Page 20 - 《高原气象》2026年第1期

高 原 气 象 45 卷
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Numerical Simulation Study on the Influence of Soil Moisture

Heterogeneity on the Convective Initiation of a Mesoscale
Convective System over the Qinghai-Xizang Plateau

ZHANG Rongping ， MENG Xianhong ， YANG Xianyu ， WEI Qian 3
1
2
1
（1. College of Atmospheric Sciences， Chengdu University of Information Technology / Sichuan Key Laboratory of Plateau Atmosphere
and Environment， Chengdu 610225， Sichuan， China；
2. Northwest Institute of Ecological Environment and Resources， Chinese Academy of Sciences / Key Laboratory of Cryospheric
Science and Frozen Soil Engineering， Lanzhou 730000， Gansu， China；
3. College of Atmospheric Sciences， Lanzhou University， Lanzhou 730000， Gansu， China）

Abstract： In order to investigate the influence of soil moisture heterogeneity on the convective initiation stage of
a mesoscale convective system over the Qinghai-Xizang Plateau， an typical case of mesoscale convective system，
developed from an isolated convective initiation process over the Qinghai-Xizang Plateau on 10 August 2022， is
studied by observational analysis and numerical experiments using satellite remote sensing data， cloud-to-ground
lightning observations and reanalysis data. The results are as follows： （1） Under weak synoptic-scale forcing， the
convective initiation stage of the mesoscale convective system occurred at 06:00 （UTC， the same as after）. The
convective cloud then moved northeastward and intensified through merging clouds， accompanied by lightning
activity during the development of the mesoscale convective system.（2） Based on the mesoscale numerical mod‐
el WRF， we simulated the surface convergence in the southwestern dry zone formed by surface thermal forcing，
as well as the development and intensification process of the updrafts caused by the surface convergence until the
formation of the convective initiation with a moving direction along the soil moisture gradient. At convective initi‐
ation time， the low-level atmosphere over the convective initiation location was in a dry adiabatic state with a
CAPE（CIN） of 946. 5 J·kg （0 J·kg ）. 2 m air temperature reached the convective temperature 1h before the oc‐
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currence of convective initiation， when the height of the planetary boundary layer was higher than the level of free
convection. The convection then strengthened rapidly.（3） The results of the sensitivity experiments show that the
removal of the soil moisture inhomogeneity weakened the intensity of the convection and shifted the position of
the convective initiation westward， which is related to the fact that the soil moisture inhomogeneity changed the
atmospheric dynamical， thermal and moisture conditions before the occurrence of the convective initiation. The
soil moisture inhomogeneity indirectly increased the sensible heat flux of the dry zone located to the southwest of
the convective initiation location by increasing the surface temperature， thus increasing the upward motion at sur‐
face before the occurrence of the convective initiation. Meanwhile， the direction of the wind field near the convec‐
tive initiation location was also changed and thus increasing the convergence of the surface wind field and water va‐
por at the convective initiation time， which led to an increase in the intensity of the convection.（4） Under the con‐
dition of homogeneous soil moisture distribution， increasing soil moisture led to more abundant surface water va‐
pour and stronger convergence of the surface wind field， which in turn led to an increase in the intensity of water
vapour convergence and enhanced the development of convection. In addition， higher soil moisture inhibited the
intensity of pre-convective initiation updraft development by decreasing surface temperature and sensible heat
fluxes， which slowed the development of convection and led to a later convective initiation time.
Key words： Qinghai-Xizang Plateau； soil moisture； mesoscale convective system； convective initiation；
numerical simulation