陕西盛夏极端降水频次及其与全球海温的相关研究

摘要

基于陕西省78个测站1961～2011年盛夏逐日降水量资料以及NOAA全球2°×2°海温场资料，分析了陕西盛夏极端降水事件气候特征及其与海温场的遥相关关系。结果表明：（1）盛夏，陕西南部、关中西部及陕北南部是极端降水事件高发区；（2）近年来盛夏极端降水事件呈上升趋势，1976年后显著上升；（3）极端降水事件与前期海温场具有较好的遥相关关系，与同期（同月）海温场相关性不显著；（4）上年秋季、冬季赤道中东太平洋和上年秋季阿拉伯海海温异常偏暖，赤道中东太平洋南北两侧海温偏冷，以及前期2月印度洋和中国近海海温异常偏暖，关中中东部及陕南中东部局地7月极端降水偏多，反之亦然；上年秋季印度洋和赤道东太平洋、上年冬季及当年春季印度洋西部海温异常偏暖，关中中西部地区8月极端降水偏多，反之亦然。%Based on the daily precipitation data at 78 metrological stations in Shaanxi and the 2°×2°sea surface temperature (SST) from National Oceanic and Atmospheric Administration (NOAA)during 1961 -2011,the characteristics of extreme precipitation e-vents in midsummer (July and August)and its teleconnections with global SST were analyzed by using trend analysis,Mann-Kendall test and singular value decomposition(SVD),respectively.The results show that:(1 )The frequency of extreme precipitation was high-er in the south part of Shaanxi,western Guanzhong and the south part of northern Shaanxi in midsummer.The accumulated frequencies of extreme precipitation in July and August reached 39 -105 and 36 -50 in Shaanxi during 1961 -2011,respectively.In recent years,the frequency of annual extreme rainfall in midsummer displayed an increasing trend,but the trend was not so significant.(2) In the past 50 years,the linear increasing rate was approximately 0.07 day per 10 years,and the decadal variability of the frequency for extreme precipitation was remarkable with higher values in the 1970s,1980s and 2000s.In additional,An obvious mutation was detected around the year 1976.(3)There was obvious teleconnection between the frequency of extreme precipitation and the SST in the previous period,but was not significant in the same period.For changes of the extreme precipitation in July,the anomalies of the SST in the previous fall and winter are the most primary factors,while for that in August,the SST in spring also plays an important role. (4)When the SST was abnormally higher in the equatorial middle-eastern Pacific in the previous fall and winter and the Arabian Sea in the previous fall and was abnormally lower in the north and south of the equatorial middle-eastern Pacific in the previous fall and winter,and was abnormally higher in the Indian Ocean and offshore of China in the current February,the extreme precipitation was greater than normal in the middle-eastern of Guanzhong and the south part of Shaanxi in July and vice versa.In August,when the SST was abnormally warmer in the Indian Ocean and the equatorial eastern Pacific in the previous fall and in western Indian Ocean in the previous winter and current spring,there would be more precipitation in the middle-western of Guanzhong.