高级搜索

“23.7”河北罕见特大暴雨过程降水演变与中尺度特征分析

Analysis of precipitation evolution and mesoscale characteristics for a severe torrential rain event in Hebei from 29 July to 2 August 2023

  • 摘要: 2023年7月29日至8月2日,受台风“杜苏芮”北上减弱低压影响,河北出现罕见特大暴雨天气过程(以下简称“23.7”暴雨过程),其中位于冀南的邢台市梁家庄自动站52 h累积降水量高达1 003.4 mm。利用常规地面与探空资料以及区域自动站资料、雷达拼图与ERA5再分析资料等,对“23.7”暴雨过程的降水演变特征、环流形势与环境条件、中尺度特征进行了初步分析。结果表明: 此次暴雨过程具有持续时间长、累计雨量大、覆盖范围广等特征;台风“杜苏芮”登陆北上后,受500 hPa华北北部“高压坝”阻挡而停滞,河北大部地区整层水汽总量达到其气候平均态的2倍以上,环境大气具有低的抬升凝结高度和自由对流高度及一定的对流不稳定能量,以及850 hPa倒槽切变线稳定少动提供的持久辐合抬升条件,使得降水回波长时间维持在河北西南部太行山前和河北中部。边界层东南风急流伴随台风倒槽向北发展,急流核风速在河北中部超过22 m·s-1,大暴雨过程中地形作用明显。边界层急流影响河北西南部期间,回波强度30~40 dBz、质心高度低于6 km的多个对流单体先后移过梁家庄站上空,造成梁家庄站累计出现24 h的短时强降水;边界层急流北移后,8 m·s-1左右的偏东风使太行山前层积混合云降水回波继续长时间维持造成雨区重叠,是梁家庄站52 h累积降水量超过1 000 mm的主要原因。

     

    Abstract: Affected by the weakening of the low-pressure system caused by the northward movement of the typhoon "Doksuri", Hebei encountered an unprecedented severe torrential rain event (hereinafter referred to as "23.7" severe torrential rain) from 29 July to 2 August 2023, in which the accumulated rainfall in 52 hours is up to 1 003.4 mm at Liangjiazhuang station in Xingtai of southern Hebei. Using routine upper-air and surface weather observations, regional automatic weather station data, radar mosaic of reflectivity factor, ERA5 reanalysis data, and other relevant data, we conducted the analysis on the precipitation evolution characteristics, circulation patterns, environmental conditions, and mesoscale features of the "23.7" severe torrential rain. The results indicate that the "23.7" severe torrential rain is characterized by long duration, large accumulated rainfall and wide coverage. After landing and moving northward, Typhoon "Doksuri" is blocked by the high pressure barrier in northern North China at 500 hPa and stagnates. Total content of water vapor over most areas of Hebei reached more than twice the climate average state. All the factors, that low lifting condensation level, low free convection height, moderate convective instability energy, as well as the lasting convergence uplift provided by the stability and stagnation of inverted trough at 850 hPa, are the causes of maintaining precipitation echo for a long time in central Hebei and in the foothills of Taihang Mountains in southwestern Hebei. The southeasterly boundary layer jet moves northwards along with the typhoon inverted trough, and the jet core is located in central Hebei, with the wind speed exceeding 22 m·s-1 and terrain plays a significant role in the rainfall event. During the influence of boundary layer jet on southwestern Hebei, multiple convective cells with echo intensity of 30~40 dBz and centroid height lower than 6 km successively pass over the Liangjiazhuang station, causing a total of 24 hours of short-term severe rainfall at the station. After the boundary layer jet moving northwards, the rainfall overlapping, caused by the continued long-term maintenance of stratocumulus mixed cloud precipitation echo in the foothills of Taihang Mountains due to the interaction of easterly wind of about 8 m·s-1 and terrain, is the main reason of the 52-hour accumulated rainfall exceeding 1 000 mm at the Liangjiazhuang station.

     

/

返回文章
返回