Climatic Characteristics of Winter Freezing Days in Guizhou in Southwest China and Their Anomalous Causes

Abstract

Based on daily gauge station datum， monthly reanalysis datasets from NCEP/NCAR and monthly SST data from Hadley Center in UK （HadISST）， The climatic characteristics of freezing days and their causes have been studied on.It is found that there are 69 stations （85.2%） of longest persistent days in the single freezing processes and 63 stations （77.8%） of total winter freezing days occurred in 1976， 1983 and 2007， Weining's 66 d （1976） and 39 d （2007） being the longest events respectively.The main mode of winter freezing days in Guizhou which the center is in central showed a consistent distribution in the whole region with a variance of 65.04%.When the winter freezing days in Guizhou were abnormally large， the abnormally active Ural Mountain blocking high pressure and the abnormally strong East Asian Trough were conducive to the formation of stable meridional circulation in East Asia.while the low value system in Central Asia guided the cold air in front of the blocking high and the Mongolian cold high southward， formed a shallow abnormal cold pad in the lower troposphere of Guizhou and its north.At the same time， the warm and humid air flow in the middle and lower troposphere from the Bay of Bengal and the South China Sea crawled and uplifted along the edge of the cold air pile near the Yunnan-Guizhou Quasi-Stationary Front under the action of the abnormal circulation circle， and formed an unstable vertical stratification anomaly of warm up and cold down in the middle and lower troposphere over Guizhou， resulting in the formation of winter freezing in Guizhou.In addition， the wave disturbance energy propagation from North Atlantic and low latitude tropical played an important role in the formation and maintenance of the blocking situation in the middle and high latitudes and the anomaly of the low trough system in Eurasia.When the freezing days were abnormal less， the situation is opposite.Finally， there is a closely relationship between the winter freezing days anomaly in Guizhou with the La Niña event in the equatorial Middle East Pacific and the SST anomaly in the North Pacific， Indian Ocean， and South China Sea.

Keywords

• guizhou
• freezing days
• climatic characteristics
• circulation anomaly