Vol.7, NO.3, 1996

Display Method:
The Real-time Forecasting Experiments with the Water-bearing Numerical Model
Xu Youping, Xia Daqing, Qian Yueying
1996, 7(3): 257-266.
By using the water-bearing numerical model, the real-time forecasting experiments were made from June to July to 1994. The results of conventional and cloud field forecasts were examined and analysed. The results show that: (1) the running of the water-bearing numerical model is stable and reliable, (2) the model has the capability to forecast the distributions of all kinds of water substances and their variations with time, and to forecast the macro and micro-structures of cloud system and cloud clusters and their cloud physical characteristics, and (3) the forecasting capabilities for weather patterns and meteorological elements, especially for precipitation, are comparable to the conventional forecasting models.
A Study on the Surface Mesoscale Systems of the Landed Typhoon Polly (No.9216)
Xu Xianan
1996, 7(3): 267-274.
In the summer of 1992~1994 the Typhoon Field Science and Operational Experiment was conducted in China. In the paper the intensive observation data from the experiment were used to analyze the surface mesoscale system in the circulation of the landed Typhoon Polly (No.9216). The data were obtained from 27, 996 intensive observations (station, times) at 673 stations in 11 provinces influenced by Typhoon Polly (No. 9216). The distribution, development and evolution of the mesoscale systems are shown in detail.
The Analysis of Errors and Their Correction for Water Vapour Retrievals of TOVS Data
Wang Chao, Zhang Fengying
1996, 7(3): 285-293.
By using the improved simultaneous physical retrieval method and with a 6 h numerical weather prediction as background field, the atmospheric parameters were retrieved from TIROS-N Operational Vertical Sounder (TOVS) data measured in January 1992 by satellite NOAA-12, and the water vapour retrieval errors were analysed and tested with conventional observational data as normal. The statistical results of the water vapour retrieval errors according to 3 satellite trajectories in the experimental area show some interesting features. The mean errors of retrieval for RH are closely correlated with the error of background field, and they are all negative. The regularity is shown obviously at high levels and high latitudes, that is, the absolute values of mean errors increase with altitude of level and latitude increasing. The interdiurnal variations of the errors are smaller at high levels, and bigger at low levels. The results of retrieval error corrected show that the retrievals above 500 hPa are better than those of background field, especially for trajectory A.
Moist Potential Vorticity and the Three Dimensional Structure of a Cold Front with Heavy Rainfall
Liu Huanzhu, Zhang Shaoqing
1996, 7(3): 275-284.
Under the constrain of conservation of moist potential vorticity (MPV), vertical vorticity may develop explosively (slantwise vorticity development) and result in severe weather such as torrential rainfall. MPV is related with stability, baroclinity and vertical wind shear. Its symbol (positive or negative) is determined by their allocation. In the middle troposphere (at about 500 hPa), the region with negative vertical component of MPV. i. e. MPV<0, is a transition region between cold dry air and warm moist air. The zero isopleth of MPV1 or the region between 0 and 20 (0.1 PVU) can be considered as the northwest limit of a torrential rain area. The horizontal component of MPV, i. e. MPV2, is determined by moist baroclinity and vertical wind shear. To the south of the front, air is convectively unstable. Positive MPV2 centre can appear above the lower-lever jet, and torrential rain may occur in the region north of the center. To the north of the front, air is convectively stable, negative MPV2 centre can appear below the upper-lever jet, and heavy rainfall may occur in the region south of the center. The vertical circulation and the three dimensional thermal structure across the front region are given.
Development of Agrometeorological Yield Forecasting Operational System
Zhuang Liwei, Wang Futang, Wang Shili
1996, 7(3): 294-299.
The programming design of Agrometeorological Yield Forecasting Operational System (AYFOS) is programmed with the languages of Quick BASIC, MS-C and MASM. The prompt message is given by using pull-down pop-up Chinese menu. The help function is provided by man-computer interaction with color highlight bar. The system has reasonable software structure, convenient operation and high quality product output of tables and graphics. It consists of six functional modules including data management, forecasting model building, forecasting model memory, real-time forecasting and forecasting model integrating, product output management and system maintenance. This system posseses a general operational software and it is objective and convenient for agrometeorological yield forecasting.
A Synthetic Analogue Model for Medium-range Forecasting by Man-machine Interaction
Chao Shuyi, Jin Ronghua
1996, 7(3): 300-307.
The synthetic analogue model of medium-range forecast was made by means of man-machine interaction. Based on the objective similarity analysis, the prevailing circulation system (key regions) and the circulation evolution field were introduced into the model, so that the forecaster’s experiences were effectively applied and the randomness of similar circulation evolution was reduced. The better results of the operational application in medium-range weather element forecasting were obtained, and the model could be widely used.
Impacts of Climate Change on the Water Deficit Status and Growth of Winter Wheat in North China
Wang Shili, Lou Xiurong
1996, 7(3): 308-315.
The water deficits in various development stages and the whole growing season of winter wheat in North China under climate change scenarios are calculated based on the meteorological data, crop development period and soil hydrological data at 43 stations. The results show that when temperature rises, the water deficit status would deteriorate, the isolines of deficit might shift southward, the climate suitable areas of wheat would contract, the yield-reduction would become serious and the output values would lose, and also the production cost resulting from additional irrigation might increase.
The Statistical-dynamic Prediction of Tropical Cyclone Track on the East China Sea
Li Huiwu, Jin Yiming
1996, 7(3): 316-322.
The scheme of the statistical-dynamic prediction for the tropical cyclone track on the East China Sea and its application are described. Based on its original scheme, the forecasting area is adjusted and the historical samples are afresh selected; the period of validity is prolonged; the correlation factors of stochastic parameters are improved and the weather empirical factors are objective; and the products of numerical prediction are introduced from ECMWF. The independent sample test and the real-time prediction show that the forecasting tracks of tropical cyclones are very similar to the real tracks, and every error of the forecasting products of the scheme is obviously less than that of other schemes.
A Sensitivity Simulation for Anomalous Factors Influencing the Monsoon Circulation in East Asia
Zhang Guangzhi, Xu Xiangde, Miao Qiuju
1996, 7(3): 323-329.
Based on the monthly temperature departure data of the underlying surface during the E1 Nino year (1927), a sensitivity simulation of anomalous SST in the Pacific and also in several key areas of the Pacific has been made by using the improved OSU global climatic model. As a thermodynamic forced source, the anomalous SST is put into the model initially as well as the spatial and temporal varieties of anomalous SST with integrated time are superimposed continuously. The results of numerical simulation indicate that the spatial and temporal anomalies for the observed SST in the Pacific, especially in key areas during the E1 Nino year bring about an anomalous change of monsoon circulation in East Asia, and the drought circulation pattern appears. For this change of monsoon circulation, the affecting factors of anomalous SST in both the central equatorial Pacific area and the eastern equatorial pacific area are all very sensitive, so they have a contain significance for weather forecast.
The Formation Mechanism of Squall Line with a Behind High Pattern over the Coast of Eastern China
Lin Xihuai, Qian Jiasheng
1996, 7(3): 330-335.
A squall line weather process on 2 May 1998 was analysed over the eastern Anhui-Jiangsu provinces. The analysed result shows that there was a deep convergence layer on the low level, and severe divergence layer on the upper; the axis of low stream let stream on the low level was almost coincident with the axis of high value of the θse field. So that the space of the squall line not only had abundant energy storage, but also was favourable to the release of disturbance kinetic energy. In the crossing site of the gravity wave along the low jet stream and that of forward sector of backflow, the impulsive force might be very strong, and a squall line just appeared there.
A Prospect Forecasting Method Study of Severe Convective Weather in Beijing Area
Sun Mingsheng, Wang Ximing, Luo Yang, Xu Huangang, Yi Zhian
1996, 7(3): 336-343.
The forming condition and the prospect forecasting method of severe convective weather in Beijing area are studied according to 276 severe weather cases in June, July and August from 1983 to 1992. By means of classification of 500 hPa patterns day by day, the largescale circulation patterns in Beijing area are divided into five types. From the cases of convective occurrence and non-occurrence in each type 298 weather samples are randomly adopted and analysed for studying the circulation pattern and difference of convective occurrence and no-occurrence. It is shown that circulation features, structure and the distribution of the scalars for convective occurrence and no-occurrence are different obviously. Therefore a concept model is summarized and the starting point about circulation pattern forecast is obtained. On this basis, after calculating dozens of physical parameters, the best forecasting factor is selected, and the prospect forecasting technique is developed by use of dicision tree method. The operational experiments in 1993 and 1994 show that the forecasting is objective, fast and automatic.
Interpolation Experiment of Missing Meteorological Data by Using Chebyshev Polynomials Method
Zhang Xiuzhi, Sun Anjian
1996, 7(3): 344-352.
By using one-dimensional Chebyshev polynomials expansion, the interpolation experiments of missing data for annual precipitation and monthly mean temperature have been made. A number of tests have been made for the selection schemes of two kinds of critical iteration times and iterative terminal value method of ideal initial values. The results are as follows: the calculating accuracy of the terminal values are higher generally; but the fitting results of ideal initial value much better for dryness-wetness year; the accuracy of interpolation of missing data for year is higher than that for continuous several years; the calculating results of two-direction interpolation method are better than that by using sequential or contrary interpolation alone.
The Response of Clear-air Turbulence to Meso- and Synoptic-scale Dynamic Forcing Processes
Tian Junjie, Zhuang Chunyi
1996, 7(3): 353-360.
By using the meso-scale objective analysis data, the forcing field of the nonturbulent deformation in Richardson number tendency equation of θ coordinates is diagnosed in order to study the response relation between clear-air turbulence (CAT) and synoptic-scale and meso-scale dynamic forcing processes. The calculating results show that CAT is often encountered in the upper troposphere or near upper air jet flows. In the stable shallow layer of upper atmosphere, when micro air mass with small Ri number encounters the strong forcing field of nonturbulent deformation, because of the coupling function of dynamic forcing with Ri number, CAT would occur frequently.
Some Palaeoclimatological Problems Associated with the Present Global Warming
Ren Guoyu
1996, 7(3): 361-370.
Increasing data and analyses of palaeoclimatology have been seen in the past decade. An attempt is made in this paper to summarize the up-to-date palaeoclimatological research results relevant to the commonly concerned global climate change. It is obvious from the review that a big contribution has made by palaecoclimatologists for the global climate change research and future climate prediction in such aspects as the past greenhouse gas records, the past greenhouse effect analyses, the study of palaeo-analog forecasting method, the investigation of the past snow accumulation rate in Antarctica and Greenland and its implication for global sea-level change, and the documentation of the rapid climate changes in the inter-glacial and late-glacial periods over North Atlantic regions. Palaeoclimatology has also played an important part in testing and calibrating GCMs models.
A Study of the Physical Mechanism for a Black Storm in Northwest China
Liu Jingtao, Li Yunjin, Wu Xuehong, Yang Yaofang
1996, 7(3): 371-376.
The physical mechanism of a black storm, which burst out in Northwest China on May 5, 1993, is studied using the methods of synoptic meteorology and diagnostic analysis. The results show that the black storm is a mesoscale phenomenon which forms and develops in particular season (spring) on the bare loose underlying surface (desert, gobi) when a strong cold wave bursts out. The results also show that there exist strong wind shears in the vertical direction of middle and lower convective layer; the wind shears are favourable to the development of turbulence; the contribution of the non-geostrophic forced function to the secondary circulation is greater than that of the geostrophic forced function. The positive thermodynamical feedback, resulting from the significant differential radiative heating before and after the appearance of the black storm, leads to the local frontogenesis of surface layer, and strengthens the positive thermodynamical circulation.
A Comparison of Two Typical Schemes for Pressure Gradient Force Calculation in Topographic Area
Zhou Tianjun, Qian Yongfu
1996, 7(3): 377-380.
Two typical schemes for pressure gradient force (PGF) calculation in topographic area have been compared. One is that PGF of topographic coordinate is got by vertical interpolating from calculation of constant pressure surface, the other is difference-differential-difference scheme. Based on the initial field diagnosis and forecast verification, the results show that the first scheme does better in upper air while the second scheme in lower air for reducing topographic influence.
Influences of Topography on Characteristics of Typhoon Crossing Leizhou Peninsula
Li Zengzhong
1996, 7(3): 381-384.
The characteristic variations of 29 typhoons and tropical storms crossing Leizhou Peninsula in years 1949 to 1993 have been analyzed. The results show that: the intensities of typhoon and tropical storms begin decreasing obviously at 6 hours before landing; the shrink of the gale area of the tropical storms is more than that of the typhoon; the influences of Leizhou Peninsula on the moving directions of typhoons are earlier than those of tropical storms; but no tropical cyclone turns southward obviously before and after crossing the peninsula.