哀牢山降水垂直分布特征

VERTICAL DISTRIBUTION CHARACTERISTICS OF RAINFALL IN THE AILAO MOUNTAIN

根据哀牢山脉北段迎风坡和背风坡地八个气象站的资料,讨论山地总降水和冷、暖平流降水的垂直分布及与东西坡地的对比特征.

This paper discusses the vertical distributions of total rainfall, and cold and warm advection rainfall on the windward and leeward slopes in the northern part of the Ailao Mountains of Yunnan Province,China according to the climatological data of eight sta-tions:(1)There are 5% and 10% of annual rain days during the period of July to August with 25% and 40% of annual rainfall,which results in 'rain disaster'. Other 50% of an-nual rain days appear most frequently in dry season,but rain is only 9% of the total.(2)Rainfall increases with altitude. It is reduced by 38%-46% in the valley com-paring with the top area of mountain where it is more than 1800mm. Rainfall gradient normals is less greater.on the west slope than on the east one,of which it is greater in rainy season than in dry season. Rainfall variability is obviously decreased by a range of 313mm and 17% at the top to 132-200mm and 12%-14% in the valley.(3)The main peak of diurnal rainfall variation appears at about sunrise and the sec-ondary one in afternoon on the slopes,but it is contrary at the top. The night rainfall ra-tio is greater on the west slope with 51%-57% than on the east one with 44%-48%.(4)The warm advection (southwest monsoon) rainfall(WR) is 200-300mm on the windward (west) slope more than that on the leeward (east) slope,while the cold advec-tion (northeast monsoon) rainfall (CR) is 100-150mm on the windward (east) slope more than that on the leeward (west) one. The WR or CR gradient is the leeward larger than the windward in a whole year and rainy season,while it is opposite in dry season.