Page 101 - 《高原气象》2023年第1期

1 期 莫绍青等：新疆南疆极端干旱区典型暴雨的水汽特征及触发机制分析 97

Analysis of the Water Vapor Characteristics and Trigger Mechanism

for a Typical Heavy Rainstorm in the Extreme Arid Region
of the Southern Xinjiang

1
MO Shaoqing ， LI Yaohui 2， 1， 3
（1. College of Atmospheric Sciences， Lanzhou University， Lanzhou 730000， Gansu， China；
2. College of Aviation Meteorology， Civil Aviation Flight University of China， Guanghan 618307， Sichuan， China；
3. Institute of Arid Meteorology， China Meteorological Administration， Lanzhou 730020， Gansu， China）

Abstract： In order to strengthen our understanding of the water vapor characteristics and trigger mechanism of
the rainstorm in southern Xinjiang， this paper analyzes a rainstorm process occurred over southern Xinjiang re‐
gion during 24 -28 June 2019. Various data includingFNL（NCEP final operational global analysis） and ERA5
（fifth version of the European Centre for medium-range weather forecasts reanalysis model） reanalysis data，
hourly observation data at the automatic meteorological station， the satellite equivalent blackbody brightness tem‐
perature data of FY-2G are used. The results show that the precipitation occurred under the background of synop‐
tic circulation with “two-ridge and two-trough” pattern over the middle and high latitude， the low vortex of
Balkhash Lake， the ridge of Iran and convergence line are the main weather systems leading to the heavy rain‐
fall. The water vapor of the heavy rainfall mainly comes from the Atlantic Ocean， Black Sea， Rio / Aral Sea，
Arabian Sea and Gulf of Bengal， along the northwest， partial west and southwest paths to the southern Xinjiang
Basin. Water vapor from the northwest and west paths to the southern Xinjiang Basin are guided by the low-level
jet， and from the southwest path is transported over the Qinghai-Xizang Plateau to the southern Xinjiang under
the guidance of the 500 hPa cyclone wind field and the southwest high-level jet on 200 hPa in the western south‐
ern Xinjiang. Water vapor revenue and expenditure calculation shows that water vapor input is mainly concentrat‐
ed on the high level of troposphere at the south boundary， low and high levels of troposphere at the north bound‐
ary； the output of water vapor is concentrated in the low and high layers of the troposphere at the east boundary.
The convergence line is the most important trigger system for this heavy rainfall， whose form is caused by the
convergence of the dominant air flow invaded from the north in front of the high and steep terrain （KunLun
Mountains） on the south side of the southern Xinjiang Basin. Meanwhile， the accumulation of water vapor
brought by the northwesterly airflow in the north of the convergence line in front of the mountain is sufficient
which is favorable for the rainstorm. Under the impact of terrain uplift， accompanied with the uplifting of air
mass and accumulation of water vapor at the foothill of KunLun mountains， unstable energy is released and the
convection system constantly generates and develops near the mountains， bringing continuous heavy rainfall to
Hotan region.
Key words： Extreme arid region； rainstorm； low-vortex system in Central Asia； water vapor characteristics；
terrain convergence