基于标准化降水蒸散指数的中国干旱趋势研究

标准化降水蒸散指数(SPEI)通过标准化潜在蒸散与降水的差值表征一个地区干湿状况偏离常年的程度,是分析干旱演变趋势的新理想指标,目前已经广泛应用于干旱评估、水资源管理等领域。用SPEI和1951—2009年中国区域160个站的月降水量及月平均气温资料,对中国59年来干旱化的空间分布、四季干旱趋势变化和全国极端干旱事件发生频次进行了分析,并定性分析了干旱发生的原因。结果表明,我国普遍存在干旱化的事实,西部、华北和东北地区干旱化最为显著。我国四季均呈现干旱化趋势,其中春、秋季干旱化趋势明显,夏季最近15年都处于干旱状态,但干旱化趋势未通过0.05显著性检验;另外全国极端干旱事件发生频率明显增多。东北和华北地区的降水呈现轻微减少趋势,而温度升高趋势明显,降水和温度的共同作用导致了明显的干旱化。四川盆地温度升高趋势不显著,但降水减少显著,降水较少是导致四川盆地干旱化的主要原因。降水频率的减少和集中也导致近几年极端干旱事件明显增多。我国普遍的干旱化趋势和明显增多的极端干旱事件可能对我国经济发展产生阻碍。

Standardized precipitation evapotranspiration index showsdrought trends in China

Standardized precipitation evapotranspiration index(SPEI),calculated from the difference between potential evapotranspiration and precipitation,showed dry and wet deviations from normal conditions.This is generally used as an indicator for drought evolution trends in drought assessments,water resources management and other fields of hydrology.Using monthly mean surface air temperature and precipitation collected from 160 meteorological stations across China for 1951-2009,spatial distributions of seasonal drought trends and frequencies of extreme drought events were analyzed via SPEI.The results showed drying trends across the whole of China.The most significant drought was in the west,north and northeast of China.It was,however,wet in some regions of northern Xinjiang and the border regions of Sichuan and Yunnan.Drying trends existed for all four seasons,and were more obvious in spring and autumn.Summer was always dry in the last 15 years,although with a drying trend insignificant at the 0.05 level.Furthermore,the frequency of extreme drought increased significantly.Significant trends in temperature increase along with moderate trends in precipi-tation decline were noted for many stations in the northeast and north of China.The combined effects of precipitation and temperature caused significant droughts in the country.In the Sichuan Basin,precipitation significantly decreased with no significant change in temperature.Drought in Sichuan Basin was largely attributed to decreasing precipitation.In recent years,extreme drought events in-creased with decreasing frequencies of precipitation events in many areas of China.Widespread drought trends and significant in-creases in extreme drought events probably hindered China’s economic development.SPEI-detected drought trends were mostly con-sistent with observed droughts in China,indicating that SPEI was an ideal index for monitoring drying trends.