bluuebunny/crossref_metadata_2025 huggingface dataset:
Progress in regional reanalyses of DWD and their use in energy applications
Authors: Kaspar Frank , Drücke Jaqueline , Bär Franziska , Borsche Michael , Kelbch Alexander , Spangehl Thomas
Published: July 2023

Germany’s national meteorological service (Deutscher Wetterdienst, DWD) has initiated the development of a regional reanalysis more than a decade ago by establishing the Hans Ertel Centre for Weather Research (HErZ), which has one focus on climate monitoring. The development of a reanalysis system is the major tool for that focus activity. The development was carried outat the meteorological institutes of the Universities of Bonn and Cologne. Based on the numerical weather prediction model COSMO of DWD, regional reanalysis datasets have been developed with grid spacing of up to 2 km (Bollmeyer et al., 2015; Wahl et al., 2017). Esp. COSMO-REA6, a reanalysis for the EURO-CORDEX domain with 6 km spatial resolution has been made available under an open-data policy and has been used in a number of applications, esp. related to renewable energies (Kaspar et al., 2019). As the production relied on ERA-Interim boundary conditions, the production ended in 2019, but a second generation (“R6G2”, with boundary conditions from ERA5) is currently produced. Also, a reanalysis based on DWD’s new NWP system ICON is being prepared.
Electricity generation with wind and solar is weather-dependent and the shift towards increased use of renewable energy leads to an increased need towards high quality meteorological data. In order to support the usage of DWD’s reanalysis data in energy-related applications, the project MEDAILLON has been started together with partners with specialized expertise in energy system analysis (MEDAILLON: “Generierung eines offenen meteorologischen Datensatzes mit zeitlich und räumlich hoher Auflösung für die Energiesystemanalyse und -wirtschaft”, coordinated by Fraunhofer IEE: https://www.iee.fraunhofer.de/de/projekte/suche/2023/medaillon.html). The aim is to better understand the user requirements and to provide optimized user-oriented products for energy applications. This includes an assessment of the quality of the relevant parameters. Previous experience has shown that users are especially interested in wind parameters from the reanalysis datasets. For solar radiation, also satellite-based products are an alternative, as e.g. the new version of the CM SAF-SARAH-dataset (also produced at DWD, most recent version is 3.0).
The datasets are also applied in climate services of DWD, as e.g. in support of offshore wind planning in Germany’s Exclusive Economic Zone or in studies related to the potential of renewable energies alongside the German transportation infrastructure.
In the presentation, we will summarize the current status of reanalysis activities at DWD and present the approach of MEDAILLON to derive user-friendly products.
Cli-DaRe: A Citizen Science project for the digitization of Italian secular precipitation records involving high school students
Authors: Beltrano Maria Carmen , Bertoldi Giacomo , Brugnara Yuri , Brunetti Michele , Ceppi Alessandro , Crespi Alice , Cat Berro Daniele , Manara Veronica , Maugeri Maurizio , Riva Isabella , Sudati Francesco , Zardi Dino
Published: July 2023

A wealth of data from past meteorological observations in Italy were published in official yearbook and other monographs as monthly totals based on data from hundreds of precipitation recording stations. However only a limited fraction of these data is currently available in a computer-readable format.
Cli-DaRe is a citizen science project initiated in spring 2022 as a result of a special session on citizen science in climate data rescue held within the 4th National Conference of the Italian Association of Atmospheric Sciences and Meteorology (ASIAM) in Milan on 18 February 2022. The project was promoted by a working group composed by the Coauthors of the present contribution and involved Italian high-school students in the digitization of these data. More than 350 students from 13 high schools were involved. Each school received a pdf copy of the pages to digitize, along with a spreadsheet template for data entry and a tutorial. Then, each student had to digitize the assigned data and the schools provided with the filled spreadsheets. Students also had the opportunity to join a training program consisting in a list of seminars and in specific training activities to make them aware of the potentialities of the recovered data.
The expected contribution from students in terms of data digitization is estimated in about 5000 man-hours. Besides the contribution of students, the project requires a great effort also from their teachers and from the authors for organising and coordinating the activities and to revise the data.
It turned out that the project has a great educational value, offering young students an easy hands-on experience with climate data and making them more aware on how science investigate past climatic trends.
This contribution aims to present the project and its first results, as well as an outlook on future developments and possible coperation opportunities.
Weather4UN – Supporting humanitarian decision-making with impact estimates
Authors: Röösli Thomas , Probst Pamela , Riedel Lukas , Pache Alicia , Flubacher Moritz , Bey Isabelle
Published: July 2023

Most disasters triggered by natural hazards and leading to humanitarian crises are caused by extreme weather- and climate-related events. Between 1970 and 2019, there were more than 11’000 disasters attributed to weather, climate and water-related hazards, resulting in over 2 million deaths and 3.64 trillion US dollars in losses. To further reduce the impacts of these hydrometeorological events, it is increasingly crucial that humanitarian organizations take anticipatory action before crises as well as responding during or after the events.
More is to be done to harness reliable and timely hydrometeorological information to support Anticipatory Action and Response. The WMO Coordination Mechanism (WCM) aims is to facilitate the access to authoritative information and expert advice in case of hydromet events to support the humanitarian community and Anticipatory Action. The WCM is an interface between WMO and its Members and the humanitarian community and thus is a key element of the Early Warning for All initiative. Under the coordination of the WMO Secretariat, all National Meterorological and Hydrological Services are invited to contribute to the WCM. Switzerland has replied to that call through a dedicated project, so-called, Weather4UN.
In the project, we develop prototypes for impact estimates based on weather forecasts of WMO Members and WMO Regional Climate Centers to support the decision making of the UN and other humanitarian agencies. This information is tailored to best meet the needs of these humanitarian actors. The HydroMet Impact Outlook estimates the humanitarian impacts of the forecasted hazard events for decision-support of the WCM and other humanitarian initiatives. These estimates are the result of a globally consistent impact modelling framework using hazard, exposure and vulnerability information. The main focus are the hazards tropical cyclone and floods and their humanitarian impacts. The prototype of the tropical cyclone impact estimates works for exposed population and direct economic damage due to the sub hazard wind. It is currently being extended to take into account more sub hazards like precipitation, river floods and surge, and to represent different types of humanitarian impacts. The river flood impact estimates are currently under development and their skill and usability to inform decisions is assessed. We work collaboratively with the end user on the communication of these impact estimates to provide useful, useable and used access to authoritative information of the WMO family.
Recent and Future Changes in Spatiotemporal Variability of Precipitation and Temperature and the Impacts on Selected Precipitation-Temperature Indices
Authors: Dubrovsky Martin , Huth Radan , Štěpánek Petr , Lhotka Ondřej , Mikšovský Jiří , Meinter Jan , Krauskopf Tomáš
Published: July 2023

While much effort has been devoted to analyzing long-term changes of temperature and precipitation in mean values and extremes, studies on changes in variability have been rather scarce. Trends in variability are, however, important, among others because their interaction with trends in mean values determines the degree with which extremes would change. The knowledge of long-term changes in temporal variability is essential for assessments of climate change impacts on various sectors, including hydrology (floods and droughts), agriculture, health, and energy demand and production.
SPAGETTA is a stochastic spatial daily weather generator (WG), which uses first-order multivariate (dimension = the product of the number of variables and the number of gridpoints) autoregressive model to represent the spatial and temporal variability of surface weather variables (including precipitation and temperature). The generator is a suitable tool for assessing changes in the spatial and temporal variability of the weather series because of following reasons: (A) The inter-gridpoint lag-0 and lag-1(day) correlations of both precipitation and temperature included in a set of WG parameters are good representatives for spatial and temporal variability of the two weather variables. (B) Statistical significance of changes in the lag-0 and lag-1 correlations derived from the calibration series may be easily assessed by comparing the changes with a variability (related to the stochasticity of WG) of the lag-0 and lag-1 correlations across multiple realizations of synthetic weather series. (C) Separate effects of changes in various WG parameters (derived, e.g., from RCM-simulated daily series representing the future climate) on any climatic characteristic may be easily assessed by modifying only selected WG parameter(s).
In the first part of the contribution, we employ SPAGETTA generator to analyze recent and future changes in spatiotemporal variability of precipitation and temperature in 8 European regions; these regions are defined in Dubrovsky et al 2020 (Theor. Appl. Climatol.). The recent changes are derived from gridded observational E-OBS time series, and the future changes (2070-2099 vs 1971-2000) are based on multiple RCM-simulated surface weather series. In the second part, we assess separate effects of changes in the means, variability and lag-0 & lag-1 correlations of temperature and precipitation. The changes in WG parameters are derived from a set of 19 RCM simulations, the changes are used to modify corresponding WG parameters calibrated from the E-OBS data, the synthetic series are generated, and the impacts on a set of compound temperature-precipitation characteristics representing “Days” with spatially significant extent of significantly non-normal weather (e.g. hot-dry spells), and the “Spells” of such days, are analyzed.
Towards a kilometre-scale Earth System Model to better predict extreme weather events: insights from the Destination Earth initiative's case studies.
Authors: Gascón Estíbaliz , Maier-Gerber Michael , Vannière Benoît , Irina Sandu , Magnusson Linus , Mogensen Kristian
Published: July 2023

This presentation will showcase research conducted at the European Centre for Medium-Range Weather Forecasts (ECMWF) as part of the Destination Earth initiative of the European Commission. This initiative aims to develop a continuous global component of Earth's Digital Twin of Weather-induced and Geophysical Extremes (Extremes DT) to be able to forecast and monitor extreme weather events with unprecedented precision worldwide within a five-day range.
We will discuss various model experiments used to evaluate how horizontal resolution, ocean-atmosphere coupling, and different forecast initializations affect the prediction of some extreme weather events (i.e. medicanes, winter European storms, or extreme alpine precipitation, among others). In the current Extremes DT, ECMWF's Integrated Forecasting System cycle 48r1 is being used with a Tco2559 grid (approximately 4.5 km in horizontal resolution). We will compare the performance of these simulations with the current ECMWF's operational deterministic 9km forecasts and even higher resolution forecasts and we will validate the simulations with high-density observations and model analyses.
This research shows the significant benefits of higher resolution in predicting near-surface fields in specific case studies, especially large precipitation amounts in regions with complex orography, and the potential for more accurate medicane forecasts (both location and intensity). However, variables such as maximum wind gusts require additional development, such as enhancing data assimilation and reviewing parametrization formulations, and evaluation using high-density observations. For these goals to be achieved, we conclude that other aspects of global models need to be improved alongside increased resolution. Ultimately, our work provides valuable insights into evaluating and improving Earth System models on a kilometre-scale.
Poland’s climate in the medieval period
Authors: Przybylak Rajmund , Oliński Piotr , Koprowski Marcin , Szychowska-Krąpiec Elżbieta , Krąpiec Marek , Puchałka Radosław
Published: July 2023

Knowledge about the climate before AD 1500 (e.g. for the medieval period) is very limited for many areas of the world, including central Europe. The paper presents the latest state of knowledge on the climate of Poland (Central Europe) in the period 1001–1500. This is achieved using: i) quantitative climate reconstructions published in the past two decades, ii) three new reconstructions exploiting dendrochronological data, iii) one reconstruction based exploiting an updated and augmented database of historical source data on weather conditions. The annual growths of coniferous trees in lowland and upland Poland is highly dependent on the temperature at the end of winter and the beginning of spring, especially February and March. All available reconstructions based on dendrochronological data represent mainly this time of the year. A limited number of reconstructions exist for summer. They are based on biological proxies and documentary evidence, the latter being limited to the 15th century only. In Poland, annual mean temperature correlates with winter temperature more closely than with summer temperature. Winter temperatures can thus be used as annual proxies. The Medieval Warm Period (MWP; also called the Medieval Climate Anomaly) is estimated to have occurred in Poland from the late 12th century to the first half of either the 14th or 15th century. Analysis of all available quantitative reconstructions suggest that the MWP in Poland was comparable to or warmer than the current temperature (1951–2000). The first half of the 11th century (both winter and summer) and the second half of the 15th century (only winter) were the coldest periods in the Middle Ages. Very limited knowledge exists about the wetness of the seasons in Poland. Information is available only from documentary evidence and mainly for the 15th century. Weather notes describing precipitation conditions are most plentiful for summer and then for winter. A very limited number exists for the transitional seasons.
            The greatest climate continentality occurred in the 15th century. Good agreement was found between the reconstructions of Poland’s climate and many reconstructions available for the area of Europe.
The work was supported by the National Science Centre, Poland project No. 2020/37/B/ST10/00710.
Climatological aspects of quasi-linear convective systems across Europe
Authors: Surowiecki Artur , Pilguj Natalia , Taszarek Mateusz , Piasecki Krzysztof , Pucik Tomas
Published: July 2023

In this work, we use 8 years of OPERA radar data, ESWD severe weather reports, and ATDnet lightning detection data to create a climatology of quasi-linear convective systems (QLCS) across Europe. In the first step, 15-minute composite animations of radar reflectivity and lightning data were used to manually identify 2201 QLCS polygons in the period of 2014 to 2021. Severe weather reports, lightning data, and morphological properties (such as the presence of bowing segments) allowed classifying QLCSs according to their intensity into 1844 marginal, 304 moderate, and 53 derecho cases. The manual evaluation also allowed us to identify: the basic archetype of the system, the location of stratiform precipitation relative to the active convective part, propagation with respect to the mean wind, areal coverage, width, length, accompanying hazards, and social impacts associated with each QLCS. Results indicate that QLCSs are the most frequent during summer in Central Europe, while in southern Europe the season of their occurrence is extended to late autumn. QLCSs are the least frequent during winter when they appear mostly in northwestern Europe in the form of narrow cold frontal rainbands (NCFR). In spring they are most common across western Europe. The vast majority of systems move from southwest and west. 22% of the systems were associated with a bow echo signature and 6% produced a mesoscale convective vortex. Among precipitation modes, trailing (53%) and embedded (45%) stratiform types were the most common. The longest classified QLCS had a length of 2200 km (9 Aug 2018), while the widest reached 1635 km (10 Jan 2015). The most frequent hazard accompanying QLCSs was lightning (produced during 95% of the total QLCSs lifetime), followed by severe winds gusts (7.7%), excessive precipitation (5.3%), large hail (2.7%), and tornadoes (0.4%). Derechos had the largest coverage of severe wind reports with respect to their path area (49%), while back-building QLCS had the largest coverage of excessive precipitation events (12%). Large hail was most common with bow-echo complexes (6.5%).
Using statistical approaches to quantify the synergy of heat stress and air pollution on human mortality for a Mediterranean city
Authors: Economou Theodoros , Parliari Daphne , Kushta Jonilda
Published: July 2023

The latest Intergovernmental Panel on Climate Change (IPCC) report estimates that the global mean temperature increase will be up to 5.4°C. One of the most affected areas globally is the Eastern Mediterranean and Middle East (EMME), a wide and highly diverse region, identified as a hotspot that is warming twice as fast compared to the global increase. Climate change, in conjunction with poor air quality are two key factors impacting human health. In this work, we use flexible statistical modeling approaches to quantify the joint effect of temperature, humidity and air quality on human mortality for the city of Thessaloniki in Greece. In this work we briefly expose the statistical methodology we propose, and how it was used to quantify the joint effects of temperature, humidity and air quality over prolonged periods of exposure, on human mortality.
More specifically, we utilize data on all-cause but also cause-specific daily mortality and model this as a function of temperature, humidity, ozone, PM10 and nitrogen dioxide – all measured from monitoring stations in Thessaloniki. We implement the well-established framework of Distributed Lag Models (DLMs) as Generalized Additive Models (GAMs), to capture the complex interactions between the aforementioned exposures on the risk of mortality. Such models capture the exposure effect through time and thus enable understanding into how prolonged periods of poor air quality and heat stress affect human health. Results confirm the intuition that exposure to extreme heat and humidity in conjunction with poor air quality significantly increases the risk of mortality. This increase in risk varies considerably by case-of-death and also by age group. We show how the type of air pollutant results in different risk profiles, but also that there are correlations across the pollutants that affect the risks.
Connecting the dots: bringing science at the heart of the European emergency management coordination
Authors: Afentoulidis Spyros
Published: July 2023

This lecture endeavours to identify the best practices and missing links between scientific input and operational activities during crises in the field of civil protection, looking at the example of the EU Civil Protection Mechanism and its operations at a global level.
Lakes as snowfall sensors: solving the precipitation problem inthe mountain cryosphere
Authors: Pritchard Hamish
Published: July 2023

The mountain cryosphere is so large, varied, inhospitable and changeable that we must rely on models of snowfall to map and manage this water resource and to predict how it will evolve. This is an important goal because snowmelt released each summer is an extraordinary generator of wealth and wellbeing in rich and poor countries, but it is among the most sensitive of all major ecosystem-services to climate change. Unfortunately, the water content of snowfall is notoriously difficult to measure accurately on a large enough scale, and conventional gauges are too sparse, small, and bias-prone to constrain precipitation climatologies or weather models. As a result, there are large biases in state-of-the-art assessments of mountain precipitation worldwide, and future projections are even more uncertain.
I present an innovative approach to measuring snowfall that solves many of the problems of existing instruments. I show that lakes, which are common in the mountain cryosphere, can be used as pressure-sensing surfaces to yield accurate observations of the water content of snowfall simply, cheaply, autonomously, and over areas that are thousands to billions of times larger than conventional gauges. Using a standard water-pressure sensor submerged on a lakebed, this approach quantifies directly, as a pressure signal, the mass of winter precipitation as it reaches the lake surface. The measurement precision is readily quantifiable and comparable to, or better than, that of commercial precipitation gauges. More importantly, it avoids the measurement biases of other instruments (like pluviometers or snow pillows) that interact with snow as it falls or accumulates. Crucially, it also senses snowfall averaged over the whole hydrostatic lake surface above, over large areas comparable in scale to model grid cells. The largest single lake tested to date, for example, has an area 100,000 times greater than all the world’s conventional pluviometers combined. In winter conditions, this new approach can therefore largely eliminate both the measurement biases and scaling biases of the global array of conventional instruments, biases that until now have propagated into errors in the output of models developed, calibrated and validated on flawed observations. Initial tests of advanced operational forecast models Arome Arctic and COSMO-1 against these novel measurements reveal model biases of up to 100%, demonstrating the potential for this new approach to transform our ability to measure and model snowfall.
A novel airborne Doppler lidar system design for highresolution wind measurements
Authors: Gasch Philipp , Kasic James , Wang Zhien
Published: July 2023

Wind is a core state variable of the atmosphere. Accurate weather predictions and a better understanding of atmospheric dynamics, transport and dispersion require improved wind information, especially inside the turbulent planetary boundary layer (PBL). The Doppler lidar technique provides advanced capabilities for remote sensing of wind using laser radiation. It has been widely deployed using ground-based and airborne platforms in the last decades. Extending the capabilities of ground-based measurement systems, airborne Doppler lidar (ADL) onboard research aircraft allows for targeted and spatially resolved wind measurements, which is crucial for localized severe weather events or in inaccessible regions such as over water and complex terrain.
This contribution introduces a novel design for ADL systems, aiming to revolutionize the field of airborne wind measurements by providing higher measurement accuracy and spatial resolution, in combination with a simplified and more robust system design. Up to now, ADL systems use a single Doppler lidar attached to a scanner to provide multi-angle measurements. Due to cost and size reductions of Doppler lidar units over the recent years, it has now become possible to construct an ADL system that uses multiple lidars with fixeddirection beams, instead of a single lidar with a scanning beam.
The new system design uses five eye-safe, compact and lightweight Doppler lidars pointing at fixed beam directions. LES-based simulation results have demonstrated that a fixed-beam system will have approximately one order of magnitude improved spatial wind measurement resolution as well as higher accuracy, compared to existing scanning systems. Further, these simulation results allow us to determine an optimal beam number and orientation. Due to the high resolution and accuracy, the retrieval of turbulence properties, such as vertical wind variance and turbulent kinetic energy becomes possible. Besides improved measurements, the greatly simplified ADL system design allows for more cost-effective manufacturing, certification, and application on a wider range of aircraft. For example, the more light-weight construction without scanner may enable measurements onboard smaller aircraft. Furthermore, routine measurements aboard larger commercial aircraft could be established.
Overall, the higher measurement quality and order of magnitude higher spatial resolution present an important step forward to meet urgent needs to improve wind measurements. Atmospheric research and weather forecasting are expected to benefit through better process understanding and data assimilation. Additionally, through the availability of ADL measurements on a wider range of airborne platforms, a significant impact on weather forecast and aviation safety can be anticipated.
European climatology of day-to-day temperature changes
Authors: Huth Radan , Krauskopf Tomáš
Published: July 2023

Substantial efforts have been made in climatic analyses of climate means and extremes, while much less has been done in understanding short-term (intraseasonal and synoptic-scale) variability. One particular aspect of short-term atmospheric variability is day-to-day temperature difference (DTD). Large DTDs negatively affect human health and impact also animals and plants, hence constituting one of the many weather-related risks to society.
In this contribution, we present European climatology of DTD, including its higher statistical moments and behaviour in distribution tails, in a variety of datasets (observations – ECA&D, gridded observed datasets – E-OBS, reanalyses – NCEP/NCAR, JRA-55, 20CR). The magnitude of DTD is – quite expectedly – largest in winter and smallest in summer, and increases from the coast to the continental interior. Skewness of DTD is negative (i.e., large temperature drops prevail over large temperature rises and/or small temperature rises prevail over small temperature drops) over most of Europe in summer, while in the other seasons, there is a tendency for positive skewness to occur in the north and for negative skewness to occur in the south and over the British Isles. Kurtosis of DTD is everywhere and in all seasons larger than Gaussian; i.e., DTD distributions have heavy tails. Comparisons among datasets reveal their specific deficiencies, such as the existence of outlying unrealistic temperature values in station data that are undetected by quality check, the underestimation of the magnitude of DTD particularly by the 20CR reanalysis, and overestimated skewness in the British Isles in winter and in teh Mediterranean in summer by all reanalyses.
Climate and bioclimate conditions in SW Greenland and eastern coast of Labrador during the International Polar Years
Authors: Araźny Andrzej , Chmist Konrad , Przybylak Rajmund , Wyszyński Przemysław , Singh Garima
Published: July 2023

The idea of holding an International Polar Year (IPY) is attributed to Carl Weyprecht, who participated in the Austro-Hungarian polar expedition of 1872–74 that discovered the Franz Josef Land archipelago on August 30, 1873. The experience of this expedition led Weyprecht to conclude that scientific work during expeditions should be based on “identical measuring instruments, identical instructions and for a period of at least one year to collect as many synchronous measurements as possible”. His idea was implemented by the International Polar Commission established in 1879, which organised the 1st International Polar Year from August 1, 1882 to August 31, 1883. Subsequent IPYs were held in 1932/33, 1957/58 and 2007/08. The next IPY is planned for 2032/33. All polar years have significantly improved our knowledge of polar regions, especially the Arctic. This is particularly true of weather and climate conditions.The aim of this study is to examine the prevailing climatic and bioclimatic conditions in SW Greenland and the eastern coast of Labrador in all the mentioned polar years, and to compare them against each other and against the modern long-term period (1986–2015). To achieve this goal, both instrumental data available in many sources (including those collected by the Moravian Brothers) and data from the twentieth-century reanalysis were used. Instrumental data were taken for SW Greenland from the weather station located at Godthab, and for the east coast of Labrador from Nain (1882/83, 1932/33 and 2007/08) and Hopedale (1957/58) stations due to the lack of data from Nain for that year. Both stations are relatively close to each other and are strongly correlated with each other in terms of climate. Climatic conditions were compared using commonly used statistics such as monthly, seasonal and yearly averages. On the other hand, analysis of the bioclimatic conditions in the study area is based on the following indices and indicators: Wind Chill Temperature (WCT), Insulation Predicted (Iclp) and day-to-day changes of air temperature and atmospheric pressure. For the calculations, sub-daily data from the measurements taken in the middle of the day (1 or 2 pm) have been used. Apparent cold and extent of frostbite risk to the human body were assessed using the WCT. This was created based on thermophysiological experiments and theoretical research in Canada and the United States relating to the influence of temperature and air movement on apparent conditions in winter. Iclp determines the thermal insulation of clothing required for a person to maintain thermal equilibrium in a given set of meteorological conditions. All biometeorological indices  were calculated using BioKlima 2.6 software (https://www.igipz.pan.pl/bioklima-crd.html).The work was supported by the National Science Centre, Poland project No. 2020/39/B/ST10/00653.
A documentary proxy for coastal upwelling
Authors: Gallego David , García-Herrera Ricardo , Mohino Elsa , Losada Teresa , Rodríguez-Fonseca Belén
Published: July 2023

Coastal upwelling is a process in which sea water from intermediate depths emerges along the west coast of continents in response to the intensity of the alongshore component of the wind. These areas are economically relevant as upwelled water is rich in nutrients, creating regions of great interest for fisheries.Quantifying upwelling intensity at multidecadal to secular time scales is quite difficult. Upwelling is typically evaluated with indices based on sea surface temperatures, a variable that at the spatial scale required, inevitably makes use of satellite retrievals. Evidently, indices based on this method are limited to the satellite era. An alternative approach makes use of the ultimate driver of the upwelling: the wind velocity. This is typically done by using reanalysis products, a kind of data that in open ocean, strongly relies on wind observations taken from the International Comprehensive Ocean-Atmosphere Data Set (ICOADS) database. However, during the last decade, it has been suggested that at multidecadal scale, due to the changes in the observations methods, ICOADS’ velocities over the oceans could be biased toward increasing values, resulting in unrealistic trends in any wind-derived climate index.In this work we bypassed these problems disregarding the wind velocity field and making exclusively use of in-situ wind direction observations to compute a so-called “Directional Upwelling Index” (DUI). This kind of “directional” indices can be tuned to measure the persistence of the alongshore winds at the coast and therefore, they are directly related to the presence of upwelling favourable conditions. As the wind direction observation was routinely taken by sailing ships traveling between Europe and Asia circumnavigating Africa since long ago, our DUI can be used to track the history of the upwelling in parts of the African coasts since the first half of the 19th century, avoiding any problem related to possible biases on the wind velocity. This is a period much longer than that covered for traditional upwelling indices.We have computed DUIs for several areas along the west African coast. In general, we have not found consistent long-term trends, although the results are dependent on the specific area analysed. At the Senegal-Mauritania latitude, the upwelling intensity has been very variable during the last two centuries and there is strong evidence of a large shift in the upwelling intensity that occurred around 1900. Further north, at the Canaries latitude, we found that the Atlantic Multidecadal Variability mode seems to control a significant part of the upwelling variability at decadal scales, resulting in an alternating change in the sign of upwelling trends computed over short periods. This could explain the contradictory results currently found in the bibliography at the time of interpreting the upwelling trends based on short series. 
Analysis of Rain Drop Size Distribution to classify the Precipitation Process using a Cloud Microphysics Conceptual Model and In Situ Measurement
Authors: Cha Joo Wan
Published: July 2023

Raindrop size distribution (DSD) is an important parameter in rainfall research and can be used for quantitative precipitation estimation (QPE) in meteorology and hydrology. DSD also improves the understanding of the uncertainty of cloud microphysical processes (CMPs) such as ice-based and warm rain growth during climate change. Changes in CMPs impact the generation of precipitation. However, the estimation of CMPs based on in situ observation is difficult because of the complexity of microphysics processes, and most previous studies on the CMP involved approximations to predict the types of microphysical processes affecting precipitation generation based on in situ observations performed in real-time. Therefore, a simple method was developed to understand CMPs of precipitation generation using a conceptual model of CMPs and in situ observation DSD data. Previously observed DSD parameters and a CMP conceptual model of the DSD observation-based microphysical process were employed. As case studies, DSD observation data obtained in Korea and East Asia were applied to estimate the CMPs. For example, the major CMP of megacities was vapor deposition in Beijing (< 1 mm h−1) and Seoul (< 5 mm h−1), as the strong updraft of the urban heat island effect in megacities results in increased liquid water content, leading to the formation of large number of supersaturated clouds at higher altitudes.  In the example case, vapor deposition is a process where water vapor condenses directly into ice crystals or water droplets without passing through an intermediate liquid phase.  So, the urban heat island effect refers to an urban area that is significantly warmer than its surrounding rural areas due to human activities. 
Acknowledgement : This research has been supported by the "Research on Weather Modification and Cloud Physics"(KMA2018-00224) project of NIMS/KMA.
Towards uniformity in the near-surface temperature profile
Authors: Boekee Judith , Verouden Iris , Nollen Paul , Dai Yi , ten Veldhuis Marie-Claire , van der Linden Steven , van de Wiel Bas
Published: July 2023

Accurate estimations of the surface temperature are crucial to determine the exchange of energy and moisture between the surface and atmosphere. Temperature profiles in the atmospheric surface layer (ASL) are generally represented by the Monin-Obukov Similarity Theory (MOST). The logarithmic behavior in the lowest part of the ASL requires the introduction of the thermal roughness length. However, existing models for the thermal roughness length, such as the ratio to the roughness length for momentum, are not well-defined and may be based on incorrect physical assumptions. Therefore, it remains a challenge to predict the surface temperature from standardized temperature measurements at higher levels.
A reason for this uncertainty is the high vertical measurement resolution that would be required to validate the models near the surface. In this study, we designed a Distributed Temperature Sensing (DTS) structure that measures the air temperature vertically up to 1 m above the surface with a resolution of 2 cm and from 1-8 m with a 30 cm resolution. We placed this structure at a grassland site in the Netherlands in May 2022. We saw how the conventional MOST model accurately describes the logarithmic layer. However, we noticed a strong misalignment with the observed temperatures in the lowest 1 to 2 m.
We have introduced an alternative length scale into the existing model concept, omitting the need for the thermal roughness length. We show how one month of temperature profile observations under stable conditions takes one universal form by normalizing the temperature observations with θ∗ and normalizing height by the new length scale. We can describe this form, from directly above the vegetation up to and including the logarithmic layer, using a fully physically based model. Comparisons are also made against alternative models, including a tall canopy model and an adapted MOST model.
Experimental investigation of the impact of tree-like obstacles on ventilation in street canyons under isothermal and different levels of non-isothermal conditions
Authors: Alexandrou Giorgos , Mouzourides Petros , Haiwei Li , Yongling Zhao , Carmeliet Jan , Neophytou Marina
Published: July 2023

Urban heat island (UHI) is a well-known phenomenon1 that affects thermal comfort of city dwellers, building energy consumption, and city sustainability in general. The planting of urban trees has been identified as one of the most effective methods for mitigating UHI effect and improving urban microclimate. The flow characteristics of an idealized symmetric urban street canyon containing trees of varying sizes is being investigated in this study. Particle Image Velocimetry (PIV) measurements in a water channel at the Environmental Fluid Mechanics Laboratory of the University of Cyprus, were used, to investigate the combination of buoyant and inertial forces in the canyon. A non-dimensional analysis of the measurements2 was conducted to quantify the competition between thermally driven and inertially driven flow in the presence of varying sizes of tree obstacles. This study aims to provide insights into the urban microclimate by examining the flow pattern, turbulence characteristics, and air exchanges between the canyon and the boundaries above. Results show that trees have a significant impact on the formation and strength of vortical flow within the canyon. Smaller trees stimulate the formation of stronger vortices, while larger trees lead to the elimination of the vortex and the existence of recirculation cells. The location of the heated surface also affects the vortex structure and elevation within the canyon. In addition, trees can reduce normalized vertical velocities, which can be restrictive to the “breathability”3,4 of the canyon. The volumetric ventilation rate 5 through the roof-level opening that refers to the time flow travels one circuit inside the canyon, is of high interest in the context of pollution escape/removal from the canyon, as well as the removal of other scalars (e.g., relating to heat, thermal comfort, and ¨breathability¨ of the urban canyon). This study found that in the case of a leeward heated surface, air removal from the canyon can change to air entrainment with the increase in tree size, whereas in the case of a windward heated surface, air removal dominates regardless of tree size. The study encompasses an examination of the vertical profiles of Reynolds Stresses (RS) and the extent of Roughness SubLayer (RSL). Our findings demonstrate that the range of layers extension, spans from 1.10 H (minimum) to 1.60 H (maximum), where H represents the height of the building. Moreover, a substantial increase in the RSL extent was observed in windward heated surfaces scenarios in comparison to leeward heated surfaces. In conclusion, our study sheds light on the impact of trees on flow characteristics and air exchange in urban street canyons. The findings of this study can inform urban areas' design and improve their overall sustainability.
Estimation of droughts and floods occurrences in central Poland under climate change scenarios
Authors: Ghazi Babak , Przybylak Rajmund , Pospieszyńska Aleksandra
Published: July 2023

Droughts and floods are the most hazardous disasters to affect the landscape and human communities. Climate change is increasing their frequency and intensity all around the world. In this research, we study the impact that climate change in central Poland (Toruń) is having on the frequency of meteorological droughts and risk of floods occurrence in the region, based on the standardised precipitation index (SPI) as one of the most common and effective indices. Although the SPI was developed for monitoring droughts, previous studies have shown that it can also be applied to recognise wet and normal conditions. Therefore, in this study, we attempt to determine the relationship between SPI values and high flood risk. First, by an average mean ensemble of several general circulation models (GCMs), precipitation for a future period (2026–2100) in Toruń was projected under two climate change socio-economic pathway scenarios (SSPs), SSP1-2.6 and SSP5-8.5. Then, based on the projected precipitation for the future period, the SPI values were calculated. The results indicated that, in general, the precipitation in the study area will increase for scenarios SSP1-2.6 and SSP5-8.5.
Estimation of future meteorological drought based on SPI calculation showed that the frequency of the “Extremely dry” (SPI ≤ ˗2.0) and “Severely dry” (˗1.50 ≤ SPI < ˗2.0) categories will decrease under scenarios SSP1-2.6 and SSP5-8.5, while the frequency of the “Moderately dry” category (˗1.0 ≤ SPI < ˗1.50) will increase for scenarios SSP1-2.6 and SSP5-8.5 relative to the historical reference period (1991–2014).
Estimation of flood risk occurrences in the future period based on SPI values showed that the frequency of “Extremely wet” (SPI ≥ 2.0) will increase for SSP1-2.6 and SSP5-8.5, excluding the future periods 2076–2100 in SSP1-2.6 and 2026–2050 for SSP5-8.5. The frequency of “Very wet” (1.50 ≤ SPI < 2.00) will increase for both scenarios. It is also expected that frequencies of other categories including “Moderately wet” (1.00 ≤ SPI < 1.50), and “Near normal” (˗0.99 ≤ SPI <1) will slightly decrease for both scenarios.
To conclude, a decrease in the frequency of “Extremely dry” and “Severely dry” categories and an increase in the frequency of “Extremely wet” and “Very wet” showed that the occurrence of floods is more probable than droughts in the study area in the future period.
The work was supported by the National Science Centre, Poland project No. 2020/37/B/ST10/00710.
Mitigating risks to UK surface transport infrastructure through physical modelling
Authors: Eyles Joe , Lake Alice , Susorney Hannah
Published: July 2023

Since the 1980s the Met Office has produced Surface Transport Forecasts (STF) for the UK. These forecasts allow mitigation of the UK surface transport infrastructure’s vulnerability to weather-based impacts across the autumn and winter season, for example road ice (roads are gritted during ice events), and low rail adhesion (the speed of trains is adapted). Although historically sufficient, these forecasts have limitations, such as not accurately forecasting high summer maximum temperatures, which are becoming more common due to the changing climate. These high temperatures lead to melting road surfaces and buckling railway lines. The current STF system additionally struggles with the future needs of Connected Autonomous Vehicles, for example hazards which specifically impact the on-board sensors such as road spray, and flexible machine-machine communication.
In order to address the limitations of the current STF system, the Met Office is building a new system. This is both a refresh of the pipeline, with a goal to make it flexible, robust, and portable, as well as a revisit of the scientific code within. Updates to the scientific core centre around upgrading the physics model to the Joint UK Land Environment Simulator (JULES). This allows us to accurately capture summer maximum temperatures and carefully model the depth of water on the road (vital for a road spray forecast). Other scientific updates include using Machine Learning based approaches for bias correction and the spin up of new forecast locations (necessary for delivering the service via an API), and building probabilistic ensemble-based forecasts.
The physics model JULES is a community model used as the land-surface component of the Met Office’s Unified Model, but which can also be used – as we do here – as a stand-alone surface-exchange-scheme driven by forecast output from Numerical Weather Prediction models. JULES models a comprehensive list of physical land-surface energy processes, as well as modelling water and snow stores. We have extended JULES to better capture processes specific to a road. Externally to JULES we have implemented a shading scheme and heating due to longwave radiation emitted by traffic.
Defense-building climate change communication and ideas of how to overcome it in meteorological studies
Authors: Mittermeier Magdalena , Böhnisch Andrea
Published: July 2023

The environmental psychologist Per Espen Stoknes mentions five inner defenses people typically build up to protect themselves from the bad news surrounding climate change. These barriers cause people to distance themselves from the topic, leaving them unmotivated to take climate action. In order to reach people, the first two inner defenses to overcome are distance and doom. Distance stands for climate impacts that seem far away and/or in the far future. Doom addresses the mainly negative headlines about climate change, which do not motivate people to act.
Potential solutions to overcome these inner defenses or avoid building them in the first place are approachable and supportive ways of communicating about climate change using storylines. Storylines consist of coherent narratives which are relatable to the broad public. Powerful storylines for example highlight personal benefits of climate action such as healthy and climate-friendly food or attractive green cities, or social components like a neighborhood full of solar panels. However, examples of such a way of communication usually address disciplines directly involved in climate change mitigation or adaptation. For meteorological studies e.g. dealing with extreme events and their threats to society, it is challenging to apply such positive storytelling when the key messages of a study are concerning.
In this talk, we describe the problem of defense-building science communication and explore the question of how strategies for their removal or rebuilding as proposed by Per Espen Stoknes could be applied to meteorological studies. We describe the specific challenges in studies on extreme events and their impacts on the basis of summer droughts in Europe. We want to introduce our following ideas for avoiding the inner defenses of distance and doom in meteorological science communication to the scientific discussion: 1. focusing research on daily life to make it approachable and near, 2. using creative science communication formats and storytelling in order to take a positive approach to the topic, and 3. referring to climate solutions of disciplines involved in climate mitigation and adaptation for a solution-based, supportive outlook.