过去半个世纪,中国经历了北方的"西湿东干"和东部的"南涝北旱"的降水分布格局.近十几年来,这种降水长期变化的分布格局是维持还是发生了变化?针对这个问题,本文基于年降水观测数据、自矫正的帕尔默干旱指数scPDSI、地表湿润指数SWI及GRACE(Gravity Recovery and Climate Experiment)卫星数据反演的陆地水储量(TWS)对中国区域干旱化问题进行了再分析.结果表明,近16年(2001~2016年),中国东部地区(100°E以东)"南涝北旱"的格局正在发生显著的变化,长江上中游及江淮流域已转为显著的干旱化趋势,而华北地区的降水已转为增加趋势,东部"南旱北涝"的格局基本形成;北方过去的"西湿东干"也转变为"西干东湿"的空间分布特征.显然,中国区域的降水格局在2001年后发生了明显的年代尺度转折性变化,两种常用干旱指数scPDSI和SWI的分析也证明了这一点.但GRACE的陆地水储量(TWS)的分析却显示,最近16年来,中国东部"南涝北旱"的格局仍未发生变化,北方大部分地区仍然处于干旱化的时段,且有加剧的趋势,其原因有待于进一步研究.
英文摘要:
There are significant changes in precipitation over China under global warming. During 1951-2000, the precipitation experienced a period when its spatial distribution showed a pattern of 'western wetting and eastern drying, WWED' in northern part of China and 'southern flooding and northern drought, SFND' in eastern part of China. Does this distribution pattern of long-term precipitation change still maintain or change after 2001? Based on observations of monthly mean temperature, monthly mean precipitation, and calculated self-calibrating Palmer Drought Severity Index (scPDSI) and surface wetness index (SWI), the drying trend in China has been revisited. Results show that the wet-dry spatial distribution in China has been changing significantly after 2001. Over northern China, the pattern of WWED switched to 'western drying and eastern wetting, WDEW'; over eastern China, the pattern of SFND changed to 'southern drought and northern flooding, SDNF' during 2001 to 2016. In central part of northern China, precipitation trend switched from a decreasing trend to a significant increasing trend; precipitation in the upper and middle reaches of Yangtze River experienced a shift from significant increasing trend to a decreasing trend. However, according to the analysis of Terrestrial Water Storage (TWS) data of The Gravity Recovery and Climate Experiment (GRACE), the wet-dry pattern of SFND over eastern China has not changed during 2001-2016, and the drying trend in northern China has been intensifying since 2001. This is opposite to the results shown in precipitation. The reason will be studied in the future.