.65) with 0-day lag for the year of 2021 case. Although further study with longer data sets, this result shows that the likelihood of cold-related illnesses become higher at the one day after a strong cold wave occurs.
Key words: cold wave, impact-based forecast, levels of impact, post-hoc analysis, evaluation.
This study was conducted as part of the project “Advancement of Regionalized Impact-based Forecasting Service” (KMA2018-00723) by the Impact-based Forecasting Promotion Team of the Korea Meteorological Administration.
The dynamic of precipitation extremes in Berlin and Brandenburg based on a generalized Pareto distribution
Authors: Bart Frederik , Ulrich Jana , Scherer Dieter , Meier Fred , Hellmann David
Published: July 2023

In recent years, Berlin and its surrounding area has experienced multiple intensive precipitation events, which caused significant damage and severely impaired the local infrastructure. An extreme value analysis of the available station data could improve the understanding of such events and provide valuable information for risk assessments in the region. Additionally, results gathered from this analysis will serve as a reference for similar evaluations with the Central European Refined analysis (CER), a gridded dataset generated via dynamical downscaling of ERA5 data using the Weather Research and Forecasting model. In this study, we assess the spatiotemporal dynamics of extreme precipitation event days in Berlin and Brandenburg using a generalized Pareto distribution (GPD).  Daily precipitation data of the last 30 years was extracted at 137 stations of the German Meteorological Service. For all stations with a sufficient amount of data a seasonal time-dependent threshold was defined and independent exceedances were extracted using an automatic declustering scheme. The resulting threshold series was used to fit a GPD at each location with a time-dependent scale parameter to investigate temporal changes in extreme event days. After evaluating the goodness of fit the distribution model was used to calculate seasonal 2-, 10-, and 20-year return levels. The results indicate a high regional variability especially for the 20-year precipitation extremes with slightly higher values around Berlin reaching up to 130 mm d-1 in the summer. Return levels also tended to be higher in the northern parts of Berlin and Brandenburg during winter and in the south during spring.
Current status of SINFONY - the combination of Nowcasting and Numerical Weather Prediction on the convective scale at DWD
Authors: Blahak Ulrich ,   Team SINFONY
Published: July 2023

The development of DWD's new Seamless INtegrated FOrecastiNg sYstem (SINFONY) has matured and a number of components have been run  continuously in near-realtime on a daily basis during the last two convective seasons. This presentation will give a short overview on the system components itself and their current status, and will report on the results of this years convective season.
There are different "optimal" forecast methods for different forecast lead times and different weather phenomena.Focusing on precipitation and convective events up to some hours ahead, we developed

a) radar Nowcasting ensembles for areal precipitation, reflectivity and convective cell objects,
b) a regional ICON-ensemble model with extensive data assimilation of high-resolution remote sensing data (3D radar volume scans of radial winds and reflectivity, cell objects, Meteosat VIS channels and lightning) and hourly new rapid update cycle forecasts (SINFONY-RUC-EPS) on the km-scale,
c) optimal combinations of Nowcasting and NWP ensemble forecasts in observation space, which constitute the seamless forecasts of the SINFONY. Gridded combined precipitation and reflectivity ensembles are targeted towards hydrologic warnings. Combined Nowcasting- and NWP cell object ensembles help evolve DWD's warning process for convective events towards a flexible "warn-on-objects",
d) systems for common Nowcasting and NWP verification of precipitation, reflectivity and objects. In particular the cell object based verification will provide new insights into the representation of deep convective cells in the model.

For b), new innovative and efficient forward operators for radar volume scans and visible satellite data (SEVIRI-VIS) enabledirect operational assimilation of these data in an LETKF framework. In late summer 2022, we finally could also activate the SEVIRI-VIS data in the daily RUC. Advanced model physics (2-moment bulk cloud mircophysics) contribute to an improved forecast of convective clouds. A stochastic PBL scheme has been developed, but is not yet in daily use.
For c), the SINFONY-RUC-EPS outputs simulated reflectivity volume scan ensembles of the entire German radar network every 5' online during its forecast runs. Ensembles of composites and cell object tracks are generated by the same compositing and cell detection- and tracking methods/software packages which are applied to the observations.
Considerable improvements in the RUC compared to the 2021 season lead to the situation that RUC starts to outperform Nowcasting already after about 1 hour lead time, both for areal Nowcasting and cell object Nowcasting. Life-cycles of simulated convective cells proved to be surprisingly realistic, although some problems in details of cell organization and cell size remain and need to be looked at.
Other presentations from SINFONY team members will give more details about particular SINFONY components.
Early spring droughts in Central Europe: Indications for atmospheric and oceanic drivers
Authors: Mayer Konrad , Haslinger Klaus
Published: July 2023

Central Europa has faced particularly dry early springs recently. Droughts in March and April are causing substantial impacts along the hydrological cycle. Especially agriculture is vulnerable at the beginning of the growing season, when sufficient moisture supply is demanded. In a recently published paper (Haslinger and Mayer 2023), we establish a link between early spring precipitation anomalies for the period 1860-2020 over Central Europe and driving large-scale atmospheric circulation conditions. Two major drought events were identified within this period, a recent one from 2005 to 2020 (and ongoing) and one within the 20th century from 1926 to 1950 with sustained negative precipitation anomalies in early spring, accompanied by two additional minor events. These were associated with the East Atlantic/Western Russia surface air pressure pattern in its positive phase, having a positive pressure anomaly extending over the British Isles and southwards to Central Europe and a negative anomaly over northwestern Russia. Consistent with literature, this pattern was identified as the main driver for early spring droughts. From further explorative analysis we inferred, that positive anomalies in sea surface temperatures in the western Atlantic lead to a Rossby wave response, resembling the East Atlantic/Western Russia pattern. These warming patterns follow internal Atlantic multidecadal variability. But, anthropogenic warming appears to be superimposed due to a weakening of the Atlantic meridional overturning circulation leading to stronger warming in the western Atlantic.
The presented study was published in Atmospheric Science Letters:
Haslinger, K., & Mayer, K. (2023). Early spring droughts in Central Europe: Indications for atmospheric and oceanic drivers. Atmospheric Science Letters, 24 (2), e1136. https://doi.org/10.1002/asl.113
Analysis of suitable weather conditions for the operation of HAPS (High Altitude Pseudo Satellites)
Authors: Lang Jürgen , Gelhardt Ulrike , Anger Falk , Wetter Thomas , Beckmann Björn-Rüdiger
Published: July 2023

Remote-controlled airplanes are increasingly being used for special purposes. For example, the use of stratospheric platforms for telecommunications purposes is planned. These so-called HAPS (High Altitude Pseudo Satellites) are lightweight aircraft-like vehicles with very large wingspans. They fly very slowly, are powered by hydrogen and can remain in the stratosphere for several days to several weeks. The OBeLiSk project, an R&D project funded by  the Federal Aeronautical Research Programme (LuFo VI-1), is currently developing an operational concept for safe and efficient airspace integration of such stratospheric platforms. Due to the structural limitations imposed by the lightweight design, HAPS can reach their limits very quickly in certain weather conditions. This applies in particular to operations at the airport during take-offs and landings. The limit values above which weather-related limitations can lead to massive impairments or even structural fractures of the HAPS are specified by the HAPS designers.
In the analysis presented here, one of the specifications was that certain wind speeds must not be exceeded during take-offs and landings and that no precipitation must occur. The specified limits can be used to define "potential operating hours", i.e. hours during which the weather situation at an airport allows HAPS to take off or land safely. Based on hourly measured values of a long-term period, frequencies of potential operating hours at airports geographically distributed over Germany were analysed. As expected, a minimum of potential operating hours in the winter months and a maximum in the summer months were observed when considering multi-year mean annual cycles. For the planned operational concept, the multi-year mean diurnal variations were of particular interest in order to find out which times of day are suitable for HAPS take-offs and landings. The results here were largely independent of the geographical location of the airports in Germany.  There was a maximum of potential operating hours at night in spring, summer and fall and in the late afternoon in the winter months.
The fact that wind plays a significant role in weather-related restrictions was to be expected. However, an additional sensitivity analysis showed specifically how many additional potential hours of operation could be achieved if the maximum limit at which HAPS could still be operated safely were increased by, say, one node. In this way, specific recommendations can be made to HAPS designers. In addition, the analyses can identify airports that are particularly well suited for conducting HAPS take-offs and landings.
Attributing Venice Acqua Alta events to a changing climate and evaluating the efficacy of MoSE adaptation strategy
Authors: Faranda Davide , Alberti Tommaso , Coppola Erika
Published: July 2023

We use analogues of atmospheric patterns to investigate changes in the three most devastating Acqua Alta (flooding) events in the lagoon of Venice associated with intense Mediterranean cyclones occurred in 1966, 2018 and 2019. Our results provide evidence that changes in atmospheric circulation, although not necessarily anthropogenically driven only, are linked to the severity of these events. We also evaluate the cost and benefit of the MoSE system, which was designed to protect against flooding. Our analysis shows that the MoSE has already provided protection against analogues of the most extreme events, which occurred in 1966, while for 2018 and 2019 events our analysis is non-conclusive because of the lack of analogues situations of those events.  These findings have significant implications for the future of Venice and other coastal cities facing similar challenges from rising sea levels due to extreme events. Our study represents one of the first examples that goes beyond identifying the circulation drivers of extreme events to quantifying the changes and their impacts. The framework we presented is general and can be applied to other case studies. However, our study also has limitations, including the limited database of sea-level for the past, the limited analogues used, and the fact that we did not use climate models. Despite these limitations, our study provides important insights into the attribution and impacts of extreme events, which are crucial for developing effective mitigation and adaptation strategies. We hope that our work will inspire future research and inform policymakers in their efforts to reduce the risks associated with extreme events.
Ice nucleation by anthropogenic aerosols downwind of industrial point sources of air pollution
Authors: Toll Velle , Rahu Jorma , Keernik Hannes , Trofimov Heido , Voormansik Tanel , Manshausen Peter , Hung Emma , Michelson Daniel , Christensen Matthew , Post Piia , Junninen Heikki , Lohmann Ulrike , Watson-Parris Duncan , Stier Philip , Donaldson Norman , Storelvmo Trude , Kulmala Markku , Murray Benjamin , Bellouin Nicolas
Published: July 2023

Satellite observations reveal the glaciation of supercooled stratiform liquid phase clouds by anthropogenic aerosols acting as ice-nucleating particles downwind of industrial aerosol point sources. Glaciation events are observed downwind of oil refineries, coal-fired power plants, cement, metal smelting and processing, chemical plants, and other anthropogenic air pollution sources in Europe, Asia, North America and Australia. Glaciation leads to snowfall, reduced cloud cover and reduced back-scattering of solar radiation to space. The polluted areas with decreased cloud cover are plume-shaped, with a distinctive head pointing towards the pollution source, similar to aerosol-polluted cloud tracks in liquid-water clouds (Toll et al 2019 Nature https://doi.org/10.1038/s41586-019-1423-9). Moreover, heavily polluted areas derived by simulating aerosol dispersion from strong anthropogenic aerosol point sources overlap with the areas of glaciation, snowfall, and decreased cloud cover strikingly well. These lines of evidence suggest that anthropogenic aerosols are the cause of the observed glaciation events.
Glaciation-induced snowfall downwind of aerosol sources is observed using ground-based precipitation radars, and tracks of snow are also seen on the ground in satellite imagery. Thus, at least locally, anthropogenic ice nucleating particles could significantly affect precipitation amounts. At multiple aerosol sources, glaciation events are more frequent than polluted tracks in liquid-phase clouds. Thus, at least locally at some aerosol sources in the middle and high latitudes, the warming effect induced by aerosols acting as ice-nucleating particles likely exceeds the cooling effect induced by aerosols acting as cloud condensation nuclei. Further research is needed to quantify the global radiative forcing by anthropogenic ice nucleating particles.
Early Warning of Drought: Climate Watch Advisories for the WMO RA VI Region
Authors: Bissolli Peter , Rösner Stefan , Körber Maya
Published: July 2023

The German Meteorological Service (Deutscher Wetterdienst, DWD) leads the climate monitoring activities within the Regional Climate Centre Network of the WMO Regional Association (RA) VI Region (Europe). One of its mandatory functions is the issuance of Climate Watch Advisories (CWAs). These are early warning advisories on weather and climate events in the extended-range-forecast (2-4 weeks), such as heat and cold waves, heavy precipitation periods and drought, all within Europe / RA VI. The advisories are based on expert assessments of climate monitoring and extended forecast results. Users of these advisories are National Meteorological and Hydrological services (NMHSs) in the RA VI Region. It is up to the NMHSs to turn CWAs into tailored national advisories or warnings to their end users.
Drought belongs to the types of events, which are very challenging for early warning. This is due to the various categories of drought (meteorological, hydrological and agricultural drought), its slow onset, its variability in duration in the atmosphere and at various soil depths, its dependency on various parameters (precipitation, temperature, evaporation, soil moisture, heterogenous geographical climate conditions, seasonal cycle), and its variety in impacts in various economical sectors (health, agriculture, energy, forest fires etc.) and different levels of vulnerability from country to country. 
Given the complexity of the drought phenomenon, an early warning approach for Climate Watch Advisories has been chosen, which has some restrictions. The advisories refer to meteorological drought, while hydrological and agricultural aspects are considered in national advisories. For meteorological drought, precipitation totals, anomalies and percentiles seem to be the most useful variables, rather than drought indices. Since the time scale of Climate Watch Advisories is subseasonal, precipitation variability of the past 30 days is taken from monitoring products and for the next 2-4 weeks from extended forecast products.
For the future, the subjective assessment (expert decision after having looked at all available products) will be replaced by an objective approach (fixed criteria are used as input for an automatic process).
In this presentation, some examples of drought advisories will be analysed and the concept of the objective approach will be described.
A Novel High-Resolution AI-based Global Precipitation Forecasting System
Authors: Gabler Marvin Vincent , Wuillaud Jair , Taheri Shahraiyni Hamid , Neupert Daniela , Grigoryev Alexey , Almeida Rodrigo , Galimzhanov Azamat , Hernandez Gabriel Martin , Daubinet Jordan Dane , Ekhtiari Nikoo , Song Roan John , Dudbridge Peter , Tarakci Emrecan
Published: July 2023

In this study, we present Jua’s Vilhelm, an innovative high-resolution AI-based global precipitation forecasting system. Vihelm exhibits significant improvements over existing state-of-the-art numerical models for prediction of binary precipitation (precipitation events) of up to 48 hours in advance, demonstrating superior performance when compared to the well-established Integrated Forecast System (IFS) model. Leveraging a combination of cutting-edge deep learning techniques and an in-depth understanding of physics, Vilhelm generates high-resolution hourly global predictions for surface parameters on a 1x1km grid. Beyond precipitation, the model is particularly adept at forecasts for a number of additional critical surface parameters including wind speed, direction and air temperature. This study focuses on its performance on precipitation prediction, notably the speed in which forecasts can be produced. The model runs in a matter of seconds, enabling the execution of hundreds of ensemble runs within a small number of minutes, an accomplishment previously unattainable. To assess the performance of Jua Vilhelm against Numerical Weather Prediction (NWP) models, we selected the IFS model of the European Centre for Medium-Range Weather Forecasts (ECMWF) as a suitable comparison. The ECMWF’s ERA5 reanalysis dataset was employed as a benchmark for evaluating the Vilhelm model on a global scale, using its full 0.25-degree resolution. We benchmarked both models at 6-hour intervals for multiple initial conditions for one year. Various metrics (Accuracy, Precision, Recall, Heidke Skill Score, F1 Score, True Negative Rate and False Alarm Rate) were used for comparative analysis between IFS precipitation forecasts and Vilhelm’s model. Vilhelm’s precipitation forecasts showed better performance than IFS over all metrics for prediction of precipitation events. Furthermore, precision, recall and P-R Curve of Vilhelm model for prediction of precipitation events were calculated using SYNOP (Surface Synoptic Observations) data as ground truth data. The results demonstrated the high performance of Vilhelm model. The results showed that development of Jua Vilhelm marks a significant advancement in the field of weather forecasting, offering unprecedented accuracy and speed.
Evaluation criteria for co-creation processes in climate services - validation by practitioners
Authors: Schuck-Zöller Susanne , Keup-Thiel Elke , Bathiany Sebastian , El Zohbi Juliane , Rechid Diana , Reith Florian , Timm Esther
Published: July 2023

National and international climate services support adaptation to climate change. Climate services should aim to deliver climate service products, which are useable, useful, accurate and suitable for users. The advancement of effective adaptation measures to climate change, therefore, requires continuous interactions between climate service providers and users of the products. Good practices for the design of climate services include transdisciplinary approaches and co-creation of climate service products.
To assess the effectiveness of this co-creation endeavours, evaluation is crucial. The concept of formative evaluation aims at assessing the co-creation of science-based climate services during the product development process with the intention to reflect and readjust the ongoing process.
Evaluation criteria for this formative evaluation were looked at in the project NorQuATrans (Normativity, Objectivity and Quality Assessment of Transdisciplinary Processes, https://www.hicss-hamburg.de/projects/NorQuATrans/index.php.en) doing accompanying research with the knowledge transfer project ADAPTER (ADAPT tERrestrial systems, https://adapter-projekt.org/). In ADAPTER, simulation-based climate service products have been developed together with practitioners from the agricultural sector.
As a result of this cooperation, a formative evaluation scheme of 17 quality criteria for all the different sub-processes in climate service development was created, based on both empirical and theoretical work. To these 17 quality criteria, 72 related evaluation aspects were assigned and can be assessed by questions.
In the following step we validated the formative evaluation scheme together with practitioners experienced in co-creation of climate services. For this validation we focused on the most important quality criteria to avoid overloading.
After pretesting several notions and terms, a survey was organized. Based on the results of the survey, the evaluation scheme was adapted and extended with some more evaluation aspects.
The poster will present results of the pretest and questionnaire and give some insights on differences in the attitude of practitioners and scientists towards co-creation and evaluation endeavours. Challenges of formative evaluation will be addressed.
Machine Learning-Based Nowcasting of Convective Storm Impacts on a Pan-European Scale
Authors: Pulkkinen Seppo , Myllykoski Heikki
Published: July 2023

Convective storms and the associated heavy rainfall, flooding, hail, wind gusts and lightning can result in significant damage to property and loss of lives. Thus, there is a need for accurate prediction of the future location and severity of such storms (i.e. in the sub-kilometer resolution for the next hour) to assist the decision making of civil protection authorities. The typical approach to produce such nowcasts is to identify storm cells as separate entities from radar images, which provides a natural way for associating the storm attributes with its severity. Following this approach, we have implemented a set of pan-European nowcast products in the TAMIR and EDERA projects funded by the EU Civil Protection Mechanism. This has been done by combining a cell tracking method with a random forest-based machine learning (ML) model and a Kalman filter model. In the nowcast products, storm cells are identified from the OPERA radar composites. The ML model is used for predicting the storm severity level. It is trained using a large database of meteorological features and weather hazard reports during summer months (May-September) between 2018-2022. The storm features include basic cell and track properties (i.e. area and age), lightning flash and wind observations, and also indicators of convective potential from ERA5 reanalyses. The target variable for training the ML model is the storm hazard level. The hazard level estimation is done based on the distances and time delays between the storms and the associated weather hazard reports obtained from the European Severe Weather Database (ESWD). We have trained different ML models against the hazard levels estimated for each event type (e.g. heavy rain, lightning and severe wind gusts). The above models are combined with a Kalman filter-based methodology to produce probabilistic nowcasts of future storm locations together with their severity level. The added value of such nowcasts for decision making is demonstrated with case studies and relevant verification metrics. Finally, we demonstrate how the nowcasts can be combined with different exposure layers to translate them into predictions of actual storm impacts.
Resolving the interannual variability in climate prediction data for statistical climate risk assessments
Authors: Schlögl Sebastian , Klein Gereon , Trefalt Simona , Gutbrod Karl
Published: July 2023

Climate prediction data from e.g., CMIP6 become more important in the future as companies, cities and municipalities must mitigate and adapt their processes and infrastructure to a changing climate. Regulatorily frameworks already exist for large companies (e.g., regulations from the Corporate Sustainability Reporting Directive (CSRD) or the EU taxonomy) and will be also affecting small and medium-sized enterprises in the future.   

One limitation of these climate prediction data is the lack of properly resolving the interannual variability and hence a loss of information regarding the uncertainty of climate data.  

Therefore, climate prediction data have been combined with data from the reanalysis model ERA5 from the ECMWF. This dataset provides a realistic interannual variability from 1940 until now with a horizontal resolution of 30 km as ERA5 is driven by measurements and satellite imagery.   

The combination of climate prediction data and the reanalysis data from ERA5 are the basis to calculate location-specific climate risks of individual variables and apply the uncertainty of the interannual variability. In this study, the climate change signal is added to the hourly time series of the ERA5 dataset allowing the calculation of climate indices such as e.g., number of tropical nights, number of hot days, or cooling/heating degree days within one time period in the future. Furthermore, this approach allows to estimate the probability that a certain climate index reaches a critical threshold. For example, the probability that the yearly number of tropical nights is higher than 5 in the time period 2070 – 2099 for the RCP8.5 emission scenario is estimated with 25 % for the location London, UK.  

Climate prediction data can be further downscaled to 10 m horizontal resolution including heat maps from cities to resolve the urban heat island effect. This downscaling approach is of high relevance for decision makers in cities as e.g., the number of tropical nights (a proxy for heat related mortality during heat waves) strongly varies in the city.  

The change of climate indices, precipitation sums and events, wind speed and storms in a future climate for different emission scenarios and time periods create a reliable information basis for city planners and companies, which are obligated to report their climate risks according to the EU taxonomy.    
Verification of the weather forecast of seven weather forecast providers for 500 locations worldwide
Authors: Schlögl Sebastian , Wenzel Caspar , Gutbrod Karl
Published: July 2023

The numerical weather forecast has been continuously improved within the last decades due to a) improved subgrid parameterisations, b) more precise initial conditions (e.g., satellite imagery) and c) more computational power allowing a finer grid resolution.  

Weather forecast providers typically rely on raw weather forecast models on the market in combination with own developed post-processing routines including e.g. weather stations and AI techniques to increase the quality of the forecast.  

In this study the weather forecast of seven different weather forecast providers was verified at 500 measurement locations worldwide for the year 2022. The analysis was conducted for air temperature, precipitation, wind speed and direction and air pressure for the forecast period 1 – 6 days. Forecast data were verified against METAR measurements in hourly temporal resolution.  

Error metrics such as mean absolute error (MAE), mean bias error (MBE), Pearson correlation, Heidke skill score (HSS), Probability of detection (POD) and False alarm rate (FAR) have been calculated for all weather forecast providers. 

The MAE for the 12 – 35 h air temperature forecast of the seven different weather forecast providers ranges between 1.26 K and 2.06 K, whereas three providers showed values below 1.5 K. The percentage of MAE values lower than 1.5 K in the 1-day forecast ranges between 67 % and 35 %, showing a high difference in the post-processing routines of the different weather forecast provider.  

The forecast quality is lowered with increasing forecast horizons due to the physical limitations of the weather forecast. For example, the best provider for the 12 – 35 h air temperature forecast showed a MAE of 1.26 K for the first day, 1.34 for the second day and 1.43 for the third day. This results additionally shows that the 3-day air temperature forecast of the best provider is even better than the 1-day air temperature forecast of 5 (out of 7) analysed weather forecast providers.  

The results in this study show a broad quality of weather forecast providers, indicating that some providers rely on simple raw weather forecast models, whereas other provider lower the errors by post processing routines based on AI techniques and additional weather stations.  
A multi-threshold-based identification and tracking of Mesoscale Convective Systems in a multi-satellite precipitation product
Authors: Rajagopal Manikandan , Skok Gregor , Russell James , Zipser Ed
Published: July 2023

Traditional tracking algorithms use a single threshold in a precipitation or infrared brightness temperature field to identify and track precipitation systems. Though valuable, these algorithms have limitations in tracking Mesoscale Convective Systems (MCSs) that sometimes occur as clusters embedded in synoptic scale disturbances such as tropical and mid-latitude waves. These embedded systems might be connected but should not be identified as a single large system since the connection is transient. The recent detect and spread (DAS) type algorithms help identify an MCS in a cluster  by identifying a core region of heavy rainfall and spreading it into adjacent regions of lower precipitation values. Also, as we move away from a single satellite and towards microsatellite constellations for various meteorological data, we need a robust method to identify and track objects of interest in a multi-satellite product. This is because each satellite in the constellation may have a different sensor that requires cross-calibration and is finally merged to create a single product.
 We present the improved version of the Forward in Time (FIT) tracking program, a multi-threshold, detect and spread type algorithm, to track MCSs in Integrated MultisatellitE Retrievals for Global Precipitation mission (IMERG), NASA's global precipitation product. IMERG is a  multi-satellite precipitation product that combines rain retrievals from passive microwave sensors on a virtual constellation of satellites and rain retrievals from Infrared sensors onboard geostationary satellites. Using the FiT algorithm, we track MCSs in the IMERG precipitation field for ten years (2011-2020) and store MCSs' properties in a publicly available dataset called Tracked IMERG Mesoscale Precipitation Sytems (TIMPS). Leveraging this dataset, we present the regional variability of MCSs properties (frequency, lifetime, and propagation velocity) and some preliminary results from ongoing studies.
Low tropospheric wind profile diurnal regimes during winter and spring according to ICON-LAM and Doppler wind profiler at a desert site
Authors: Berkovic Sigalit , Tzadok Tamir , Ronen Ayala , Khain Pavel , Levi Yoav
Published: July 2023

StreamLine XR Doppler LiDAR measurements during the four months of January-April 2022 provided first time high resolution temporal and spatial measurements of the boundary layer wind profile variability over Sde-Boker, located in the central Negev desert. This work presents characterization and comparison of the daily low tropospheric wind profile according to measurements and simulations with the new regional ICON-LAM (ICOsahedral Nonhydrostatic weather model in a Limited Area Mode) model with a convection-permitting resolution of ~2.5 km.
Two main regimes of daily wind profile are observed:

“Regular days”, with no sharp wind direction change. Most of these days present westerly component flow in the boundary layer (BL) up to 500-1000 m a.g.l, and typical daily variability of the boundary layer height (BLH) according to the solar heating with or without wind direction shear above the BL. Such events are mostly under high pressure from the West. Winter lows present strong (> 5 m/s) westerly flow with constant BLH.

“Transitional days” presenting sharp wind direction change in the BL (at least 90° within an hour). Their frequency is ~ 30% during February-April, while during January single event occurred. The synoptic conditions present pronounced change in the synoptic gradients or mild synoptic gradients allowing the development of local mountain breeze. Mild gradients may occur under winter highs, Red Sea trough approaching winter lows and Sharav lows.
Case studies of each group and their synoptic pressure gradients at the lowest troposphere (1000-500 hPa) are presented. The comparison between the model and measurements has temporal and vertical spatial resolutions of 1-hour and 100 m accordingly. Two sets of predictions from 12 UTC and 0 UTC initializations are separately applied.
The absolute differences between the predicted and measured wind direction and speed are mostly up to 40 °and 3 m/s during the case studies. The predicted sharp wind direction transition times of the "transitional days" cases are 1-2 hours earlier than their measured counterparts. Due to this mismatch, large differences between the predicted and measured wind directions are observed (~ 100°). The 12 UTC initialization better predicts the transition times.
January-April monthly absolute mean errors (AME) of wind direction and wind speed are 7°– 40 ° and 0 – 3.6 m/s (events with speed > 1 m/s). The biases are mostly -15 °– 22 ° and -1 – 1 m/s. The model nicely reconstructs the variability of the wind profile.
Aerosol sun photometry state of the art and progress and the COST action Harmonia
Authors: Kazadzis Stelios , Kouremeti Natalia , Masoom Akriti , Groebner Julian ,   Harmonia Core group Team
Published: July 2023

We intend to present and overview of ground-based sun photometry for aerosol optical properties retrieval, including:- the state of the art on basic principles of direct sun and sky radiance measurements and retrieval methods used worldwide- Calibration procedures for aerosol optical depth- Global efforts for aerosol optical properties homogenization- An estimation of the aerosol optical depth uncertainty and the factors affecting it- Examples of aerosol retrievals, trends and spatiotemporal variability on a global scale.Currently, global networks retrieving aerosol properties (e.g. aerosol optical depth (AOD)) are using different calibration principles and hierarchy and also there are differences on the post processing of solar direct sun measurements, in order to retrieve AOD (e.g. inclusion of trace gases, cloud elimination , Rayleigh scattering effects). Concerning the calibration, the most common methods are the Langley calibration (with certain limitations) and the traceability to defined (e.g. from WMO) standards. Lately a link of such standards with SI traceable ones helped towards the goal of the transition from "artificial" standards towards SI traceable ones.Long term measurements of various instruments belonging to different networks showed, in the case of network reference instruments, very good agreement within initatives supported by the world meteorological organization ( e.g. filter radiometer comparisons in Davos, Switzerland from 2000 to 2021 organized by the World Optical depth Research and Calibration Center)  and European infrastructure initiatives such as ones supported by the Calibration center for Atmospheric remote sensing of the EU infrastructure ACTRIS (Aerosol, Clouds and Trace Gases Research Infrastructure).Recently these aspects have been investigated and communicated through a networking COST action project called Harmonia (International network for harmonization of atmospheric aerosol retrievals from ground based photometers) where more than 100 scientists are participating.Acknowledgement: The presenter would like to acknowledge funding for the participation at EMS2023  from  the COST Action HARMONIA (International network for harmonisation of atmospheric aerosol retrievals from ground based photometers), CA21119
Various approaches using ensemble prediction system in KMA
Authors: Shin Hyuncheol , Kim Eun Jung , Park Jong Im , Yun Sug-gyeong , Ha Jong-Chul , Kwon Young-Cheol
Published: July 2023

The ensemble prediction system based on the Korean Integrated Model (KIM) has been in operation at Korea Meteorological Administration (KMA) since October 2021. KIM is KMA’s new generation global model which is based on the cubed sphere grid system and has 12km horizontal resolution and 91 vertical levels. It was developed over 9 years from 2011 to 2019 and operationally launched in April 2020. KIM-based ensemble forecast system consists of 50 perturbation members (25 members for long-range forecast) and 1 control member. Four-dimensional LETKF (Local Ensemble Transform Kalman Filter) with additive and RTPS inflation scheme is used to make initial perturbation.The performance of KIM-based ensemble system was evaluated. It is generally more skillful compared to the KIM deterministic global model and shows similar performance with UM-based ensemble system which KMA is operating. An increase in the number of ensemble members results in an overall improvement in prediction performance, especially at higher latitudes. Details of results from KIM ensemble system and impacts of increased ensemble size will be discussed.Multi-model ensemble is another type of ensemble prediction system KMA is operating. KMA’s multi-model ensemble prediction system that merges six global domain models(KIM, UM, ECMWF global and global ensemble models) is used for short and medium-range forecast. Multi-model ensemble mean shows better performance than the ECMWF ensemble model, which is the best member model. In addition, multi-model ensemble system that incorporate regional models in addition to global models is used for impact-based forecast of heat waves and cold waves.  Impact-based forecast for high risk level(`warning` and `alarm`) is improved by using multi-model ensemble system.