淮河流域近50年降水异常及其大尺度环流特征

根据国家气象中心整编的全国714站月平均降水量资料，运用REOF分析、Morlet小波分析、差值分析等方法，通过对淮河流域代表站点的选取，分析了1960～2009年淮河流域降水的趋势变化特征、周期特征，以及多雨、少雨年的大气环流异常特征。结果表明：（1）淮河流域年降水总量呈缓慢增长趋势，20世纪80年代初期由负距平转为正距平。冬季和夏季降水量呈显著增长趋势，春季和秋季降水量呈显著减少趋势，80年代前期为降水变化的转折期；(2)淮河流域夏季降水存在准3 a的显著振荡周期和准10 a的次显著振荡周期，同时在60～90年代还存在准6 a振荡周期；（3）淮河流域多雨年，500 hPa经向风偏强且范围广，850 hPa上从孟加拉湾经南海向华东地区的水汽输送明显偏强，在江苏、安徽地区有水汽的正涡度辐合区；少雨年，经向风偏弱，华东地区方向的水汽输送明显减弱；（4）多雨年与少雨年的500 hPa风场差值场、高度场差值场分析表明，多雨年贝加尔湖西部和鄂霍次克海地区阻塞高压活动频繁，东北冷涡异常活跃，副高偏强，3者共同作用使得降水偏多。500 hPa温度场差值场分析表明，多雨年中国东部、华北和东北地区冷空气偏强，同时南方大部分地区暖空气也偏强，冷暖空气共同作用使降水偏多

PRECIPITATION AND THE FEATURES OF ATMOSPHERIC CIRCULATION IN THE HUAIHE RIVER BASIN IN RECENT 50 YEARS

Using the national average monthly precipitation data of 714 stations from the National Meteorological Center, we selected representative sites, performed difference analysis, REOF analysis, Morlet wavelet analysis, and analyzed the changing trend characteristics of precipitation in the Huaihe River Basin during 1960-2009, periodic characteristics, and atmospheric circulation abnormal characteristics in rainy and drought years. The results showed as follows. (1) From 1960 to 2009, the least precipitation year was 1979 when the annual precipitation was 600 mm; while the most precipitation year was 1991 when the annual precipitation was 1100 mm. The total annual precipitation of the Huaihe River Basin showed a slow growing trend, the rainfall changed from the negative anomaly to positive in the early 1980s. Winter and summer precipitation showed a significant growing trend, the precipitation in autumn showed a significant decreasing trend, spring precipitation showed a decreasing trend, but the trend was not significant. The transformation of four seasonal precipitation from positive to negative anomaly occurred in the early 1980s. (2) Wavelet analysis showed that the summer precipitation in the Huaihe River Basin had a significant oscillation cycle of 3 years and 10 years oscillation cycle, and their variance contribution were 103% and 36%. At the same time in 1970s-1990s, there was an oscillation cycle of 6 years, and the variance contribution was 81%. (3) In rainy years in the Huaihe River Basin, 500 hPa meridional wind was strong and wide. In the level of 850 hPa the water vapor transportation from the bay of Bengal through the South China Sea to the east area was obviously strong, and there was positive vorticity convergence zone of water vapor in the Jiangsu and Anhui area; while in the dry years, meridional wind was weak, the water vapor transport to East China area was decreased and the water vapor convergence area slanted small and located easterly and southerly. (4) The difference of 500 hPa wind field, height difference in wet and dry years were calculated, the analysis showed that in wet years the cold vortex was unusually active, and subtropical high was strong, the blocking high in the west of the Lake Baikal and the Okhotsk was active, the three factors together induced more precipitation. The difference of 500 hPa temperature field in wet and dry years showed that, in drought years, cold and warm air were weak at small scale, while in rainy years the cold air in East China, North China and Northeast China was strong, and the warm air in most areas of the South was also strong, the interaction of cold and warm air caused more precipitation