The Effect of Moscow Megapolis on Warm-Season Precipitation Depending on Large-Scale Atmospheric Conditions

The effect of Moscow megapolis on precipitation of different intensity under contrasting physical–synoptic conditions was estimated. The analysis of long-term standard observations at weather stations in the Moscow Region and the data of high-resolution reanalysis ERA5 over 1988–2020 were used to demonstrate that the effect of the city on heavy precipitation is largest in the cases with higher static instability of the atmosphere, combined with a weak large-scale flow, high moisture content of the atmosphere, and the absence of pronounced frontal zones in the region. On the average over the study period, the excess of the total seasonal precipitation in Moscow relative to the background values over the Moscow region is 5.3%. It was found that the effect of the city on precipitation of various intensity is different: the precipitation of low and medium intensity was less in the city (statistically insignificant), while the heaviest precipitation (above 95 percentile) increased over the city by 11.6% above the background value.