Page 153 - 《高原气象》2021年第5期

高 原 气 象 40 卷
1114

Comparative Analysis of Two Disaster-Induced Rainstorms

in Hunan Province in Flood Season of 2019

1，2
1，2
3
1，2
LIU Hongwu ，HU Yan ，SU Tao ，LIU Huanqian ，FU Chenghao 1，2
（1. Hunan Meteorological Observatory，Changsha 410006，Hunan，China；
2. Hunan Key Laboratory of Meteorological Disaster Prevention and Reduction，Changsha 410006，Hunan，China；
3. Hunan Meteorological Observation Technology Support Center，Changsha 410006，Hunan，China）
Abstract：In the main flood season of 2019，there were two rare extreme rainstorms in Hunan Province，in
which rainfalls of several meteorological observation stations exceeded historical extremes，resulting in more
than 10 deaths（missing）. By using Global Data Assimilation System（GDAS）data and reanalysis data from the
National Centers for Environmental Prediction（NCEP），and observation data，based on the particle trajectory
tracking and clustering algorithm from Hybrid Single-Particle Lagrangian Integrated Trajectory（HYSPLIT4），
the similarities and differences of two disaster-induced rainstorm processes from June 6 to 9（process 1）and July
6 to 9（process 2）in 2019 are comparatively analyzed. The results show that the two processes are characterized
by extreme，continuity and convection，and the second process has greater rainfall intensity，more concentrated
heavy rainfall areas and more serious disasters than the first one. Besides，there are obvious difference in that cir‐
culation field between the two processes. For the process 1，the intensity of the subtropical high was significantly
stronger，its location was northerly，and the western ridge point of 588 dagpm was westward by 26 longitudes
than that of the same period over the years. The northeast cold vortex developed deeply. The maximum wind
speed of the 850 hPa jet stream core reached 14 m·s ，and there were double vortex and shear lines. While for
-1
process 2，the subtropical high was stable，the ridge line was south by over 8 latitudes. There was a significant
cold shear at 850 hPa，and the wind speed on the south side of the shear was large，which led to the strong cold
and warm convergence，causing the convective characteristics of the rainstorm clearer. Furthermore，the occur‐
rence and evolution of mesoscale cloud clusters in the two processes are slightly different. For process 1，there
was the eastern section of the herringbone shear line triggering the generation of mesoscale convective clouds，
which developed and grew in an organized way after the adding of the weak cold air. For process 2，the warm
and humid airflow and cold airflow met in front of the long wave trough in the westerlies，and mesoscale cloud
clusters of α，β and γ were continuously emerging，merging and developing. The "train effect" of multiscale con‐
vective cloud clusters moving through the same place caused strong disaster-induced rainstorm. At last，that
source and distribution of water vapor are different. For process 1，the significant convergence center of water va‐
por was located at 850 hPa. The source of water vapor was the South China Sea. There were three water vapor
transmission channels，and the main water vapor channel was the southerly airflow in the South China Sea. For
process 2，the significant convergence center was located at 925 hPa. The water vapor sources were the Indian
Ocean. There were four water vapor transmission channels，among which the main water vapor transmission
channel came from southwest air flow in the Bay of Bengal.
Key words：Disaster-induced floods；mesoscale characteristics；water vapor transportation；comparative analysis