Abstract:In this paper the relationship between the typhoon activity in northwest Pacific and the El Nino phenomenon has been analized using the data from 1950 through 1984. It is found that a pronounced difference exists between the typhoon activies during the summer months (June-August) of the E1 Nino of moderate intensity and more year and of the next year. Two case studies of the strong E1 Nino in the periods of 1972-1973 and 1982-1983 show that the difference is closely related to the anomalously warm water in east equatorial Pacific and the characteristics of the low-latitude summer circulation in northwest Pacific. On this basis a possible linkage between the typhoon activity in northwest Pacific and the E1 Nino phenomenon is discussed.

Abstract:Based on the analysis of the effect of temperature on the development of crops, a hypothesis of the mechanism of the effect is advanced. Two quadratic non-linear differential equations are thus constructed. By working out an approximate solution to the differential equations,a new mathematical model showing the relationship between temperature and the development of crops is established. With the new model, a function of temperature, called the effective accumulated temperature variable, is defined. The model is proved to have better results than the old ones in practice.

Abstract:Based on the meteorological data and diffusion parameters measured, a set of atmospheric models and fume rise formulas are used for the calculation of the SO₂ and other pollutant distributions when the Yangzi Ethylene Plant goes into operation. The findings from the calculation provide important oriterions for the atmospheric pollution control and environmental planning in this district.

Abstract:Effects of cumulus precipitation and artificial seeding on the rainfall and raindrop size are simulated in Gutian area, Fujian province in terms of a one-and-a-half-dimensional time-dependent icebearing cumulus model. It is shown that 120 mimutes after the ice crystals increase at the upper layer of clouds upon seeding, the total rainfall will increase by 0.5mm and its relative increment by 7.1%. The mechanism of the increased rainfalI is also discussed in the paper. In addition, experiments are made in the AgI seeding amount for the comparison of the raindrop size and rain intensity in this area.

Abstract:By using the equation of the kinetic energy in the wavenumberfrequency domain together with the ECMWF/WMO data, the mechanism for the oscillation of the kinetic energy of the mean zonal flow and ultra-long waves at the 200 hPa level over the tropics in the period of 64 days from June 11 to August 13, 1983 is discussed.The oscillation of kinetic energy with a period around 20 days is very obvious. The kinetic energy of the mean zonal flow and waves of wavenumbers 2-7 are all of this oscillation. The kinetic energy of the wave of wavenumber 1 seems to oscillate with a 40-day period. Besides, for waves of wavenumbers 1, 4 and 7, the period around a week of the kinetic energy is also clear.The important reason for the 20-day oscillation of the mean zonal flow is the interaction between the mean flow and waves. However, the reason why the kinetic energy of the waves oscillates is somewhat complex. The conversion of the energy available, the work done by the boundary pressure and the nonlinear interaction between waves are all important.There exists a relation between high and low frequency oscillations of kinetic energy. When the low frequency oscillation gets to its peaks, the amplitude of the high frequency oscillation becomes maximum. When the low frequency oscillation gets to its valleys, the amplitude of the high frequency oscillalion becomes minimum.

Abstract:In this paper the monthly mean height fields at 500 hPa over the northern hemisphere are expanded. In the expanding the whole hemisphere can be divided into a northern and a southern latitudinal zones. Some statistical features of the main expansion coefficients and parameters of the harmonic waves are determined. Facts show that the flow fields and their seasonal variations are very different in the two zones. Results in this study suggest that in practice the expansion in the zones is better than that in the whole hemisphere.

Abstract:In this paper the climatic characteristic feature of the lake-land breeze over the Dongtinghu Lake and its effect on heavy rain are studied by using the meteorological data from the Yueyang, Changde and Yiyang Stations around the lake. It is shown from the analysis that the lake-land breeze occurring over the Dongtinghu Lake is remarkable, about 300m in thickness. It is found that the reverse of the lake and land breezes can cause variations in divergence and vorticity of the breezes. As a result, the precipitation can be intensified around the lake in the early morning and evening. It is also found that the lake-land breeze develops throughout the year. However, it is strong in summer and weak in winter.

Abstract:The cross-correlation method of tracking radar echoes is theoretically analyzed. It is indicated that the correlation coefficient, which is used as a discriminating factor in the method, is only the reflection of the structure character of the echoes tracked. The echoes do not change their structure as they move in a uniform wind field so that the method can be used to track the echoes with great accuracy. In a nonuniform wind field, however, great changes take place in the structure, causing an increase of errors.

Abstract:Based upon the cloud condensation rate and the precipitation rate on the ground, a formula for calculating the precipitation efficiency in stratiform clouds is presented on the assumption that the air rises adiabatically. The primary advantage of this method is that the precipitation efficiency can be obtained by using only the routine sounding data and rainfall measurement. In this paper the cloud vertical velocity and condensation rate are also estimated from the sounding data at Nanjing, Fuyang and Anqing during the plum rain seasons of 1980 and 1983, and the average areal rainfall and condensation rate are calculated by use of the data from the station network in the rain area for the two years. The precipitation efficiency of the plum rain are thus obtained.

Abstract:The formation, initial location, track arid life duration of convective cloud clusters are examined by use of the geostationary satellite pictures in May-July of 1979-1984 over the lower reaches of the Changjiang River and the relation between the clusters and synoptic-scale clouds are analyzed. The characteristics of the satellite pictures are finally discussed on the development and enhancement of the cloud clusters.

Abstract:A preliminary statistical analysis is made of the solar radiation data over China. It is found that the frequency distribution of solar radiation is of normal distribution feature. The relationship between the relative mean square error (C_v=σ/√x) and the mean value of solar radiation obey the negative exponent rule and there is found close relationship between the space distribution of the relative mean square error and the general circulation of the atmosphere. The statistical characteristcs shown are of significance for studying the statistical climatology of solar radiation and the utilization of solar energy.

Abstract:A diagnostic analysis is made on the weather regime at the middle stage of a severe cold wave occurring from late February to early March, 1986 by using the wavenumber domain energy equation. The energitical characteristic features are thus revealed in the process of the weather event. The analysis on the relation of the interaction between the long waves and uttra-long waves at different latitudes to the cold wave at its middle stage provides clues and criterions for the cold wave prediction in South China.