近50a青藏高原东部夏半年强降水事件的气候特征

基于青藏高原东部47个站点1963-2012年的5~9月逐日降水资料,分析了近50 a该区夏半年强降水的时空分布特征和相对强度。结果表明:青藏高原东部夏半年强降水事件在7月出现的频次最多,以持续1 d的单站暴雨为主;强降水量和频次在近50 a呈弱增长趋势,其存在准12 a的年代际震荡,且在1978年之后,强降水量同时存在大致准3 a的演变周期,在各自然分带强降水量和频次的变化趋势存在差异;夏半年强降水量和频次呈现出自东南向西北阶梯性递减的分布特征;青藏高原东部夏半年强降水的相对强度与强降水量呈反向特征,其中以柴达木地区相对强度为最大,藏东川西区为最少;各自然分带的强降水量和频次与夏半年降水量有很好的相关关系,而强降水的相对强度与夏半年降水量表现出不同的正负相关性。

Climatic characteristics of heavy precipitation events during summer half year over the Eastern Tibetan Plateau in recent 50 years

Based on the daily precipitation data of 47 meteorological stations from May to September during 1963-2012 in the eastern Tibetan Plateau, the methods of linear trend analysis, polynomial curve fitting analysis, wavelet transform, inverse distance weighted interpolation method etc. are employed to analyze the temporal and spatial distribution of heavy precipitation, frequencies and relative intensity in nearly 50 years and applying R/S method to predict the heavy precipitation variation in future. According to the actual precipitation during summer half year in the eastern Tibetan Plateau, more than 25 mm of daily precipitation are used as the standard of heavy precipitation. The climatic characteristics of heavy precipitation events in the eastern Tibetan Plateau have an important influence on global climate change and in order to better contrast the internal differences of heavy precipitation over the eastern Tibetan Plateau, the study region was divided into five different natural zones. The results are as follows:(1) Heavy precipitation events often occurred in July and dominated by 1 d single-station in summer half year over the eastern Tibetan Plateau.(2)In recent 50 years, the heavy precipitation and frequencies showed weak increasing trend, the linear trend rate is 0.25 mm·(10a)^-1 and 0.01 d·(10a)^-1 respectively and they will be increasing in the future. In the five natural zones, the linear trend rate is different, only Naquyushu area showed a decreasing trend and the increasing trend is the most notable in the Chaidamu area.(3) Heavy precipitation and frequencies existed a decadal oscillation cycle with quasi 12 years, as well as, after the 1978, the heavy precipitation had inter-annual oscillation cycle with 3 years during summer half year over the eastern Tibetan Plateau.(4)During summer half year, the spatial distribution patterns of heavy precipitation and frequencies was very similar to each other, which decreased from southeast to northwest, its highest and lowest value occurred in the east Tibet-west Sichuan and Chaidamu area respectively.(5)The relative intensity of heavy precipitation increasing from south to north during the summer half year, among them, the relative intensity of Chaidamu area is the largest and the east Tibet-west Sichuan area is the least, so the relative intensity and heavy precipitation showed a reverse characteristic.(6)In the five natural zones, there are positive correlations between heavy precipitation, frequencies and total precipitation in the summer half year, the differences correlations in relative intensity and total precipitation in the summer half year still exist significantly. At the same time, the correlation between the three index and total precipitation during the summer year is the most significant in Chaidamu area. Through a series of analysis, the paper aims at providing some reference to climate change, ecological environment protection and disaster reduction. According to these conclusions, some predictive information of heavy precipitation events over the eastern Tibetan Plateau can be provided to the relevant apartments.