bluuebunny/crossref_metadata_2025 huggingface dataset:
Exploring Urban Climate Seasonal Dynamics over Cyprus with WRF Model: Implications of Urban Parameterizations
Authors: Constantinidou Katiana , Hadjinicolaou Panos , Vurro Giandomenico , Kushta Jonilda
Published: July 2024

Urbanization has become a dominant factor in shaping local climate dynamics, manifesting profound impacts on the environment and human well-being. This effect is even more important over areas that are expected to become vulnerable to climate change in the future. Cyprus, which is located in the eastern Mediterranean and Middle East (EMME) region, is considered as a climate change “hot-spot”.In this study, we employ the Weather Research and Forecasting (WRF) regional climate model driven by ERA5 reanalysis dataset coupled with different available urban parametrization schemes to simulate prevailing climatic conditions over the EMME and the island of Cyprus. The main objective of this research is to investigate the performance of -different in complexity- urban canopy models in simulating urban heat island over our region of interest, the capital city of Nicosia. The outcome of this investigation is the definition of the most suitable model set-up to be used over the area of Cyprus.The simulations are performed at 1 km horizontal resolution for the year 2021, a year that Cyprus experienced a prolonged heatwave during summer, with 12 consecutive days of temperatures exceeding 40 degrees Celsius. We examine the seasonal variability of urban climate properties in Nicosia during this year.The outcomes of this study provide valuable insights into the complex interactions between urbanization and climate. Understanding how different urban parametrization influence seasonal climate dynamics and selecting the best performing scheme aims in better representation of the local climatic conditions which can be further used in mitigation and adaptation assessments of the impacts of the ongoing global climate change. 
Assessing Heavy Precipitation Event Response to Global Warming Using the Pseudo-Global Warming Approach: Implications for Future High-Impact Weather Events in Southern Europe
Authors: Calvo-Sancho Carlos , Montoro-Mendoza Ana , González-Alemán Juan Jesús , Díaz-Fernández Javier , Bolgiani Pedro , López-Reyes Mauricio , Martín María Luisa
Published: July 2024

On September 2-4, 2023, a heavy precipitation event (HPE) affecting numerous places of the Iberian Peninsula and Balearic Islands, provoked very high-socioeconomic impacts with several floods, damages to the basic and critical infrastructures and three fatalities in the Iberian central area. Previous to the event, the weather pattern over Europe was governed by two prominent ridges in the North Atlantic basin and the Mediterranean Sea, and a deep trough covering a large part of Western Europe. The combination of a deepening trough and the strengthening of two ridges, extending from the Azores to the British Isles and from Tunisia to the English Channel, induced the formation of a cut-off low over the western part of the Iberian Peninsula. At surface, a low was formed. Such setup in juxtaposition with very high Mediterranean and North Atlantic SSTs promoted vorticity advection and a high amount of moisture in low-levels.In this study, the response to a warming climate that would affect this HPE at the end of the century is studied by applying the Pseudo-Global Warming Approach (PGWA). The SSP5-8.5 scenario of several climatic models from CMIP6 is used to obtain the climate change increment [FUTURE – PRESENT] needed to apply the PGWA. The increments are computed for all the prognostic variables and added to the IFS analysis to be used as initial/boundary conditions. The WRF-ARW model is used to simulate the event. A control simulation is performed using the IFS analysis as initial conditions without perturbation to compare it with the future-like climate simulation.The results indicate notable changes in the surface low in a future-like climate, affecting to low-level moisture fluxes. The precipitation distribution is modified, with significant increments in the southern of the Iberian Peninsula and the Mediterranean coast. Although in the future-like climate simulation, the places of the socioeconomic impacts would change, the HPEs maintain very high levels of occurrence.This study proves the PWGA utility in analyzing high-impact weather events enhancing our comprehension of how these events could change in a warming climate, thereby enhancing current early-warning systems.
Record-breaking European meteorological droughts in 1921-2024
Authors: Spinoni Jonathan , Cammalleri Carmelo , Chiani Leonardo , Dosio Alessandro , Ghirri Jacopo , Mastropietro Marta , Toreti Andrea , Tavoni Massimo
Published: July 2024

Pan-European summer drought of 2022 affected different sectors as agriculture, energy, ecosystems, and population health, with both large-scale and local remarkable impacts. In the last decades, similar extreme droughts hit Europe, to the point that in some areas as the Mediterranean Region such events are becoming the new normal. This study moves from two questions: can we find comparable events as we move back in time? Has Europe ever experienced a period with more frequent and/or severe droughts? To provide the answers, we constructed a new database of meteorological drought events from 1921 to 2014. As input, we used the E-OBS gridded daily precipitation and temperature data, we computed the Standardized Precipitation Index (SPI) and the Standardized Precipitation-Evapotranspiration Index (SPEI) at multiple accumulation scales, and we set a multi-parameter system (including duration, severity, intensity, extent, and peak) to assign a 0-100 score to droughts at country scale. The single events are therefore classified into five big categories to provide decadal statistics and investigate the trends of mega-droughts over the last one hundred years. For the events occurred after 1950, we also estimated population and land-use exposure. According to our analyses, no other summer drought in 1921-2023 exceeded that of 2022, confirming its exceptional features, in particular regarding intensity and extent. Our findings show that - in the last two decades - the meteorological drought severity actually increased through most of Europe, if compared with the second half of the 20th century. However, they also show that Europe already experienced a period of comparable drought hazard from the late 1930s to the late 1940s, including long multi-country droughts never recorded again. Being aware that high-quality climatic data are sparser as we go backwards in time, the results presented here suggest that recent extreme droughts might not be record-breaking – in particular regarding duration - if we extend the analyses to a hundred years ago. 
Identify Patterns of Flash Heavy Rainfall in Limited Area by FConvNeXt
Authors: Zhong Qi , Jing Linguo
Published: July 2024

The properties and distributions of precipitation are often determined by speciﬁc synoptic patterns. Hence, the objective identiﬁcation of corresponding impact patterns is an important ﬁeld of research for improving rain forecasting. However, the identiﬁcation of the weather patterns producing intense rainfall is much more challenging. Since they are violent and local, impact patterns tend to be meso- or smaller-scale systems and are often incompletely presented or only presented in limited regions. In this paper, a deep learning network with a feature cross-fusion module, FConvNeXt, was proposed to address this difﬁculty and showed great potential. Four major patterns corresponding to intense rainfall in the Beijing–Tianjing–Hebei Region were studied. Statistical testing showed that FConvNeXt performed better than ConvNeXt and ResNet and that the model could identify the weak synoptic forcing type, the subtropical high-pressure type, and the low-vortex pattern with high accuracy. Furthermore, a strictly independent 2021 dataset was tested, and FConvNeXt maintained an equal if not even slightly better performance in spite of a decrease in the subtropical high-pressure type. Meanwhile, the study showed that the accuracy in identifying the upper-level trough type is the lowest for the three deep learning methods, which maybe because the northeast vortex was intercepted in the limited region, making  it difﬁcult to distinguish from the shallow upper-level trough type. This study is useful for improving the ﬁne objective of forecasting intense rainfall.In summary, in contrast to previous objective classiﬁcations on large-scale weather systems in large regions, this study explored the objective classiﬁcation of meso- and small-scale weather patterns that correspond to heavy rainfall and ﬂash ﬂooding within a limited region. Advanced deep learning models were employed that showed signiﬁcant potential for this application. Furthermore, a new cross-fusion feature extraction module was proposed that improved the accuracy of the LVT classiﬁcation within a limited region. Moreover, the study introduced a pre-training model to improve the training speed, which improved the accuracy and signiﬁcantly shortened the training time.
Kelvin–Helmholtz Waves during the Morning Evolution of the Turbulent Layer at Dome C, Antarctica: Regimes and Patterns
Authors: Petenko Igor , Casasanta Giampietro , Kallistratova Margarita , Lyulyukin Vasily , Genthon Christophe , Conidi Alessandro , Cecilia Andrea , Sozzi Roberto , Argentini Stefania
Published: July 2024

Understanding processes of wave-turbulence interactions in stably stratified shear flows is a challenging problem in atmospheric physics and hydrography. This observational study illustrates the importance of carefully considering Kelvin–Helmholtz (KH) waves and their interaction with small-scale turbulence for an adequate description and parametrization of the stable boundary layer.
The study investigates two phenomena, traditionally discussed separately, occurring during the morning transition from stable to unstable stratification at Dome C, Antarctica. Using high-resolution sodar echograms, the simultaneous occurrence of (i) the morning rise of the inversion turbulent layer, and (ii) KH waves within this layer was observed. Regular braid-like structures associated with KH shear instabilities within the elevated turbulent layer were observed in more than 70% of days over a four-month summer period November 2014 – February 2015.
Two regimes of the morning evolution (when KH waves occurred) are identified, depending on the presence or absence of turbulence during the preceding night. The weather and turbulent conditions favoring the occurrence of these regimes are analyzed corresponding the morphology of the wind and temperature fields retrieved from an instrumented 45-m tower with six measurement levels.
Two distinct patterns of KH waves are observed: (1) quasi-periodical (with periods ≈ 8−15 min) trains containing 5−10 braids, (2) about continuous series lasting 20–60 min containing 20−80 braids. A composite shape of KH waves is determined. The periodicity of these waves is estimated to be between 20 and 70 s, and their wavelength is estimated roughly to be 100−400 m. The vertical thickness of individual braids at the wave crests ranges between 5 and 25 m. The total depth of a rising turbulent layer containing these waves varies between 15 and 120 m.
Numerical simulations face challenges in reproducing turbulent wavelike structures, particularly KHBs. Further investigation is needed to unveil the precise mechanisms driving the morning elevation and growth of KH waves along with the developing convective layer.
Characterizing hail-prone environments using convection-permitting reanalysis and overshooting top detections over south-central Europe
Authors: Giordani Antonio , Kunz Michael , Bedka Kristopher M. , Punge Heinz Jürgen , Paccagnella Tiziana , Pavan Valentina , Cerenzia Ines M. L. , Di Sabatino Silvana
Published: July 2024

Among severe weather events related to deep moist convection, hail represents one of the most hazardous perils for terrestrial ecosystems and human-related activities such as agriculture and building and insurance sectors. Furthermore, the severity and frequency of high-impact hailstorms is increasing throughout Europe, with the highest potential to worsen expected over northern Italy. However, multiple limitations hinder a comprehensive understanding of where and when severe hail can occur. Indeed, the scarcity and incompleteness of information provided by the available observations, and the approximate representations possible with numerical simulations limit a thorough assessment of hail occurrence. These challenges call for new approaches that combine information from different available sources, such as remote sensing instruments, observations, or numerical modeling.In this work, a proxy for hail frequency is developed by combining overshooting cloud top (OT) detections from the Meteosat Second Generation (MSG) weather satellite with convection-permitting SPHERA reanalysis predictors describing hail-favorable environmental conditions. Atmospheric properties associated with ground-based reports from the European Severe Weather Database (ESWD) are considered to define specific criteria for data selection. Five convection-related parameters from reanalysis data quantifying key ingredients for hailstorm occurrence enter the filter built to sub-sample the OTs, namely: most unstable convective available potential energy (CAPE), K index, surface lifted index, deep-layer shear, and freezing level height. A hail frequency estimate over the extended summer season (April-October) in south-central Europe is presented for a test period of 5 years (2016-2020). OT-derived hail frequency peaks at around 15 UTC in June-July over Italian pre-Alpine regions and the northern Adriatic sea. The hail proxy statistically matches with ∼63% of confirmed ESWD reports, which is roughly 23% more than the previous estimate over Europe obtained by coupling deterministic satellite detections with coarser global reanalysis ambient conditions. The separation of hail events according to their severity highlights enhanced appropriateness of the method for large-hail-producing hailstorms (with hailstones diameters ≥ 3 cm). Further, signatures for small-hail missed occurrences are identified, which are characterized by lower instability and organization, and warmer cloud-top temperatures.
Are unprecedented climate extremes unavoidable with temperature overshoot pathways?
Authors: Spinoni Jonathan , Chiani Leonardo , Dosio Alessandro , Ghirri Jacopo , Mastropietro Marta , Rodriguez-Pardo Carlos , Tavoni Massimo
Published: July 2024

According to climate and socioeconomic projections, a global development based on high-emission scenarios is likely to see a progressive increase in magnitude of climate extremes, resulting in large impacts who can lead to devastating impacts and hinder the stability of ecosystems. To minimize the risk of such events, the Paris Agreement recommended pursuing the strongest efforts to keep the global temperature increase – compared to pre-industrial level – to 1.5°C or, at least, well below 2°C. Considering the global temperature tendency of the last decades, it is likely that the World would exceed the 1.5°C threshold, and so the efforts to limit the temperature increase, and possibly revert it, fit into the 1.5°C (or 2°C) overshoot pathways. However, if the World will follow low-emission scenarios, will such overshoot trajectory prevent us from unprecedented climate extremes or are we unavoidably bound to experience new record-breaking events? To answer this question, we used the bias-adjusted multi-model ISIMIP3b data, we constructed a dataset of 12 hazards (including heat and cold waves, droughts, precipitation extremes, fire danger, snowfall, and compound events), and we evaluated – for each hazard – whether, where, and when the most severe event recorded in the past is likely to be exceeded in the future. The results are presented at grid point scale (0.5°) and separately for the SSP1-1.9 and SSP1-2.6 scenarios. To expand the analyses, we coupled the integrated assessment model WITCH with a climate emulator to create multiple overshoot curves (still at 1.5°C, but with different timing and duration), and we again estimated the possible occurrence of such unprecedented events. In this presentation, we also discussed the population and land-use shares exposed to such events, depending on the scenario and the shape of the temperature overshoot.
On the sensitivity of turbulent flux profiles to turbulent inflow generation with the eddy recycling method
Authors: Rauchöcker Andreas , Stiperski Ivana
Published: July 2024

Large-eddy simulations (LES) are an important tool in studying meteorological processes on the local scale. However, specific techniques are needed to generate turbulence when initializing these models. While random perturbations in the initial condition might be sufficient for periodic boundaries, their effect will rapidly diminish when performing simulations with open boundaries, which are needed to analyze undisturbed flow over isolated topographic features. Hence, more elaborate techniques are needed to generate and maintain turbulence for such boundaries.Eddy recycling is one of those turbulent inflow generation techniques and already implemented in atmospheric LES codes such as CM1 and PALM. The eddy recycling method captures the turbulent structures a certain distance downstream of the inflow and injects the captured turbulent field in the inflow region. While eddy recycling successfully generates turbulence in the inflow region, flux profiles are very sensitive to the distance between capture region and injection region as well as the geometry of these regions. In addition, artificial periodicity in the fluxes might be introduced when placing injection region and capture region too close together. The sensitivity of turbulent flux profiles towards the shape of the capture region, the specification of the turbulent field and the effect of artificial periodicity of these fluxes has so far received little attention in atmospheric LES.To address this issue and investigate the sensitivity of the profile shape of turbulent moments to the specification of the eddy recycling module, a set of idealized LES were conducted for a shear and buoyancy driven atmospheric boundary layer with the Cloud Model 1 (CM1). Each simulation had an identical inflow profile but differed in the shape of the capture region and the distance between the capture and injection region. Preliminary results show that the shape of TKE and variances of wind components as well as temperature is highly sensitive to the shape and location of both capture and injection regions, while average profiles are less affected.
Monofractal technique to assess extreme precipitation concentration: A reference study of Barcelona (Spain)
Authors: Santuy David , Monjo Robert , Negro Darío
Published: July 2024

The current climate change scenario raises the need to study the variability of extreme precipitation patterns of Mediterranean climates, where hydrological risk assessment plays a key role in building resilience. This is why the study of future precipitation characteristics, including concentration at different time scales, emerges as a priority. We present a sophistication of the n-index approach, useful to estimate the monofractal dimension of precipitation, allowing the seasonal characterisation of its regularity at supra-daily scale and of its concentration at a sub-daily scale. The higher the n-index, the more irregular the precipitation, that is, most of the amount is accumulated in shorter duration and more dispersed events. In contrast, if the index is close to zero, precipitation is associated with a more regular regime. By applying the FIClima statistical downscaling to ten Earth System Model outputs for three observatories located in the city of Barcelona (Spain), local climate projections of the n-index have been obtained for the period 2015-2100 under different climate change scenarios (SSP1.26, SSP2.45, SSP3.70, SSP5.85). These projections show a clear upward trend of the index, increasing with the radiative forcing implied by the scenario, and marked by interannual and multidecadal variability. Given this situation of future increase in the irregularity of precipitation for the city of Barcelona, the seasonal distribution of these increases has been studied, characterising trends for each month according to the different scenarios. Increases in rainfall concentration are expected between June and October, associated with intensified and more abrupt convection. To support the spatial coherence of our results, a climatological analysis of the daily n-index has been carried out using a high-resolution data grid (0.2°) for the period [1971-2015] covering the Northeast Spain, observing consistent trends during this period and the spatial distribution of the index. The techniques presented in this study are useful to replicate in other Mediterranean regions in order to improve decision-making in society, where water resource management becomes even more important given the projected decrease in precipitation over the Mediterranean.
Evaluating the role of time lag between climate extremes and socioeconomic impacts
Authors: Mastropietro Marta , Chiani Leonardo , Ghirri Jacopo , Rodriguez-Pardo Carlos , Spinoni Jonathan , Tavoni Massimo
Published: July 2024

In the last decades, climate-related extremes are becoming a recurrent feature in many hotspot regions, as southern Latin America, the Mediterranean, the sub-Saharan Africa, north-eastern China, and southern Australia. Depending on the type of the extreme, reported damages of single events – often on specific sectors – are becoming available with increasing detail, but this is limited to recent years and does not apply to all countries. Consequently, to estimate the socio-economic impacts of climate change, the usual approach is to regress climate variables versus indicators as the Gross Domestic Product (GDP), resulting in annual temperature being the major or the only driver for most sectors, with heterogeneous marginal influence of precipitation. In this presentation, we focus on the benefit of including climate extremes in such models, specifically – as single or compound events – heatwaves, cold waves, rainfall extremes, droughts, and snowfall. Using daily and high-resolution climate data and sub-national socioeconomic indicators over the past decades, we explore the role of the lagged effect between climate extremes and the economic response, represented by GDP, but also other indicators as the Human Development Index. To include the climate extremes in damage functions, a parameterization for such lagged effects is needed, but its explicit modelling is not free from uncertainties, which can be very large, to the point that they might suggest excluding some extremes over specific areas. We also present – in preliminary form – an SSP-based estimation of future impacts of climate extremes, using a set of different global damage functions, also tentatively including regional aggregation for specific climate extremes.
Deep Learning for Improving Numerical Weather Prediction of Daily Maximum Air Temperature
Authors: Zhao Linna , Lu Shu , Qi Dan
Published: July 2024

Objective forecast of maximum temperature is an important part in numerical weather prediction (NWP). Due to the influence of complex factors such as atmospheric dynamic processes, physical processes and local topography and geomorphology, the prediction of near-surface meteorological elements in the numerical weather model often has deviation. In recent years, on the one hand, meteorological observations expand rapidly, making traditional error correct method difficult to deal with the massive data. On the other hand, artificial intelligence has an increasingly obvious advantage in processing big data.   In view of this, here we correct the European Centre for Medium-Range Weather Forecasts (ECMWF) Integrated Forecast System (IFS) both general statistics and local events, by post-processing its maximum temperature output with a deep neural network. Based on the fully connected neural network, four sensitivity experiments are designed in order to investigate the importance of auxiliary variable, time-lagged variable and the effectiveness of embedding layer in the neural network. The observations of basic meteorological elements of totally 2238 basic weather stations and the output of NWP during 15 January 2015 to 31 December 2020 are employed. The training period is from 15 January 2015 to 31 December 2019, and the rest part is test period. The results show that the forecast error of daily maximum air temperature from the IFS in test period is reduced greatly by the sensitivity experiments, which add auxiliary variables, daily maximum air temperature with 1-2 lag days and embedding layer structures and their combination. The root mean square error is reduced by 29.72%-47.82% and the accuracy of temperature forecast are increased by 16.67%-38.89%, and the effects for Qinghai-Tibet Plateau is especially remarkable where the forecast error of IFS model is very high. It is preliminarily proved that the fully connected neural network with embedding layer has better overall performance than the raw fully connected neural network, and the features also affect the forecast errors and forecast skills of the model. Besides, the prediction error of neural network model with embedding layer is more stable when auxiliary variables and lag time variables are added. Positive forecasting techniques are available for almost all stations in the study, and it is possible to reduce the mean absolute error to less than 1℃ at many stations. Tests of 1-year daily maximum temperature forecasts at four in situ stations show that FCNN forecasts with embedded layers are closest to observations, both for the whole year and for extreme points.
Traditional knowledge at IA and climate change times
Authors: Camacho Jose Luis , Alvar Jorge , Busto Montserrat , Romero Ramiro , de Cara Juan Antonio
Published: July 2024

Since COP 27, three UN agencies (FAO, UNESCO, and WMO) have established a partnership to place users at the center of the co-production of weather and climate services in agriculture. This initiative not only aligns with the 2030 Agenda for Sustainable Development and the Koronivia Joint Work on Agriculture recognizing solutions that are context-specific, but it also contributes to the Early Warning for All initiative, which recommends the integration of scientific and technological advancement with local, traditional, indigenous, and generational knowledge. On this regard, AEMET and SMC have developed solid databases and observations methodology for phenology observations based on EU action COST 725.Indigenous and Local knowledge  (ILK) is a diachronic database of know-how, skills and practices that are developed, sustained, and passed on from generation to generation within a community, often forming part of its cultural or spiritual identity. Thus, ILK is grounded on nature observation based on empirical evidence of stars, skies, birds, insects, and plants and transformed into decision making  at community level. ILK inclusion in societal science and climate change adaptation plans is a challenge for the UN, international and national agencies because the inclusion of citizen science into national policies and plans is often neglected. Weather and climate information and derived services lack contextual specificity and are not tailored to user’s needs, are not delivered on a timely manner, and/or communicated in a user-friendly way or are too technical.Phenology is the study of cyclic and seasonal natural phenomena, especially in relation to climate and plant and animal life. National Meteorological Services (NMS) in Europe have long term practices recording data on crops and tree phases, birds and insect behavior and mapping changes across the territory and along the years. These observations are related both to climate variability and climate change at local level. Phenology databases, observation manuals and guides on operational practices are easy tools to blend with traditional knowledge. This enables the incorporation of local culture, languages and religious aspects into comprehensive documents, reports and plans in developing countries, preserving those traditions for future generations.  Data recorded is of great support for the co-creation of national adaptation plans and the development of climate services at local level.Based on this experience, a respectful approach with ILK on climate change oriented projects for developing projects will include an update of phenology observations adapted to country ILK and enlarged databases to record climate change aspects based on plants, birds and insect behavior impacts that are highly significant for biodiversity, climate and societal studies. 
Operational weather forecasting in Antarctica with the WRF model in sub-kilometer resolution
Authors: Matějka Michael , Láska Kamil
Published: July 2024

The coastal regions of Antarctica are subject to frequent passages of low-pressure systems and transient pressure ridges. This synoptic-scale setup favors abrupt weather changes and occurrence of dangerous outdoor conditions such as snowstorms, extremely low wind-chill values due to low air temperature and strong winds, or intense solar radiation potentially leading to snow blindness. In this coastal zone most Antarctic research stations are located, and numerous scientific and logistical field activities are conducted. Under these circumstances, operational weather forecasts are of utmost importance. In this contribution, a WRF-based high-resolution weather prediction system is presented and evaluated. This experimental system was run to support the 2023 and 2024 summer expeditions to the J. G. Mendel Station on James Ross Island, Antarctic Peninsula. Initial and boundary conditions were provided by the GFS model, model topography by the Reference Elevation Model for Antarctica. The model configuration included the 3DTKE boundary layer scheme suitable for sub-kilometer resolutions, Thompson microphysics, RRTMG longwave and shortwave radiation schemes and the NoahMP land surface model. The model was run once a day in 500-m horizontal resolution (132-h lead time) and 1.5-km horizontal resolution (96-h lead time, more recent initial conditions). Forecasted time series of air temperature, wind speed and direction, precipitation amount, snow height, global radiation and sea-level pressure for multiple field locations were sent to the Mendel Station via a satellite internet service. The WRF model forecasts were validated with in-situ observations at the coastal Mendel Station (10 m a.s.l.) and the top of Davies Dome glacier (514 m a.s.l.). Furthermore, the model accuracy was compared with the output of publicly available Antarctic Mesoscale Prediction System (AMPS). Compared to AMPS, the WRF model in 500-m resolution massively improved air temperature prediction at Mendel Station, reducing mean bias from -4.2 °C to -0.8 °C in 2023. In late 2023, multiple AMPS physical parameterizations were updated, possibly contributing to reduced bias of -2.9 °C in the 2024 season. However, the WRF model still performed significantly better with bias of ‑0.5 °C. On Davies Dome, the WRF model performed slightly better in 2023 (by 0.4°C) while in 2024 the models performed similarly well.  Regarding wind speed, both the WRF model and AMPS provided comparable results with mean bias 1.5 - 1.9 m·s‑1 at Mendel Station (more favourable for WRF) and 0.1 - 0.7 m·s‑1 on Davies Dome (more favourable for AMPS). Prediction of two significant snowfall events in 2023 was done with a very good accuracy.
Atmospheric response to the winter Atlantic Niño/Niña
Authors: Gil-Reyes Laura , García-Serrano Javier , Kucharski Fred
Published: July 2024

Tropical Atlantic Variability (TAV) exerts a significant influence on the climate of different regions through distinct mechanisms that can be identified. Understanding these mechanisms and their impacts can improve the predictability of the North Atlantic-European winter climate. The Atlantic Niño (ATLN) or Equatorial Mode is known for being the dominant pattern of TAV, whose dynamics are similar to El Niño-Southern Oscillation in the tropical Pacific. This study aims at exploring the atmospheric response to positive/negative winter ATLN, as it has been much less documented than the summer ATLN. To this end, a set of sensitivity experiments has been performed with two global atmosphere models of different complexity (EC-EARTH and SPEEDY) to ensure that results are model-independent. The experiments have been designed as atmosphere-only simulations that comprise 150-year long integrations keeping the radiative forcing fixed at present-day climate conditions, covering the extended winter season from November to March: a control run with observed climatological SSTs over 1980-2010 (CTRL), and two sensitivity runs prescribing positive (ATLNiño) and negative (ATLNiña) SST anomalies with climatology elsewhere. The atmospheric response is evaluated by comparing the ensemble mean of each sensitivity run with CTRL. The results show a local Gill-type structure, symmetrically straddling the equator, whose amplitude is slightly larger in response to the heating than to the cooling, and increases from November-December to January-February. In the extratropics, the upper-tropospheric circulation displays a dipolar structure with cyclonic (anticyclonic) anomalies at mid-latitudes and anticyclonic (cyclonic) anomalies at subpolar latitudes, associated with ATLNiño (ATLNiña), which is different from the North Atlantic Oscillation (NAO). In addition to the impact on tropical convection, depicting a southward (northward) shift during ATLNiño (ATLNiña), the precipitation anomalies show a robust and approximately-linear signal on the European continent.
Desert dust outbreaks at the Mediterranean Basin: Optical properties and impact on surface solar radiation
Authors: Chadoulis Rizos-Theodoros , Aslanoğlu S. Yeşer , Charalampous Georgia , Herrero-Anta Sara , Herrero del Barrio Celia , Kouklaki Dimitra , Moustaka Anna , Mytilinaios Michail , Papetta Alkistis , Solomos Stavros , Gkikas Antonis , Spyrou Christos , Papadimitriou Nikolaos , Vandenbussche Sophie , Fountoulakis Ilias
Published: July 2024

The Mediterranean Basin is one of the sunniest regions globally. Thus, aerosols, and especially dust, play a key role in radiative transfer processes in the atmosphere, which locally can be comparable to or even more significant than the role of clouds. The physical (i.e., size, shape) and chemical (e.g., composition) properties of dust that is transported across the Mediterranean Basin depend strongly on its origin, as well as on its ageing and mixing with other atmospheric constituents. For instance, the mixing of dust with anthropogenic particles can alter its chemical composition and hygroscopicity/ hygroscopic properties. Changing physical and/or chemical properties of dust also alter its optical properties and subsequently its radiative effects.By analyzing synergistically back-trajectories of the air masses at different altitudes from the HYSPLIT model, aerosol optical properties from Aerosol Robotic Network (AERONET), and dust optical depth from the ModIs Dust AeroSol (MIDAS) climatology, we identified three strong dust events in the period 2015 – 2022 where dust originated from different regions of Africa and the Middle East and travelled over many AERONET stations located in (and near) the Mediterranean Basin (in an area covering latitudes from 30° N to 45° N and longitudes from -10° E to 40° E. After identifying the origin of desert dust, we studied the changes in its optical (Optical Depth, Angstrom Exponent, Single Scattering Albedo) and microphysical (size distribution) properties as derived from different AERONET stations, using quality assured, AERONET level 2 (version 3), products. Finally, Radiative Transfer (RT) simulations for clear sky (cloudless) conditions were performed, employing the UVSPEC model from the libRadtran package in order to estimate the impact of dust, as well as the effect of its changing optical properties, on downwelling surface solar radiation in terms of Global Horizontal Irradiance (GHI) and Direct Normal Irradiance (DNI).Acknowledgements: Authors would like to acknowledge the Action Harmonia CA21119 supported by COST (European Cooperation in Science and Technology).
Summertime characteristics of a thunderstorm in April? Environmental causes and numerical investigation of a severe thunderstorm in Northern Greece using the WRF model
Authors: Tegoulias Ioannis
Published: July 2024

In the early afternoon hours of April 17, 2024, a severe thunderstorm hit northern Greece and more precisely the administrative area of Central Macedonia. The storm developed extreme characteristics, unexpected for an early spring storm. Its maximum height reached almost 11 kilometers and the maximum reflectivity was about 62dBZ. Seeding operations for the prevention of hail were performed in the context of the National Hail Suppression Program (NHSP) of Hellenic Agricultural Insurance Organization (ELGA). Even after the operations, hail was recorded in some of the hail pads along the storm’s 50 kilometers path.Radar data from the C-band weather radar located at Filyro (30 kilometers east - southeast of the storm) are used to present the storm’s evolution while the synoptic environment of the onset and the following development of the storm is examined. The unusual high temperatures (+10°C above the climatic mean) in the days that preceded the storm seem to have played an important role in its final intensity.The non-hydrostatic Weather Research and Forecasting model with the Advanced Research dynamic solver (WRF-ARW 4.3.3) is used to perform multiple simulations to explore the model’s sensitivity to different parametrizations for this -out of its season- extreme storm. Three model domains with grid-spacings of 15km, 5km and 1.67km were used with the finer ones covering Greece and Northern Greece respectively. The parameterization used for operational forecast in the NHSP (inherently lighter due to limited computational power) proved good enough, giving almost the exact position and intensity but lagging for about a couple of hours in the time of the storm. The temporal evolution of the storm was better captured using more complex parameterizations.
Application of atmospheric modelling to understand wildfires environment in Southern Portugal
Authors: Purificação Carolina , Henkes Alice , Kartsios Stergios , Couto Flavio T.
Published: July 2024

Meteorological conditions are an important factor contributing to extreme fire environment. Southern Portugal has some susceptible regions to fire with at least 4 mega fires occurring in the last two decades. Aiming to investigate in detail the atmospheric environment of large fires, several numerical simulations were performed using the Meso-NH non-hydrostatic research model. Some simulations were configured using a simple domain with a horizontal resolution of 2.5 km, while others were performed using a grid nesting technique with an inner domain of 500 m resolution. The vertical grid was configured with 50 stretched levels following the terrain. Initial and boundary conditions were provided by the ECMWF analyses and updated every 6 h. The simulations have shown the important role played by regional orography in creating favourable fire weather conditions. For instance, the interaction of the airflow with orographic effects created conditions for the rapid spread of the fire fronts in some cases, namely downward motions on the leeward side of the mountains. These effects were associated with strong wind gusts and turbulent motion at surface. Moreover, the numerical simulations indicated air temperatures near the surface above 30⁰C, and relative humidity below 30% influencing the fine fuel availability in the mega-fire cases. The study highlighted the advantages of using atmospheric modelling to better understand the significant wildfires in Southern Portugal, especially in a region marked by its fire susceptibility and vulnerability. This study was funded by national funds through FCT-Foundation for Science and Technology, I.P. under the PyroC.pt project (Ref. PCIF/MPG/0175/2019).
Seasonal Data Evaluation in MED-HOT Index Hotspots: A Climatological Perspective on Mediterranean Subregions
Authors: Anagnostopoulou Christina , Lazoglou Giorgia , Papadopoulos-Zachos Alexandros , Georgiades Pantelis , Velikou Kondylia , Manios Errikos Michail , Zittis George
Published: July 2024

Climate change has a noticeable impact on the Mediterranean region, causing changes in the seasonal patterns and yearly variations of important meteorological variables along with the occurrence, strength, duration, and timing of unusual and extreme events. While the Mediterranean is recognized as one of the  prominent global hot spot for climate impacts, it's imperative to dissect its sub-regions more meticulously. These areas exhibit significant meteorological shifts due to climate change and merit classification as unique hotspots. The Mediterranean Hotspot Index (MED-HOT index) is utilized to identify hotspot sub-regions in the Mediterranean region, followed by a detailed assessment of the seasonal data on these regions.MED-HOT index is designed to assess regional climate extremes by simultaneously analyzing  changes in frequency and intensity of key climatic variables, specifically precipitation and temperature. The MED-HOT index offers a comprehensive assessment of the major climate challenges in the Mediterranean, including heatwaves, extreme rainfall, and drought events, pinpointing regions requiring necessitating immediate attention and intervention . It calculated utilizing ERA5 daily maximum and minimum temperatures as well as precipitation data spanning into two time periods between 1981 to 2020 across 30 Mediterranean subregions. The analysis of the MED-HOT index reveals that Mediterranean hotspot region identification primarily relied on changes in the frequency of extremes, as the contribution of intensity changes was less important. Notably the change in extreme maximum temperature appears to play a crucial role in the most subregions. On an annual basis, the primary hot spots in the Mediterranean are identified as northern Greece, southern Italy, and the southeastern Mediterranean.Moreover, this study examined the performance of ECMWF-SEAS5 in predicting extreme temperature and precipitation in the Mediterranean hot spot regions. It assessed the quality of seasonal temperature and precipitation forecasts over the subregions by analyzing predictions from all members of the hindcasts and forecasts ensemble across the two seasons (winter and summer). The analyses included seasonal mean fields, anomaly correlations, statistical indicators, and seasonality index. ECMWF-SEAS5 successfully replicated the extreme precipitation anomalies observed in recent decades, with effectiveness varying based on lead time and subregion. Nevertheless, the system exhibited only moderate predictive ability in regions with medium and low predictability.AcknowledgmentsThe work was supported by PREVENT project. This project has received funding from Horizon Europe programme under Grant Agreement No: 101081276.
The project EURAMET BIOSPHERE, instrumentation development and atmospheric measurements
Authors: Doppler Lionel , Bolsée David , Van Laeken Lionel , Rapp Benjamin , Al-Qaaod Amer , Faton Krasniqi
Published: July 2024

The European Partnership on Metrology (EPM) joint research project BIOSPHERE aims to develop the necessary instrumentation, methods, and measurement infrastructure to assess how the increasing ionization of the atmosphere, caused by extraterrestrial radiation fields (cosmic rays and solar UV radiation) and amplified by anthropogenic emissions, affects the human and ecological health of our planet.Both electron precipitations of extraterrestrial origin and energetic bursts of protons released from the sun during solar flares or coronal mass ejections have the potential to affect lower stratosphere ionization and interfere with catalytic ozone depletion reactions. This can lead to an increase of the biologically active UV radiation flux, with significant implication for ecosystems, plants and human health, like cancers and cellular dysfunctions. To estimate the impact of these extraterrestrial radiation fields on the biosphere, the EPM project BIOSPHERE will provide traceable metrological data on cosmic ray fluxes, UV solar radiation at the earth surface, and the total ozone column which are key to assessing the role of cosmic rays in the atmospheric dynamics. For this purpose, dedicated instrumentation for determining the dependence of secondary cosmic rays (SCRs) on primary cosmic rays (galactic cosmic rays, solar particle events) and atmospheric parameters (e.g., temperature, density and aerosol concentration) has been developed and characterized. This instrumentation measures the SCR flux rate during measurement campaigns, side-by-side with spectra of UV solar radiation at ground level and total atmospheric ozone, with the aim of identifying and correlating changes of extraterrestrial cosmic radiation (revealed with SCR fluxes increased) with changes in atmospheric parameters (ground-based UV radiation, total ozone column). As the cosmic ray flux measured at ground level is influenced by the overlying atmosphere, a metrological methodology is currently being developed to correlate SCR flux rates with temperature and pressure. This method will also help to quantify the rates of ionizing particles in the lower stratosphere that can interfere with catalytic ozone depletion reactions. Traceable measurements of cosmic ray fluxes, UV radiation spectrum and ozone column are being carried out in measurement campaigns at four European sites. We will present here the instrumentation developed, the instrumental methodologies and the results of the first two campaigns.
Limited-Area Version of the Korea Integrated Model for the High-Resolution Regional Forecast System
Authors: Cho Heeje , Kim Junghan , Noh Ilseok , Jang Jiyeon
Published: July 2024

This presentation introduces the limited-area version of the Korean Integrated Model (KIM). KIM is a global atmospheric weather prediction model which has been operational in producing medium-range forecasts for the Korea Meteorological Administration since 2019. In efforts to develop a high-resolution short-range forecasting system for the Korean Peninsula and East Asia, we developed a model framework capable of running KIM as a limited-area model (LAM). The LAM version shares model components with the global KIM model, including the cubed-sphere grid system, spectral element method solver, non-hydrostatic dynamical core, and scale-aware physics package; with the distinction that the model domain is confined to the first panel of the cubed-sphere. The related modules to accommodate this configuration in the model framework has been newly developed accordingly. Utilizing the Schmidt transformation of the cubed-sphere enables adjustment of the size and center position of the first panel through stretching and rotating the cube. The functionality of the LAM framework is demonstrated through idealized dynamics-only test runs nesting global KIM simulations. In real-case dynamical downscaling experiments refining 100 km global simulations to 25 km, the LAM exhibits stable simulations beyond 10 days of integration, closely aligning with global simulation results. Minimal generation of numerical spurious waves is observed, even without utilizing Newtonian-relaxations toward the global simulation near the lateral boundaries, suggesting the effectiveness of dynamical cores with spectral element solvers for dynamical downscaling. The presentation also addresses challenges related to high computational costs, sensitivities to varying domain size and resolution, and the model's applicability to operational kilometer-scale short-range weather prediction.