Abstract:The propagation features, stabilities and dynamical characteristic structuresof coupled Kelvin inner modes and second order Rossby inner modes are studied using asimple tropical coupled air-sea model in this paper. It is shown that there is mechanismof selecting scale and frequency in the tropical air-sea system. The effects of air-seacoupling are mainly on the large-scale modes and nonuniform These effects make the frequency of Kelvinmodes decrease that of Rossby inner modes increase,and even excitethe eastward propagating Rossby inner modes. These effects make the unstable development of Kelvin modes and result in the decay of Rossbt modes. The effects of atmo-spheric damp are opposite to those of air-sea coupling. The oceanic damp only makesthe wave amplitudes decay Simuitaneously, this paper shows the dynamical charac teristicstructures of air-sea coupled system and the phase relationships between the atmo-spheric and oceanic wave component.

Abstract:Problems of establishing the optimum regression forecasting model are ex-amined. In general,the optimum forecasting model is not obtainable by stepwise regression. By calculation of all possible regressions with Mallows' C_p statistic,average prediction mean square error(S_p) and prediction sum of squares (PRESS),the optimum forecasting model can be obtained. In this study,the methods and steps for choosing the optimum forecasting model are proposed. Some examples are also given.

Abstract:By using rainfall data at 160 stations from 1951 through 1987 and the methodof EOF through time and space transformation, the temporal and spacial characteristicsof the rainfall in China are analysed. According to the geographical distribution of thefirst five eigenvectors. six natural rainfall regions in China are obtained. Results showthat the division is reasonable.

Abstract:By using turbulence data obtained from the atmospheric boundary layer,thecharacteristic quantities describing chaos in respect of power spectra,correlation dimension,Lyapunov exponents and Kolmogorov entropy are calculated and analyzed. Resultsshow that the atmospheric turbulence is a chaotic motion and possess strange attractorsin phase space,and a deterministic nonlinear differential equation with at least 7-8 or-ders (or 7-8 variables) for holding the strange attractors in phase space is needed to describe the turbulence.

Abstract:A statistical simulation method for reconstrucing precipitation fields in thehistorical time is suggested from Monte-Carlo random simulation idea and the interrelation of distribution of drought and flood order in neighboring regions. With thismethod,the conditional distribution model of precipitation amount corresponding to thedifferent orders of drought and flood is fitted and the simulated precipitation records corresponding to the different orders of drought and flood are obtained through many numerical experiments for the last 500 years in China. These simulated records reproduce,to a certain extent,the characterisitcs of the large-scale precipitation fields in the history,thus turning them into precipitation fields. Results show that the reconstructed precipitation fields are useful to the study of climatic variations during very long historicaltime.

Abstract:A Doppler velocity dealiasing algorithm is described that tracks aliased lineson full PPI data, and determines each bin’s Nyquist Number by analysing the characteristics of the aliased line. The algorithm works well on the data of typhoons and severestorms on which there are many aliased areas. It has the advantages of high efficiencyand full consideration.

Abstract:The physical basis is examined concerning the correlation between total radi-ation and net surface radiation by virtue of the equation of surface radiation balance,demonstrating the rationality of R=bQ-a. Based on the bulk of measurements,studiesare made of the correlation between their instantaneous values and their daily andmonthly totals. Results show that the correlation between their instantaneous values isthe highest, that between their daily totals may decrease owing to the daily changes insurface albedo and cloudiness,and that between their monthly totals is high, which generally has somethimg to do with some kind of mutual compensation of the annual cyclesof surface albedo and effective radiation.

Abstract:A new agrodrought index, which can be used to analyse agrodrought happen-ing in China,is established on the basis of the agrodrought indices available in differentplaces of the country. With this index the temporal and spatial distribution of agrodrought in China is discussed in detail.

Abstract:By using the precipitation data in four areas of the Qinghai-Xizang Plateau,the variation of summer precipitation over the plateau is discussed and by using the dataof the Eurasian snow cover and the 100 hPa height field, the correlation between theplateau precipitation and the Eurasian snow cover, with which the teleconnection mechanism causing the variation of the plateau precipitation is explained. Analysis shows thatmore preciptation is experienced in the east and south than in the west and north of theplateau, The precipitation has quasi-three-yesr oscillation and is influenced enormously by the Eurasian snow cover occurring simultaneously. The quasi-stationary planetary wavetrain correlated with the Eurasian snow cover is a physical mechanism of thesummer precipitation over the plateau.

Abstract:The nonlinear dynamic characteristics of advection are studied for subgeostrophic motion. And the necessary conditions for nonlinear frontogenesis are obtained from analytical solution describing the variation of horizontal momentum.

Abstract:By numerical integration of the ecluation of the atmospheric boundary layermotion,a study is conducted of the influence of the horizontally nonhomogeneous, non-stationary disturbance of the free atmospheric (at the top of the boundary layer) wind onthe internalparameter u./G (u. is the friction velocity and G the wind velocity of thefree atmosphere). Results indicate that in the parameterization of the large-scale modelboundary layer, owing to the non-stationariness and horizontal non-homogeneousnessof the large-scale wind pressure field there exist errors when the classic stationary,horizontally homogeneous resistance law is directly used. It is, therefore, necessary toconsider a revision of non-stationariness and non-homogeneousness as well as topographic forcing.

Abstract:A physical model derived from Darcy's Law and the continuity equation and abudget model based on water balance are used to simulate respectively the daily changesin soil water from the jointing to maturing phases for winter wheat grown in Jingyang,Shanxi in 1987 and 1988 and Tianshui, Gansu in 1986 located in the semi-arid zone.Both the models achieve good results as compared with measured values. The physicalmodel has higher accuracy than the budget model for predicting the water content in theupper soil layer. The latter model is more sensitive to the distribution of root,but the evapotranspiration predicted is on the high side and the percolation predicted on the lowside.

Abstract:The relation between the factors,such as the quantity of coal burned, thenumber density of aerosol particles and relative humidity, and the meteorological visibility in Chongqing urban districts is analysed and the physical causes of the low visibilityare revealed through theoretical calculation.

Abstract:On the basis of the Monin-Obukhov similarity theory,the turbulence char-acteristic parameters.U.,T. and L are determined by means of the iteration method,using the ground gradient observational data. The Semi-empirical expression of the universal functions Φ(Z/L) and Φ(R_i), and the empirical relationship between Monin-Obukhov length L and stability factor ΔT/(ΔU)² are thus given. The change of turbulence flux and temperature-wind profile with the stability parameter is examined and themethod of calculating the turbulence flux in the ground layer is provided.

Abstract:Based on the analysis of experimental observation data for grapes Jufeng and Red Fuji cultivated in different ways, models are established for the grapes at their development stage. The dynamic variations of unit grain weight and sugar content are thussimulated and the meteorological conditions for the formation of grape quality examined.

Abstract:The resolution methods of empirical orthogonal function (EOF)and exten dedempirical orthogonal function (EEOF) are used to analyse the Northern Hemisphere500hPa height field in January and the total rainfall at Xian and other seven weather stations in the flood season (from June to September),obtaining not only the primary pattern describing the teleconnection structure but also the close relation between the basic teleconnection pattern of the general circulation and the flood season rainfall in Shanxi.

Abstract:A more practicable computation method for drought index on a good physicalbasis is established by comparing and analysing the components of water balance. Results suggest that the drought index obtained by this method can well reflect the climatic characteristics of drought and flood. and their influence on agriculture.

Abstract:By using the cross spectrum analysis method,studies are made of the multifrequency oncillation characteristics of the N unit average of the surface atmospheric refraction index related to the total monthly rainfall and the relative number of sunspots.It is found that in early summer there exists a very close relation between the N unit andsunspots (or rainfall) around the periods of quasi-five and quasi-two years (or quasi-seven, quasi-four and quasi-three years) and in early autumn a close relation be-tween the N unit and sunspots around the periods of quasi-five and quasi-two years.And the N unit is found to have a close relation with rainfall not only around the shortperiods of quasi-three and quasi-two years but also around the long period of quasi-35 years.

Abstract:The evolution period of time function with the monthly surface temperature eigenvector over the middle reaches of the Huanghe River from January 1957 to December 1977 and their relation with the monthly SST (sea surface temperature) over thewest,east and north equatorial Pacific and the SOI (Southern Oscillation index) arediscussed by means of the expanded empirical orthogonal function and the spectrumanaltsis method. Results indicate that the monthly air temperature over the middlereaches of the Huanghe River has pronounced periods of 80 and 20 months. The monthly surface temperature in this area is correlated,to some extent,with the monthly SSTand SOI over the above-mentioned sea surface, with their relation strikingly distinct inthe period of quasi-two years (20 months).