湖北省结冰日数年际变化特征及其与大气环流的关系

利用1961-2010年湖北省16个气象站观测资料和NCEP/NCAR再分析资料，对湖北省冬季结冰日数的分布及其演变特征规律进行了分析，探讨结冰日多寡年份1月的异常大气环流特征。结果表明：湖北省冬季年均结冰日8.2 d，空间分布特征为整体上西多东少、北多南少，鄂西地区高山多、河谷少，鄂中地区高值舌自北向南突出，空间分布与湖北马蹄形层状地理特征有着密切的关系。近50 a湖北省结冰日年代际变化显著，空间分布由西多东少的阶梯状转换为北多南少，时间演变出现了先增加后减少，近5 a又增加的趋势，并在20世纪90年代初呈现突变减少特征。另外，湖北沿江及以南地区为候结冰日集中程度较高的地区，其集中期为1月4-5候。1月，500 hPa亚洲高纬度地区乌拉尔山东侧（西西伯利亚北部上空）高压脊和东亚大槽异常强（弱），中低纬度地区里海以东的中亚低压槽和印缅槽也偏强（弱），同时海平面气压场上东亚大陆被蒙古偏强（弱）冷高压控制，使得湖北省结冰日数偏多（少）。

Interdal-annual variation of freezing event and its relationship with atmospheric circulations in Hubei province

Based on the daily observation data from 16 meteorological stations and the NCEP/NCAR reanalyzed data from 1961 to 2010 in Hubei province,the distributions of the numbers of freezing day and its evolution char- acteristics were analyzed. The atmospheric circulation characters were discussed in more and less year of freezing day. The results indicate that the mean annual freezing day in winter is 8.2 days, and its spatial distribution is char- acterized with more in the west and less in the east and more in the north and less in the south, which is related to the topography of Hubei province. There are many mountains in the west of Hubei province and less river valley. The inter-decadal variation of freezing day is obvious in recent 50 years. Its spatial distribution changes with ladder shape from more in the west and less in the east to more in the north and less in the south, while temporal distribu- tion is in a increasing trend firstly and then in a decreasing trend and in a increasing trend again in recent 5 years. There is an abrupt change of decreasing in the early of 1990s. Additionally, the pentad freezing day concentrates in the areas and the southern areas along the Yangtze River, especially in the fourth and fifth pentad of January. The high ridge in Ural Mountain and the East Asia trough strengthen（weaken） abnormally at 500 hPa in high latitude area of the Asia, and so are the central Asia trough over the east of the Caspian Sea in the middle and low latitude areas and the Indian-Burma trough. At the same time ,Mongolia strong（weak） cold high controls the East Asia ma- inland on sea surface pressure field ,and it makes the freezing day more（less） in Hubei province.