Analysis On The Characteristics Of Temporal And Spatial Variation Of Heavy Rainfall In Tibet

Based on the data of daily precipitation data from 1980 to 2012,the spatial and temporal characteristics of heavy precipitation in Tibet wereanalyzed by statistical method.Using the linear sliding averaging method with 10 a step length to simulate the variation of the interannual trend of meteorological elements,the following conclusions were reached by further analysis of the change trend and the change of cycle in combination with wavelet analysis,EOF analysis and REOF analysis:(1).The spatial distribution of rainfall in Tibet is seriously uneven,with the main features of low West and East and low South and North,and several strong precipitation centers exist simultaneously.(2).In the past 33 years,the number of heavy annual rainfall in Tibet has shown an upward trend of shock,rising to 0.28 times 10 a.Strong precipitation has had a remarkable 11-year cycle,but since the 1980 s,the quasi-three-year period of strong precipitation in Tibet has also been quite obvious.(3).Precipitation concentration in Tibet ranged from 0.2 to 0.9,with an overall trend of gradual increase from south to North.Precipitation in Tibet mainly ranges from the 32 nd to the 45 th,between the first half of May and the middle of August.Among them,the area along the Yarlung Zangbo River has a high concentration of rainfall,with the highest concentration in Tibet and the lowest in southern Tibet.The annual precipitation concentration period in Eastern Tibet is the most obvious change of the rainfall concentration period in Tibet.(4).The spatial distribution of rainfall concentration in Tibet has five typical patterns.The first one is that the precipitation concentration is consistently high or low.The second is based on the Gondis Mountains,which shows the opposite distribution pattern of precipitation concentration.The third is the reverse degree of concentration in the South-East and North-West.The fourth is the opposite pattern in the Ali region,the Laza region,the southern part of Tibet,and the eastern part of Nacho and Xigaze,Western Tibet and Eastern Tibet.The fifth is based on the Gondis Mountains,which,in addition to the opposite distribution pattern of precipitation concentration in the North and South,also exhibits the opposite distribution pattern of precipitation concentration east of 95°E and west of 95°E。(5).The main rainfall concentration anomaly areas in Tibet are;The Xigaze area and the eastern part of Nachu to the northern part of Linzhi,the northern part of Changdu,in the northern part of Ali to the western part of Nacho,the middle part of the Yarlung Zangbo River Valley,the northern part of Arty.