A link between surface air temperature and extreme precipitation over Russia from station and reanalysis data

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 degrees C and 20 degrees C. At higher temperatures, the negative scaling prevails. Analyzed data show a pronounced decrease in relative humidity with increasing surface temperatures beyond the 15 degrees C-20 degrees 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.