Abstract:The data of rawinsonde observations from the two experiments ofweather prediction in the northern part of Anhui Province and thecentral part of Hunan Province, as well as other data are analyzedto depict the features of stratification prior to the occurrence of thesevere convective storm. One of the features revealed is that a V-shapeseparation occurs between the temperature and the dew point profiles,which shows a large convective instability existing in the lower tropos-phere before development of the hailstorm and the squall line. Thetemperature curve nearly coincides with the dew point curve and thestratification is neutral in stability. There is a good relationshipbetween the Showalter’s Index and severe convective weather. Thatthe air layer of temperafure 0℃ and that of -20℃ be at proper heightsis necessary for the formation of the hailstorm or the rainstorm. Besides, the geopotential height in the lower levels uaually decreases considerably in advance of the rainstorm.

Abstract:The characteristics are analysed of the meso-and microscale system,which produced the heavy rainfall under the action of the southerlyjet stream at the periphery of the Typhoon 7315 after its landing onChina’s coast. It is shown that the meso- and microscale rain coresand their pressure disturbances are found in the moist-static energyfrontal zone associated with the convergence line. The conditionsfavourable to stimulate the convective precipitation are the topographiceffect of V-shape coast line and the gulf where the sea surfacetempreatures are higher than the air ones. These rain cores and thepressure disturbances associated are moving along the moist-static energy frontal zone prior to the occurrence of convection.

Abstract:The data at several levels of the Longyan experimental stations areanalysed. It has been found that the heavy rain on the night of May 25,1980 ahead of a cold front was formed by a shallow cold currentinvading over the Wuyi Mountains from the upper and middle levels ofthe planetary boundary layer, which resulted in a heavy rain of amesoscale system. The features of the system and its difference fromthe cold front are examined. The mesoscale pressure waves in therear of the front are also discussed.

Abstract:Classification of temperature variations with time and space is usefulto climate research and long-range weather prediction. For thesepurposes analyses have been made of the time series of January temperature at 35 stations in China. These series can be divided intoeleven groups according to the analogous coefficients between them. Thecharacteristics of January temperature distribution have also beenstudied by using some statistical methods. It is shown that there arefour main types of January temperature distribution and all of them arerelated to the circulation indices. It is also found that there exist somesignificant statistical relationships between the temperature anomalies in China and the sunspot activities.

Abstract:It is shown that the empirical orthogonal expansion of time series of awind field containing n points in space can be performed by expandingthe time series of a scalar field formally in 2n points. Based on this,a method by which the eigenvectors of a wind field can be calculated ispresented. In expanding by the technique one of the time series froma pentad average tropical wind field the eigenvectors obtained are foundof value in weather analysis and numerical forecasting. Obviouslythere exits a close relationship between the evolution of time coeffi-cients of the first two eigenvectors and the seasonal variation in themain low-latitude circulation systems of Asia. Such eigenvectors ofeach level have space distributions of divergence and vertical motion.These distributions and their evolutions have been analyzed so that the basic cause of monsoon precipitation is better clarified.

Abstract:The first 5 coefficients of empirical orthogonal function of thepentad mean circulation at 500 mb level over Asia were obtained inpaper. The correlations between each of these coefficients and thepentad precipitation data from 49 stations of the network are calculatedrespectively. The method of cross-spectral analysis is used to discussthe characters of the correlations of the mean circulation to theprecipitations, and the coherence functions are computed as well. Apreliminary research has been made on the time-space structure andsome quasi-periodic oscillations have been found. The findings willcontribute new information on the problem of long-range precipitation forecasting in China.

Abstract:Observation has been made of horizontal wind pulsation beneath thecanopy of crop by using the QDF hot-wire microanemometer. It isshown that the pulsation has greater turbulivity, more intense short-period oscillation, less pulsation intensity and smaller turbulent integ-ral scale than that in a field without vegetation. It is also foundthat the pulsation observed varies steadily with time and its structurefunction of time may approximately be expressed as D(τ) =2.9×10^-4t^2/3,τ≤16sec

Abstract:In terms of climatic conditions during the growing season of hybridrice are determined the safe stage of the fully-heading and the periodsuitable for sowing in the different cropping systems. The thermal conditions in spring and autumn are found to be the leading factorsinfluencing on both the cropping systems and high, stable rice yields.It has been found that the last fall day of the spell of air temperature≥22℃ with probability of 80% is defined as the final day for a safestage of the hybrid fully-heading and the first spring day of the spellof air temperature ≥15℃ with the same probability as the starting ofthe safe seeding period for well-grown seedlings. With respect to thedifferent cropping systems in various parts of the province a detailed analysis is made concerning the use of local climatic resources. The demarcation of the rice-growing region based on the climatological data are also presented.

Abstract:A study is made of the structure of supercell hailstorms, the featuresof vertical air flow and its behavior of propagation in terms of 3 radar observations and an in-cloud ridaosonde one. For the weather conditions associated in the supercell hailstorms, emphasis is laidupon the analyses of the effects on the cloud both of vertical shear of ambient winds and of the precipitational process before the hailstorms.The problem of supercell modification is also discussed.