Abstract:

Based on the precipitation and NECP data of 131 observation stations in southwestern and southern China during 1961 －2010，the autumn drought was divided into five levels，namely no drought，light drought，moderate drought，severe drought and excessive drought according to the precipitation anomaly percentage，firstly． And then，the temporal and spatial distributions of the different levels drought in autumn were studied by using linear trend analysis，synthetic analysis and power spectrum analysis methods in the past 50 years in the southwestern and southern China area，and the causes of different grades drought in autumn were preliminarily discussed．The results showed that the autumn drought mainly distributed in eastern Sichuan and central and eastern Guizhou to southern　China，and the moderate drought，severe drought and excessive drought primarily appeared in southern China． The autumn drought had　significant increasing trend in the recent 50 years，and it mainly reflected a increase in light drought，while the change trends of moderate drought and excessive drought were not obvious．The drought in autumn was relatively more from the 1960s to the early 1970s and after the late 1980s，was less from the early 1970s to the late 1980s，and mutationally increased since 2002，with extending the range of drought，the intensity strengthened．The drought frequency in autumn had significant 2．2 years cycle，the cycle of severe drought and excessive drought were significant 12 and 2．7 years，respectively．The high frequency area of autumn drought had high frequency of continuous drought，the high frequency area of continuous drought distributed in east of Sichuan to north of Chongqing and central Guizhou to southern China，and the continuous drought more than five years was less，while for the individual continued up to six，years．The western Pacific subtropical high，India and Burma trough and trough in eastern Tibetan plateau at 700 hPa height field were the main circulation factors affecting the autumn dry or wet in southwestern and southern China．

Key words: autumn drought, frequency, continuous drought, precipitation anomaly percentage, in southwestern and southern China

摘要：

利用我国西南和华南地区131个测站1961～2010年近50 a降水和NECP资料，采用线性趋势分析合成分析功率谱分析等方法，基于秋季降水距平百分率，研究分析了近50 a我国西南和华南地区各级别秋旱的空间分布及时间变化特征，并初步讨论了各级别干旱形成的原因结果表明：秋季干旱集中在川东贵州中东部华南，中旱、重旱、特旱主要出现在华南;近50 a来秋旱有显著增多的趋势，主要体现在轻旱的增多，而重旱和特旱趋势不明显1960年代秋旱相对较多，1970年代初至1980年代后期秋旱较少，此后秋旱频繁，其中2002年以后秋旱突变性增多，干旱范围扩大的同时，其强度也在增强;秋旱频率具有显著的2．2 a周期，其中重旱有显著的12 a周期，特旱有显著的2．7 a周期；秋旱频率高的地方连旱频率也高，连旱高频区在川东渝北黔中华南，连续5 a以上的秋旱较少，个别地方可达到6 a，700 hPa上，西太平洋副热带高压印缅槽高原东部槽等是影响西南、华南地区秋季干湿的主要环流因子。

关键词: 秋旱, 频率, 连旱, 降水距平百分率, 西南和华南