| 摘要: |
| 【目的】为了探索山脉与其下游平原暴雨的关系。【方法】基于ERA5 0.25°×0.25°再分析资料、地面加密观测资料、FY-2G卫星TBB资料、多普勒雷达组合反射率因子产品等，应用天气学方法，对2022年7月27—28日河北山前平原局地暴雨的触发和维持机制进行研究。【结果】特殊的“拐角”地形使风场发生相应改变，形成偏北、西北2支气流，2支气流与来自渤海的东风气流在下游平原形成中尺度辐合线或中尺度气旋性环流；太行山山前层状和积状混合云降水形成下山冷出流，冷平流的输送，导致山前平原形成较强的中尺度温度梯度，中尺度系统东侧的暖平流使地面气压降低，温压场出现不平衡，在气压梯度力的作用下，中尺度辐合线加强，触发第一阶段局地暴雨；入夜之后，河北南部层状、积状混合云降水强度增大，雨滴降落过程中因蒸发对环境温度产生冷却作用，局地冷平流加强，东北部和西北部弱的暖平流与南部冷出流形成气旋性辐合环流，触发第二阶段局地暴雨；下山冷出流与平原暖气流在下游平原形成水平锋生，为中尺度对流系统提供不稳定能量，使其得以维持和发展。【结论】研究成果利于提高太行山下游平原局地暴雨的预报水平。 |
| 关键词: 山脉“拐角”；局地暴雨；下游平原；中尺度辐合线；中尺度气旋性环流 |
| DOI： |
| 投稿时间：2024-04-26修订日期：2024-08-20 |
| 基金项目:保定市科技计划项目(2211ZN001) |
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| Characteristic Analysis of a Local Rainstorm in Plains Downstream of Mountain |
| Ma Hongqing,DING Heyue,DONG Jiangnan,XU Yiguo,WANG Yating |
| (Baoding Meteorological Bureau of Hebei Province) |
| Abstract: |
| To explore the relationship between the mountains and heavy rain in the downstream plain, based on ERA5 0.25°×0.25° reanalysis data, densely observed data from automatic weather observation system, temperature of blackbody data from FY-2G satellite, Doppler radar composite reflectivity factor product, etc., this article analyzes the trigger and maintenance mechanism of local heavy rain in Hebei piedmont plain during July 27–28, 2022 by synoptic methods. The results show that the special “corner” topography changed the wind field accordingly, forming two airflows to the north and northwest, and the two airflows formed mesoscale convergence line or mesoscale cyclonic circulation in the lower plain with the easterly air from the Bohai Sea. The stratified and accumulated mixed cloud precipitation in the piedmont of Taihang Mountains formed cold outflow, and the transport of cold advection led to a strong mesoscale temperature gradient in the piedmont plain. The warm advection on the east side of the mesoscale system reduced the surface pressure and caused the imbalance of the temperature and pressure field. Under the action of the pressure gradient force, the mesoscale convergence line was strengthened, which triggered the local rainstorm in the first stage. After into night, the precipitation intensity of stratified and accumulated mixed clouds in southern Hebei increased, and the cooling effect of evaporation on the environment temperature during the falling process of raindrops resulted in the strengthening of local cold advection. The weak warm advection in the northeast and northwest and the cold outflow in the south formed a cyclonic convergence circulation, which triggered the local heavy rainfall of the second stage. In the lower plain, the cold flow down from the mountain and the plain warm airflow formed horizontal frontogenesis, providing unstable energy for the mesoscale convective system to maintain and develop. The research results are beneficial to improve the local rainstorm forecast level in the lower plain of Taihang Mountains. |
| Key words: mountain "corner"; local rainstorm; lower plain; mesoscale convergence line; mesoscale cyclonic circulation |
