Current Issue

• STUDIES OF DYNAMIC INFLUENCE OF QINGHAI-XIZANG PLATEAU ON THE EASTWARD MOVING TROUGH IN WINTER PART Ⅱ. THE CONSTRUCTIONS OF THE IDEALIZED INITIAL FIELDS AND OROGRAPHIC FIELD AND THE DESIGN OF SIMULATION EXPERIM
• Jiao Yanjun;Qian Zhengan
• 1994 Vol. 13 (4): 383-393. 
• Abstract ( ) PDF (395KB) ( )
• In order to reproduce quantitatively the influence of Qinghai-Xizang Plateau on the eastward moving trough (EMT) in winter and to, also, discuss the differences among the terrain impacts under the different circulation, in this paper, the second part of the series papers, a limited area grid point model with 6 levels in the vertical and resolution of 1.875°×1.875° Lon./Lat. in the horizontal is used. According to the demand for the model initial fields and the characters of the Asian upper circulation observed in winter, the idealized initial fields including environmental flow field, characterized by superposed a sine wave shaped trough turbulence on the basic baroclinic westerly flow and westerly Jet, and idealized orographic field are firstly constructed, then a set of 13 experiments, which consist of different member of flow field and orography, are designed. After that, initialization scheme of non-divergence on all levels and fixed lateral boundary condition are utilized to integerate each experiment for 4-5 days. Finally, the behaviour of EMT in each experiment are analysed. The results analysis in the third part of the series papers show that the model is computed stably and the simulated results are reasonable, namely, the idealized initial fields are constructed harmoniously and reasonably, and also argeed quite well with the actual situation. The treatments of lateral boundary condition and initial fields are also appropriate.

• ANALYSIS AND CORRECTIONS OF FGGE LEVEL Ⅲb RELATIVE HUMIDITY FIELD AND NUMERICAL EXPERIMENTS FOR THEIR EFFECTS ON FORECASTS OVER THE QINGHAI- XIZANG PLATEAU
• Chen Bomin;Hui Xiaoying;Qian Zhengan
• 1994 Vol. 13 (4): 394-403. 
• Abstract ( ) PDF (397KB) ( )
• In the paper, sixty times relative humidity fields of FGGE level Ⅲb data over the Qinghai-Xizang Plateau were analysed and corrected by using of the observed data during QXPMEX and Cressman's successive correction method. Then two cases of the Qinghai-Xizang Plateau vortices were chosen and their 72 h or 48 h forecasting experiments were performed by utilizing a limited numerical model, incorrected and corrected FGGE level Ⅲb relative humidity data as the model initial fields. The results show that relative humudity has a high value,it is located over the south-east area of the Qinghai-Xizang Plateau,then it moves successively northward and the minimum is located over the western Qinghai-Xizang Plateau. FGGE level Ⅲb data give a rather real distribution of relative humidity over the eastern Qinghai-Xizang Plateau, but the relative humidity values were overestimated over the western Qinghai-Xizang Plateau; the pattern and precipitation forecasted over the Qinghai-Xizang Plateau can obviously be improved and even predicted circulations can be influenced to the east, north and south flank of the Qinghai-Xizang Plateau by correcting the model initial relative humidity field (that of FGGE level Ⅲb data), which indicates the importance of intensive observational data over the western Qinghai-Xizang Plateau.

• THE RELATIONS BETWEEN ATMOSPHERIC LOW-FREQUENCY FLUCTUATION AT 50 hPa AND SUDDEN STRATOSPHERIC WARMING (SSW) IN WINTER OVER THE NORTHERN HEMISPHERE
• Jin Jiming;Qu Zhang
• 1994 Vol. 13 (4): 404-410. 
• Abstract ( ) PDF (296KB) ( )
• The power spectra of height at 50 hPa by using the data from seven winter seasons(1969-1976) are revealed,it is found that the typical time scale of 30-60-day oscillations is more obvious over high latitude than over middle and low latitude. The correlation coefficients of SSW are higher in strong SSW year than in weak SSW year over the path of Aleutian high moving northward and the polar point. it proves that 30-60-day oscillations over high latitude are tightly associated with SSW. The basic characteristics of SSW process are analysed by using the strong SSW data in winter of 1970-1971. The results show undoubtedly that there are larger contribution for 30-60-day oscillations of height to SSW.

• THE STUDY FOR THE MECHANISMOF FORMING QXP-VORTEX ON 600 hPa
• Ding Zhiying;Liu Jinglei;Lu Junning
• 1994 Vol. 13 (4): 411-418. 
• Abstract ( ) PDF (306KB) ( )
• In this paper, the mechanism of forming QXP-vortex on 600 hPa are simulated during 16-17 July, 1986.The result s show that the formation of vortexes is close related to the QXP-short wave radiation.The surface sensible heat is the important factor for it.The QXP can relax the cold air moving towards south.When the cold air met the air in the west of subtropical high, the phenomenon of convective instability, QPX-vortex disturbance and precipitation are easily formed due to the air is heated by the QXP underlying surface.

• THE CONJUGATE METHOD AND ITS NUMERICAL RESEARCH FOR FOUR DIMENSIONAL ASSIMILATION OF MESOSCALE REMOTE SENSING DATA
• Pu Zhaoxia;Chou Jifan
• 1994 Vol. 13 (4): 419-429. 
• Abstract ( ) PDF (396KB) ( )
• In this paper,we find a new way to solve these problems:the mesoscale remote sensing data assimilation and the formation of the initial field in numerical weather prediction. We put them forward as a kind of mathematical inverse problem,then using the theory of conjugate equations of the model to solve it. In the process of the forming initial field,the multiple-time data assimilation and time-variation dynamic model have been unified. In this way,we overcome the defects in the traditional method. Theory and numerical research indicate the method is useful. It is evident that this method has latent capacity to solve practical problems.

• SIMULATIVE ANALYSIS FOR THE CHARACTERISTICS OF RIDGE TURBULENT FLOW FIELD BY USING A TWO-DIMENSION FINE-MESH NON-HYDROSTATIC HIGHER ORDER TURBULENCE CLOSURE MODEL
• Liu Hongnian;Jiang Weimei
• 1994 Vol. 13 (4): 430-440. 
• Abstract ( ) PDF (330KB) ( )
• The effects of a 2-D ridge flow field on the mean flow and turbulence structure in the neutral surface layer were numerically investigated by using a non-hydrostatic higher-order turbulence closure model developed in this paper. The influences of the shape of the hill and the surface roughness of ridge on the fluctuation of flow around hill were discussed. The results show that a large discrepance was produced when the hydrostatic assumption was adopted, especially on the mean flow field. When the hill become steeper or background wind speed become larger,this discrepance is more considerable.

• THE INFLUENCES OF URBAN AEROSOLS ON HEAT BUDGET IN BOUNDARY LAYER
• Wang Haixiao;Chen Changhe
• 1994 Vol. 13 (4): 441-448. 
• Abstract ( ) PDF (280KB) ( )
• By using longwave and shortwave radiation models and a ground energy balance model,the heat budget in the boundary layer and the ground surface under the smog layer have been calculated. The results show that the all-day radiative effect of the smog layer makes the incoming radiative energy in the upper part of the low layer to be positive,and the middle and lower part to be negative. The total result is cooling slightly air of the low layer and increasing the stability. The computations also indicate that the attenuation of the shortwave radiation reaching ground due to the smog layer can be compensated by the increment of longwave radiation,and the smog layer makes the amplitude of ground surface temperature to be decreased.

• A NUMERICAL STUDY OF EFFECT OF MODEL ERRORS ON VARIATIONAL DATA ASSIMILATION
• Qiu Chongjian;Gao Jidong
• 1994 Vol. 13 (4): 449-456. 
• Abstract ( ) PDF (331KB) ( )
• Some numerical experiments are performed on a shallow water equation model to investigate the effect of model errors on variational four-dimensional assimilation. It is showed that the errors in the model are aliased to the initial fields. This aliasing is particularly serious in the case of without the observation of some model variables.

• APPLICATION OF MULTIVARIATE MEMBERSHIP FUNCTION TO RECOGNIZE HAIL CLOUD
• Li Zuoyong;Liu Shaonong
• 1994 Vol. 13 (4): 457-462. 
• Abstract ( ) PDF (203KB) ( )
• In order to set up the recognition equation of hail cloud by multivariate membership function,the approach in this paper is based on the consideration of a linear model of multi-factors including parameter variables(β) for hail cloud and thunder cloud. The parameter variable (β) is determined by the least square method and recognition equation of multivariate membership function is designed. The threshold value between hail cloud and thunder cloud is selected according to the best fitting of multivariate membership degree and practical cases. This method is applied to the recognition equation for 5 data sets,it is shown that the method have a good impact as compared with other recognition methods of hail cloud.

• GEOGRAPHICAL DISTRIBUTION AND SEASONAL VARIATION OF MONTHLY MEAN 500 hPa HEIGHT CORRELATION
• Wang Guomin;Zhou Kaiquan
• 1994 Vol. 13 (4): 463-467. 
• Abstract ( ) PDF (182KB) ( )
• The characteristics of month-to-month correlation of the monthly mean 500 hPa height anomalies for 34 years in Northern Hemisphere are analysed. It is shown that the correlation of height anomalies in Northern Hemisphere is positive and the value is more than 0.3 in subtropics and a lower value is about 0.0-0.3 in midlatitudes. The correlation of circulation anomalies in midlatitudes over the Asia and North America shows also clear seasonal variations,with maxima in winter and summer and minima in spring and autumn.

• NUMERICAL EXPERIMENTS OF INFLUENCES OF SURFACE ALBEDO VARIATION IN QINGHAI-XIZANG PLATEAU ON EAST-ASIA SUMMER MONSOON
• Liu Xiaodong;Tian Liang;Wei Zhigang
• 1994 Vol. 13 (4): 468-472. 
• Abstract ( ) PDF (248KB) ( )
• The comparative analyses of two sets of numerical experiments show that summer monsoon over East Asia is weakened when the surface albedo is increased in the main part of the Plateau. For example,when surface south wind advances northward slowly,easterly jet in upper troposphere is set up late and the sea level air pressure rises over East Asia continent, and the precipitation in the monsoon area of eastern China decreased.

• THE CORRELATION ANALYSES BETWEEN THE EMPIRICAL ORTHOGONAL FUNCTION CHARACTERISTICS OF THE SPRING PRECIPITATION IN EASTERN QINGHAI WITH SST AND 500 hPa HEIGHT
• Qin Ningsheng;Wu Yongsen
• 1994 Vol. 13 (4): 473-478. 
• Abstract ( ) PDF (217KB) ( )
• Based on the analyses of EOF characteristics by using precipitation from April to June at 13 weather stations in eastern Qinghai,temporal and spatial features of spring precipitation in this region are given. The time coefficient of the main characteristic vector has remotely correlation with Pacific SST during the same period. Meanwhile, using the time coefficient of the first characteristic vector as the dought flood index in spring in eastern Qinghai,we investigated the correlation between it with the previous Pacific SST and 500 hPa height. The results show that the equatorial eastern Pacific SST in spring of last year and the 500 hPa height over Pacific ocean in winter have instructive significance for the spring precipitation forcasting in eastern Qinghai.

• THE STUDY ON RECONSTRUCTING PAST CLIMATIC ELEMENT FIELDS BY USING EOF ANALYSIS
• Zhang Wancheng;Yan Huasheng;Zheng Jianmeng
• 1994 Vol. 13 (4): 479-484. 
• Abstract ( ) PDF (233KB) ( )
• In this paper,based on Empirical Orthogonal Function (EOF) analysis, the past climatic element fields are reconstructed through reconstructing the time coefficient of typical fields The rainfall fields data of 19 stations was rebuilt by using the six stations rainfall data in May of Yunnan province,the records which was rebuilt reappeared the characters of past special rainfall fields.

• THE ANALYSIS FOR THE PRIMARY FACTORS AFFECTING THE SOLAR GLOBAL RADIATION
• Bai Jianhui;Wang Gengchen
• 1994 Vol. 13 (4): 485-188. 
• Abstract ( ) PDF (193KB) ( )
• Based on solar global radiation and routine meteorological observational data from January to December in 1990,a regression equation for description solar global radiation reached ground under different sky conditions is developed. The primary and secondary role of the factors affecting the solar global radiation is anaysed,emphatically.

• A VIEWPOINT FOR FORMATION OF THE El Nino EVENT DURING 1991-1992
• Liu Houzan;Liu Mengyu
• 1994 Vol. 13 (4): 489-494. 
• Abstract ( ) PDF (262KB) ( )
• Some precursors and formation process of El Nino event during 1991-1992 are analysed,and are compared with that during 1982-1983 and 1986-1987. The forming characteristics and spread rule of El Nino event from west to east propagating are interpreted.