ENSO和NAT对河南汛期降水的协同影响

Synergistic Effect of ENSO and NAT on Precipitation in Flood Season in Henan Province

利用1981—2020年河南夏季114站降水资料和欧洲中心第五代再分析资料,通过合成分析、t检验等气候诊断方法,对河南汛期降水异常大气环流特征及其早期驱动因子进行分析.合成分析结果表明:河南汛期降水偏多年,强盛的南亚高压与低层气旋性异常环流配合,利于高空风场辐散及大气的上升运动;河南上游的气旋性异常环流不断输送冷空气,并与西伸偏强的西太平洋副热带高压配合,使得南海、孟加拉湾和西太平洋有水汽输送至河南,而汛期降水偏少年仅有西太平洋的水汽输送至河南;汛期降水偏多年对应太平洋海温从厄尔尼诺转为拉尼娜和冬季到夏季持续的北大西洋三极子负位相.经波作用通量诊断结果表明:大西洋和太平洋的海温异常上空向西太平洋输送波通量,使得西太平洋副热带高压加强西伸北抬,进而形成有利于河南汛期降水的水汽输送异常和大气环流.

Based on the precipitation data of 114 stations in Henan during 1981-2020 and the fifth generation reanalysis data of the European Center,the atmospheric circulation characteristics and early driving factors of abnormal precipitation in Henan flood season were analyzed by the climate diagnosis methods such as synthetic analysis and t-test.The results show that for the years with abundant precipitation in flood season,the strong South Asian high cooperated with the cyclonic abnormal circulation at the lower level,which was conducive to the divergence of the upper wind field and the upward movement of the atmosphere.The cyclonic abnormal circulation in the upper reaches of Henan continuously transported cold air,and coordinated with the strong western Pacific subtropical high,so that water vapor from South China Sea,Bay of Bengal and western Pacific Ocean was transported to Henan,while only water vapor from the western Pacific Ocean was transported to Henan during the flood season in the years with less precipitation.The precipitation corresponds to the Pacific SST changing from El Nino to La Nina and the North Atlantic tripole negative phase lasting from early winter to the same summer.The diagnostic results of flux through wave action show that the wave flux transported over the SST anomalies in the Atlantic and Pacific oceans to the western Pacific Ocean strengthened the westward extension and northward uplift of the western Pacific subtropical high,and then formed the water vapor transport anomalies and atmospheric circulation conducive to the precipitation in flood season in Henan Province.