Abstract:

Daily precipitation observational data from 95 stations in the Songhua River Basin from May to September during 1961-2020, monthly JRA-55 reanalysis data, and sea surface temperature data were utilized to analyze the main precipitation patterns and causes of anomalies in crop growing season in this region, and to explore its mechanism and precursor signals. The results showed that there are primarily two spatial modes of precipitation during the crop growing season in the Songhua River Basin, i.e. the basin-wide mode and the east-west opposite mode. The basin-wide mode is dominant in the 1980s and 1990s, while the east-west opposite mode prevails in the first decade of the 21st century. In recent years, the basin-wide mode has been predominant. The basin-wide precipitation mode is influenced by both mid-high latitude and low latitude systems, while the east-west opposite precipitation mode is mainly affected by the mid-high latitude circulation over Eurasia. The circulation systems influencing precipitation in the Songhua River Basin are primarily located in the Baikal Lake and Okhotsk Sea regions. For the basin-wide precipitation mode, the water vapor budget shows input from the western boundary and output from the eastern boundary. In the years of above-normal precipitation, both southern and northern boundaries experience water vapor input, while during below-average periods, water vapor input is found from the northern boundary and output from the southern boundary. For the east-west opposite precipitation mode, the water vapor budget exhibits input from one boundary and output from the other for both the south-north and east-west boundaries.

Key words: Spatial patterns, Water vapor budget, Precipitation, Circulation systems