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The description and analysis of compound extremes affecting mid and high latitudes in the winter requires an accurate estimation of snowfall. Such variable is often missing for in-situ observations, and biased in climate model outputs, both in magnitude and number of events. While climate models can be adjusted using bias correction (BC), snowfall presents additional challenges compared to other variables, preventing from applying traditional univariate BC methods. We extend the existing literature on the estimation of the snowfall fraction from near-surface temperature, which usually involves binary thresholds or fitting parametric nonlinear functions. We show that, combining breakpoint search algorithms to define threshold temperatures and segmented regression models, it is possible to obtain accurate out-of-sample estimates of snowfall over Europe in ERA5 reanalysis, and to perform effective BC on the IPSL-WRF high resolution EURO-CORDEX climate model only relying on bias adjusted temperature and precipitation. This method offers a feasible way to reconstruct or adjust snowfall observations without requiring multivariate or conditional bias correction and stochastic generation of unobserved events. [ABSTRACT FROM AUTHOR]

This study investigates changes in seasonal runoff and low flows related to changes in snow and climate variables in mountainous catchments in Central Europe. The period 1966–2012 was used to assess trends in climate and streamflow characteristics using a modified Mann–Kendall test. Droughts were classified into nine classes according to key snow and climate drivers. The results showed an increase in air temperature, decrease in snowfall fraction and snow depth, and changes in precipitation. This resulted in increased winter runoff and decreased late spring runoff due to earlier snowmelt, especially at elevations from 1000 to 1500 m a.s.l. Most of the hydrological droughts were connected to either low air temperatures and precipitation during winter or high winter air temperatures which caused below-average snow storages. Our findings show that, besides precipitation and air temperature, snow plays an important role in summer streamflow and drought occurrence in selected mountainous catchments. [ABSTRACT FROM AUTHOR]

We perform simulations with the WRF regional climate model at 12 and 3 km grid resolution for the current and future climates over Central Europe and evaluate their added value with a focus on the daily cycle and frequency distribution of rainfall and the relation between extreme precipitation and air temperature. First, a 9 year period of ERA-Interim driven simulations is evaluated against observations; then global climate model runs (MPI-ESM-LR RCP4.5 scenario) are downscaled and analyzed for three 12-year periods: a control, a mid-of-century and an end-of-century projection. The higher resolution simulations reproduce both the diurnal cycle and the hourly intensity distribution of precipitation more realistically compared to the 12 km simulation. Moreover, the observed increase of the temperature–extreme precipitation scaling from the Clausius–Clapeyron (C–C) scaling rate of ~ 7% K−1 to a super-adiabatic scaling rate for temperatures above 11 °C is reproduced only by the 3 km simulation. The drop of the scaling rates at high temperatures under moisture limited conditions differs between sub-regions. For both future scenario time spans both simulations suggest a slight decrease in mean summer precipitation and an increase in hourly heavy and extreme precipitation. This increase is stronger in the 3 km runs. Temperature–extreme precipitation scaling curves in the future climate are projected to shift along the 7% K−1 trajectory to higher peak extreme precipitation values at higher temperatures. The curves keep their typical shape of C–C scaling followed by super-adiabatic scaling and a drop-off at higher temperatures due to moisture limitation. [ABSTRACT FROM AUTHOR]

Chornohora is the highest mountain ridge in the Ukrainian Carpathians with 6 peaks of an altitude over 2,000 m above sea level (Hoverla is the highest peak, 2,061 m a.s.l). Its climate is explored less than other mountain ridges in Europe. The massif is a climatic barrier for air masses on NW-SE line. To describe the climate of this area data from the weather station at Pozhyzhevska alpine meadow for the years 1961–2010 were used. The seasonal and long-term variability of air temperature, atmospheric precipitation and snow cover were investigated on the background of air circulation types. The results show that general features of Chornohora climate depend both, on elevation above sea level and on air circulation. Lowest temperature is observed at N-NE circulation and highest precipitation – at western air inflow. Long-term changes of examined climate elements in Chornohora show significant increase in mean (0.13°/10 years) and minimum (0.22°C/10 years) air temperature as well as in snow cover depth and number of snowy days. [ABSTRACT FROM AUTHOR]

The article analyzes continentality changes in Europe in the period between 1938 and 2018. We use the raw data of monthly air temperature averages, obtained from the website: European Climate Assessment & Dataset, collected by 443 climate stations. The data is processed with the program MATLAB and the results are plotted with Excel and ArcGIS. The results show that there are differences between the Supan, Gorczynski and Conrad Continentality Indices. We also found that in the period from 1938 to 2018, the trends of continentality indices have changed. Our results have shown that the climate in some parts of Europe is becoming more maritime, especially in the Northern and Eastern regions, while in other territories it is becoming more continental, especially in the Mediterranean coastal regions. [ABSTRACT FROM AUTHOR]

ABSTRACT Due to imperfections inherent to numerical climate simulations, projections of climate change need to be accompanied with an uncertainty estimate, typically derived from multi-model ensembles. Here, an analysis of regional climate model outputs spread and its temporal evolution is presented, for the European air temperatures simulated over the 21st century. To quantify the overall uncertainty, standard deviation (sd) is used and compared to median absolute deviation and inter-quartile range. The outcomes are shown for annual and seasonal means of air temperature at 2 m, 850 hPa, 700 hPa, 500 hPa and 300 hPa levels, simulated by ENSEMBLES regional climate models for eight geographical areas across Europe. Our results indicate that the estimated uncertainty of simulated air temperature changes over Europe generally increases during the 21st century, and typically decreases with height of the studied vertical level. The influence of driving global climate model on the regional simulation generally increases with height of the studied vertical level. In lower tropospheric levels, the clustering of regional climate models according to driving global climate model is stronger in winter than in summer. [ABSTRACT FROM AUTHOR]

The extratropical cyclone is one of the basic systems that characterize the weather and climate in mid-latitude areas, where the mean meridional temperature gradient is large. As for in Europe's middle or higher latitude areas. Although the climatological mean meridional gradient of the air temperature there is rather weak compared to that from autumn to spring around Japan in East Asia, many extratropical cyclones appear throughout a year. Thus it would still be necessary to re-examine the seasonal cycle of the daily cyclone and anticyclone activities around Europe, paying attention also to their intraseasonal variations and the effects on the behaviors of daily cyclone and anticyclone systems together with the variety of their characteristics. Our previous case studies for 2000 (Kuwana et al., EGU2017 and 2018) pointed out that daily cyclones and anticyclones were greatly reflected by the alternation of the intraseasonal-scale ones with equivalent barotropic structure in northwestern Europe in summer. In addition, the intraseasonal and daily behaviors of the Icelandic low in the seasonal cycle showed the seasonal progression from autumn to the next spring.The present study will further examine the detailed features on the above mentioned topics, together with their relationship to the weather conditions in Europe, mainly based on the NCEP/NCAR re-analysis data. From late May to August, intraseasonal-scale low and high areas (as for the deviation fields) with the equivalent barotropic structure extended from the Norwegian Sea to Northern Germany. In the negative deviation period (stage with the intraseasonal-scale low there), baroclinic zone in the lower layer just on the south of that low was periodically enhanced. It is interesting that, in one of the negative periods, the southward shift of intraseasonal-scale baroclinic zone seemed to be related to the temporal activity of baroclinic ibstability wave cyclones, or the rather lower air temperature stage in central Europe. The detailed description on there will be made at the poster presentation. As for the asymmetric seasonal progression, not only the differences of intraseasonal features of the Icelandic lows between the former half and latter half of winter as shown in EGU2018, but also the differences of the daily variations between early summer and early autumn were notable. As for early autumn, amplitude of the short-period SLP variation in northern Europe, corresponding to the temporal appearance of the "Icelandic low-like" cyclone with relatively short persistency, increased greatly one month earlier than the formation timing of the seasonal mean Icelandic low in middle October. Interestingly, that event occurred just when the air temperature began to decrease seasonally. [ABSTRACT FROM AUTHOR]