Over the past 30 years, there has been a catastrophic reduction of the glacierized area in the mountains of the Greater Caucasus, with the values reaching 0.69% per year. Physical mechanisms accountable for such intense melting are investigated in this study. The main trends in the temperature‐moisture regime of the Caucasus and adjacent areas for the period 1982–2015 were recovered based on instrumental data and the ERA‐Interim data reanalysis. It is demonstrated that there is statistically significant warming for the summer season in the region as a whole. No statistically significant changes were detected in the precipitation regime, despite the increase in the integral moisture content of the atmosphere and in the potential convective energy. The integral moisture content growth is compensated by the increase in the moisture divergence. This happens due to the intensification of large‐scale descending atmospheric motions. As a result, the seasonal and annual precipitation amounts do not change significantly. Such effects are possibly the consequence of the global process of “widening of the tropics.” This process is most clearly manifested in the expansion of the Hadley cell and the northward shift of its descending branch. This process can lead to an increased frequency of anticyclones over the southern regions of Europe during the warm part of the year. This, in turn, leads to a negative cloud cover trend as well as an increase in the closely related radiation balance. Apparently, this process is the cause of the intensive reduction of the glaciation area in the North Caucasus.

Precipitation extremes are widely thought to intensify with global warming due to an exponential growth following the Clausius–Clapeyron (C–C) equation which links the atmosphere water vapor saturation pressure with air temperature. However, a number of recent studies based on station and reanalyzes data for the contemporary period showed that scaling rates between extreme precipitation and temperature strongly depend on temperature range, moisture availability, and a region of interest. Being performed for some regions, such estimates, however, lack for Northern Eurasia, where prominent temperature changes and rapid shift from large-scale to convective precipitation are observed. Here, we examine the scaling between daily precipitation extremes and surface air temperature (SAT) over Russia for 1966–2017 using meteorological station data and for 1979–2020 using ERA5 reanalysis. The precipitation-temperature relation is examined for total precipitation and, separately, for convective and large-scale precipitation types. In winter, we reveal a general increase in extreme precipitation of all precipitation types according to the C–C relationship. For the Russian Far East region, the stratiform precipitation extremes scale with SAT following even super C–C rates, about two times as fast as C–C. However, in summer we find a peak-like structure of the precipitation-temperature scaling, especially for the convective precipitation in the southern regions. Extreme precipitation reaches their peak values at the temperature range between 15 °C and 20 °C. At higher temperatures, the negative scaling prevails. Analyzed data show a pronounced decrease in relative humidity with increasing surface temperatures beyond the 15 °C–20 °C threshold. This indicates that moisture availability is the major factor for the peak-shaped relationship between extreme precipitation and temperature revealed by our analysis.

This study presents a dataset on long-term multidisciplinary glaciological, hydrological, and meteorological observations and isotope sampling in a sparsely monitored alpine zone of the North Caucasus in the Djankuat research basin. The Djankuat glacier, which is the largest in the basin, was chosen as representative of the central North Caucasus during the International Hydrological Decade and is one of 30 “reference” glaciers in the world that have annual mass balance series longer than 50 years (Zemp et al., 2009). The dataset features a comprehensive set of observations from 2007 to 2017 and contains yearly measurements of snow depth and density; measurements of dynamics of snow and ice melting; measurements of water runoff, conductivity, turbidity, temperature, δ¹⁸O, δD at the main gauging station (844 samples in total) with an hourly or sub-daily time step depending on the parameter; data on δ¹⁸O and δ²H sampling of liquid precipitation, snow, ice, firn, and groundwater in different parts of the watershed taken regularly during melting season (485 samples in total); measurements of precipitation amount, air temperature, relative humidity, shortwave incoming and reflected radiation, longwave downward and upward radiation, atmospheric pressure, and wind speed and direction – measured at several automatic weather stations within the basin with 15 min to 1 h time steps; gradient meteorological measurements to estimate turbulent fluxes of heat and moisture, measuring three components of wind speed at a frequency of 10 Hz to estimate the impulse of turbulent fluxes of sensible and latent heat over the glacier surface by the eddy covariance method. Data were collected during the ablation period (June–September). The observations were halted in winter. The dataset is available from PANGAEA (https://doi.org/10.1594/PANGAEA.894807, Rets et al., 2018a) and will be further updated. The dataset can be useful for developing and verifying hydrological, glaciological, and meteorological models for alpine areas, to study the impact of climate change on hydrology of mountain regions using isotopic and hydrochemical approaches in hydrology. As the dataset includes the measurements of hydrometeorological and glaciological variables during the catastrophic proglacial lake outburst in the neighboring Bashkara valley in September 2017, it is a valuable contribution to study lake outbursts.

A study has been made of changes in some characteristics of daily precipitation in Russia for the winter and summer seasons in the 20th and 21st centuries using Coupled Model Intercomparison Project Phase 6 (CMIP6) climate models. In the modern period, model data are compared with data from meteorological stations and ERA5 reanalysis. For winter and summer, changes in mean seasonal precipitation, the number of days with precipitation, and the frequency of extreme precipitation are analyzed. For the modern period 1991–2020, according to empirical data, in winter on the territory of Russia, a significant increase in seasonal precipitation amounts and the frequency of days with extreme precipitation on the Far East coast and in the central part of European Russia (ER) are detected. A decrease in the frequency of days with precipitation at most meteorological stations in Russia by 4–6 days/10 years is also noted. In summer, an increase in precipitation amounts and the frequency of days with precipitation is found in Western Siberia and on the coasts of the Sea of Okhotsk and the Pacific Ocean. A decrease in the amount and frequency of precipitation is obtained for southern ER and the south of Eastern Siberia. Climate models, on average for the ensemble, show an increase in the relative amounts of precipitation and the extreme precipitation frequency over most of the Russia territory in winter, and these trends may intensify in the coming decades. In summer, on the contrary, for southern ER, as a whole, there is a slight decrease in the seasonal precipitation totals and the number of days with precipitation. However, strong intermodel differences, especially in the summer season, do not allow us to draw unambiguous conclusions about changes in precipitation characteristics in Russia in the next 30 years. By the end of the 21st century, changes will become more pronounced. For example, in ER and northern Siberia, a noticeable increase in winter precipitation amounts and the frequency of extreme precipitation may occur. By the end of the 21st century, a slight decrease in the precipitation totals and the number of days with precipitation is possible in summer in ER.

Estimates of the contribution of direct radiative forcing (DRF) to the surface air temperature trends over the Northern Hemisphere (NH) continents for the period 1979–2012 have been obtained based on an ensemble of numerical experiments with an atmospheric general circulation model using the prescribed historical sea surface temperature and sea ice concentration data with and without time-varying concentrations of greenhouse gases and aerosols in the atmosphere. The contribution of DRF to the simulated ensemble mean temperature variations over land in the NH in winter and summer is approximately 30% or 0.3°С and 0.2°С, respectively. The maximum warming associated with DRF was found, in particular, in winter and summer over the eastern part of the European territory of Russia. The results indicate that the response of atmosphere circulation to DRF may lead to a nonlinear DRF contribution to the temperature changes in the NH, in particular mitigating the temperature increase in the winter season.