Impact of Rossby Waves Breaking on the Heavy Rainfall in the Selenga River Basin in July ^†

The Selenga is one of the crucial transboundary rivers of the semi-arid Northern Eurasia belt. The Selenga basin is located in Mongolia and Russia, and it is 83.4% of the Lake Baikal basin. Atmospheric precipitation is the primary source of the river supply; most of its amount falls like rain from June to August (about 70% of the annual). In the present paper, the relationship between the heaviest rains (HR) around the Selenga River basin in July (above 90th percentile) and Rossby wave breaking (both cyclonic and anticyclonic type, AWB and CWB) was examined. The total number of HR events from 1982 to 2019 was 83. For each event, the synoptic analysis and automatic detection of breaking based on potential vorticity from 2 to 9 PVU on the 350 K were utilized. In most cases (85%) of HR, events were accompanied to the RWB. It was revealed that waves propagating along the subtropical jet were the most important. Precipitation was observed both for the period of amplitude growth and period of waves breaking (CWB or AWB). CWBs on the subtropical jet stream that occurred east to Lake Baikal were observed in most HR events.