Analysis of the Rainstorm Falling Zone in Guangxi during Influence Period of the 0906 Typhoon "Molave"

[ Objective] The research aimed to analyze rainstorm falling zone in Guangxi during influence period of the 0906 typhoon ＂ Molave＂. [ Method] For the heavy precipitation falling zone in southern and central parts of Guangxi after 0906 typhoon ＂ Molave＂ landed, 500 hPa circula- tion, physical quantity field, satellite cloud chart and terrain effect were analyzed. [ Result] 500 hPa subtropical high caused asymmetry of the ＂Me- lave＂ circulation, playing a key role for the strong precipitation falling zone in Guangxi. Physical quantity field analysis pointed out that after ＂ Me- lave＂ landed, water vapor convergence center was in southeast Guangxi, providing adequate moisture condition for the heavy precipitation in south- ern and central parts of Guangxi. The maximum positive vorticity center appeared at the middle and low layers in southern and central parts of Guangxi for a long time. At 200 hPa, there was a maximum divergence center. At 700 hPa, there was a maximum convergence center. High-level divergence and low-level convergence created conditions for heavy precipitation in the region. From satellite cloud chart, the heavy precipitation fall- ing zone related to asymmetric structure of the ~ Molave＂. In addition, uplifting effect of the terrain was conducive to occurrence of the large precipi- tation. [ Conclusion] The research provided reference for reduction and prevention of this kind of heavy precipitation.

Analysis on the Moist Potential Vorticity and Conditional Symmetric Instability of a Rainstorm

[Objective] The research aimed to analyze the moist potential vorticity (MPV) and conditional symmetric instability (CSI) of a rainstorm in Guangxi in the prior flood season. [Method] Based on the conventional observation data, precipitation data from the automatic station and 1°×1° six-hourly reanalyzed data from NCEP, MPV and CSI in a rainstorm process which occurred in the prior flood season in Guangxi were analyzed. The characteristics of MPV component and role of CSI before and after the rainstorm occurrence were discussed. [Result] The dense belt of isoline in the southeast of MPV1 positive-value area (MPV2 negative-value area) at 925 hPa, the underneath of sloping MPV1 positive-value column (MPV2 negative-value column) on the profile map and the underneath of dense belt of θe isoline had the good corresponding relationships with the falling zone of strong precipitation. After the system developed strongly, the enhancements of gradient and intensity of MPV1 and MPV2 predicted the rainstorm increase. In the beginning period of strong precipitation occurrence, the convective instability at 850-650 hPa co-existed with CSI. The convective instability and vertical movement played the main role. In the middle and latter periods of strong precipitation, the high-altitude weak cold air further invaded southward. It triggered the release of unstable energy, and compelled that the original sloping θe dense belt became steep. It was favorable for the development of sloping vorticity, and the atmosphere gradually turned into the neutral state of convection. CSI and ramp motion played the major role. Then, the rainstorm continued. [Conclusion] The research provided the theory basis for the application of MPV and CSI into the local routine business.