藏南峡谷地形对山南市强降水的影响研究

Study on the influence of topography of canyon in southern Tibet on heavy precipitation in Shannan area

文章运用多元回归方法对地形高程和强降水数据进行非线性建模,分析了藏南峡谷地形对山南市强降水的影响。研究表明:(1)山南市强降水出现日数呈不明显增加的趋势,沿江(泽当、贡嘎、琼结、加查)大部地区、西部浪卡子在全年的日降水量≥25mm的日数超过1d,南部错那、隆子一带出现强降水日数不足1 d;高海拔地区出现强降水概率远远低于低海拔地区,表明特殊地形、海拔高度对降水有一定影响。(2)山南市月平均降水量集中在20～40 mm之间,且分布呈现明显的左偏态分布;在3.5～4.0 km的高度降水最集中,随着地形高度的增加降水并非呈线性趋势。(3)山南市降水量随着藏南峡谷地形起伏的变化以4.0km附近为转折点,整体呈现先减弱后增加的趋势。

The influence of the topography of canyon located in southern Tibet on the heavy precipitation in Shannan area was studied through constructing a non-linear model in terms of topography, elevation, and heavy precipitation data using multi-regression method. Our results showed that:(1) There is no significant increase in the number of days of heavy precipitation in Shannan area. The number of days for which the daily precipitation is higher than 25 mm for the most area along the Yangtze River(Zedang, Gonggar, Qonggyai, Gyaca) and western Nagarzê exceeds 1 d, while the number of days with heavy precipitation in the southern Cona area and Lhünzê region is less than 1 d. The probability of heavy precipitation taken place in high altitude area is much lower than that of low altitude area, which indicates that special topography and altitude have certain influence on precipita.tion.(2)The average monthly precipitation in Shannan area is mainly between 20 mm and 40 mm, and it shows a significant left deflection distribution. Moreover, the high precipitation mainly takes place in the area with altitude of 3.5 ~ 4.0 km, however it does not show a linear trend with the increase of altitude.(3) The precipitation in the city of Shannan shows a trend of decreasing first and then increasing with a turning point at an altitude about 4.0 km of the canyon located in southern Tibet.