干旱区研究

Arid Zone Research >

2025 , Vol. 42 >Issue 4: 600 - 612

DOI: https://doi.org/10.13866/j.azr.2025.04.03

Weather and Climate

Formation mechanism and energy source of a heavy rainfall event in the eastern northwest region

  • SHI Xia ,
  • LIU Weicheng ,
  • CHEN Xiaoyan ,
  • HUANG Yuxia ,
  • TAN Dan ,
  • WU Jiye
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  • 1. Institute of Arid Meteorology, China Meteorological Administration, Gansu Key Laboratory of Arid Climatic Changeand Reducing Disaster, Key Laboratory of Arid Climatic Change, Lanzhou 730020, Gansu, China
    2. Lanzhou Central Meteorological Observatory, Lanzhou 730020, Gansu, China
    3. Nanjing University of Information Science and Technology, Nanjing 210044, Jiangsu, China

Received date: 2024-07-31

  Revised date: 2025-01-01

  Online published: 2025-04-10

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Abstract

This study analyzes the spatial and temporal distribution, circulation patterns, and water vapor transport characteristics of a heavy precipitation event in Longnan City, Gansu Province, on July 10, 2020, using hourly precipitation observations and ERA5 reanalysis data. Additionally, atmospheric moisture energy (MSE) was introduced to investigate the unstable energy sources of convective activity, providing a new perspective for the re-evaluation and diagnosis of severe convective weather in the northwest region, as well as new reference indicators for business forecasting. The results show that: (1) The heavy precipitation exhibited high intensity, obvious locality, and strong convection. At 500 hPa, the plateau shortwave trough facilitated the convergence of cold and warm air, while at 700 hPa, the southerly airflow combined with cyclonic shear provided favorable conditions for water vapor transport and dynamic uplift. (2) The occurrence of heavy precipitation was accompanied by MSE charging and discharging. The MSE accumulates continuously before the peak of heavy precipitation, putting the atmosphere in a charging state. After peaking, the MSE significantly decreased, and the atmosphere was in a state of energy release. (3) The mechanisms of atmospheric charging differed by vertical height, with vertical MSE transport in the lower troposphere contributing positively, whereas horizontal advection contributing negatively. Horizontal advection, particularly meridional advection, positively contributed to the middle layer, whereas vertical transport contributed negatively. The increase in MSE transport in the upper troposphere is mainly driven by meridional advection. (4) The vertical transport of water vapor influenced the MSE in the lower troposphere, whereas the latent heat energy from water vapor controlled MSE in the middle layer. The meridional advection of water vapor increases the MSE due to abnormal southerly winds. High-level MSE is dominated by the internal energy term, and the main contribution to the increase in MSE is the meridional advection caused by the combination of westerly winds and temperature gradients that are warm in the west and cold in the east.

Key words： heavy precipitation; atmospheric instability energy; moist potential energy; water vapor flux; Northwest China

Cite this article

SHI Xia , LIU Weicheng , CHEN Xiaoyan , HUANG Yuxia , TAN Dan , WU Jiye . Formation mechanism and energy source of a heavy rainfall event in the eastern northwest region[J]. Arid Zone Research, 2025 , 42(4) : 600 -612 . DOI: 10.13866/j.azr.2025.04.03

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