The Relationship between Melt Season Sea Ice over the Bering Sea and Summer Precipitation over Mid-Latitude East Asia

Independent datasets consistently indicate a significant correlation between the sea ice variability in the Bering Sea during melt season and the summer rainfall variability in the Lake Baikal area and Northeastern China. In this study, four sea ice datasets (HadISST1, HadISST2.2, ERA-Interim and NOAA/NSIDC) and two global precipitation datasets (CRU V4.01 and GPCP V2.3) are used to investigate co-variations between melt season (March-April-May-June, MAMJ) Bering Sea ice cover (BSIC) and summer (June-July-August, JJA) East Asian precipitation. All datasets demonstrate a significant correlation between the MAMJ BSIC and the JJA rainfall in Lake Baikal-Northeastern China (Baikal-NEC). Based on the reanalysis datasets and the numerical sensitivity experiments performed in this study using Community Atmospheric Model version 5 (CAM5), a mechanism to understand how the MAMJ BSIC influences the JJA Baikal-NEC rainfall is suggested. More MAMJ BSIC triggers a wave train and causes a positive sea level pressure (SLP) anomaly over the North Atlantic during MAMJ. The high SLP anomaly, associated with an anti-cyclonic wind stress circulation anomaly, favors the appearance of sea surface temperature (SST) anomalies in a zonal dipole-pattern in the North Atlantic during summer. The dipole SST anomaly drives a zonally orientated wave train, which causes a high anomaly geopotential height at 500 hPa over the Sea of Japan. As a result, the mean East Asian trough moves westward and a low geopotential height anomaly occurs over Baikal-NEC. This prevailing regional low pressure anomaly together with enhanced moisture transport from the western North Pacific and convergence over Baikal-NEC, positively influences the increased rainfall in summer.