| In order to obtain the typical synoptic situation in spring and autum precipitation process of Henan province, the influence systems and the characteristics of clouds-precipitation were analysed by using the normal data. Then, through analysis of satellite data, Radar data, precipitation data and NCAR/NCEP reanalysis data, the typical trough-shear stratiform rain clouds with their multi-scale structures and preciptation mechanisms were studied deeply. At last, we discussed the catalyze potentials of the stratiform rain clouds combining the analysis of example. The main results are given below.In Henan's spring and autum, upper trough or trough-shear situation and the ground middle and easterly cold front or inverted trough situation are the main precipitation synoptic situations. When one of the upper situations and one of the ground situations influence Henan at the same time, the favorable rain will occour and the combinations are the typical synoptic situation becauae they have better moisture condition and dynamic convergence condition.The analysis of satellite data showes that trough-clouds' structure and precipitation characteristics are distinct from shear-clouds'. There are low brightness temperature bands in the trough-clouds and the structure is not uniformity, but the shear-clouds' structure is uniformity and their brightness temperature is high. After the trough-clouds moving to eastward splice the shear-clouds moving to northward, the meso-and-small scale clusters will come into being on the joint, and then the clusters will move to eastward or to northeast. The active meso_β-scale dusters among 700hPa-shearline and 850hPa-shearline and the front of 500hPa-trough correspond with the strong rain in the south of 700hPa-shearline, and the similar varying trend is showed between the average of brightness temperature and the precipitation intensity in the example area. The relationship is not clear in the north of 700hPa-shearline. We studied the macroscopical structure of the precipitation clouds and found that Henan province was affected mainly by the uniformity rain echo during the precipitation process. The floccus-echo developed and moved toward the east in the area that the meso-and-small scale clusters were active, and radar(RHI) data indicated that there was developing columnar echo, but the echo in the other area of the province was weak. TRMM(PR) data indicated that the stronger precipitation center could be observed in the south of 700hPa-shearline precipitation-clouds and there were some waves in someplace in the relative uniform stratiform precipitation clouds. The retrieval cloud top height data also showed that the top of the clouds was not very smooth.In the south of 700hPa-shearline there were better moisture condition and dynamic convergence and the nature rain was easy to form. However, in the north of 700hPa-shearline, the low-level' s moisture condition was weak, and at the same time dynamic convergence and lifting force were weak too though there was convective instability on the middle-level, therefore nature rain rate was low.Through analysis the microcopical structure of the precipitation clouds we found that the structure was difference in the developing period and in the differ part of the clouds. Snow, graupel and supercooled cloud-water were important for rain to form and increase.In Henan, the trough-clouds moving to eastward and the shear-clouds moving to northward have catalyze potential, and the potential can be forecasted ahead for 18 to 24 hour. The condition in the south of 700hPa-shearline clouds is better than that in the north of 700hPa-shearline clouds. The precipitation clouds in the south of 700hPa-shearline are 'seeder-feeder' clouds and have better seeding conditions in the period that rain developes and keepes. The clouds in the north of 700hPa-shearline have not seeding conditions until the hydrometeors have developed. The result consists with the analysis on the macoroscopical catalyze potential. |
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