According to CMA meteorological satellite remote sensing monitoring for snow cover, up to January 28, the total area covered by snow at 15 provinces (autonomous regions and municipalities) is 128.21 million square kilometers.

    More than 90% of Shanghai, Jiangsu, Anhui, Henan, Hubei and Shannxi were covered by snow. The depth of snow cover at central Anhui and south Jiangsu is 30~45 cm and some areas even reached 50 cm.

    China suffered rare and sustained low temperature, rain, snow and freezing weather since January 10.

    Experts said that there are two reasons of this weather process, La Nina event and abnormal atmospheric circulation.

    The La Nina event is the main reason of this weather process. The La Nina state came into being at August 2007 and developed rapidly. Up to January, 2008, the sea-surface temperature of east-central equatorial Pacific had been keeping over 0.5℃ lower than that of the conventional years. Stronger La Nina event can strengthen the middle latitudes atmospheric circulation and may consequently bring lower temperature and more precipitation to east China, especially Yangtze River basin and its north area.

    The rare, sustained, steady abnormal atmospheric circulation at Eurasia is the direct reason of the weather process. The abnormal circulation had last 19 days (the average in January is 6 days), was favorable for invasion of cold air through Gansu Corridor. The strong northwest Pacific subtropical high has been staying above the sea southeast of China, so the cold and warm air join mainly at the middle and lower reaches of Yangtze River and its south. The southern branch trough at south of Qinghai-Tibet Plateau is most active for more than ten years and brings more warm and wet air to China. A temperature inversion layer caused by cold and warm air is the main reason of the widespread freezing rain. (Feb.1)

By Lin Lin

Editor: Xu Hui