Simulation of a Freezing Rain and Snow Storm Event over Southern China in January 2008 Using RIEMS 2.0

Abstract

The Regional Integrated Environmental Model System (RIEMS 2.0) with NCEP Reanalysis II is utilized to simulate the severe freezing rain and snow storm event over southern China in January 2008, which caused severe damage in the region. The relationships between the freezing rain process and the large-scale circulation, in terms of the westerly and low-level jets, water vapor transportation, and northerly wind area/intensity indices, were analyzed to understand the mechanisms of the freezing rain occurrence. The results indicate the following: (1) RIEMS 2.0 reproduced the pattern of precipitation in January 2008 well, especially for the temporal evolution of daily precipitation averaged over the Yangtze River valley and southern China; (2) RIEMS 2.0 reproduced the persistent trough in the South Branch of the westerlies, of which the southwesterly currents transported abundant moisture into southern China; (3) RIEMS 2.0 reasonably reproduced the pattern of frequencies of light and moderate rain, although it overestimated the frequency of rain in southern China. This study shows that RIEMS 2.0 can be feasibly applied to study extreme weather and climate events in East Asia.

Key Words:

• RIEMS 2.0
• climate extremes
• freezing rain
• snow storm