Abstract: Based on the data of 64 meteorological stations from 1971 to 2017 in Karst region of Guangxi Zhuang Autonomous Region, standardized precipitation evapotranspiration index (SPEI) was adopted as a drought evaluation index to analyze the spatial-temporal evolution rules of drought in this region. The results show that in the study area, the annual droughts generally occurred once every two years and their frequency increased from the middle part to the east and west, which were mainly light drought or moderate drought. By contrast, the seasonal drought was mainly concentrated in autumn, followed by winter drought, with low frequency of spring drought and summer drought. Besides, spring drought occurred every 3 to 4 years, and the frequency decreased from southwest to northeast. Summer drought also appeared every 3 to 4 years, but its frequency showed a weakening trend from east to west. The autumn drought occurred almost every year and its frequency was higher in central and eastern part than that in western part, with more severe drought and extreme drought than other seasons. The frequency of winter drought was similar to the autumn drought, but it was higher in the northwest and decreased from west to east. From 1971 to 2017, the winter drought and summer drought of studying area showed a fluctuating and weakening trend, while the spring drought and autumn drought showed an increasing trend. On the time scale of 15 to 20 years, there was an obvious dry-wet cycle in annual and seasonal drought, and the drought cycle below 5 years oscillated more frequently. The significant positive correlation between SPEI and soil moisture made it possible to use SPEI objectively to reflect the drought situation in the region.

Key words: drought, standardized precipitation evapotranspiration index, Guangxi karst area, spatial and temporal distribution

摘要： 利用广西喀斯特地区64个气象站1971—2017年逐日气温和降水量观测资料，采用标准化降水蒸散指数（SPEI）作为干旱评价指标，分析该地区干旱时空演变规律。结果表明，广西喀斯特地区年尺度干旱基本为2 a一遇，发生频率中部低、东西部高，以轻旱和中旱为主。秋旱发生频率最高，冬旱次之，春旱和夏旱发生频率较低，各季节干旱多以轻旱为主。其中，春旱3~4 a一遇，发生频率由西南向东北呈递减趋势；夏旱3~4 a一遇，发生频率由东向西呈减弱趋势；秋旱接近1 a一遇，发生频率中东部高于西部，该季节中旱、重旱和特旱发生频率也明显高于其他季节；冬旱1~2 a一遇，发生频率西北部较高，且由西向东呈递减趋势。1971—2017年，广西喀斯特地区冬旱、夏旱呈波动减弱趋势，春、秋旱呈增强趋势。在15~20 a时间尺度上，年和各季节的干旱存在明显的干湿循环，5 a以下小尺度干旱周期振荡更频繁。SPEI与土壤湿度呈显著正相关，利用SPEI可较客观反映该地区旱情。

关键词: 干旱, 标准化降水蒸散指数, 广西喀斯特地区, 时空演变