资源环境科技发展态势分析平台

Interannual variability and long-term changes in winter air temperature extremes in Moscow (1949-2017) are investigated using observational and reanalysis data. Significant interdecadal changes in principal characteristics of temperature extremes are revealed. Strong warming (0.50 degrees K per decade) is identified contrasting to the previously identified summer trend of 0.25 degrees K per decade. This is attributable to middle-to-late winter. Winter and summer daily air temperature variabilities are fundamentally different with wintertime anomalies strongly negatively skewed, while summer displays Gaussian variability. A reduction in the number of cold days and an increase in warm days in December and March are found. In January and February, the probability of warm extremes increases, while the probability of cold extremes remains constant. Intensification of January extremes (cold and warm) is revealed along with daily temperature variability reduction. In aggregate, potential shortening of Moscow's winter season, suppression of the previously strong seasonal cycle in daily temperature variability, and intensification of midwinter extremes are identified. Dynamical linkages are found to North Atlantic and Mediterranean storm track variability as well as synoptic activity over the Barents-Kara Seas. Lagrangian analysis shows associations of wintertime extreme warm events to air masses originating over the North Atlantic and Mediterranean regions. Air masses implicated in cold extremes are mostly of Siberian and Arctic origin. On interannual time scales cold event frequency in Moscow is impacted by the negative phase of North Atlantic Oscillation, whereas frequency of warm events is influenced by the positive phase of North Atlantic Oscillation and the negative phase of Scandinavian teleconnection.

Plain Language Summary A lot of contemporary research is currently focused on quantifying and understanding how global annual mean and seasonal mean warming impacts extreme events at the regional scale. Here we show that in Moscow changes to wintertime temperature characteristics suggest a potential shortening of the winter season. This is manifested in a warming of middle-to-late winter months, in an increasing number of extreme warm days in December and March and less day-to-day temperature changes in the middle of winter. Meanwhile, cold extremes are getting colder and warm extremes are getting warmer in the middle of winter. We show that cold extremes in Moscow are associated with air coming from Siberia and the Arctic regions. Warm extremes are formed by air advected from the North Atlantic and Mediterranean regions. We show that this is related to changes in the paths that weather systems originating in the North Atlantic take in getting to European Russia and thermal conditions over the Barents and Kara Seas.