2018—2022年成都汛期短时强降水时空分布特征

Temporal and Spatial Distribution Characteristics of Short-term Strong Precipitation in the Flood Season of Chengdu from 2018 to 2022

利用成都市2018—2022年汛期(5—9月)14个国家气象观测站逐小时降水资料,运用统计学方法和ArcGIS普通克里金插值法,对成都市短时强降水时空分布特征以及地形作用进行分析。结果表明:短时强降水频次年变化呈显著下降趋势;月变化呈单峰型,集中发生在7—8月,占汛期的77.3%,主峰在8月;夜间短时强降水频次高于白天,集中在01—07时,峰值出现在01-03时,夜雨特征明显,高值区位于彭州-都江堰-崇州-大邑-邛崃-蒲江一带,中心城区和东南山区午后易出现强度较大的短时强降水;短时强降水量和总频次呈现西部高于东部的分布特征,且与海拔高度密切相关,短时强降水量随海拔增高而显著增加。

Based on NCEP reanalysis data,FY-2G geostationary meteorological satellite data and precipitation data,the circulation and physical quantity field characteristics of eastbound heavy precipitation in Liangshan Prefecture from June to September during 2019—2021 were analyzed by synthetic averaging method.The results showed that the special topographic conditions were favorable to trigger the convection.Trumpet-shaped topography of Mianning area belonged to the windward slope for the south wind in the low level of Panxi area,and the airflow climbing was favorable to trigger the convection.The 700 hPa vortex shear and 850 hPa vortex were stable for a long time to lead to the formation of energy front and water vapor convergence center.At the same time,the continuous moisture transport from the lower southerly winds in the Panxi region had made the northern part of Liangshan be an unstable region with high energy and humidity,which was more conducive to the generation,development,and long-term maintenance of convection.The ridge line of the eastward-moving South Asian high was slightly southerly,and the upper-level divergence was conducive to strengthen the development and maintenance of the mid-low-level ascending motion.The ridge line of the in-situ developing South Asian high was slightly northerly,and the upper-level convergence weakens the upward movement of the upper layer,but the upward movement of the middle and lower layers was still strong.Therefore,compared with the developing eastward type,the rainfall level was slightly smaller,but it could also be rainstorm.