Characteristics of Two Types of Rainstorms in Northeastern Guizhou Affected by the Transverse Shear Line over the Yangtze River
To explore the characteristics of rainstorms and the formation causes of severe precipitation in the northeast part of Guizhou Province under the impact of the transverse shear line in the Yangtze River,this article analyzes the rainstorm processes in northeastern Guizhou affected by the Yangtze River transverse shear line in the past 10 years by using the observations and NCEP 1° × 1° reanalysis data.The results show that:(1)The warm-humid southwestern air flowing northward from the west side of subtropical high pressure and the dry and cold air of the Northeast China low vortex trough flowing southward converge in the middle and lower reaches of the Yangtze River and the northern part of Guizhou,making the transverse shear line between the north and south airflows in the lower and middle layers maintained.However,different systems of shadow lines on the surface cause the differences in the area and intensity of rainstorms.(2)The first type of rainstorms is influenced by the surface low pressure.Under sufficient moisture and strong thermodynamically unstable stratification conditions,strong dynamic uplift in the middle and lower layers and boundary layer frontogenesis,severe precipitation occurs and develops in the superposition area of the surface convergence line and the low-level shear line,with the hourly rainfall intensity exceeding 50 mm and the 24 h rainfall more than 50 mm and less than 100 mm.The second type of storm is impacted by the easterly airflow behind the offshore high pressure.Under the conditions of sufficient moisture,strong dynamic uplift and weak thermodynamically unstable stratification,severe precipitation develops in the vicinity of the low-level shear line and in the easterly airflow on the surface,which results in wide range of severe rainfall with the hourly rainfall intensity higher than 20 mm and lower than 50 mm,and the 24 h rainfall surpassing 100 mm in localized regions.In conclusion,by analyzing the characteristics of the two types of rainstorms in northeastern Guizhou affected by the transverse shear line in the middle and lower reaches of the Yangtze River as well as the similarities and differences of the influencing systems,we have made efforts to reveal the differences and causes of rainstorms,which is expected to help improve the forecasting ability of such rainstorms.
shear lineheavy raincharacteristicsthe northeast of Guizhou Province
NETL
NSTL
万方数据
