Water Vapor Transport Paths and Accumulation during Widespread Snowfall Events in Northeastern China

Abstract

his study aims to identify the distinct characteristics of water vapor transport (WVT) and its role in supplying moisture for widespread snowfall (WS) events in northeastern China (NEC). Fifty WS events in NEC were selected based on cumulative precipitation gauge data taken at 12-h intervals from 1980 to 2009 and a qualified set of criteria. The evolution of WVT during WS events in NEC was analyzed using 6-h ECMWF Interim Re-Analysis (ERA-Interim) data and discussed in regard to WVT paths and water vapor budgets over NEC. The results of this analysis indicate that southerly WVT, which carries moisture over eastern China, its adjacent seas, and the Sea of Japan, has played a key role in supplying water vapor for WS, which is quite different from the climatology of winter WVT. Moreover, the results indicate that there tends to be an 18-h lag between the WVT budget and precipitation, resulting in a great amount of water vapor accumulating over NEC before WS. The amount of preaccumulated water vapor could account for about 47% of the total precipitation, whereas synchronous WVT could only supply a limited amount of moisture that could hardly sustain WS. In addition, the original atmospheric moisture over NEC has likely made a considerable contribution to WS. The lag between the WVT budget and precipitation appears to be an outcome of the cooperation between the atmospheric flow field and the specific humidity field.