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山东半岛“平行”双支海风锋的中尺度特征分析及对流触发机制初探

Mesoscale characteristics analysis of "parallel" dual sea breeze fronts and associated convection initiation mechanism in the Shandong Peninsula

  • 摘要: 海风锋是沿海地区触发对流天气的重要系统,其中双支海风锋的观测和研究极少。利用2023年7月9日常规观测、多普勒雷达、葵花-9卫星和ERA5再分析等资料,对山东半岛东部导致强对流天气的两条“平行”且相向移动的海风锋进行中尺度特征分析,初步分析了其触发强对流的机制。结果表明:(1)触发本次强对流天气的双支海风锋分别位于福山至牟平沿岸(北岸海风锋)和海阳至乳山沿岸(南岸海风锋),其出现时的地面环境风为西南风。北岸海风锋建立初期呈西北—东南向,在向南推进过程中逐渐转为与南岸海风锋“平行”的东北—西南向。(2)极大风可以辅助雷达判断海风锋的位置。海风锋过境时南北岸的地面气象要素变化差异较大,北岸存在明显的南北风转换,而南岸相对湿度的激增最显著。(3)强对流发生前期,山东半岛东部南北两侧的海域中均伴有低层大气扰动抬升且向内陆推进。随着双支海风锋的建立,南北两侧低层大气扰动抬升区分别与两支海风锋的抬升区合并且均得以增强,两个合并的抬升区继续相向移动直至合并成最强上升气流,随后触发了短时强降水和雷暴大风等强对流天气。

     

    Abstract: The sea breeze front is an important system that triggers convective weather in coastal areas, but few observations and research on the dual sea breeze fronts are reported. This article uses conventional observation data, Doppler radar, Himawari-9 satellite, and ERA5 reanalysis data on July 9, 2023, to analyze the mesoscale characteristics of two "parallel" sea breeze fronts moving towards each other that cause severe convective weather in the eastern part of the Shandong Peninsula. The mechanism that triggers strong convection is preliminarily explored. The results are as follows. (1) The dual sea breeze fronts that triggered this severe convective weather were located along the coast from Fushan to Mouping (northern sea breeze front) and from Haiyang to Rushan (southern sea breeze front). The surface environmental wind at the time of their appearance was the southwest wind. At the initial stage of the northern sea breeze front, it showed a northwest-southeast direction. But it gradually turned into a northeast-southwest direction as it advanced southward, which was parallel to the southern sea breeze front. (2) Peak gusts can assist radar in determining the location of the sea breeze front. When the dual sea breeze fronts passed through, there was a significant difference in the changes of surface meteorological elements between the northern and southern coasts. There was a clear north-south wind transition on the north coast and a significant increase in relative humidity on the south coast. (3) In the early stage of strong convection, there were low-level atmospheric disturbances and uplifts in the sea areas on both the northern and southern sides of the eastern Shandong Peninsula, which advanced inland. With the establishment of the dual sea breeze fronts, the low-level atmospheric disturbance uplift areas on both the northern and southern sides merged with the uplift areas of the dual sea breeze fronts. These two merged uplift areas continued to move towards each other until they merged into the strongest updrafts, which subsequently triggered short-term heavy rainfall and downburst severe convective weather.

     

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