Research On The Characteristics Of Droughts And Floods In Zhejiang Province And Its Relationship With Ocean Temperature

Based on the meteorological data supplied by Chinese National Meteorological Information Center, Global Seas Surface Temperature (SST) from Hadley center, and NECP reanalysis and the monthly mean precipitation, utilize ECHAM5 climate model, SVD analytical approach and composition analytical approach to study the key ocean areas influence the droughts and floods of Zhejiang in the next spring from year 1980 to 2009, and the influence mechanisms and the way of general atmospheric circulation and remote correlation type it caused to droughts and floods in Zhejiang in next spring:(1) An obvious 3-4 years periodic feature of spring precipitation is existed in early 1990’s and 2000’s. It is a distribution type that precipitation distributes consistently; also, it is divided into three abnormal significant zones. As part of coastal areas, the relationship of sea, land and air is complicated at Zhejiang, so the article analyses the temporal and spatial characteristics of the spring droughts and floods under the related interannual variability and interdecadal variability. (2) Utilize the bridging mechanism of 500hpa height field analyses the rough sea zone of which the abnormal SST influence the droughts and floods in spring. And then to find out the most and less important specific significant correlation areas by applying a singular value decomposition analysis (SVD) between the global ocean temperature and spring droughts and floods. The positive significant correlation area is Mascarene basin in the Indian Ocean and mid-east equator Pacific Ocean, and the negative significant correlation area is SPCZ waters. And this SVD conclusion is verified by ECHAM5 method. When the temperature of the main positive key ocean rises, and the negative ocean drops, the East Asian jet stream becomes weaker, the geopotential height of 500hpa becomes higher, and the East Asian trough becomes weaker, these all leading to more transportation of water vapor to the middle and lower reaches of Changjiang River. (3)SIOD presence in the Indian Ocean is the subcritical area. Winter SIOD is capable to activate remote correlation types of middle and upper latitude region, causes abnormal convection current movement at middle of subtropical zone of Pacific Ocean in spring, and reinforces and maintains the remote correlation types of middle- and upper-latitude region in spring form the variation of Strength of East Asia Trough and it will cause the rainfall anomaly in coastal areas of east China.