四川省乐山市近51年极端气温变化研究

Research on annual extreme temperature in recent 51 years in Leshan,Sichuan Province

基于1962—2012四川省乐山市每日气温资料,运用线性拟合及累积距平、Morlet复数小波等方法对WMO发布的10种极端气温指数进行了计算和分析。结果表明:(1)极端最高气温、极端最低气温都有上升趋势,霜冻、冷夜、冷昼呈下降趋势,夏日、热夜、暖夜、暖昼呈现出波动上升趋势。(2)年极端最高气温、暖夜、暖昼存在着27 a左右的周期,夏日、霜冻、热夜、冷夜、冷昼存在着28 a左右的周期,年极端最低气温存在着11 a左右的周期。除年极端最低气温外,其他的极端气温指数虽然主控周期不一致,但都存在28 a左右的周期。冷昼和暖昼变化较为复杂,存在4个周期。(3)极端天气暖指数呈上升趋势,夏日、热夜、暖夜、暖昼分别增加了15天、21天、32天、29天,极端天气冷指数呈下降趋势,霜冻、冷夜、冷昼分别减少了2天、24天、4天,乐山地区发生极端天气事件的可能性增加。(4)乐山市极端天气现象的发生与日益增加的人类活动以及全球变暖的大趋势密切相关。由于乐山市独特的地理位置,随着乐山市极端天气现象可能性的增加,乐山市发生干旱、洪涝、山地灾害的可能性也随之提高,需要做好预防准备。

Based on the daily temperature data of Leshan from 1962 to 2012, the methods of linear fitting, accumulative anomaly and morlet complex wavelet are employed to calculate and analyze ten extreme temperature indexes which are released by WMO. The results are as follows： （1） The extreme maximum temperature and extreme minimum temperature have rising trend, frost days, cold nights and cold days are on the decline, summer days, tropical nights, warm nights and warm days are on fluctuant rise. （2） The annual extreme maximum temperature, warm nights and warm days have a cycle of 27 years around, summer days, frost days, tropical nights, cold nights and cold days have a cycle of 28 years around, the annual extreme minimum temperature has a cycle of 11 years around. Besides the annual extreme minimum temperature, the others have a cycle of 28 years around while they have different master cycles. The variation of cold days and warm days is more complex,they have four cycles. （3） The warm indexes of extreme temperature are on the rise, summer days, tropical nights, warm nights, warm days respectively increased 15 days, 21 days, 32 days, 29 days, cold indexes of extreme temperature are on the decline, frost days, cold nights, cold days respectively decreased 2 days, 24 days, 4 days. （4） The possibility of the occurrence of extreme weather events has increased in Leshan. The extreme weather is closely related to the increasing human activities and the global warming trend. Due to the unique geography of Leshan, the possibility of drought, floods and mountain disasters will increase along with the increasing possibility of extreme weather. So we need to make good preparations for prevention.