复杂下垫面在一次干环境对流天气中的作用分析
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济南市气象局

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2023年中国气象局复盘专项(FPZJ2023—074);济南市泰山山脉气象科学试验团队资助。


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The role of complex underlying surface in a convective weather event under dry conditions
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Jinan Meteorological Bureau of Shandong Province

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    摘要:

    利用加密自动气象观测站资料、闪电资料、多普勒雷达资料、风廓线雷达资料及ERA5等多源资料,对一次山东漏报的干环境下的对流天气进行分析,重点探讨复杂下垫面在此次天气过程中的作用。研究表明:(1)这次对流天气的发生得益于复杂下垫面(黄河水面、泰山山脉与大城市)提供的水汽条件、动力条件与热力条件,使得原本在不利于对流系统发展的大尺度环境背景下,对流单体触发、发展、增强,最终形成一条对流回波带,持续2-3小时,造成山东中部的雷电、大风等强对流天气。(2)对流单体首先在高温区与湿舌相叠加的黄河西岸沿地面中尺度辐合线的走向触发。对流单体越过黄河后,受市区高温区与露点锋的共同影响逐渐排列有序,发展成一条东北-西南走向的回波带。(3)回波带东移,对流天气产生,在贴地层形成冷池,冷池东扩,受山脉阻挡停滞,与其前方高温区之间形成明显的温度梯度,再加上回波带爬山,地形抬升,致使回波强度进一步增强。但是未受地形影响的那段回波,移速偏快,带状回波逐渐演变成反弓形。当回波到达山顶后,环境场不利于对流云维持,回波减弱。(4)随着低空急流建立,山脉西侧处于有利的局地小环境中,使该处的回波加强、维持。同时,加强的西南气流形成越山气流,造成山北侧低空急流增速、急流厚度增厚,对流云在山脉北侧得以发展。(5)值得注意的是,复杂下垫面会形成局地小环境,如沿黄河走向的湿舌,真实存在的城市热岛,流经泰山山脉后气流的演变等。当有弱的天气系统经过这些复杂下垫面时,会使得天气系统增强或减弱。

    Abstract:

    Using encrypted automatic meteorological observation station data, lightning data, Doppler radar data, wind profile radar data, and ERA5 multi-source data, an analysis was conducted of a convective weather event in dry conditions that was missed in Shandong, with a focus on the role of complex underlying surfaces in the weather process.The results show that: (1)? The occurrence of this convective weather was facilitated by the water vapor conditions, dynamic conditions, and thermal conditions provided by the complex underlying surface (such as the Yellow River water surface, Mount Tai mountain range, and large cities), which enabled convection systems to suddenly triggered, developed, enhanced despite the unfavorable large-scale environmental background for convection, and finally formed a convective echo zone, lasting 2-3 hours, causing a strong convective weather in central Shandong. (2) The convective cells were firstly triggered at the ground mesoscale convergence line along the west bank of the Yellow River where the high temperature area and the wet tongue are superimposed, and then the convective cells were arranged in an orderly manner after crossing the Yellow River, which was influenced by the high temperature area and the dew front, and developed into a northeast-southwest echo band. (3) The echo belt moved eastward, convective weather generated, forming a cold pool in the strata, and the cold pool expanded eastward, blocked by the mountains, and formed an obvious temperature gradient between the high temperature area in front of it. In addition, the echo belt climbed the mountain, and the terrain rose, resulting in further enhancement of echo intensity. However, the echo belt not affected by the terrain moved faster, and the banded echo gradually developed into an anti-bow shape. When the echo reached the top of the mountain, the environmental field was not conducive to the maintenance of convective clouds, and the echo weakened. (4) With the establishment of the low level jet stream, the west side of the mountain is in a favorable local environment, so that the echo there is strengthened and maintained. At the same time, the strengthening of the southwest airflow forms the cross-mountain airflow, resulting in the growth and thickening of the low-level jet stream on the north side of the mountain, and the convective cloud develops on the north side of the mountain. (5) It is worth noting that the complex underlying surface will form local micro-environment, such as the wet tongue along the Yellow River, the real urban heat island, and the evolution of the air flow after flowing through the Taishan Mountain. When a weak weather system passes over these complex underlying surfaces, it can cause the weather system to strengthen or weaken.

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  • 收稿日期:2024-01-11
  • 最后修改日期:2024-05-31
  • 录用日期:2024-08-23
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