双月刊

ISSN 1006-9895

CN 11-1768/O4

复杂地形强降雪过程中垂直运动诊断分析
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中国科学院大气物理研究所

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国家重点研发计划2018YFC1507104,中国科学院战略性先导科技专项XDA17010105,吉林省科技发展计划项目20180201035SF,国家自然科学基金项目41775140


Diagnosis and analysis of vertical motion during complicatedly topographical heavy snowfall
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Institute of Atmospheric Physics,Chinese Academy of Sciences

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    摘要:

    利用WRF模式对2018年11月30日伊犁河谷和天山北坡强降雪过程进行数值模拟,并分析复杂地形强降雪过程垂直速度和垂直动能变化机制。研究表明,冷锋过境造成地表气压升高,干空气气柱质量增大,从而导致垂直气压梯度力和干空气气柱浮力发生变化,进而引起垂直运动发生发展。垂直速度局地时间变化主要取决于扰动垂直气压梯度力、水物质拖曳力和扰动干空气浮力。在天山北坡,气流过山时,迎风坡的扰动垂直气压梯度力较大,扰动干空气浮力较小,二者合力促进上升运动;在背风坡,扰动垂直气压梯度力和扰动空气浮力形成向下的合力,产生下沉加速度,导致背风坡下沉大风。扰动垂直气压梯度力做功和扰动干空气浮力做功情况基本相反,背风坡扰动垂直气压梯度力和综合强迫做功项抑制垂直动能,扰动干空气浮力和水物质拖曳力做功项增强垂直动能。此外,扰动垂直气压梯度力和扰动干空气浮力做功项主要出现在中低层,水物质拖曳力做功项主要位于低层,平缓地形处的综合强迫做功明显小于地形复杂处。

    Abstract:

    The WRF model was used to numerically simulate the heavy snowfall process in the Ili River Valley and the Northern slope of Tianshan Mountains on November 30, 2018, and analyze the vertical velocity and vertical kinetic energy change mechanism of heavy snowfall under complex terrain. Studies have shown that the passage of a cold front causes an increase in surface pressure and an increase in the dry air mass in column, which leads to changes in the vertical pressure gradient force and the dry air column buoyancy, which in turn causes the development of vertical motion. The local time variation of vertical velocity mainly depends on the perturbation vertical pressure gradient force, drag force of the water substance and perturbation dry air buoyancy. When the airflow crosses the Tianshan Mountains North Slope, the perturbation vertical pressure gradient force on the windward slope is larger, and the perturbation dry air buoyancy is smaller, which promotes the upward movement; On the leeward slope, the perturbation vertical pressure gradient force and the perturbation air buoyancy form a downward total force produces sinking acceleration, which causes the leeward slope strong sinking gale. The work done by the perturbation vertical pressure gradient force is basically opposite to the work done by the perturbation dry air buoyancy. On leeward slope, the work items of the perturbation vertical air pressure gradient force and the comprehensive force are to suppress the vertical kinetic energy, when the work item of the perturbation dry air buoyancy and the drag force of the water substance enhances the vertical kinetic energy. In addition, the perturbation vertical pressure gradient force and the perturbation dry air buoyancy work items mainly appear in the middle and low layers, the water material drag force work items are mainly located in the lower layers, and the comprehensive force work in flat terrain is significantly less than that in complex terrain.

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  • 收稿日期:2020-10-09
  • 最后修改日期:2021-05-17
  • 录用日期:2021-05-19
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