Features and Variations of Precipitation in Jiuzhaigou-Huanglong Tourist Scenes
九寨沟、黄龙风景区的降水特征及其变化

By using wavelet and composed analysis methods,features of precipitation and water vapor transport in Jiuzhaigou-Huanglong are studied based on NCEP/NCAR monthly reanalysis data and rainfall observation from the representative stations in Jiuzhaigou-Huanglong tourism scenes from 1959 to 2002.It is found that the annual total precipitation in the region is 693.7 mm and mostly distributes between May and September.The total precipitation from May to September is 538.5mm,which is 77.6 percent of the annual rainfall in the region,especially the precipitation in July can reach 130.9mm;but the precipitation in winter,including December,January and February,is just 13.1mm,especially the value in Deceber is only 2.3mm.So the dry season and rainy season are obvious in Jiuzhaigou-Huanglong.The annual precipitation in this region had decreased in 44 years,and this decrease trend is most obvious in summer,especially in July.It is shown that long-term variation trends of precipitation in four seasons are different: there is a linear decreasing trend in summer and autumn,and this decreasing trend is more obvious in winter;on the contray,there is an increasing linear trend in spring and winter,and this increasing trend is clearer in winter.Climatological characteristics are investigated for large-scale water vapor transport over Jiuzhaigou-Huanglong based on the vertically integrated water vapor flux from 1959 to 2002 by integrating NCEP/NCAR specific humidity and wind data.The water vapor transport in Jiuzhaigou-Huanglong has obvious seasonal characteristic: in winter and spring,the moisture of the region is mainly from the middle-latitude westerly water transport;in June and July,the water transport is mainly from the Bay of Bengle and South China Sea;in August,the water vapor mostly comes from South China Sea and the west Pacific Ocean;in September,the moisture comes from South China Sea,the west Pacific Ocean and the Bay of Bengle.This seasonal difference of the water transport has a close connection with the circulation of monsoon,so the anomaly of monsoon cycle plays an important role in variation of precipitation of Jiuzhaigou-Huanglong,especially in summer.The weakness of northward march of the water vapor transport with summer monsoon has an important influence on the variation of precipitation in Jiuzhaigou-Huanglong.Results show that in the drought years in Jiuzhaigou-Huanglong,the water vapor transports from the west Pacific Ocean and East Sea,which are weak,are significantly different from those of wet years,which are strong.