祁连山地区夏季强降水的年代际变化及其成因OA

In recent years,the Qilian Mountains region has experienced frequent heavy precipitation events,resulting in significant casualties and property damage.However,the physical mechanisms behind the frequent occurrence of heavy precipitation remain unclear.Based on rainfall station observations in the Qilian Mountains region from 1961 to 2023 and NCAR/NCEP reanalysis data,this paper investigates the interdecadal variation characteristics of summer heavy precipitation in the study area and its causes.The results indicate that(1)over the past 63 years,there were 555 heavy precipitation days during summer in the Qilian Mountains region,primarily distributed in the exorheic river valleys of the southeastern part.Both the number of heavy precipitation days and the total heavy precipitation amount increased significantly after an abrupt change in 1992.A survey of weather maps on heavy precipitation days revealed a notable increase in heavy precipitation days associated with Tibetan Plateau Vortices(TPVs).(2)On heavy precipitation days in the Qilian Mountains region,the tropospheric atmosphere over Eurasia exhibited an anomalous wave train pattern,resembling the Silk Road Pattern(SRP).The southerly winds on the eastern side of the anomalous cyclone near the Qilian Mountains enhanced the transport of warm and moist airflow to the northeastern Tibetan Plateau,which tends to facilitate the formation and development of the TPV and the occurrence of heavy precipitation.(3)After 1992,the SRP index underwent an interdecadal shift from a negative to a positive phase,leading to a significant increase in the meridional moisture flux transported to the northeastern Tibetan Plateau.These factors collectively contributed to the increased activity of TPVs,which in turn became the main mechanism driving the interdecadal increase in summer heavy precipitation in the Qilian Mountains region.