Changes in Cold Wave Events and Warm Winter in China during the Last 46 Years

Abstract

This study used the data of 572 stations from the China Meteorology Data Sharing Service System,from 1 January 1960 to 31 December 2005.The variables including the daily minimum temperature,mean surface pressure,mean wind speed and the Arctic Oscillation(AO) index were used for analysing the relationship between cold wave events and warm winter in China.The arrival of cold wave is generally characterized by a sharp drop of temperature,steep rise of pressure,and strengthening of wind at the surface.In the nationwide view,the temperature drop above 10℃ in one or two days was defined as cold wave,that above 20℃ as extreme cold wave.Cold wave occurred most frequently in northern China(north of 35°N) and south parts of the middle-lower reaches of the Yangtze River(i.e.,Jiangnan).Climatologically,cold wave began in October in Northeast China.A peak period was found in April over central North China and the Jiangnan.Cold wave was active from October to April,which was the winter monsoon period.Among all temperature-drop events,less than one third of them were accompanied with pressure rise and strong wind. In the last 45 winters,the frequencies of cold waves and extreme cold waves were generally decreasing,significantly in Xinjiang,central North China,Northeast China and East China,with the maximum negative trend about 1-2 times per decade.Decreasing trends were observed from those events of temperature drop,pressure rise and strong wind.The increase of AO index denoted the weakening and reducing of baroclinic waves along westerly zone,which was not in favor of the cold wave in China.To some extent,the frequency decrease of temperature drop affected the mean minimum temperature in winter,and led to continuous warm winters.