Abstract:

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