THE INTRASEASONAL CHARACTERISTICS OF WINTERTIME PERSISTENT COLD ANOMALY IN CHINA AND THE ROLE OF LOW FREQUENCY OSCILLATION IN THE LOW LATITUDE AND MIDLATITUDE
Based on the daily mean temperature datasets at 553 stations in China from 31 winters (1979/1980-2009/2010),an objective method is adopted to depict the winter PCAs (persistent cold anomaly) over China.According to the definition,the intraseasonal characteristics of the PCAs are analyzed by EOF analysis,spectrum analysis,filter and composite analysis.Further,the impacts of low frequency activities in tropical and midlatitude atmosphere are explained.The results show that the convections over the equatorial Indian Ocean affect the PCAs by the local meridional-vertical circulation.In addition,in midlatitude,an enhanced intraseasonal anticyclone over the central part of northern Pacific is helpful for the maintenance of the PCAs.The PCAs are also associated with an enhanced subseasonal Siberian high,which persistently provides cold air.The intensified intraseasonal transverse trough between Lake Baikal and Lake Balkhash is favorable for the cold air to continuously move southward to China.Hence,the wintertime PCAs result from the interaction between intraseasonal activities in the tropics and in the middle latitudes.
climatologypersistent cold anomalyobjective definitionlow frequency oscillation
国家科技期刊平台
NSTL
万方数据
维普
