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Numerical Study on the Impacts of Hydrometeor Processes on the "21·7" Extreme Rainfall in Zhengzhou Area of China.

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Title: Numerical Study on the Impacts of Hydrometeor Processes on the "21·7" Extreme Rainfall in Zhengzhou Area of China.
Authors: Gao, Wenhua1 (AUTHOR) whgao@cma.cn, Li, Chengyin1 (AUTHOR), Tang, Lanzhi1 (AUTHOR)
Source: Advances in Atmospheric Sciences. Oct2024, Vol. 41 Issue 10, p2061-2078. 18p.
Subject Terms: *Rainfall, *Latent heat, *Buoyancy, *Vertical drafts (Meteorology), *Air flow
Abstract (English): The impacts of hydrometeor-related processes on the development and evolution of the "21·7" extremely heavy rainfall in Zhengzhou were investigated using WRF simulations. Surface precipitation was determined by the hydrometeor microphysical processes (all microphysical source sink terms of hydrometeors) and macrophysical processes (local change and flux convergence of hydrometeors). The contribution of hydrometeor macrophysical processes was commonly less than 10%, but could reach 30%–50% in the early stage of precipitation, which was largely dependent on the size of the study area. The macrophysical processes of liquid-phase hydrometeors always presented a promotional effect on rainfall, while the ice-phase hydrometeors played a negative role in the middle and later stages of precipitation. The distributions of microphysical latent heat corresponded well with those of buoyancy and vertical velocity (tendency), indicating that the phase-change heating was the major driver for convective development. Reasonable diagnostic buoyancy was obtained by choosing an area close to the convective size for getting the reference state of air. In addition, a new dynamic equilibrium involving hydrometeors with a tilted airflow was formed during the heavy precipitation period (updraft was not the strongest). The heaviest instantaneous precipitation was mainly produced by the warm-rain processes. Sensitivity experiments further pointed out that the uncertainty of latent heat parameterization (±20%) did not significantly affect the convective rainfall. While when the phase-change heating only altered the temperature tendency, its impact on precipitation was remarkable. The results of this study help to deepen our understanding of heavy rainfall mechanisms from the perspective of hydrometeor processes. [ABSTRACT FROM AUTHOR]
Abstract (Chinese): 摘要: 本文利用WRF中尺度模式探究了水凝物过程对"21·7"郑州极端暴雨发展演变的影响。地面降水由水凝物的微物理过程(水凝物所有源汇项)和宏物理过程(水凝物局地变化及通量散度)决定。水凝物宏物理过程对降水的贡献通常小于10%,在降水早期可达30%–50%,但很大程度上依赖于研究区域的大小。液相水凝物宏物理过程总体为促进降水,而冰相宏物理过程在降水中后期起负作用。微物理相变潜热的分布与热浮力、垂直速度(倾向)分布基本一致,表明相变潜热是对流发展的主要驱动因子。这里建议通过选取一个接近对流大小的区域平均(表示大气参考态)来诊断热浮力,而更合理的计算是有效浮力(热浮力与其引起的垂直扰动气压梯度力之和)。此外,在强降水阶段(此时上升速度并非最强),形成了一个包含水凝物拖曳及倾斜上升气流的新动态平衡,最大瞬时降水由暖雨过程产生。敏感性试验进一步指出,相变潜热参数化的不确定性(±20%)对模拟结果的影响有限,但当相变潜热仅改变温度倾向项时,其对对流降水的影响显著。该研究从水凝物全过程的视角加深了人们对强降水演变机理的理解。 [ABSTRACT FROM AUTHOR]
Database: Energy & Power Source
Description
Abstract:The impacts of hydrometeor-related processes on the development and evolution of the "21·7" extremely heavy rainfall in Zhengzhou were investigated using WRF simulations. Surface precipitation was determined by the hydrometeor microphysical processes (all microphysical source sink terms of hydrometeors) and macrophysical processes (local change and flux convergence of hydrometeors). The contribution of hydrometeor macrophysical processes was commonly less than 10%, but could reach 30%–50% in the early stage of precipitation, which was largely dependent on the size of the study area. The macrophysical processes of liquid-phase hydrometeors always presented a promotional effect on rainfall, while the ice-phase hydrometeors played a negative role in the middle and later stages of precipitation. The distributions of microphysical latent heat corresponded well with those of buoyancy and vertical velocity (tendency), indicating that the phase-change heating was the major driver for convective development. Reasonable diagnostic buoyancy was obtained by choosing an area close to the convective size for getting the reference state of air. In addition, a new dynamic equilibrium involving hydrometeors with a tilted airflow was formed during the heavy precipitation period (updraft was not the strongest). The heaviest instantaneous precipitation was mainly produced by the warm-rain processes. Sensitivity experiments further pointed out that the uncertainty of latent heat parameterization (±20%) did not significantly affect the convective rainfall. While when the phase-change heating only altered the temperature tendency, its impact on precipitation was remarkable. The results of this study help to deepen our understanding of heavy rainfall mechanisms from the perspective of hydrometeor processes. [ABSTRACT FROM AUTHOR]
ISSN:02561530
DOI:10.1007/s00376-024-3365-x