低纬高原地区不同强度降水日数变化及其与20092011年干旱的联系

根据低纬高原地区19612011年逐日降水量台站观测资料，利用趋势分析、小波分析等统计诊断方法对低纬高原地区不同强度降水的时空分异特征进行研究，结果表明:低纬高原地区降水事件以小雨和中雨为主，其日数占总降水日数的90 %以上，产生的降水量也达到总降水量的60 %以上.小雨和中雨量级降水日数与低纬高原总降水日数及总降水量的U型分布特征较为相似，但大雨及暴雨量级降水日数与总降水日数的空间分布差异明显.伴随着全球增暖，低纬高原地区东部小雨及中雨量级降水事件发生频率显著减少，导致低纬高原东部地区的总降水量呈现明显减少的趋势.而低纬高原西部地区，各量级降水日数变化趋势在空间上存在较大差异，各量级降水日数对总降水量贡献相互抵消，导致低纬高原西部地区总降水量变化趋势不明显.对造成20092011年连续严重干旱的各等级降水频次贡献进行分析，结果表明中雨量级降水频次异常偏少在此次严重干旱事件的发生、发展中起决定性作用.

The variation and influence to droughts of different intensity precipitation days

Based on the low-latitude highlands(LLH) daily precipitation station observations from 1961 to 2011,by applying trend analysis and wavelet analysis,this study has analyzed the LLH precipitation characteristics of spatial and temporal variation in different intensity. The result indicates that the LLH precipitation is mainly light rain and moderate rain.They account for more than 90% of the total precipitation days.The precipitation also reaches more than 60% of the total precipitation.At the same time,the light rain and moderate rain magnitude precipitation days,the LLH total precipitation days and total rainfall of U pattern of distribution are relatively similar.However,the spatial distribution of heavy rain,rainstorm days and total rain days are obviously different.The east of the LLH has less light rain and moderate rain along with global warming.Thus the eastern total rainfall has significantly reduced.In the west of the LLH,different magnitude precipitation presrnts different spatial distributions,which lead to the increase of weak trend of total rainfall.The different precipitation frequency contribution of continuous drought from 2009 to 2011 has been analyzed,showing that moderate rain is the most important.