大理地区所代表的青藏高原东南缘降水日变化类型的分析

Type Analysis of Precipitation Diurnal Variation in Dali Region, the Tibetan Plateau Southeast Margin

用谐波分析法对大理地区各气象站2005—2014年的小时降水量做日变化分析,结果表明,各站点降水量日变化可用前3个谐波做拟合,方差贡献率≥30%的谐波是显著谐波,降水量日变化呈现4种形态:洱海盆地内呈夜间单峰型,后半夜降水高峰由持续≥3 h的降水事件引起;哀牢山起始西侧和点苍山西侧峡谷低地呈夜间峰值是午后峰值1.5倍的双峰型,后半夜降水高峰多由持续≥6 h的长时降水事件引起,傍晚降水次高峰一般由持续≤5 h的短时降水事件造成;区域北部高山峡谷区属午后峰值是夜间峰值1.5倍的双峰型,午后至傍晚的降水峰值由持续≤10 h的降水事件引起,夜间降水次峰值由持续4~10 h的降水事件造成;南部和西部区域呈午后峰值与夜间峰值持平的双峰型,持续≤4 h的短历时降水事件易引发午后峰值,而持续≥5 h的降水事件则造成夜间降水高峰。这些降水特性的区域差异主要是由于太阳辐射日变化和复杂地形因素引起的湖陆风和山谷风效应造成。

The precipitation diurnal variations at 12 stations in Dali region were analyzed by using the harmonic analysis. The results show that the diurnal variations of rainfall at 12 stations, may be fitted by the first three harmonics, and the harmonic was significant when its variance contribution rate was bigger than 30%. Four types were found： Only one single peak in night in the Erhai basin, with rainfall events occurred usually 3 hours or more. Two peaks at the night and afternoon respectively in the valley of the western of Mount Ailao and Diancang： the rainfall at the night peak may last for 6 hours and is 6 times of that of that at the afternoon peak. Two peaks in afternoon and night in the Northern area of alpine valleys： rainfall may lasts 10 hours at the afternoon peak and was 1.5 times of that at the night peak which lasts for 4 hours or more. Two peaks at afternoon and night in Southern and western regions： rainfall events at the afternoon peak and the night peak, were all last around 4-5 hours The differences between these types are mainly due to the lake-land wind and the hill-valley wind caused by the diurnal change of solar radiation and the complex terrain factors.