The Advanced Weather Research and Forecasting Model （ARW） is used to simulate the local heavy rainstorm process caused by Typhoon Matsa over the northeastern coast of Zhejiang Province in 2005. The results show that the rainstorm was caused mainly by the secondary spiral rainband of the Stationary Band Complex （SBC） structure. Within the secondary spiral rainband there was a strong meso-β-scale convergence line generated in the boundary layer, corresponding very well to the Doppler radar echo band. The convergence line comprised several smaller convergence centers, and all of these convergence columns inclined outward. Along the convergence line there was precipitation greater than 20 mm occurring during the following one hour. During the heavy rainstorm process, the Doppler radar echo band, convergence line, and the precipitation amount during the following one hour, moved and evolved synchronously. Further study reveals that the vertical shear of radial wind and the low-level jet of tangential wind contributed to the genesis and development of the convergence columns. The combined effect of the ascending leg of the clockwise secondary circulation of radial wind and the favorable environment of the entrance region of the low-level jet of tangential wind further strengthened the convergence. The warm, moist inflow in the lower levels was brought in by the inflows of the clockwise secondary circulation and uplifted intensely at the effect of convergence. In the convectively instable environment, strong convection was triggered to produce the heavy rainstorm.
The Advanced Research Weather Forecasting （ARW） model was used to simulate the sudden heavy rainstorm associated with the remnants of Typhoon Meranti in September 2010. The results showed that the heavy rainfall was produced when the remnant clouds redeveloped suddenly, and the redevelopment was caused by rapid growth of micro/mesoscale convective systems （MCSs）. As cold air intruded into the warm remnant clouds, the atmosphere became convectively unstable and frontogenesis happened due to strong wind shear between weak northerly flow and strong southwesterly flow in the lower levels. Under frontogenesis-foreing and warm-air advection stimulation in updrafts, vertical convection developed intensely inside the remnant clouds, with MCSs forming and maturing along the front. The genesis and development of MCSs was due to the great progress vertical vorticity made. The moist isentropic surface became slantwise as atmospheric baroclinity intensified when cold air intruded, which reduced the convective instability of the air.Meanwhile, vertical wind shear increased because the north cold air caused the wind direction to turn from south to north with height. In accordance with slantwise vorticity development （SVD）, vertical vorticity would develop vigorously and contribute greatly to MCSs. Buoyancy, the pressure gradient, and the lifting of cold air were collectively the source of kinetic energy for rainfall. The low-level southwesterly jet from the western margin of the Western Pacific Subtropical High transported water and heat to remnant clouds. Energy bursts and continuous water vapor transportation played a major role in producing intense rainfall in a very short period of time.
The CloudSat satellite data from June 2006 to April 2011 are used to investigate the characteristics of cloud vertical profiles over East Asia （20°-50°N, 80°- 120°E）, with particular emphasis on the profiles of precipitative clouds in comparison with those of nonprecipitative clouds, as well as the seasonal variations of these profiles. There are some obvious differences between the precipitative and nonprecipitative cloud profiles. Generally, precipitative clouds mainly locate below 8 km with radar refiectivity in the range of-20 to 15 dBZ and maximum values appearing within 2-4-km height, and the clouds usually reach the ground; while nonprecipitative clouds locate in the layers of 4 12 km with radar refiectivity between -28 and 0 dBZ and maximum values within 8-10-km height. There are also some differences among the liquid precipitative, solid precipitative, and possible drizzle precipitative cloud profiles. In precipitative clouds, radar reflectivity increases rapidly from 11 to 7 km in vertical, implying that condensation and collision-coalescence processes play a crucial role in the formation of large-size drops. The frequency distribution of temperature at -15℃ is consistent with the highest frequency of radar reflectivity in solid precipitative clouds, which suggests that the temperatures near -15℃ are conductive to deposition and accretion processes. The vertical profiles of liquid precipitative clouds show almost the same distributions in spring, summer, and autumn but with differences in winter at mainly lower levels. In contrast, the vertical profiles of solid precipitative clouds change from spring to winter with an alternate double and single high-frequency core, which is consistent with variations of the frequency distribution of temperature at 15℃. The vertical profiles of nonprecipitative clouds show a little change with season. The observations also show that the precipitation events over East Asia are mostly related to deep convective clouds and nimbostratus clouds. These results
