bluuebunny/crossref_metadata_2025 huggingface dataset:
The impact of the extratropical North Atlantic SSTs on the ENSO signal in the North Atlantic-European region
Authors: Herceg-Bulić Ivana , Ivasić Sara , Popović Margareta
Published: July 2024

Tropical sea surface temperatures (SSTs) play a crucial role as a source of boundary-forced predictability for the atmosphere in the extratropics, influencing atmospheric dynamics characterised by significant internal variability and limited predictability. One of the most influential events determining global climate variability is the El Niño-Southern Oscillation (ENSO). Over the North-Atlantic European region (NAE), many processes obscure the manifestation of ENSO. In this study, we analyse the ENSO-induced signal over the NAE region and investigate the contributions of the individual tropical basins and the mid-latitude North Atlantic SSTs. Using an intermediate-complexity atmospheric general circulation model (ICTP AGCM), we performed a set of targeted experiments using 35-member ensembles of long integrations with SST anomalies in different regions that served as a lower boundary forcing for the model. This experimental framework facilitated the separation of the influences from individual basins and allowed the estimation of their respective contributions to the overall signal. Our analysis shows a recognisable atmospheric response occurring primarily in the late winter months, with the strongest signal associated with ENSO events. The competing influences emanating from individual tropical basins are highlighted. At the same time, the superposition effect of the extratropical North Atlantic SSTs is demonstrated through the modulation of the storm tracks. Although the atmospheric response to the midlatitude SST forcing is weak, extratropical air-sea interaction still can be an important modifier of local atmospheric variability.  Both the model results and the NOAA-CIRES-DOE 20th Century Reanalysis variance of geopotential heights (GH200) show the presence of an ENSO signature, which manifests itself as a distinct pattern in the North Atlantic and projects onto the East Atlantic pattern.
Exploring dynamic and thermodynamic drivers associated with heavy sub-hourly precipitation events in Portugal
Authors: Cruz José , Belo-Pereira Margarida , Fonseca André , Santos João
Published: July 2024

This study investigates the dynamics and thermodynamics driving sub-hourly heavy precipitation events (SHHPs) associated with Regional Low-pressure (RegL) systems in mainland Portugal. SHHPs are significant natural hazards, impacting various sectors such as agriculture, particularly viticulture. Using observations from automated surface weather stations from the Portuguese Weather Service (IPMA) from 2000 to 2022, with a 10-minute temporal resolution, this research focuses on three representative stations across different climatic regions. Viana do Castelo station represents the northernmost region, known for high precipitation and strong Atlantic influence. Castelo Branco station, in the central region, is less exposed to Atlantic systems and more influenced by convective systems from western Spain. Faro station, in the south, experiences less influence from maritime polar air masses and more from maritime tropical air masses or Mediterranean/North African systems. The southern region of Portugal demonstrates higher precipitation variability, characterized by intense events occurring on fewer rainy days. The study establishes a link between SHHPs and low-pressure systems west of the Iberian Peninsula (IP). These systems exhibit a cold core, particularly evident at mid-levels, and feature a positive vorticity anomaly extending from the upper troposphere to lower levels. This configuration induces differential positive vorticity advection, especially increasing with height, developing upward motion east of the low-pressure systems over western Iberia. Moreover, these systems facilitate moisture advection over western Iberia at lower levels, evident in positive anomalies of 2-meter dew point temperatures, and promote instability conditions, as diagnosed by various instability indices. Additionally, higher values of total column cloud ice water during heavier precipitation events suggest its potential as a predictor for such occurrences. The study also suggests a potential association of some SHHPs with cut-off lows, though this hypothesis requires further validation. Overall, this research provides a systematic assessment of atmospheric conditions driving SHHPs, contributing to a better understanding of these hazardous events in mainland Portugal.Acknowledgments: Research funded by National Funds by FCT – Portuguese Foundation for Science and Technology, under the project UIDB/04033/2020 and LA/P/0126/2020 (https://doi.org/10.54499/UIDB/04033/2020). Vine & Wine Portugal—Driving Sustainable Growth Through Smart Innovation, PRR & NextGeneration EU, Agendas Mobilizadoras para a Reindustrialização, Contract Nb. C644866286-011.
Influence of physical drivers on the variability of shoreline position in western South America
Authors: Escobar Franco Maria Gabriela , Almar Rafael , Boucharel Julien , Dewitte Boris
Published: July 2024

Coastal zones play an important role for coastal communities, infrastucture and ecosystems.They are considered as complex systems that are constantly affected by the human activities andthe climate. Due to the configuration of the coastline, some drivers have a greater impact on thecoastline at different times of the year. Here we present a regional evaluation of the shorelinechanges over 27 years (1999-2019) based on satellite observations and reanalysis data. We studythe main hydrodynamic drivers of the coastal variability: the sea level, ocean waves and wind stress(alongshore) on intraseasonal timescales in the western of South America. We analyse the monthlychanges in the shoreline as a linear function of the physical drivers, which are modulated by: theEquatorial Oceanic Kelvin Wave and the coastal trapped wave that have the major variability inthe austral winter at the equator, the Coastal Jet that characterize the wind bursts in the Pisco andCentral Chile region in the austral fall and the extratropical storm activity that module the waves.We found that theses drivers contribute to the most of the variability in the northern region (fromEcuador to the central Peru region 15°S) during June-August, and to the southern region (fromcentral Peru to the central Chile 35°S) during December-February. Our results provide insightinto the effects of physical forcing over the coastline on intraseasonal timescales, which can resultfrom atmospheric and oceanic perturbations from tropical-extratropical teleconnexions, that canbe considered in the context of community resilience.
Pit stop of the cross-sectoral programme “NCCS-Impacts”: preliminary results, lessons learnt and the way forward
Authors: Fischer Andreas , Hama Angela Michiko , Gubler Lena , Vicedo-Cabrera Ana Maria , Möller Andrea , Croci-Maspoli Mischa
Published: July 2024

The currently running “NCCS-Impacts” programme of the Swiss National Centre for Climate Services (NCCS) is dedicated to the analysis of selected cross-sectoral climatic impacts under future climate change in Switzerland. Previous work within the NCCS network such as the climate change scenarios CH2018 and hydrological scenarios Hydro-CH2018 serve as central pillars to carry out projects on the following aspects: (1) socioeconomic scenarios, (2) human and animal health, (3) ecosystem services, (4) supply chains, and (5) economic costs. The different projects are inter-linked with each other, share manifold synergies and jointly elaborate the two cross-cutting themes ‘social justice’ and ‘extreme events’.In addition to the generation of new science-based insights on climatic impacts in Switzerland and their central challenges for the environment, economy and society, NCCS-Impacts also has a clear focus on the development and provision of actionable products for decision-makers in the field of climate adaptation and mitigation. To this end, the work in the five different projects follow a co-production approach with consortia composed of 17 partners from research and practice. The projects run from 2023 until 2025. 2026 will be devoted to a programme-wide synthesis.Serving as a pit stop of the programme, this presentation will cover the main achievements reached so far. This includes intermediate results regarding the newly elaborated Swiss Socioeconomic Pathways (SSP-CH) and future projections on heat mortality and heat vulnerability aspects. The presentation will also reflect on experiences and lessons learnt made in terms of governance of the programme and provide a framework on how the project results are consolidated into the joint programme synthesis.
First results of the snow-atmosphere coupling analysis in the CERISE project 
Authors: Vorobeva Ekaterina , Orsolini Yvan
Published: July 2024

In early 2023, the European project CERISE started, under the auspices of the Copernicus Climate Change Service (C3S), devoted to enhancing the quality of the C3S reanalysis and seasonal forecasts with a focus on land-atmosphere coupling and land surface initialization. Studying snow cover is an important part of the CERISE project as it affects surface energy budget and hydrology, leading to shifts in atmospheric circulation and potential remote climate impacts. The impact of snow initialization on (sub-)seasonal atmospheric forecasts has received renewed attention in recent years.In this study, a first attempt is made to analyze snow-atmosphere coupling in seasonal forecasts produced by the European Center for Medium-range Weather Forecasts (ECMWF) as the phase 0 demonstrator in the CERISE project. In phase 0, the atmospheric and land initial conditions (including snow) were taken from the ERA5 and the experiments were run with Integrated Forecasting System (IFS) Cycle 48R1.1. The snow initial conditions in ERA5 comprise assimilation of Interactive Multi-Sensor Snow and Ice Mapping System (IMS) satellite observations and in-situ station data. The 4-month forecasts consist of 51 ensemble members, and 4 start dates are available per year (in months 2, 5, 8, and 11).  To assess the snow-atmosphere coupling, we map the temporal correlation between the daily snow depth and near-surface temperature over winters 2000 – 2022. Based on this (and other) metrics we identify regions of snow-atmosphere coupling. These “cold spots” are mainly situated in the snow transition regions at mid-latitudes, where the snow cover is highly variable. We further discuss the role of snow in large-scale land-atmosphere interactions. The accuracy and fidelity of the snow forecasts is also examined against satellite observations and re-analyses. The satellite observations include snow cover fraction and/or snow water equivalent products from the ESA-CCI (European Space Agency – Climate Change Initiative) dataset. 
A high-resolution temperature climatology over France using a spatialization of daily temperatures extremes from 1947 to present
Authors: Sorel Matthieu , Tiriau Malo , Van Hyfte Stéphane
Published: July 2024

Climate normals have been set up at Météo-France to characterize climate trends and to situate a day in its climatic context. First, these normals have been calculated for more than a thousand reference observations and have been recently updated with the 1991-2020 reference as stated by the World Meteorological Organization.In order to assess more accurate temperature climatology of France, a high-resolution temperature climatology over France has been performed, based on a spatialization of extreme daily temperatures (called ANASTASIA) on a 1 km regular grid using a regression-kriging method. ANASTASIA data are available 1947 onwards.Classic temperatures climatological indices are computed such as number of days above or below temperature thresholds, mean temperatures, etc. Less common indices are computed like the first/last date of temperature threshold or the climatological equivalent date of an observed temperature for a given day.Those climatology variables are of great interest in daily climate monitoring in order to fully understand exceptional meteorological situations such as heatwaves. That is why real-time products are also produced, sometimes with an indication of the geographical area impacted as a percentage of France total area, and latter with the number of people impacted. Records on extreme temperatures and the year of the record, earliest/latest date of temperature threshold are also computed in order to complete the climatological dataset.ANASTASIA product is of great interest and allows climatologists to have a better spatial representation of temperature patterns. However, the method used in ANASTASIA does not reproduce well inversion temperatures for example and may lead to great errors in such situations in mountain areas as the product is highly dependent on the observation network.
Impact of stratospheric polar vortex variability on Antarctic surface climate and sea ice
Authors: Mezzina Bianca , Palmeiro Froila M. , Goosse Hugues
Published: July 2024

The interannual variability of Antarctic sea ice is considered to be mainly driven by tropospheric and oceanic processes. However, the stratosphere also constitutes a possible source of sea ice variability. The stratospheric variability in the southern high latitudes is dominated by the stratospheric polar vortex (SPV), an extremely cold air mass confined to the pole by strong westerly winds. While there is robust evidence of a downward impact of the polar stratospheric variability on the Northern Hemisphere surface climate, including sea ice, whether a similar link is present in the Southern Hemisphere is still unsettled. 

Here, we perform a multi-model assessment of the impact of the dynamical state of the SPV on Antarctic surface climate and sea ice by applying the same experimental protocol to three state-of-the-art general circulation models (GCMs): EC-EARTH, CMCC-ESM and CanESM. The three GCMs have similar ocean and sea ice components but different atmosphere.  

First, we examine 200-year control experiments and compare them to observations. To assess the impact of the SPV state on the surface and sea ice, we build composites of “strong” and “weak” SPV years based on the spring (September-November) stratospheric conditions. We find that zonal-mean zonal wind anomalies propagate downwards from the stratosphere into the lower troposphere, but with differences in amplitude and timing between strong and weak years. Composites of sea-level pressure in late spring and of sea ice concentration in summer suggest a delayed impact of the SPV on sea ice through changes in the surface winds. However, not all models are able to fully capture the downward propagation and surface signals. 

To further isolate the potential role of the polar stratosphere in driving Antarctic surface climate, we run an additional set of sensitivity experiments with suppressed stratospheric variability. For each model, we build 200-member ensembles of 1-year long runs initialized from the control experiment, with the polar stratosphere nudged to the models' climatology, while the troposphere and the extra-polar stratosphere evolve freely. We then compare the variability of Antarctic sea ice and surface climate in these sensitivity experiments to that of the control run and investigate changes in the suggested mechanisms for the stratospheric downward influence. 
Temperature Extremes and Human Health in Cyprus: Investigating the Impact of Heat and Cold Waves
Authors: Kekkou Fragkeskos , Lazoglou Georgia , Economou Theo , Anagnostopoulou Christina
Published: July 2024

Climate change poses a substantial threat to both the Earth’s ecosystems and human society. InMediterranean countries like Cyprus, extreme temperatures and especially heatwaves during summermonths are increasingly common as it is observed in the past years due to anthropogenic climatechange. While cold waves are less frequent, they also pose significant health risks, as some studiesshow that more deaths actually occur during cold weather than hot, especially in warmer cities(southern) rather than colder (northern) in Europe. Extreme temperatures leads to heightenedbio-climatic stress and can adversely affect the human body, disrupting physiological functions andexacerbating preexisting health conditions, ranging from discomfort and severe illnesses that requirehospitalization to mortality.This study examines temperature trends in Cyprus over the past four decades, focusing on extremetemperature events from 2000 to 2019. Using ERA5-Land reanalysis data, we analyzed both maximumand minimum daily temperatures for both the warm (May-Oct) and the cold (Nov-Apr) season.Extreme hot days were defined as those where both maximum and minimum temperatures exceededthe 95th percentile of each month in the warm season. Conversely, extreme cold days were defined asthose where both temperatures fell below the 5th percentile in the cold season. Our analysis revealedan upward trend in temperatures over the past four decades, with a statistically significant increasein the number of extreme hot days and a decrease in extreme cold days for the last 20 years. Statisticaland machine learning methods, including Distributed Lag Models (DLMs) and GeneralizedAdditive Models (GAMs), were employed to estimate mortality and morbidity risks over a 21-day lagperiod using health statistics from Ministry of Health and Statistical Service in Cyprus. We observeda notable increase in mortality risk associated with both high and low temperatures extremes. Incontrast, the morbidity risk showed a different profile; overall morbidity risks were lower comparedto mortality and the maximum risk occurred at lower temperatures. In general, lower temperaturesexhibited pronounced health risks compared to higher temperatures. Additionally, we calculatedthe optimal temperatures that corresponded to the lower risk as well as the attributable fraction ofdeaths and hospitalizations for extreme temperature days and extreme temperature events, lastingfrom two or more consecutive days. The findings indicated that both deaths and hospitalizationswere notably higher during the cold period in comparison to the warm period. Nevertheless, duringperiods of extreme high temperatures, the rate of increase in attributable deaths was greater thanduring the cold period when compared to days with non-extreme temperatures.
A diagnostic study on a southward southwest vortex track forecasted by CMA-GFS: the role of initial field
Authors: Wang Lei , Chen Qiying , Jiang Ning , Hu Jianglin , Xu Guoqiang
Published: July 2024

This study presents a comprehensive diagnostic analysis of a southward deviation in the forecasted track of a southwest vortex (SWV) by the China Meteorological Administration's Global Assimilation and Prediction System (CMA-GFS). The SWV is a significant weather system in China, often responsible for severe weather events such as rainstorms. The study aims to identify the sources of forecast errors and propose improvements for more accurate tracking of SWVs. A severe convective weather process occurring on 11–13 April 2022 is selected for case study, where the CMA-GFS forecast exhibits a noticeable southward deviation in the SWV track, leading to incorrect rainfall area predictions. The analysis traces the deviation to the steering flow at 500 hPa, finding that the SWV shift is directly attributed to the deviation caused by the weak forecast of the upper-level trough. The underestimation of the initial vorticity advection by CMA-GFS is identified as the dominant factor contributing to the weak development of the trough. This underestimation is linked to the weak geostrophic wind resulting from the weak initial meridional and zonal gradients of the midlevel height in front of the trough. The study further examines the assimilation process of CMA-GFS, revealing that it has a negative effect on the SWV track forecast. The assimilation process is found to weaken the π field at mid-model level, leading to a weak midlevel height gradient in front of the trough. A verified numerical experiment using a more reasonable initial field significantly modifies the southward shift of the SWV, underscoring the importance of accurate initial analysis for precise SWV track forecasting.The research also explores the impact of initial field deviation in key regions on late-period forecasts, emphasizing the need for systematic diagnosis and improvement of SWV track forecasts. The study suggests that the initial height field, particularly at midlevels, can significantly influence the SWV track in the late forecast period. The use of ensemble prediction with initial condition perturbation strengthens the conclusions drawn from the diagnosis.The important impact of initial field deviation in key regions on the forecast in the late period is highlighted and a systematic diagnosis process for identifying and addressing forecast issues on SWV track is proposed in this study. This research could provide a comprehensive approach for diagnosing the forecast deviation associated with SWV track.
On the influence of weather regimes on high shortfall days during winter for European countries
Authors: Rouges Emmanuel , Shepherd Theodore , Kretschmer Marlene
Published: July 2024

In the context of climate change, countries are increasing their proportion of renewable energy generation, such as wind and solar. The integration of renewable energy sources into the current energy network is a challenging task, as these sources are highly dependent on weather. The main challenge is to balance energy demand and supply, as both are now weather dependent.  

During the winter season, cold temperatures lead to high demand. If these cold conditions coincide with periods of low winds, renewable generation becomes low at the same times as energy demand is high. These periods of high demand and low generation have gained a lot interest in the scientific literature and are defined as periods of high energy shortfall.  

Recent studies have highlighted the influence of weather regimes or large-scale circulation patterns on both renewable energy generation and energy demand and shortfall. 

In this research, the influence of weather regimes on energy shortfall days is investigated across 28 European countries during the winter. To this end, modelled energy data is analysed with respect to a weather regime classification. 

The results show how blocking type regimes such as the Scandinavian Blocking, the Atlantic Ridge and the negative North Atlantic Oscillation, are most likely to favour periods of high shortfall. Additionally, large regions of Europe, and therefore multiple countries, are most likely to experience high shortfall during the same regime. This would suggest that multiple countries can simultaneously experience high shortfalls. In these circumstances, connection between the energy networks of multiple countries might not be sufficient to mitigate such high energy shortfall. The coldest winter (1962-1963) of the 20th century is used to highlight worst case scenarios, for which current and future energy networks need to be prepared. 
ARRA: A kilometer-scale reanalysis over France with AROME
Authors: Bazile Eric , Le Moigne Patrick , Selly Yannick , Van Hyfte Stephane , Willemet Jean-Marie
Published: July 2024

The ARRA (ARome ReAnalysis) project was launched at Météo-France in 2022, in order to replace the old existing reanalysis system SAFRAN by a system based on the numerical weather prediction (NWP) system AROME. The objective is to cover a period of 60 years at 1.3 km over France with the last version of the operational AROME system, and produce surface and upper air variables , which are of interest for many uses, especially in the energy sector. There is a strong interest in producing this reanalysis with a recent version of AROME in order to promote the joint use of the results of this reanalysis with real-time analysis or forecasting products , as is currently the case with SAFRAN. The production of this reanalysis is part of Météo-France's 2022-2026 Contract of Objectives and Performance (COP), which sets out the institution's strategic directions and objectives for the next five years to better meet the expectations of citizens, the French government and the business community, each of them facing the challenges of climate change at its own level. With this new reanalysis, small-scale phenomena, such as convection or orographic wind circulation, will be significantly improved compared to the existing SAFRAN system or the European Copernicus CERRA reanalysis, produced at 5.5 km resolution. Beyond the replacement of SAFRAN-based products and systems, this new reanalysis is also necessary for the post-processing of the next generation of kilometer-scale climate projections using AROME. It will also constitute a key dataset for the further use and deployment of machine learning (and other AI methods) for high- resolution weather and climate applications.The ARRA reanalysis will have two components: the atmospheric part with a 3-hour cycle for the surface analysis (air temperature and humidity at 2 meters, snow and soil moisture) associated with the Increment Analysis Update (IAU) technique based on CERRA or UERRA reanalysis for the upper air and a specific product for the surface called ARRA-Land also at 1.3 km. ARRA-Land will be the SURFEX offline surface model driven by ARRA atmospheric forcing fields and by a 24-hour cumulative precipitation analysis based on MESCAN (Soci et al. 2016). The ARRA-Land product will contain hourly surface fields to produce estimates of surface and soil conditions (soil moisture, snow, etc.), with more advanced physics for the surface than in ARRA.After a brief description of the project and system configuration, preliminary comparison with other reanalysis (SAFRAN, UERRA, CERRA) will be presented and discussed.
Climate Indices and Measurements Application for Agrometeorological Services in Kenya
Authors: Musyimi Peter K. , Székely Balázs , Weidinger Tamás
Published: July 2024

Determination of climate variability and change for agriculture define necessity to map tropical relevant indices and carry out meteorological measurements capable for agrometeorological services. In this study ERA5 reanalysis data were used to characterise precipitation and climate based indices spatial patterns from 1991 to 2020 (30 years) climate normal. In our study, five precipitation-based and two temperature-based climate indices were analysed and visualised based on their agricultural importance and tropical position of Kenya. They include annual total wet day (PRCP), consecutive dry days (CDD), consecutive wet days (CWD), very wet days (R95P), extremely wet days (R99P), summer days (SU35) and diurnal temperature range (DTR). ERA5 data was pre-processed in climate data operator (CDO).The resultant network common data Form (NetCDF) generated from CDO were visualized in own python programme to obtain spatial pattern distribution maps. In addition, high-quality temperature, humidity and soil moisture data measurements were carried out in from 2023. Trends, variation  and correlations for the measurements were analysed and compared using different regression methods, ordinary least squares (OLS) and Theil-Sen regression. Results indicate average S35 of between 260.7 to 365 days in arid Northwestern Kenya in the 2011-2020 decade. Most parts of the country show average DTR between 10 °C to 12 °C while mean annual average CDD ranged between 0 (minima) to 300 days per decade with Kenyan highlands and coastal strip recording 0 to 60 days. Higher number of CWD were observed with an average between 219 to 292 per decade in highlands. However, spatial distribution patterns and the changes in the extreme events are inconsistent from one decade to the other. Increasing CDD and decreasing CWD is a constraint to crop yield and maturity and determinants to crop developmental stages. The risk of reduced yields can be monitored. Meteorological and soil moisture preliminary results indicate variability between seasons. Comparison of temperature (2m) and temperature from the soil moisture sensor from two different elevations and depths reveal a partly linear and  heteroscedastic pattern. Regression models produced similarities in behavioural patterns of measurements from the two elevations. Soil moisture deficiency informs irrigation requirements (IRR), a strategy for crop's evapotranspiration and optimal yields. Further, the measurements act as a reference for comparison with nearby weather station measurements as well as gridded datasets for better understanding of quality control. Overall, the results demonstrates importance of quality measurements and indices analysis for agrometeorological services for farmers during cropping and irrigation seasons and monitoring of agricultural yields in Kenya.Keywords: Agriculture, Climate indices, Measurements, Services, Soil moisture, Kenya 
Numerical Experimentation to Study the Influence of Various Urban Features on Microclimate Using Different Urban Scenarios 
Authors: Pauly Lippin , Ferrero Enrico
Published: July 2024

Rapid urbanization, compounded by climate change, exacerbates temperatures in urban regions by intensifying the urban heat island (UHI) effect. This study explores the influence of urbanization patterns on urban microclimate in Turin, Italy, through numerical simulations. Various urban design scenarios were investigated using weather research and forecast models integrated with a multilayer urban canopy model (MLUCM) over the June 2019 heatwave period. High-resolution urban land use/land cover data derived from local climate zone (LCZ) maps generated through the World Urban Database and Access Portal Tools (WUDAPT) were utilized. Results indicate a significant impact of urbanization on UHI, demonstrating an average nighttime temperature reduction of 2.4°C and daytime temperature reduction of 1.6°C in urban areas when urban built-ups are replaced with vegetation. Replacement of compact-rise buildings alone notably impacts local climatic conditions, decreasing average temperatures by 1.75°C in the city center, with an overall urban temperature decrease of 0.9°C. Conversely, the substitution of industrial zones yields a 1.4°C average urban temperature decrease, with minimal impact in city centers (0.14°C reduction). Substituting compact-rise buildings with open-rise buildings slightly reduces urban nighttime temperatures and significantly reduces the critical velocity required to mitigate UHI. Furthermore, the adoption of open-rise buildings fosters enhanced wind flow in downstream rural areas, potentially contributing to a reduction in urban temperatures on windy days by facilitating ventilation and other cooling processes. This research emphasizes the critical role of specific urban features in mitigating UHI and improving thermal comfort. By strategically incorporating green spaces, open-rise buildings, and wind-channeling designs, urban planners can create more resilient and thermally comfortable cities.
Classification of convective episodes in different climatic zones
Authors: Ruiz-Leo Ana Maria , García de Arboleya Juan Luis , González Payo Javier
Published: July 2024

The study of precipitation due to convective phenomena is one of the most challeging tasks in climate and meteorological research and especially from the perspective of collected surface precipitation since they can lead to natural disasters in various regions, impacting entire populations. This work aims to classify convective phenomena after identifying them based on a methodology that separates precipitation components into convective and stratiform.Based on statistical properties of precipitation, a threshold value, or critical precipitation ratio, has been computed in order to classify every precipitation event into a stratiform or convective episode. The criterion to identify a convective phenomenon consists of knowing if rain rate exceeds such critical value. Rain events, particularly convective ones, may vary in intensity, duration, and frequency depending on the climatic zone, and thus they will be categorized according to these areas.To conduct this study, precipitation data, both hourly and daily measurements, from surface rain gauge stations have been utilized. These data cover all of Peninsular Spain and Balearic Islands from 1998 to 2023 and have been provided by Aemet (the Spanish Meteorological Agency).Previous findings indicate that convective episodes occur less frequently in the Eastern Iberian Peninsula compared to the Cantabrian area. However, they exhibit shorter duration and higher maximum rainfall intensity in the former. Despite these variations, the accumulated precipitation amounts per episode and per station are similar in both regions. Furthermore, it is noted that the number of rain gauge stations affected by convective phenomena is greater in the Cantabrian area, suggesting a broader distribution of these episodes in the northwest of Spain. It hints at potential atmospheric and geographical factors influencing convective processes in different parts of Spain. 
Hot or Boom? The Influence of Atmospheric Deserts on Heat Wave and Thunderstorm Formation
Authors: Fix Fiona , Mayr Georg , Stucke Isabell , Zeileis Achim
Published: July 2024

Atmospheric deserts are air masses originating in the hot, dry boundary layers in semi-arid or desert source regions, which are then advected across target regions with cooler, moister boundary layers. The novel approach in this study tracks the air masses and the development of their properties directly along their path from the source to the target region. This is done using trajectories calculated with the Lagrangian analysis tool (LAGRANTO), which are initiated at a very high spatio-temporal resolution in the source region.Typical pathways can be identified using k-means-clustering. Based on these clusters, we find that most of the atmospheric desert air is modified along the path due to diabatic processes. Radiative cooling and especially latent heating and cooling in consequence to cloud formation and  re-evaporation of falling precipitation are the main causes for the changes in the thermodynamic properties of the atmospheric desert air.Due to their higher potential temperature, atmospheric deserts can form a lid over the local boundary layer in the target region. The lid can prevent the local boundary layer from growing, which leads to heat build-up under clear sky conditions. If the atmospheric desert prevails long enough, this can lead to a heat wave. Similarly, the warm air aloft suppresses the formation of thunderstorms in its centre, while at the same time the convective available  potential energy can grow. However, thunderstorms do erupt violently closer to the edges of the atmospheric desert, where the lid can be expected to be higher and weaker and where trigger mechanisms initiate rising motion.In this study we use case studies from March and June 2022, and June 2021 to analyse the processes modifying the air mass enroute, and its influence on heat wave and thunderstorm formation. In June 2022, Europe experienced extreme heat, in June 2021 tornadoes were observed in Bohemia, and March 2022 can serve as a case from a different season. These diverse case studies are therefore a good starting point for analysing the above questions.
Terrestrial temperature, sea levels and ice area links with solar activity and solar orbital motion
Authors: Zharkova Valentina , Vasilieva Irina
Published: July 2024

We explore the links between terrestrial temperature, sea levels and ice areas in both hemispheres with solar activity indices expressed through averaged sunspot numbers together with the summary curve of eigenvectors of the solar background magnetic field (SBMF) and with the changes of Sun-Earth distances caused by solar inertial motion resulting from the gravitation of large planets in the solar system. Using the wavelet analysis of the GLB and HadCRUTS datasets two periods: 21.4 and 36 years in GLB, set and the period of about 19.6 years in the HadCRUTS are discovered. The 21.4-year period is associated with variations in solar activity defined by the summary curve of the largest eigenvectors of the SBMF. A dominant 21.4-year period is also reported in the variations of the sea level, which is linked with the period of 21.4 years detected in the GLB temperature and the summary curve of the SBMF variations. The wavelet analysis of ice and snow areas shows that in the Southern hemisphere, it does not show any links to solar activity periods while in the Northern hemisphere, the ice area reveals a period of 10.7 years equal to a usual solar activity cycle. The TSI in March-August of every year is found to grow with every year following closely the temperature curve, because the Sun moves closer to the Earth orbit owing to gravitation of large planets (SIM), while the variations of solar radiation during a whole year have more steady distribution without a sharp TSI increase during the last two centuries. The additional TSI contribution caused by SIM is likely to secure the additional energy input and exchange between the ocean and atmosphere.
Estimation of Distribution of Indoor and Outdoor Population Using Location-Based Serviced Data
Authors: Kimura Teru , Suzuki Tomoki , Ohashi Yukitaka , Takane Yuya , Yamaguchi Kazuki , Ihara Tomohiko
Published: July 2024

It is important to determine the distribution of indoor and outdoor populations when assessing the risk of extreme summer temperatures in urban areas, the heat island effect, air pollution, and disasters. However, conventional indoor/outdoor determination using sensors and survey forms has problems in scale and immediacy, and it is difficult to determine the population distribution by time of day and by subregion. This study developed and verified a new estimation method using location-based service data with the aim of accurately estimating the distribution of indoor and outdoor population in urban areas and clarifying its temporal and spatial variation in some wards of Tokyo Metropolis, Japan.The research methodology used point-type data from the global positioning system (GPS) communication, grid-type data acquired from mobile phone base stations, and building polygon data, and combined them to estimate the indoor and outdoor population by time and grid. Specifically, the grid-type demographics were used to recover confidential population data from point-type location service data, which were superimposed on building polygons and determined the indoor/outdoor population based on travel distances. The estimated indoor population was compared and validated with the person-trip survey (PT survey) data at the grid level.As a result, validation with the PT survey in Nerima Ward confirmed that the estimated behavior of the indoor population, including confidential data restoration, was close to the actual behavior. The model is capable of capturing indoor and outdoor population movements by time of day and by grid, and its results are expected to have a wide range of social applications in the future, including risk assessment for heat stroke, air pollution, and disasters.
The Analysis of Utilizing Urban High-Density Street-level Air Temperature Observation Networkto Analyze the Urban High Temperature Changes with Different Geographical Environment Features
Authors: Hsieh Chiao-Jou , Lin Tzu-Ping
Published: July 2024

Under climate warming, urban areas with concentrated populations and high-density development are facing the challenge of increasing temperature. Due to Taiwan’s diverse geographical environment, the features of the urban heat island effect are affected by various geographical factors. It is necessary to rely on long-term observational climate data in order to present the complex urban microclimate changes. This study aims to identify hot spots in urban areas, comprehensively compareing the impact of different geographical environmental features on urban heat islands, and establish predictive models and adaptative strategies.Our research team established a high-density street-level air temperature observation network (HiSAN) in Taiwan cities such as Taipei, Taichung, Tainan and Kaohsiung to collect hourly temperature data at the urban block scale from 2020 to 2023. Through these data, a comparative analysis of the heat island effect is carried out, taking into account the geographical features of each place, such as basins and sea-land breezes, and visualizing them with climate maps. The study found that, in summer, Taipei often experiences temperatures 2-3°C higher than surrounding areas, as the basin topography restricts air circulation, leading to the accumulation of warm air in the city which exacerbates the heat island effect. Taichung city demonstrates a relatively uniform temperature distribution and maintains temperatures 1-2°C above suburban averages. Tainan city’s temperatures are approximately 2°C higher than suburban averages. In Kaohsiung City, the urban temperatures often 3-4°C higher than suburban areas, especially in central areas, with high building density and less green space, the urban heat island effect is most obvious.The research results also show that the heat island effect in Taipei and Taichung is closely related to the topography of their basins, while Tainan and Kaohsiung are more affected by sea-land breezes. The terrain features of Taipei and Taichung urban areas cause the urban heat storage area to be located in the basin; while the terrain of Tainan and Kaohsiung urban areas is flat, the urban heat island phenomenon is affected by the distance from the sea (sea-land breeze), and the heat island center moves significantly during the day and night. The high-density street-level air temperature observation network system contributes to urban microclimate research. It also helps to identify hot spots in urban areas, and provides useful information in analyzing the temperature and outdoor human thermal comfort of local climate zones in cities and surrounding areas. The research results also provide important references for urban planning and climate adjustment.Keywords: urban heat island, geographical environment features, sea-land breeze, high-density street-level air temperature observation network
Forest edge flows and fluxes under unstable atmospheric conditions.
Authors: Grulois Myrtille , Dupont Sylvain , Irvine Mark , Ogée Jérôme
Published: July 2024

Microclimate within the rural landscape is difficult to predict due to its strong spatial heterogeneity resulting from the juxtaposition landscape elements contrasted in terms of biophysical parameters. Canopy edge is one of the dominant heterogeneities in rural areas, whose influences on microclimate and turbulent structures have mainly been described under neutral thermal stratification.This study focuses on the micrometeorology over and within a crop-forest transition under unstable atmospheric conditions, when shear and buoyancy have a combined action on turbulence motions within the atmospheric boundary layer (ABL). This study is based on both field and numerical experiments. The field experiment was carried out in Lannemezan (South of France) from March 2023 to March 2024 as part of the MOSAI project (Model and  Observation for Surface-Atmosphere Interactions, https://mosai.aeris-data.fr/). High-frequency sensors were used to measure wind speed and direction, air temperature and humidity, and CO 2 mixing ratio at varying distances from the forest edge. The numerical experiment was performed using a Large Eddy Simulation (LES) atmospheric model, coupled to a one-dimensional multi-layer soil and canopy energy and gas exchanges model. The novelty of this simulation is to resolve both within- and above-canopy turbulence, allowing the characterization of turbulent exchanges during free convection.We will show how the forest edge flow differs depending on the thermal stability, and the influence of canopy- and ABL-scale motions on the canopy-atmosphere turbulent exchanges. This study is a first step towards simulating micrometeorology over heterogeneous landscapes in unstable conditions. Such detailed simulations should contribute to a better understanding of surface-atmosphere exchanges, and in particular to a better account of surface heterogeneity in meteorological models.
Operational use of the Lightning Mapping Array for tracking, nowcasting and warning about severe weather
Authors: Pineda Nicolau , Rodríguez Oriol , Fabró Ferran , San Segundo Helen , Montanyà Joan , Romero David , van der Velde Oscar A. , López Jesús Alberto
Published: July 2024

In order to overcome the legacy of perceiving lightning information as tertiary in importance for weather surveillance tasks, this study documents severe weather signatures observed by the largest Lightning Mapping Array (LMA) network operating in Europe. Weather offices like Servei Meteorològic of Catalunya (SMC) are taking advantage of total lightning data in real-time in the short-term forecast process, as well as for the automatic generation of severe weather warnings.The joint venture of the Polytechnical University of Catalonia (UPC) and the SMC has allowed the deployment of a network of more than 20 LMA stations to cover Catalonia and its surroundings (NE of the Iberian Peninsula).The LMA system locates the impulsive very high frequency (VHF) breakdown processes produced by the lightning channels. Each LMA station records the time and magnitude of the electromagnetic radiation received in successive 80 μs intervals and relays, in real-time, this information to the base station. With data from 5 or more stations, processed with the time-of-arrival technique, the system calculates the horizontal, vertical, and temporal location of each source. Typically, hundreds of sources per flash can be reconstructed, which in turn produces accurate three-dimensional lightning image maps. Indeed, these VHF sources then can be used for various operational products in either their raw form (i.e., source densities) or recombined into flashes.Since lightning discharges tends to connect opposite charged parts of storm, plots of the density of LMA resolved sources reveal features of severe-storm structure, complementary to those revealed by the weather radar. Animations of lightning density can reveal strong updrafts (overshooting tops, V-shaped patterns), storm intensification (lightning jump) and early stages of a mesocyclone (transient minimum in lightning density, also named lightning “holes”).In this work, LMA severe weather signatures are presented, corresponding to tornadic supercells and large hail events occurred during the 2023 thunderstorm season.