In order to further investigate the mechanism associated with a sustained rainstorm process occurred in Sichuan, Shanxi and Gansu province in late July 2010, analysis were conducted on the circumfluence background and the directly related weather systems, e. g., the plateau vortex, the tropical cyclone, the mesoscale convective and the warm/cold advection together with their interactions. The data used in this study includes MICAPS data, FY-23 radiation brightness temperature, TRMM satellite rainfall product, and NCEP Reanalysis dataset (1°×1°, 6 hours). The results show that:(1) The sustained rainstorm process occurred under favorable conditions when the South Asia High in the upper troposphere changed from a zonal pattern to a meridional pattern, the subtropical high in the middle troposphere shifted from east to west, the landed tropical cyclone moved to the west, the plateau vortex was blocked on the east and the mesoscale convection systems kept reoccurring. (2)The interaction between the plateau vortex and the tropical cyclone decreased the velocity of both systems, enhanced the shear field in the vortex area, therefore a strengthened vortex was maintained by the positive vorticity advection transport. (3) The low vortex provided favorable uplifting conditions for rainstorms to occur and produced strong positive vorticity as well as convergence upward movement during precipitation in the vortex area. The maximum rainfall occurred concurrently with the strongest convergence ascending motion. The positive z-helicity during precipitation process in the lower troposphere helped to maintain low vortex system and sustain precipitation; the position and time of high z-helicity provide certain indicative to the occurring time and location of heavy rainfall. (4) The transport of warm advection in the lower troposphere continuously accumulated energy in the rainstorm area, incurred frequent mesoscale convection system activities and thus resulted in sustained rainfall.
HE Guangbi
,
XIAO Yuhua
,
SHI Rui
. Analysis of a Sustained Rainstorm Accompanied by a Plateau Vortex and a Tropical Cyclone[J]. Plateau Meteorology, 2019
, 38(5)
: 1004
-1016
.
DOI: 10.7522/j.issn.1000-0534.2018.00131
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