Periods with very low discharge, anomalously low precipitation or anomalously low soil moisture content are all considered droughts, although different types. The differentiation is relevant from an impact perspective. For example, low discharge (hydrological drought) is challenging for transportation and fish, low precipitation (meteorological drought) is challenging for energy production and agriculture, and low soil moisture for agriculture and soil subsidence. If the different types of droughts occur simultaneously impacts may compound, e.g. if discharge is low irrigation water can no longer be taken from rivers.

We quantify the co-occurrence of the three different drought types in Switzerland in the extended summer season under current and future climate conditions using the Swiss climate change scenarios (CH2018, CH2018-hydro). These scenarios are a set of 44 GCM-RCM model chains based on CMIP5. Temperature and precipitation information from these scenarios is then used to run a hydrological model for more than 80 catchments in Switzerland to generate discharge time-series but select only catchments that are not strongly influenced by glaciers and snow melt.

Compound drought days are prevalent under current climate conditions both north and south of the Alps (on average more than 3 days per year).  Compound drought days tend to affect several catchments across the country at the same time and the simultaneously affected area increases with climate change. We find a significant and substantial (more than a doubling) increase in the number of compound drought days in all catchments both north and south of the Alps under RCP8.5 forcing conditions. Under an effective mitigation forcing (RCP2.6) the increase is not significant.

How to cite: Martius, O., von Matt, C., Gudmundsson, L., and Muelchi, R.: Compound droughts in Switzerland under current and future climate, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-45, https://doi.org/10.5194/ems2023-45, 2023.

Heat waves represent meteorological phenomena with serious impacts on human society and environment. Coincidence of their increased occurrence and intensity with increased frequency and severity of the summer drought episodes in the Czech Republic, particularly in the last decade of the 2010s and early 2020s calls for the study of their long-term spatiotemporal variability and compound effects. As an example serve the year 2015, when the Czech Republic experienced a record number of hot days and during July and August the soil moisture was very low. Our analysis of these effects and relationships is based on homogenised data of climatological stations of the Czech Hydrometeorological Institute and on soil moisture outputs coming from calculations of the SoilClim water-balance model for the 1961–2022 period. Different methods of statistical analysis are used to find changes in long-term fluctuations, trends, severity and spatial features of heat waves and soil droughts over the territory of the Czech Republic. Anticyclonic, cyclonic and directional circulation types derived from objective classification taken in account flow strength, flow direction and vorticity are used to investigate possible drivers of related changes in both heat waves and soil droughts and their spatiotemporal relationships. It is also tested whether a stronger relationship exists between soil moisture and heat waves represented by at least three consecutive days with a maximum temperature above 30°C or defined by a certain percentile threshold (e.g., 90 or 95%). Results obtained are discussed with respect to their impacts on the occurrence of wildfires and numbers of related fatalities and injures in the Czech Republic as well as in the context of a broader European scale.

How to cite: Zahradníček, P., Brázdil, R., Řehoř, J., Dolák, L., and Trnka, M.: Relationships between heat waves and soil drought in the Czech Republic, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-228, https://doi.org/10.5194/ems2023-228, 2023.

Several droughts during the last decade seriously affected large parts of Europe, including Croatia, causing significant economic losses, particularly in the agriculture and energy sectors. Though rainfall is the main driver of drought, high temperatures during summer months may intensify its development with devastating consequences. Such was the case in 2022 when long dry spells were accompanied by several heat waves. In this study, climatological drought monitoring with the Standardized Precipitation-Evapotranspiration index (SPEI) was analysed with the primary aim of finding the best theoretical distribution for fitting the water balance in Croatia before implementing the index in the official operational procedure for drought monitoring. Monthly precipitation amounts and air temperature values were employed at 31 main meteorological stations for the period 1961-2022 and the water balance (defined as a difference between precipitation and potential evapotranspiration) was calculated for different time scales (1 - 24 months). Among five selected distributions, a three-parameter generalized logistic (GLO) distribution was found as the most appropriate one. There is a general agreement between SPEI and SPI time series, both in sign and intensity of droughts. However, a tendency toward higher drought intensity prevailed with the SPEI, particularly in periods with a light to moderate lack of precipitation and high air temperature. Comparison in precipitation and water balance in the two reference climate periods (1961-1990 and 1991-2020) revealed: a consistent trend toward drying conditions from March to August; an increase in the frequency of dry spells; and a tendency toward longer dry spells (for time scales up to 9 months). A comparative analysis of the 2022 drought in Croatia confirmed the ability of SPEI to detect drought earlier than the SPI, also suggesting that a larger area of the country was affected by drought due to high-temperature anomalies.

How to cite: Loncar-Petrinjak, I., Pasaric, Z., and Cindric Kalin, K.: Drought monitoring in Croatia using the Standardized Precipitation-Evapotranspiration Index, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-226, https://doi.org/10.5194/ems2023-226, 2023.

Catalonia is currently affected by a severe drought episode which is reporting unrecorded impacts in most part of the country. It is well known that precipitation presents a high temporal variability in the Mediterranean climate. Consequently, drought episodes are frequent, and they are an intrinsic characteristic of this type of climate. However, drought events are showing a higher frequency during the last few decades.

In this work we have studied drought and pluvial episodes derived from the calculation of the Standardized Precipitation Index (SPI) in Catalonia during the instrumental period 1915-2022. Series of precipitation aggregated at 12 and 72 months, lead to a first approximation for temporal variability of drought and pluvial events at high and low frequency, respectively. From the temporal evolution of the SPI-12, it is derived that the frequency of dry(wet) episodes has increased(decreased) in recent decades (statistically significant). This behaviour is observed in all Catalan hydrological catchments. The increase in the drought frequency is also corroborated when analysing the SPI-72 dry/wet area time series. The SPI-72 signal also reveals that the natural transition between pluvial and drought periods (and vice versa) has been broken since the 1980s, with domination of droughts since then. From the total number of drought episodes, two of them emerge: the 2004-2008 event and the current 2021-2023 drought episode. Depending on the analysed basin, one of these events can be considered the most severe one ever recorded in Catalonia since 1915.

In fact, the severity of the current event has motivated the creation of a new drought severity index (DSI), which considers the pick, mean intensity, duration and extension of the drought area. In the context of climate change, this index is called to be useful to rank future drought episodes when compared with historical ones.      

How to cite: Altava-Ortiz, V., Barnolas, M., and Barrera-Escoda, A.: Characterisation and temporal evolution (1915-2022) of drought and pluvial periods in Catalonia, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-496, https://doi.org/10.5194/ems2023-496, 2023.

Mountainous and highland regions are among the most sensitive and vulnerable areas to climate change and to its impacts since these ecosystems support a remarkable level of biodiversity. Small changes in temperature and precipitation with altitude could have major habitat implications for animal and plant species living in upper mountain environments leading to important social and economic consequences. However, although some authors pointed out a faster warming at highland elevation than the global average it is still unclear whether the trend of different climatic variables has an altitude dependence or not. We present a long-term assessment of temperature, relative humidity and vapor pressure deficit data over the whole Bolivia for the period 1961–2021 using in-situ observationsat different elevation ranges over a gradient of more than 4000 meters. The analysis shows statistically significant increments of the mean (0.17ºC decade^-1), the maximum (0.16ºC decade^-1) and the minimum temperature (0.17ºC decade^-1) records over the whole study period. The relative humidity trend reflects a slightly decrease (-0.08% decade^-1) although it was not statistically significant. Besides, the vapor pressure deficit data display an increment of 0.01 hPa decade^-1 (p < 0.05). Contrary to previous studies based on shorter records, we detected by using long-term and quality controlled series no statistically significant relationship among the trend in the climatic variables analyzed and the altitude. Just an inverse and statistically significant relationship for the minimum temperatures and altitude was found for the dataset during the warm season but the opposite is found when considering the maximum temperatures during the cold season. This study contributes to understand climate processes in complex topographic areas of South America, which are poorly studied up to date.

Keywords:climatic variables, altitude dependence, in-situ observations, trends, South America.

How to cite: Fernández-Duque, B., Vicente-Serrano, S. M., Maynard, O., Domínguez-Castro, F., Peña-Angulo, D., Noguera, I., Azorín-Molina, C., and El Kenawy, A.: Long-term temperature, relative humidity and vapor pressure deficit trends in Bolivia, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-173, https://doi.org/10.5194/ems2023-173, 2023.

The warming climate evokes increasing frequency of extreme precipitation in some region. Better understanding of the processes that cause extreme precipitation events under the current climate could support the climate model simulations. The investigation of the sub-daily precipitation can help understanding of the nature and drivers of precipitation extremes.

Automatic stations replaced the ombrometers in many places in Hungary particularly from the late 1990s. According to the recent practice the 10 min precipitation data are stored at the meteorological database at the Hungarian Meteorological Service. In a recent a project we have possibility to digitize ombrometer registering papers. We decided to enter the 10 min sums from the registering paper as it could have been measured by the automatic weather station. As a result of the digitization process 10 in rainfall depth for five stations will be available for trend analysis to detect changes from the first half of the early 20th century.

A set of hydroclimatic indices on 1-hour sum have been defined in the INTENSE project is in correspondence with the World Climate Research Programme (WCRP)'s Grand Challenge on 'Understanding and Predicting Weather and Climate Extremes' and the Global Water and Energy Exchanges Project (GEWEX) Science questions. Some of the indices defined in INTENSE and implemented in INDICES computer program developed at Newcastle University describes the maximum rainfall totals and timing, the intensity, duration and frequency of heavy precipitation, frequency of rainfall above specific thresholds and some of them is related to diurnal cycle. A few of these indices are analysed for Hungary in this work. We also refer for the joint effort in the recent past in the Carpathian Basin focusing on the change of the sub-daily precipitation extremes (Lakatos et al., 2021).

Lakatos, M.; Szentes, O.; Cindrić Kalin, K.; Nimac, I.; Kozjek, K.; Cheval, S.; Dumitrescu, A.; Irașoc, A.; Stepanek, P.; Farda, A.; Kajaba, P.; Mikulová, K.; Mihic, D.; Petrovic, P.; Chimani, B.; Pritchard, D. Analysis of Sub-Daily Precipitation for the PannEx Region. Atmosphere 2021, 12, 838. https://doi.org/10.3390/atmos12070838

Acknowledgements:

The research presented was carried out within the framework of the Széchenyi Plan Plus program with the support of the RRF-2.3.1-21-2022-00014 National Multidisciplinary Laboratory for Climate Change project.

How to cite: Lakatos, M., Szentes, O., Izsák, B., Bokros, K., and Bihari, Z.: Long term changes of the sub-daily precipitation extremes in the Carpathian basin, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-560, https://doi.org/10.5194/ems2023-560, 2023.

Mountainous areas are uniquely susceptible to climate change, making them good indicators of these changes. Research results from different parts of the world indicate recent warming of mountainous regions, particularly located since the 1980s, with different intensity in particular vertical zones. Temperature growth is not followed by significant trends in annual precipitation totals however it brings the change in precipitation annual structure and types what influences the occurrence and persistence of snow cover.

As snow cover is a key element of the Earth’s system with the impact on hydrology, climate, and ecological environment any changes in snowpack patterns will have a complex effect. The aim of the study is to examine the variability of snow cover variables (snow depth and snow cover duration) and they sensitivity to the main atmospherical drivers (temperature and precipitation) including inter-annual variations, and trends over various time scales.

The research has been conducted for mountain areas in Central Europe, defined as the terrain with the elevation above 500 m a.s.l. in the domain of 5°E - 25°E and 47°N-55°N. The analyses cover the period 1981-2022 and are based on various meteorological data sources, i.e. in-situ snow depth observations and near ground temperature and precipitation measurements (serving as reference data) as well as regional reanalysis ERA5-Land and CERRA-Land.

The primarily research results confirm the significant impact of temperature and precipitation change on snow cover characteristics with the differentiation of its intensity dependent on geographical and terrain variables as the altitude, landform, slope and exposition. Nevertheless multiannual variability of snowpack persistence with its decreasing trend over the whole research area has been observed.

Detailed understanding of the timing of snow accumulation and snow ablation is necessary as it controls the mountain runoff rate during the spring, water infiltration and groundwater storage as well as the transpiration rate, crucial elements of hydrological cycle.

How to cite: Wypych, A., Ustrnul, Z., and Sałaja, J.: Snow cover response to temperature and precipitation variability in Central European mountain ranges, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-581, https://doi.org/10.5194/ems2023-581, 2023.

Substantial efforts have been made in climatic analyses of climate means and extremes, while much less has been done in understanding short-term (intraseasonal and synoptic-scale) variability. One particular aspect of short-term atmospheric variability is day-to-day temperature difference (DTD). Large DTDs negatively affect human health and impact also animals and plants, hence constituting one of the many weather-related risks to society.

In this contribution, we present European climatology of DTD, including its higher statistical moments and behaviour in distribution tails, in a variety of datasets (observations – ECA&D, gridded observed datasets – E-OBS, reanalyses – NCEP/NCAR, JRA-55, 20CR). The magnitude of DTD is – quite expectedly – largest in winter and smallest in summer, and increases from the coast to the continental interior. Skewness of DTD is negative (i.e., large temperature drops prevail over large temperature rises and/or small temperature rises prevail over small temperature drops) over most of Europe in summer, while in the other seasons, there is a tendency for positive skewness to occur in the north and for negative skewness to occur in the south and over the British Isles. Kurtosis of DTD is everywhere and in all seasons larger than Gaussian; i.e., DTD distributions have heavy tails. Comparisons among datasets reveal their specific deficiencies, such as the existence of outlying unrealistic temperature values in station data that are undetected by quality check, the underestimation of the magnitude of DTD particularly by the 20CR reanalysis, and overestimated skewness in the British Isles in winter and in teh Mediterranean in summer by all reanalyses.

How to cite: Huth, R. and Krauskopf, T.: European climatology of day-to-day temperature changes, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-70, https://doi.org/10.5194/ems2023-70, 2023.

Grape berries and their yields can be strongly affected by the complex connections and interactions between the grapevines and the conditions of the local environment. In areas of known wine production, the yield and quality are usually improved by considering the climate, planting the best grape variety, and using specific agricultural techniques. Thus, sustainability in the winemaking sector worldwide is under pressure due to ongoing climate change, requiring adaptation at multiple levels. Portuguese vineyards will experience increasingly dry and warm conditions due to climate change, with varying degrees of intensity and frequency of weather extremes. Nevertheless, the potential effects of these extraordinary occasions and their effects on viticulture in the future are not well known. In this research, we calculated seventeen climate extreme indices for the Portuguese wine denomination of origin regions/subregions in the historical period (1981–2010) and future periods (2041–2070 and 2071–2100), under the Representative Concentration Pathway 8.5, and based on a five-member ensemble of Regional Climate Model-Global Climate Model chain simulations. Moreover, a principal component analysis was performed for both precipitation and temperature extremes independent of each other. All of Portugal's wine regions experienced an increase in temperature extremes, predominantly in the westernmost regions. When it comes to the precipitation extremes, they show a decrease in the future and a general decline in precipitation but still are a major risk in the northeastern regions. In contrast, the dry extremes, likely bringing on severe droughts, will become much stronger. Finally, it was then possible to recognize which wine regions will be the most vulnerable to extreme weather conditions in the future. This information is essential for enabling smarter choices in the sector, including for long-term planning, climate change adaptation and risk reduction.

Acknowledgments: Soil recover for a healthy food and quality of life (SoilRec4+Health). Projeto cofinanciado pelo Fundo Europeu de Desenvolvimento Regional (FEDER) através do Programa Operacional Regional do Norte (NORTE-01-0145-FEDER-000083).

How to cite: Fonseca, A., Andrade, C., Claro, A., Fraga, H., and A. Santos, J.: Future exposure of Portuguese viticulture to weather extremes, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-338, https://doi.org/10.5194/ems2023-338, 2023.

Sweet cherry (Prunus avium L.) is an important fruit tree for Slovenia, often threatened by spring frosts, especially the early flowering varieties. In recent decades, the occurrence of frost events has steadily increased, which has negatively affected cherry fruit production, especially in the Submediterranean part of Slovenia. Although fruit trees can tolerate severe cold during their dormant stage, the resistance of flower buds gradually decreases with phenological development in spring. Therefore, spring frost events that occur after the beginning of the growing season pose a major risk to fruit trees. An analysis of the probability of frost events in Slovenian cherry orchards was performed based on historical temperature data from the E- OBS database and climate model projections, in particular regionally downscaled EURO-CORDEX projections (ensemble of 6 models) for scenarios RCP4.5 and RCP8.5. The presented analysis is based on two phenological models for calculation of budburst - the growing degree days (GDD) model and the BRIN model. The projections showed an overall increase in frost risk for the majority of models and all selected sweet cherry varieties during the periods 2011–2040 and 2041–2071 compared to the reference period 1981–2010. For the end of the century (period 2071–2100), all of the ensemble projections showed a large increase in frost risk for the analyzed sweet cherry varieties. The projected increase in frost risk under the RCP4.5 scenario was calculated to be the highest for the Early Bigi variety, while under the RCP8.5 scenario the largest increase was calculated for the Germersdorf variety - a more than 40-fold increase in spring frost risk compared to the reference period.

How to cite: Žnidaršič, Z., Gregorič, G., Sušnik, A., and Pogačar, T.: Frost risk climate change projections for sweet cherry (Prunus avium L.) in Slovenia, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-443, https://doi.org/10.5194/ems2023-443, 2023.

As a result of climate change, projections show that the increasing urban population will be exposed to higher air temperatures (Hayes et al., 2014; Sheffield and Wood, 2008). In addition, due to climatic changes, the frequency and duration of heatwaves are expected to increase while the Urban Heat Island effect (UHI) is expected to become more severe (Emmanuel and Krüger, 2012; Kovats and Hajat, 2008; Mirzaei and Haghighat, 2010), causing increasing heat-related mortality and morbidity (Garssen et al., 2005; Xu et al., 2012). Meditteranean-type climate regions have been characterized as particularly vulnerable to climate change due to their high exposure to extreme weather phenomena (Diffenbaugh and Giorgi, 2012; Paz et al., 2016). The intensity of heat waves in these regions is expected to increase further, leading to other life-threatening consequences for urban populations in the Mediterranean region  (Legasa et al., 2020; Zittis et al., 2021). Under this context, the detailed investigation of the impact of climate change on the urban microclimate and human health is considered highly important. This study investigates the impact of climate change on urban microclimate and pedestrian thermal comfort through a series of numerical simulations. For this purpose, 3D Computational Fluid Dynamics (CFD) simulations are performed based on the Unsteady Raynolds-Average Navier-Stokes (URANS) equations for urban microclimate in a real compact heterogeneous urban area. The CFD validation is based on high-resolution field and laboratory measurements of the case study area in Nicosia, Cyprus (Antoniou et al., 2019, 2017). Simulations are performed for meteorological conditions based on field measurements performed in 2010, and for predicted meteorological conditions for 2050 derived from downscaled Regional Climate Models (RCMs). The RCM data are derived from the European Coordinate Regional Downscaling Experiment (EURO-CORDEX) database. CFD results are combined with radiation modeling results of the same urban area to calculate pedestrian thermal comfort using the Universal Thermal Comfort Index (UTCI). The results show that by 2050, a 2.3 °C  increase in the maximum air temperature is expected to occur, which can lead to a more than 240% increase in heat-related mortality. In addition, an increase of UTCI levels is also expected, which is more pronounced in the late afternoon hours, reaching up to 4.3 °C increase at 20:00. A significant change in the thermal stress categories is also identified between the 2010 and 2050 scenarios, where “very strong heat stress” conditions (UTCI: 38-46 °C) are expected to prevail for twice as long, increasing from 3.3 to 6.6 hours, and  “extreme heat stress” conditions (UTCI > 46 °C) appear at some locations of the area in 2050.

How to cite: Antoniou, N., Montazeri, H., Blocken, B., and Neophytou, M.: Multiscale numerical simulations of climate change impact on urban microclimate and human health, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-239, https://doi.org/10.5194/ems2023-239, 2023.

Wind energy fluxes over Portugal and the nearby Atlantic Ocean were estimated under an IPCC future socioeconomic scenario (IPCC SSP5-8.5) for the 2046–2065 and 2081–2100 periods, using wind speed data from WRF 6 km regional simulations. CMIP6 (Coupled Model Intercomparison Project) global model ensemble simulations were also used to assess future anomalies in the Euro-Atlantic large-scale circulation, through kinetic energy and sea level pressure data. Projections show a winter southward displacement of the mid-latitude jetstream, along with a northward displacement during spring, summer, and autumn, which leads to a summer strengthening of the northern winds along the northwestern Iberian coast. Moreover, offshore the northwest coast of Portugal and in the Serra da Estrela mountain range, a 25% to 50% increase in the summer wind power density (WPD) should occur in 2046–2065, and up to more than 100% in 2081–2100. This is also seen in the CMIP6 global projections. In 2046–2065, the WPD’s daily variability and extreme values should increase offshore northwestern Portugal during winter, spring and summer. During autumn, extreme WPD event intensity should decrease. Furthermore, the WPD’s inter-annual variability should increase offshore the northwest coast, and decrease along the central western and southern coasts.

Acknowledgments:

This work was co-funded by FEDER (European Fund for Regional Development), under the project ATLANTIDA – Platform for the monitoring of the North Atlantic Ocean and tools for the sustainable exploitation of the marine resources (NORTE-01-0145-FEDER-000040). This work was also funded by National Funds by FCT - Portuguese Foundation for Science and Technology, under the project UIDB/04033/2020.

How to cite: Claro, A., A. Santos, J., Andrade, C., and Carvalho, D.: Projections of wind energy potential in Portugal assessed with CMIP6 simulations, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-342, https://doi.org/10.5194/ems2023-342, 2023.

Near-surface wind speed (SWS) has been the forgotten part of the climate system, compared with other viables as temperature or precipitation, due to poor quality of observational data and the challenges in the homogenization process. During the last two decades the interest in long-term SWS variability and trends has increased and two main phenomena were discovered using observational data: the first one is termed “stilling” (decline until the 2010s), followed by the “reversal” (increase since then) of SWS. For a complete characterization of SWS changes, extremes also need to be evaluated as they have wide socioeconomic and environmental implications. The majority of the studies dealing with wind extremes are focused on high wind speeds associated with extratropical cyclones, hurricanes, tornados, storms, etc., which represent a threat for human lives and cause large damages. However, low wind speed events (known as “wind droughts”) have received less attention, representing a research gap in climate studies, and they are crucial due to the strong impacts on, for example, wind power generation a key motor of decarbonization. The main objective of this study is to define a Wind Drought Index (WDI) to identify and quantify the magnitude and extend of low wind speed events over the Iberian Peninsula. Our analyses are based on quality controlled and homogenized observational data series from 86 stations over Spain and Portugal for 1961-2022. Here we present for the first time the long-term and spatio-temporal changes in the occurrence and intensity of wind drought events over the study region.

How to cite: Andrés-Martín, M., Azorín-Molina, C., Vicente-Serrano, S. M., Bedoya-Valestt, S., Utrabo-Carazo, E., and Plaza Martín, N. P.: Wind Drought Index: a proposal to assess low wind speed events over the Iberian Peninsula, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-425, https://doi.org/10.5194/ems2023-425, 2023.

The Arctic Oscillations (AO) are connected with various regional and global climatic events. These oscillations are important to study recent climate change and to improve our knowledge about the dynamics of climatic disasters. The main sources of these oscillations are the influences of global warming, solar activity and cosmic rays on climatic variations. The solar activity affects climatic processes by the Total Solar Irradiance (TSI) variations, solar wind and solar magnetic field. The variations of solar magnetic field are connected with the asymmetrical distribution of sunspots around the solar equator. These variations modulate heliosphere, geomagnetic field and galactic cosmic rays, whose influence on climate oscillations depends on ozone production in high latitudes. The solar influence on Arctic Oscillations are analyzed by centennial time series of TSI and North-South (N-S) solar asymmetry. The time series of Arctic Oscillation since 1850 are combined by data, prepared by David W. J. Thompson with the data from the NCEP/NCAR Reanalysis after 1958. The combined Arctic long time series are analyzed by the Method of Partial Fourier Approximation (PFA) and compared with solar cycles in several narrow frequency bands. In addition, time series from 20th Century Reanalysis V3 dataset of surface monthly means air temperature inside the North polar circle are analyzed and compared with solar data. Various common solar and atmosphere cycles in narrow frequency bands are detected, whose periodicity is between 3 and 80 years. The mean variations of atmosphere data are determined by averaging in moving 2-year window. The AO and temperature time series have positive trends after 1960, where the rate of temperature rise is 0.107 degree per year since 1988. The solar influence on AO variations is dominated by the N-S solar asymmetry, and this points out to the important role of cosmic rays and geomagnetic field on climatic cycles. These results can help to divide natural solar from anthropogenic effect in recent global warming and to improve scenario of future climate change.

How to cite: Chapanov, Y.: Solar influence on Arctic Oscillations, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-58, https://doi.org/10.5194/ems2023-58, 2023.

Climate strongly influences not only the distribution and abundance of species on Earth but also the distribution of ecosystem types. Since the climate is defined as a long-term pattern of weather conditions at a given location or region both the distribution and evolution of its conditions are considered highly relevant. The Köppen-Geiger climate classification is based on temperature and precipitation and has been widely used to assess climate shifts worldwide.

In this study, high spatial resolution (10 min) monthly precipitation (in mm) and maximum, minimum, and mean temperatures (in °C) gridded datasets were retrieved from the WorldClim data website. The Köppen-Geiger climate classification was then computed worldwide between 1970 and 2000 (historical baseline) and between 2041 and 2060 under two Shared Socio-economic Pathways (SSPs) SSP2‒2.6 and SSP5‒8.5; from an ensemble of 14 Global Climate Models (GCMs).

Results point out an overall decrease of type E (Polar) around 4.6% for ET (Tundra) and 3.8% for EF (Icecap) under both SSPs. A noticeable decrease of type Dfc (Temperate subpolar oceanic) 7.34% and 7.53% under SSP2-2.6 and SSP5-8.5, respectively is also projected. Climate types Csa (Temperate with hot summer) and Cfb (Temperate oceanic with warm summer) are also projected to decrease by about 1% under both SSPs. Conversely, in decreased order of magnitude, types Dfa (Continental humid with hot summer, 6%), Cfa (Temperate humid subtropical, 2.8 and 2.9%), BWh (Hot desert, 1.4%), BSh (Hot semi-arid or steppe, 1.3%), As (Tropical, 1.2%), Dwa (Monsoon-influenced hot-summer humid continental, 1%) are projected to increase under SSP2‒2.6 and SSP5‒8.5, respectively. The projected changes mainly in locations like Siberia (reduction of type E areas, for example), will have a detrimental effect on the environment since the melting of the permafrost will release methane a powerful greenhouse gas, thus contributing to global warming.

Acknowledgments: This research was funded by National Funds by FCT ‒ Portuguese Foundation for Science and Technology, under the project UIDB/04033/2020.

How to cite: Andrade, C., A. Santos, J., and Fonseca, A.: Worldwide Köppen Geiger Climate classification changes projections (SSP2-2.6 and SSP5-8.5), EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-336, https://doi.org/10.5194/ems2023-336, 2023.

Climate is defined by the statistics of the weather. We are thus used to the notion that weather depends on climate in the sense that a weather state is a quasi-random realization drawn from the climatological distribution of weather states. Consequently, weather obviously also depends on climate change. Here it is argued that it can be very instructive to consider this dependence the other way around and to investigate how climate change depends on the weather. More specifically, the question is how different parts of the climatological distribution change, depending on certain relevant characteristics of the weather. For example, one may ask how the climate at some time of the year and at some location changes between a pre-industrial and a globally +4K warmer climate, considering only days where the local winds at some height blow from a specific direction. Alternatively, one may investigate how the climate change pattern differs between certain large-scale atmospheric circulation regimes, such as NAO⁺ and NAO^- situations. While such conditional climate change analyses can be based for example on reanalysis or CMIP-type climate model data, a more extreme variant are storyline simulations where the evolution of the large-scale circulation is imposed in a climate model using different climate backgrounds, allowing to assess climate change conditional on a specific evolution of the large-scale circulation. Storyline simulations inevitably ignore possible changes in the likelihood of circulation patters. In contrast, analyses based on sufficiently large samples of reanalysis or CMIP-type data also allow for quantifying changes in likelihoods and constitute a proper decomposition of the complete (unconditional) climate change signal. Here the concept of weather-dependent climate change is described and its potential to help unravel the complexities of climate change is demonstrated.

How to cite: Goessling, H.: Weather-dependent climate change, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-304, https://doi.org/10.5194/ems2023-304, 2023.

Bias-adjusted and downscaled climate data are essential for regional impact studies. In some cases, a “counterfactual” baseline climate data that isolates the human-induced influences is also required for impact studies that focus on the anthropogenic influence. We examine how human activities have influenced the frequency and intensity of extreme temperature and precipitation events in Central Asia (CA) from 1960 to 2014. We use two sets of simulations from six climate models that are part of the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP) and the Coupled Model Inter-comparison Project phase 6 (CMIP6). One set (labelled as hist-nat) includes only natural factors (solar and volcanic activity) and the other set (labelled as hist) includes both natural and human factors (such as greenhouse gas emissions). We bias-correct and statistically downscale these simulations using the Climatologies at high resolution for the earth’s land surface areas dataset (CHELSA) to a finer spatial resolution (0.25°× 0.25°) to better capture the regional climate variability and impacts. We find that human factors have increased the risk of extreme heat events by four times across most of CA in the hist simulations compared to the hist-nat simulations. We also find that human factors have enhanced the likelihood and magnitude of extreme precipitation events over CA in the hist simulations, especially over Kyrgyzstan and Tajikistan, where landslides and floods are common hazards. Our results suggest that human-induced climate change has contributed to more severe weather extremes over vulnerable regions of CA. Our high-resolution data set is publicly available and can be used for further studies on the causes and consequences of extreme events in CA.

How to cite: Fallah, B., Russo, E., Menz, C., Hoffmann, P., Didovets, I., and Hattermann, F. F.: The Human Factor: Increasing the Risk of Weather Extremes in Central Asia, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-196, https://doi.org/10.5194/ems2023-196, 2023.

How to cite: Carvalho, D., El Akkraoui, A., Errico, R. M., Bosilovich, M., and Privé, N. C.: On the convergence of reanalysis produced by different data assimilation streams: a case study with NASA-GMAO MERRA-2 reanalysis system, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-209, https://doi.org/10.5194/ems2023-209, 2023.

Due to its high influence on agriculture, infrastructure, water management, and other areas, precipitation is one of the most important climate factors. Furthermore, climate change is likely to produce more extreme precipitation events and lead to an excess of surface water and floods, which have severe impacts on society. However, it is still one of the major challenges for climate models to realistically reproduce the regional patterns, temporal variability, and precipitation intensity due to the intricate interactions between atmospheric precipitation processes, including cumulus convection, large-scale circulations, planetary boundary layer processes and cloud microphysics. This is especially true for terrains with heterogeneous orography, like the Carpathian region.

For the sake of quantifying the uncertainty and improving the accuracy of the precipitation simulations of the RegCM4.7 regional climate model over the Carpathian region, we evaluate the performance of different physical options at 10 km horizontal resolution, using ERA-Interim reanalysis data as initial and boundary conditions. Altogether 24 simulations were carried out by using various combinations of the physics schemes (2 land surface, 2 microphysics, 3 cumulus and 2 boundary layer schemes) for the year 2010, which was the wettest year in the Carpathian region since the beginning of the regular measurements. Different parameterization combinations lead to different simulated climates, so their variance can serve as an estimate of model uncertainty due to the representation of unresolved phenomena.

The analysis of the RegCM ensemble indicates systematic precipitation biases, which are linked to different physical mechanisms in the summer and winter seasons. Furthermore, problematic interaction between some parameterizations causes large overestimation of the precipitation. Due to the different treatment of moisture in the schemes, there are differences not only between the representations of the precipitation cycle, but also in other climatological variables such as soil moisture, temperature and cloud cover. Based on the results, RegCM4.7 is the most sensitive to the applied convection scheme, but the interactions with the other schemes (e.g., microphysics and land surface) affect not only the total precipitation, but also the convective and stratiform precipitation in some cases.

Acknowledgements. Research leading to this study has been supported by the following sources: the Hungarian National Research, Development and Innovation Fund (under grant K-129162), and the National Multidisciplinary Laboratory for Climate Change (RRF-2.3.1-21-2022-00014).

How to cite: Kalmár, T., Pongrácz, R., and Pieczka, I.: Sensitivity of simulated precipitation to different RegCM configurations over the Carpathian region in the wettest year, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-502, https://doi.org/10.5194/ems2023-502, 2023.

Climate change has various effects in different regions on Earth. The shift of global circulation patterns, most importantly changing cyclone tracks and strengthening blocking episodes have serious influence on the regional climate in the midlatitudes. In this study, a 180-year long historical dataset was used to track the change of the circulation patterns over Europe, since different weather types and precipitation can be associated with different synoptic situations. An automated cyclone/anticyclone detection method was applied on the mean-sea level pressure data from the Twentieth Century Reanalysis Project (NOAA). The European domain was split into the areas of low and high pressure systems, thus in each location we were able to investigate the distribution of cyclonic and anticyclonic effects. Clustering methods were used to study the long-term shift of pressure centers.

In the 1836–2015 period, largely increasing anticyclonic influence can be seen in the Mediterranean, underlining the increasing risk of droughts. In the European domain, anticyclonic clusters generally shifted towards the Mediterranean, while cyclone centers showed a northward shift and a weakening tendency. However, the temporal trend of shifts was not consistent over the long study period with multiple breakpoints over the 20^th century. The statistically significant increase of anticyclonic influence over the 180-year long period was between 5–10% for Central Europe and reached 10% in the Mediterranean. Increasing frequency of low-pressure systems was found in Northern Europe. Results coincide with the regional climate impacts reported in literature and highlight the importance of the investigation of changes in climate dynamics over this highly populated area.

How to cite: Varga-Balogh, A., Leelőssy, Á., Varga, L., and Mészáros, R.: Increasing anticyclonic influence over Central Europe between 1836–2015, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-421, https://doi.org/10.5194/ems2023-421, 2023.

In October 2022 a cyclone that deepened explosively over the South Pacific - the "Peter I Storm" - acquired a central pressure close to 900hPa, which by some margin is lower than has been seen before (in modern times) for a cyclone in either the northern or southern hemisphere extratropical regions. Whilst observation coverage in the area was sparse, the exceptional central pressure value was supported by operational numerical model output from both ECMWF and GFS models, and also by the ERA5 re-analysis. This talk will examine the evolution of the cyclone, that spanned more than 10 days: from its tropical origins near to Tonga to its final decay on the fringes of Antarctica. We pose the question: what might have contributed to the occurrence of such an extreme? Surface characteristics, such as roughness and sea ice coverage, and large-scale dynamics will be referenced. Operational ECMWF ensemble predictions will also be shown; these suggest that the event was remarkably predictable for lead times of 5 days and less. The ECMWF forecasts will also be compared with some modern data-driven AI-based forecasts, to examine if they were as good. 

The extreme event will then be placed in a climatological context, using ERA5, to reference questions about 'trends in extremes', examining also northern hemisphere behaviour, and comparing the cyclone's life-cycle with that of the northern hemisphere "record holder" from 1986. We will also cross-reference another extreme cyclone case from 1941, to further examine the question of re-analysis integrity in the face of sparse data coverage. It seems that the ERA5 representation of cyclones with extreme central pressures is quite robust. This is probably because such cyclones tend to have a large areal extent. The talk will conclude with contrasting remarks about representativeness for smaller cyclones, that can have particular relevance for high impact weather over Europe.

How to cite: Hewson, T.: A Record Breaking Extratropical Cyclone in 2022: A Sign of Climate Change ?, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-303, https://doi.org/10.5194/ems2023-303, 2023.

Climatological Standard Normals (CLINO) are the mean or average values of a climate variable over a standard reference period. The World Meteorological Organization (WMO) established that the length of the reference period should be 30 years, with a recommendation to update the climate normals every 10 years, to provide representative reference values for recent climatic conditions. 

Climate normals are used for two principal purposes. They serve as a benchmark against which recent or current observations can be compared, including providing a basis for many anomaly-based climate datasets. They are also widely used as a reference baseline to provide context for future climate projections.

By applying the WMO data requirements and criteria, Met Éireann has compiled a set of climate normals for the period 1991-2020 for a range of parameters including temperature, precipitation, solar radiation, wind and pressure. Annual, seasonal, and monthly normal values for the period 1991-2020 were compiled using quality assured data obtained from Met Éireann’s observation network. Values are averaged for each month over the 30-year period to obtain the long-term average. Where there are gaps in data, estimates are made using data from neighbouring stations. Long-term averages for stations are then used to generate maps and gridded data at a 1km resolution.

A comparison of the most recent 30-year period with the 1961-1990 period shows an increase in annual mean temperature of approximately 0.7°C. All seasons experienced a rise in mean temperatures, with Spring displaying the greatest differences between the two periods.

On an annual basis, averaged over the country, there has been an increase of approximately 7% in rainfall totals between the two normal periods (1961-1990 and 1991-2020), with the greatest increases observed in the western half of the country. All seasons show an overall increase in rainfall but there are regional variations.

Here we present the data and methods used to produce the latest set of climate normals for Ireland as well as an assessment of trends between the two normal periods, 1961-1990 and 1991-2020.

From September 2023, weather and climate statistics will reference the new long-term average period 1991-2020, unless otherwise stated. These will replace the 1981-2010 long-term averages that are currently in use. The historical baseline period of 1961-1990 will be retained for use in climate change assessments.

How to cite: Curley, M., Coonan, B., Ryan, C., and Ruth, C. E.: Ireland’s Climatological Standard Normals (CLINO) 1991-2020, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-517, https://doi.org/10.5194/ems2023-517, 2023.

Recently, interest in analysing regional climate change impacts in light of global warming levels (GWLs) has risen, not least because the IPCC used them in their current report cycle. GWLs shift the focus point in the uncertainty chain compared to classical scenario approaches like SRES or RCPs, and allow a more comprehensive analysis of the differences and implications of a 1.5°C vs. a 2°C warmer world. Although a lot of research has been done to link GWLs to regional climate change signals within global circulation model (GCM) outputs, or between GCMs and regional climate model (RCM) outputs, there is a lack in studies to link GWLs to localised climate scenarios. In contrast to analysing regional signals within GCMs and between GCMs and RCMs, often no direct link can be established between the global and the downscaled models, especially when they are driven by an older version of GCMs (e.g. CMIP3, CMIP5), because many local climate scenarios have not been updated since the release of CMIP6.

Here, a version-agnostic methodology of linking local climate scenarios to GWLs derived from CMIP6 GCMs is presented for the example of the Austrian climate scenarios (ÖKS15). It is an extension of the time sampling method where time slices around the crossing point of global mean temperature over the respective GWL threshold are derived from GCMs. When using those time slices directly, uncertainties emerging from the local scale would intersperse the anthropogenic warming signal with natural climate variability. To avoid this, instead of explicit time periods, the respective climate change signals are used to select the period of interest from the local scenarios. This approach promises a more robust analysis compared to the time sampling method, because it considers error propagation biases due to the downscaling method and ambiguous reference periods to derive the anomalies.

The study is expected to contribute to locally adapted assessment reports on climate change impacts that intend to use the IPCC methodology, like the second Austrian Assessment Report on Climate Change (AAR2).

How to cite: Becsi, B. and Formayer, H.: Linking global warming levels to local climate scenarios: applicability, prospects and uncertainties, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-526, https://doi.org/10.5194/ems2023-526, 2023.

Reanalysis as well as satellite data from TRMM show a decreasing trend in the daily precipitation area between 50°S and 50°N throughout the past decades. The trend is highly correlated to global mean temperatures and indicates the change in the hydrological cycle may be connected to the warming climate, resulting in increased drought frequencies and more intense rainfall. However, changes in the satellite networks provide inhomogeneous data sets and have possibly affected the precipitation area in the satellite and reanalysis dataset. Global climate and Earth system models, although suffering from biases in precipitation amounts and frequencies, are not influenced by changing observation systems. Thus, they provide a possibility to test the hypothesis of a decreasing precipitation area in a warming climate.

Here, we have used simulations from CMIP6 and CMIP5 to test this hypothesis. The models following the high-emission scenarios SSP5-8.5, SSP3-7.0 and RCP8.5 showed a clear decrease in the precipitation area towards the end of the 21st century. Compared to changes in the satellite and reanalysis data, the magnitude in the CMIP models was smaller. The decrease was apparent globally but most pronounced between 50°S and 50°N. Zonal averages of the daily precipitation area showed a general decrease from 5° to 50° on both hemispheres and an increase from 55° towards the poles, indicating a poleward shift of precipitation. In the Arctic region, the daily precipitation area was increasing from 20% to 30% on average.

Along with the precipitation area changes, the precipitation frequency decreased between 5° and 50 °S and increased in the polar regions. In the Northern Hemisphere, the precipitation frequency decreased over the North Atlantic, the Mediterranean region and Middle America. At the same time, precipitation intensity increased mostly everywhere.

Our analysis supports that in a warming climate, the daily precipitation area may indeed shrink, as found in reanalysis and satellite data. The results also showed that an increase in precipitation is coupled with an increase in precipitation intensity, while a decrease in precipitation is coupled with a decrease in frequency. However, the latter was generally coupled with an increase in precipitation intensity, suggesting increased drought frequencies and more intense rainfall at the same time.

How to cite: Dobler, A., Benestad, R., Lussana, C., Lutz, J., Landgren, O., Haugen, J. E., Mezghani, A., and Parding, K. M.: Decrease of the global precipitation area in CMIP6 projections, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-546, https://doi.org/10.5194/ems2023-546, 2023.