湖北异常初雪日的成因分析及预测

Cause Analysis and Prediction of Abnormal First Snow Date in Hubei

统计湖北省76站1961/1962—2012/2013共52年大范围初雪偏早/偏晚年份,揭示初雪日异常早/晚年同期环流特征,初雪偏晚当年11月至次年2月海温、高度场及低层风场的典型分布表现为:中高纬的西北太平洋海温及新西兰东侧南太平洋海温异常偏高,有利于乌拉尔山脊减弱、贝加尔湖低压及阿留申地区低压减弱,东亚大槽偏强同时孟加拉湾槽偏弱,对应500 hPa高度距平场上欧亚大陆自北至南呈"—+—"的波列分布,中国大陆地区低层风场被北风距平控制;反之,初雪偏早。2013/2014年关键区海温及环流分布符合典型的初雪偏晚对应特征。利用1961—1992年11月关键区海温首次建立湖北初雪日预测模型,准确预测2013年冬季初雪偏晚,同时针对1993—2012年初雪早晚的回报检验准确率达75%,为预测湖北初雪发生的早晚提供了新方法。

Based on the first snow date(FSD) data of Hubei from 1961/1962 to 2012/2013,we reveal the atmospheric circulation features in abnormal early/late FSD.For the late FSD years in Hubei Province,the circulation distribution of the sea surface temperature anomaly(SSTA),the height anomaly and lowlevel wind field from November to February that year can be illustrated as follow:SSTA in Northwest Pacific and in the Southern Pacific Ocean to the east of New Zealand is abnormally higher,which is good for the weakening of Ural Mountains Ridge,and the weakening of Lake Baikal low-pressure and Aleutian low.Meanwhile,East Asian trough is strengthened and Bengal Bay trough is weakened.The corresponding 500 hPa height field shows a '— + —' wave train distribution from north to south in Eurasia.In China's Mainland,the low-level wind field is controlled by abnormal north winds.Otherwise,the FSD comes early.Typical circulation distribution in 2013/2014 agrees with the late FSD in Hubei.In addition,prediction model for FSD is established by using SSTA in the key areas,which accurately predicts the late FSD in2013/2014 and gives a good reforecasting test with the accuracy getting to 75%.So,this is a new method for the prediction of FSD in Hubei.