Wave Propagation Patterns Associated with Summer Extreme Precipitation Events in South Siberia and Mongolia

The southern part of East Siberia (SES) is highly vulnerable to flooding caused by the extreme precipitation events (EPEs) during summer. Building on previously detected EPEs in SES and Mongolia, we examined wave propagation patterns for two periods: 1982-98 and 1999-2019. Our analysis revealed distinct wave train configurations and geopotential anomalies preceding EPEs, with an increase in wave activity flux across the Northern Hemisphere, followed by a subsequent decrease during EPEs. Consequently, Eastern Siberia has experienced a significant rise in wave activity. Based on geopotential anomalies over Central Siberia accompanying EPEs, we identified two main types. The first, the ridge type, is predominant during the first period and features a meridional contrast with a positive geopotential (and temperature) anomaly over Central Siberia and a negative anomaly over the subtropical regions along the same longitude. The second type, termed the trough type, is more typical for the second period. It involves either a negative geopotential anomaly or the zonal proximity of positive and negative geopotential anomalies over Central Siberia. The trough type, marked by zonally oriented anomalies in geopotential and temperature, results in a more pronounced temperature decrease before EPEs and significant zonal temperature contrasts. Further, it is related to more stationary waves over Northern Eurasia, with persistent positive geopotential anomalies over Europe linked to quasi-stationary troughs over Central Siberia and positive anomalies east of Lake Baikal. Our findings align with shifts in boreal summer teleconnection patterns, reflecting significant changes in wave propagation patterns that have occurred since the late 1990s.