东北地区春季透雨早晚年的环流特征及与前期海温的关系

Circulation Characteristics of Early and Late Spring Soaking Rain in Northeast China and Its Relationship with Previous SST

利用1960-2017年4-5月东北地区109个代表站点逐日降水量资料,NCEP/NCAR-I月平均再分析资料(位势高度场、风场等数据),以及NOAA重构的月平均海温资料,分析了东北地区春季透雨出现典型早、晚年的环流特征及与海温的关系。结果表明:(1)典型透雨偏早年的日期集中在4月中下旬,偏晚年的日期集中在5月中下旬。(2)透雨偏早年4月,东北地区上空高度场明显偏低,受偏南风控制,且有两条明显的水汽输送带,垂直上升运动强烈,有利于产生降水;透雨偏晚年4月,该地区受高压脊控制,水汽辐散,整层下沉运动强烈,不利于产生降水。(3)东北地区春季透雨出现的早晚与前期(1-3月)热带印度洋、赤道太平洋和邻近海域的海温有关,前期关键区海温偏暖(冷),有利于透雨出现偏早(晚)。

Daily precipitation data from 109 representative stations in Northeast China from April to May in 1960-2017,NCEP/NCAR-I monthly mean reanalysis data(including geopotential height and winds),and monthly mean sea surface temperature(SST)data reconstructed by NOAA are used to analyze the atmospheric circulation characteristics and relationship with previous SST in typical early and late years of first spring soaking rain in Northeast China.Results show that:(1)Dates of typical early soaking rain are concentrated in mid-to late-April,and dates of typical late soaking rain are concentrated in mid-to late-May.(2)In April,the geopotential height field over Northeast China is obviously low and controlled by southerly winds,and there are two obvious water vapor conveyor belts with strong vertical upward motion,which are favorable for precipitation generation.Late years of soaking rain are basically opposite of the above.Northeast China is controlled by high-pressure ridges and northerly winds,with sinking movements dominating and water vapor dispersion,which are not conducive to the occurrence of heavy rain.(3)Early and late years of soaking rain in Northeast China are related to SST in the tropical Indian Ocean,equatorial Pacific Ocean and adjacent seas in early period(January to March),and previous warm(cold)SST in the key areas are conducive to early(late)years of soaking rain.