Abstract:The present paper has defined a blocking index in terms of the range and intensity of the monthly mean blocking over the Urals in winter(December, January and February). Correlation analysis indicates that monthly mean blocking over the Urals has a pretty large anticorrelation with the monthly mean temperature in China. Between the blocking index and the global SST there exist three Significant correlation regions.eastern part of the Northern tropic Pacific, Northern tropic Atlantic and midlatitute sea region,and the South-west Aleutians. Using the spectral model of a two-level primitive equation, numerical cxperiments have been conducted on the above-three sea regions after steady diabatic isolated heatsource forcings have been added. Results show that the heatsour ceforcings in the three sea regions have an effect upon the Ural blocking through exciting the quasistationary Rossby wavetrain. The dynamic diagnosis of the numerical experiments indicates that the heatsource forcings have intensified the cut-off low in the upper stream and downstream doughs of the Ural blocking region ;and the LF enstrophy of tam and downstream doughs of the Ural blocking region; and the LF enstrophy of the blocking region comes mainly from the interactions of the LF eddies themselves.

Abstract:The study is devoted to the structure of low-frequency dipole of the East-Asian westerly jet entrance and exit regions and to the characteristics of Asian/Pacific low-frequency vortex activities in terms of the bandpass filter for 30-60 days and composite technique and with the 1984—85 winter ECMWF grid data. Results show that the low-frequency cycle of the zonal wind dipole is accompanied by the east-west shift of the eastern Asian westerly jet core and low-frequency meridional circulation at the jet entrance is important to the oscillation in zonal wind. NW-SE wavetrain runs from Ural to mid Asia and then to East Asia and the low-frequency vortices of Ural origin travel southward and then eastward,leading to the change in phase of the wavetrain. Over the central Pacific there is a meridional wavetrain and the counterclockwise loop of the couple of cyclone and anticyclone gives rise to the change in the low-frequency wavetrain in this area.

Abstract:Based on the summer precipitation index (June-August) of North China determined in the relevant paper,the present paper calculates the synthetic contrast field of the mean circulation of the typical drought/flood years. It is found that the discrepance of atmospheric circulation is distinct in the previousperiod of the drought/flood year,especially in winter. The correlative features of the drought and flood index(DFI) and the circulation are consistent with those of the drought/flood synthetic contrast field. The calculation result shows that the propagation path of the teleconnection is the same as that of the wave energy theoretically calculated. And their positive and negative regions in the teleconnection map are also consistent with those of the drought/flood synthetic contrast field.

Abstract:With the eigenvalues extracted from the picturepreprocessed PPI digital echo data,the system developed is used to identify automatically the presence of the 0℃-level bright zone in a three-level manner. Experimental results indicate the system to be of high accuracy.

Abstract:Based on the gradient measurements of six heat-balance record stations operating in China the approach is tentatively investigated to climatological computation of surface latent heat regime, proposing a new expression of the form LE=14.73exp(0.5H+0.069e)(1+0.013ΔT)u^-0.16 Thereupon the monthly and annual mean latent heat flux densities of all the stations across the country are figured out with the spatial distribution and annual variation features examined. Some significant results are acquired.

Abstract:The present paper gives an analysis of the low frequency (LF) vortex and divergent circulation systems and their interactions in terms of the ECMWF/WMO data (summer of 1984). Results show that the LF vortex in West Pacific and South Indian Ocean have the characteristics of the three-dimensional circulation of the convective synoptic system and ,the divergent/convergent intensity of the LF velocity potential field is the strongest and the divergent/convergent area is the widest in the above-mentioned regions. The energy disperse of LF divergent wave stimulates the divergent circulation from Indian Ocean to West Pacific to produce a conspicuous quasi-40-day oscillation.

Abstract:The present paper has obtained a special solution of the system of nonlinear equations. Results show that there exists obvious difference in horizontal structure and time variation of perturbation between nonlinear and linear Kelvin waves. Compared with the linear Kelvin wave,the nonlinear Kelvin wave is much more complicated in the way of propagation. Waves concerned with the barotropic mode have the similar features to those mentioned above.

Abstract:A two dimesional static model is developed in the present paper,taking into account the physical processes such as the solar longwave and shortwave radiations,moisture of air,roughness of the earth-surface,albedo,temperature of the soil layers. Some effects of the longwave and shortwave radiations on seawind are discussed by using this model. It is found that if the radiations are neglected,seawind will be confined to only a small space without reaching further into the inland.

Abstract:In this paper,the directional filtering method is used for compressing the primitive data of the digital weather radar echoes. First,2-dimensional Fourier Transformation is applied to the data so as to divide them into low frequency and high frequency components; then,the directional filter is used to get the edges and tectures from the high frequency component and finally ,the low frequency component and all of the directional pictures are encoded in order to compress the data.

Abstract:Based on ECMWF 7-level monthly mean geopoptential height anomaly data. the present paper has calculated the Correlation coefficient distribution of several key circulational teleconnection indices and the geopotential height anomaly of each level. Results show that the barotropieal and baroclinic geological difference of circulational abnormality is closely related to the vertical structure of the teleeonnection pattern with the PNA,WP,WA,EA and EU being barotropical; however, the correlation distribution of the SO index and height anomaly of each layer changes in the tropical Pacific from the east-west out-of-phase seesaw oscillation of the low troposphere into the even anticorrelation of the mid and high troposhere,whieh proves the existence of the strong baroclinity in east tropical Pacific. The cireulational abnormality from December to February in the tropical Indian Ocean appears to be barotropical;from June to August, baroclinic. Same results are obtained through analysis of hybrid empirical orthgonal functions.

Abstract:In this paper,the data—processing method for velocity and echo intensity data before display obtained with conical scan of Doppler Radar is introduced and the technology is described of displaying Doppler velocity field with high—resolution mode (800×600,256 colors) of TVGA Graphics Adaptor.

Abstract:The present paper has made some research on the amplitude increment effect of topography—caused landfall typhoon No. 7805. Numerical experiments show that the neutral typhoon track, typhoon rainfall distribution and intensity are obviously affected by the interactions of the factors including outer—region circulation,ambient subtropical high system, subsynoptic scale jet steam and topographic forcing.

Abstract:In terms of the wind data measured with three-axes anemometers in Chongqing city (Dec. 16,1989-Jan. 14,1990),the turbulent characteristic vectors including the turbulent parameters, the Eulearian-time correlation, the integral time-scale of turbulence, the turbulent intensity,the friction velocity and the Reynolds stress in the surface layer have been calculated under winter light wind condition in Chongqing so as to understand the surface-layer turbulent characteristics of the city.

Abstract:In terms of the climatological methods for calculating components of surface net radiation (SNR) proposed by Weng et al. (1988),annual and monthly mean flux densities of SNR and its components at 173 stations over the Qinghai-Xizang Plateau and its surroundings are computed and their geographical distribution features are analyzed. Results show that the main part of the highland is marked by a high-value zone of total and effective radiations and great difference exists in the SNR patterns between winter and summer. In winer a weak positive-value zone is displayed with a set of relatively low-value centers distributed in groups over the Qilian mountains and some other places,while summer SNR gets intensified in much of the Plateau on account of nocturnal rain and thus very moist ground. Besides,annual variations of SNR are basically similar to those of total radiation for all these stations,and effective radiations show,in its yearly change,a bi-peak pattern with the peaks (valleys) in spring and autumn (winter and summer).

Abstract:In this paper,with a view to the effect of sea-land thermal forcing contrast in East Asian,the early summer circulation in East Asia and Meiyu cause of formation in Jianghuai valley are studied. The results show that the summer precipitation in Jianghuai valley is related to zonal sealand thermal contrast in East Asia of early days surface air temperature.The high correlation area between early summer precipitation in Jianghuai valley and corresponding-period 500hPa geopotential height field of the northern hemisphere corresponds to the circulation system of "double blocking"pattern at the entering period of Meiyu with the highest correlation system being subtropical high. The numerical experiments indicate that sea-land thermal forcing contrast in East Asia is closely related to summer monsoon and the formation of Meiyu blocking system. The forming mechanism of circulation features and thermal structure factors at the first period of Meiyu are revealed.

Abstract:The teleconnection structure of the monthly mean temperature fields in China has been studied in this paper. Results show that the seesaw features of monthly mean temperature fields during winter months is not distinct While there is an obvious teleeonneetion structure during summer months. The monthly teleconneetion models and intensities are presented. It is pointed out that the teleconnections of monthly mean temperature appear in a radial pattern (from south to northeast and northwest,to the east of 105°E,northeast-southwest;to the west of 105°E,northwest-southeast.) These structures are caused by the anomalous circulation and can be used in the forecasting of monthly mean temperature in large areas.

Abstract:Based on the precipitation data obtained in the 1991 Meiyu period ,Statistical analysis is made on the time-space scale and movements of the meso -βscale rainbands on the Meiyu front,so as to reveal the connection between the movements of meso-β scale rainbands and the flooding in the late perild of 1991 Meiyu.

Abstract:The present paper makes an analysis on the precipitation in the Three-Gorges of Changjiang River and its connected sea region’s temperature and southern oscillation from January 1953 to December 1977 by means of spectral analysis. Some significant results are obtained through power-spectral and crossspectral analysis.

Abstract:In the present paper,a semi-empirical model is introduced to calculate the evapotranspiration from paddy rice in Nanjing,with only the general meteorological data and data about leaf area,the evapotranspiration can be estimated rather accurately. The method is better than Penman-Monteith formula which has a bigger error and needs wind gradient observation. The reliability and feasibility of the model has been proved through the sensitivity analysis of the parameters. It is found that in the whole growth period there are two water loss peaks occuring respectively at the jointing stage and heading-to-flowering stage,when the weather condition is favourable to evapotranspiration.

Abstract:The designing of a stepwise threshold autoregressive model is presented in this paper to improve the ordinary threshold autoregressive model that is imperfect in recognition. Numerical experiments show that the designed model is better to some extent.