干旱区生态环境知识资源中心

Prolonged dry episodes, defined by the 90th percentile of long durations without efficient precipitation (above the 0.1 mm/day threshold) in both the wet and dry seasons, have been investigated from 1958 to 2008 at 404 stations over China. Associated with droughts over northern China in summer, the enhancement of the prolonged dry episode duration is an essential feature, together with a lack of precipitation and the negative Palmer drought severity index (PDSI) in the wet season. In the dry season, durations of prolonged dry episodes have significantly increased over southern China and the Yellow River valley during the last 51 years. The prolonged dry episodes highlight the impact of a decrease in precipitation frequency, and are useful for representing short-term droughts, particularly over semi-arid regions and in the dry season. The occurrence of the maximum prolonged dry episodes over vulnerable regions in the early twenty-first century is suggestive of a greater risk of droughts during both the wet and dry seasons in a warmer climate over China. Copyright (C) 2010 Royal Meteorological Society