Influence Analysis Of The Northwest Pacific Ocean Typhoon On The Precipitation In The Eastern Part Of Northwest China

The NCEP/NCAR global reanalysis data, the surface and upper-air observed data, the northwest pacific ocean typhoon path data and the precipitation data at 48 stations in the eastern part of northwest China during 1961 to 2000 are used in this paper. We present a preliminary study on the relationship between the northwest Pacific Ocean typhoon and the precipitation in the eastern part of northwest China. Through the contrast analysis of the precipitation in the eastern part of northwest China, East Asia circulation, the wind vector fields in years with more typhoons and fewer typhoons, and the contrast between weather cases of different typhoon paths, it has been discovered that the relationship between them are very closely. The main results show as following:(1) The relationship between the northwest Pacific Ocean typhoon and the precipitation in the eastern part of NW China is positive correlation, and the positive correlated center is in He Tao area of NW China, the precipitation in the eastern part of NW China is more (less) in the years with more (fewer) typhoons.(2) In the years with more typhoons, the SUBH (subtropical high) located at an area quite further north and was weaker than usual, that the south wind in the eastern part of NW China is strong, and it provides advantages for the rain form. In the years with fewer typhoons, the SUBH located further south and was stronger than usual, that the north wind is strong and it's disadvantaged for the rain form in the eastern part of NW China.(3) The influence of typhoon on the precipitation in the eastern part of NW China is an indirect effect, which mainly carries out through the SUBH. The emergence of typhoon provides advantages for the west and north stretch of the SUBH, and builds up good water vapor passage for the precipitation in the eastern part of NW China, interaction between the westerly cold weather system in medium high latitude and the SUBH is a direct form of the influence of typhoon on the precipitation in the eastern part of NW China.(4) The northwest and west turning north path typhoons can pass through the SUBH easily, and divide the SUBH into two parts, the part in the west side would stretches west and impacts the precipitation in the eastern part of NW China. When the northwest Pacific Ocean typhoonmoves to the East Asia continent, it's easy to builds high pressure in the northeast of Asia. The precipitation in the eastern part of NW China usually begins with the builds up of the high pressure in the East Asia, and breakdown to end with the collapses of the high pressure in the East Asia.(5) Through the build up of the weather concept model of the influence of typhoon on the precipitation in the eastern part of NW China, we find that, in the typhoon frequent period, the westerly trough act frequently from Mongolian country to the northeast side of Qinghai-Tibet Plain, the cold front in the eastern part of NW China builds easily, and there are more frontal precipitation.