贵州秋绵雨的气候特征及异常成因浅析

利用贵州省83个气象观测站点1961—2021年逐日降水数据,定义贵州省单站秋绵雨过程,构建了综合考虑秋绵雨最长时段日数、其余时段累计日数、9—10月雨量占年雨量比例的秋绵雨综合强度评估指标,通过小波分析、突变分析、合成分析、相关分析等方法,对贵州秋绵雨的时空特征及其与北半球500 hPa高度场、全球海温场的关系进行了研究。结果表明：秋绵雨指数大致呈东北—西南向的条带状分布,自西北部向东南部递减;秋绵雨指数年际波动大,近61 a来以0.064/10a的速率呈下降趋势;秋绵雨指数EOF分析第1模态空间型表现为全区一致分布型,是贵州秋绵雨气候变率的主模态;贵州省秋绵雨存在2~4 a的年际变化周期;1997年为贵州秋绵雨突变点;重秋绵雨年500 hPa高度场欧亚大陆上空位势高度距平呈“北正南负”的距平分布,有利于北方冷空气南下,850 hPa距平风场南海及其周边地区为显著的反气旋性环流,加强了西南暖湿气流的输送;ENSO对贵州秋绵雨的影响是非对称的,当前期8月热带东太平洋偏暖、热带西太平洋偏冷时,对应El Niño年贵州秋绵雨偏重。

Climatic Characteristics and Abnormal Causes of Autumn Rain in Guizhou

Based on the daily precipitation data of 83 stations in Guizhou from 1961 to 2021, the single station autumn rain processes in Guizhou were defined, and the comprehensive intensity evaluation index of autumn rain was constructed, which comprehensively considered the longest period of autumn rain days, the accumulated days of other periods, and the proportion of autumn rainfall in annual rainfall, the spatial-temporal characteristics of autumn rain and its relationship with 500 hPa geopotential height in northern Hemisphere and global SST are studied. The results show that the index shows a belt distribution from northeast to southwest, decreasing from northwest to southeast; the inter-annual fluctuation of the index was relatively large, showing a downward trend at a rate of 0.064/10 a in recent 61a; according to the EOF analysis, the first modal spatial pattern was consistent in the whole region, which was the main mode of climate variability of autumn rain; the inter-annual variation cycle of autumn rain was 2~4 a; 1997 was the mutation point;in heavy autumn rainy years, the 500 hPa geopotential height over the Eurasian continent shows a "north positive and south negative" anomaly distribution,which was beneficial to the southward movement of cold air from the north, and the 850 hPa wind anomaly over the South China Sea and its surrounding areas was a significant anticyclonic circulation, which strengthens the transport of warm and wet air from the southwest; the effect of ENSO on autumn rain in Guizhou was asymmetrical, when the tropical eastern Pacific was warmer and the tropical western Pacific was colder in August, the autumn rain in Guizhou in EL Niño is heavier.