Analysis of climatic characteristics, Palmer Drought Severity Index and largescale river runoff basing on observational data (CRUTEM.5, GISS, CRU TS4.05, CRU-scPDSI) and 20th century reanalysis (ERA20C, CERA20C) shows that the Early 20th Century Warming period, in particular 1930-s, in the East European Plain was marked by the strong long-lasting drought that have no analogues during the observation period. Atmospheric circulation patterns and the drivers of this phenomenon, as well as possible analogues in the period of modern climate warming, are studied.
Empirical orthogonal functions (EOF) of the geopotential height of 500 hPa variability over the extratropical zone of the Northern Hemisphere in winter season on the base of 30-year running periods are examined in order to reveal change in the atmospheric circulation patterns for 1948-2018. Analysis of the first EOF patterns and their features associated with changes in the intensity and localization of the atmospheric centers of action shows significant shifts the regional structure of the geopotential height anomalies. Comparison of the first five EOFs contribution to the total variability for two periods: 1968-1997 (warming of temperate NH latitudes) and 1988-2017 (sharp warming of the Arctic), reveals definite changes in the structure of circulation variability at the turn of the 20th and 21st centuries, primarily the prevalence of their negative phase occurrence and the increasing role of regional centers of action, in particular ЭОΦ3 responsible for 56% of temperature variability in the northeast Atlantic and over the Barents sea.
The ability of three 20th century reanalyses (NOAA20C, ERA20C and CERA20C) to reproduce the observed features of the atmospheric circulation structure in the Northern Hemisphere is being analyzed. The leading modes of seasonal mean sea level pressure variability for winter season are analyzed using three reanalyses and HadSLP2.0 empirical data for two periods - the Early 20th century warming and the ongoing warming. It is shown that in general the reliability of the reanalyses in the first half of the 20th century is significantly worse than in the modern period. The leading mode of winter circulation variability, Arctic oscillation, is well reproduced in reanalyses throughout the 20th century, whereas the second and, especially, the third leading variability modes are characterized by significant discrepancies both in different reanalysis and periods. Systematic differences for sea level pressure in atmospheric circulation centers of action in the Northern Hemisphere are revealed in reanalyses throughout the 20th century.
Variations of the frequency of extreme daily precipitation events in winter and summer in the Russian Federation were studied for the 1961-2013 period using meteorological stations data. Future changes were estimated using data of the global climate models from CMIP5 model ensemble. In winter, there is a slight increase in the extreme precipitation frequency throughout Russia except for the Far East. By the end of the twenty-first century, models predict an overall strengthening of this trend. In summer, current changes are less significant and characterized by strong spatial heterogeneity. According to the CMIP5 models, the frequency of extreme precipitation will decrease in western and southern parts of Russia by the end of the 21st century and will increase in the northern and eastern regions.
Observational and reanalyses data on surface air temperature and sea level pressure anomalies in the Northern Hemisphere during the 20th century are compared with a focus on the Arctic region. The evolution of temperature anomalies, the spatial distribution of temperature trends and the changes of the atmospheric centers of action (ACA) are analyzed. It is found that changes in temperature and pressure in the Northern Hemisphere extratropic latitudes throughout the 20th century have been more realistically reproduced by the European reanalyses, most successfully in CERA20C reanalysis. The NOAA20C reproduces the evolution and patterns of surface air temperature and sea level pressure anomalies changes significantly worse throughout the 20th century.
Variations of the frequency and intensity of extreme daily precipitation in summer in the southeast of the Far East Federal District of the Russian Federation, - in region with high risks of extreme seasonal floods, were studied for the period 1970- 2015 using data of 54 meteorological stations. Future changes for the period 2041-2060 were estimated using data of the global climate models HadGEM and MPI-ESM. It is shown that the observed and projected changes in frequency extreme daily precipitation events in summer are diverse and statistically insignificant when averaged for the whole study area. However, a growth of extreme daily precipitation intensity in the north of the study area and in the south of Sakhalin island is found in obserations for the recent period 2000-2015 being relative to 1970-1999. Such a tendency is projected by the middle of the 21st century according to the HadGEM and MPI-ESM models.
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