Observations‐based analysis of the summer temperature extremes in Moscow

Interannual variability and long-term changes of summer temperature extremes and hot spells in Moscow during 1949-2012 are investigated using air temperature station data, the National Centres for Environmental Prediction/the National Centre for Atmospheric Research (NCEP/NCAR) reanalysis and the Climatic Research Unit (CRU) data sets. Significant interdecadal changes in different characteristics of the temperature extremes are revealed. It is shown that summertime warming detected in the Moscow region in recent decades is not solely due to an increase in the number of hot days, but also due to a decrease in the number of cold days. Statistically significant positive (negative) trends in the number of anomalously hot (cold) days since the mid 1970s are detected. Respective trend values are 5%/decade(-1) for the positive trends and -6%/decade(-1) for the negative trends. We find that in 1981-2012 the number of summer seasons with extremely hot days has doubled with respect to earlier period (1949-1980). However, we do not find statistically significant trend-like changes in the duration of the hot events in Moscow. A chronology of temperature extremes in Moscow has been constructed. This can be used as a diagnostic tool allowing the detection of extremes. Typical regional sea level pressure patterns associated with air temperature extremes in Moscow are defined and briefly described.