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• THE DESIGN OF A NESTED FINE-MESH MODEL OVER THE COMPLEX TOPOGRAPHY PART ONE： BASIC STRUCTURE OF THE NUMERICAL MODEL
• Yan Hong
• 1987 Vol. 6 (s1): 1-63. 
• Abstract ( ) PDF (3923KB) ( )
• The basic structure of the oue-way interaction nested fine-mesh model with the C-type staggered grid and P-o mixed vertical coordinate is discussed in detail in this paper. "J he basic dynamic equations and their finite analogs in the model are introduced at the first three chapters with the emphasis on the index arithmetic for the finite difference schemes on the C-type staggered grids. One of the most important aspects of the regional numerical modeling is the treatment of the lateral boundary conditions. Though only brief descriptions are given to the nesting scheme of this model, the vertical dry la diaba tic adjustment scheme and the initialization methods, because the more detailed discussion may be found in the separate papers in this special issue.Arakawa-Lamb^s Potential Enstrophy and Energy Conserving scheme is applied in this model to simulate the dynamic process over the complex topography as realistic as possible. Some new numerical schemes are presented in this model in order to increase the computational accuracy o f the term of pressure gradient force over the steep terrains.A series of up-to-date developed techniques are introduced into the model such as the numerical schemes for the time integration and the horizon tal diffusion. Some considerations for the model programming are also addressed brie fly in the pa per for the readers w li o are interested in the model program structure.

• THE DESIGN OF A NESTED FINE-MESH MODEL OVER THE COMPLEX TOPOGRAPHY PART TWO: PARAMETERIZATION OF THE SUB-GRID PHYSICAL PROCESSES
• Yan Hong
• 1987 Vol. 6 (s1): 64-139. 
• Abstract ( ) PDF (4636KB) ( )
• The parameterization schemes of various sub-grid physical processes for the nested fine-mesh primitive equation model with a mixed P-Sigma coordinate are discussed in detail in this paper. The processes include the horizontal and vertical eddy diffusions, the dry adiabatic adjustment, the adiabatic processes of the moist atmosphere, the physics in the Planetary Boundary Layer (PBL) and radiative processes in the atmosphere and on the ground surface. The more detailed discussions are given to those schemes which are designed or modified by author for this model, such as the concept of active and passive adjusted variables and their application in the dry adiabatic adjustment, the consideration of the cloud amount in the radiative processes and the effect of terrain gradient on the surface radiation balance. The attention also is taken to those up-to-data developed new techniques, for an example, the force-restore method which is used to predict the ground surface temperature. Similar to the part one of this paper, some considerations of the model programming are also addressed briefly in the paper for further understanding the numerical methods used in the parameterization of model physics.

• A THREE-DIMENSIONAL INTERPOLATION METHOD OVER STEEP TERRAIN FOR DIAGNOSING TEMPERATURE AND HEIGHT AND ITS APPLICATION TO THE NUMERICAL WEATHER ANALYSIS AND PREDICTION
• Yan Hong;Wang Qiang;Wu Yong
• 1987 Vol. 6 (s1): 140-159. 
• Abstract ( ) PDF (1168KB) ( )
• The error source of temperature and height associated with the accuracy of the one-dimensional vertical interpolation is investigated. Further more, its effect on the computation of pressure gradient force in forecast model and the diagnostics of temperature and geopotential over the steep terrains are discussed in detail. It turns out that amplification of computational error due to the extrapolation of one-dimensional interpolation method in the lowest layer of model atmosphere is one of the most serious error sources for PGF and temperature/height diagnostics. Based on the review of previous studies, a new method(γKLAX method) which uses the three-dimensional interpolation for diagnosing over the steep terrain is proposed. It has been proved by means of the error estimation that new scheme has some particular advantages over steep terrains. The case study and forecast test show that it may be applied to calculate the PGF term over steep terrain more accurately. The fields of temperature and geopotential in the lower troposphere as well as the sea-level pressure which are obtained with this scheme,even over steep terrains are improved remarkably. Therefore this new three-dimensional interpolation method provides a more accurate and relatively pragmatic scheme for the numerical model with realistic topography.

• A COMPARATIVE TEST OF THE DRY ADIABATIC ADJUSTMENT SCHEMES
• Qian Zhengan;Yan Hong;Gu Hongdao;Nai Kang
• 1987 Vol. 6 (s1): 160-170. 
• Abstract ( ) PDF (685KB) ( )
• The dry adiabatic adjusment schemes used in our nested fine-mesh model and the associated comparative study are discussed in this paper. Based on the review of previous works on designing the dry adiabatic adjustment scheme, we have introduced a more generalized criterion to judge the vertical instability and the concepts of active and passive adjustment of physical varaibles. Five possible schemes for adjusting the active quantities are presented and compared in the paper based on the conservation of internal energy or potential temperature, which adjust the temperature or potential temperature first as the active adjustment and then adjust those passive quantities (such as U, V and Q) according to the amount of adjusted active quantities in each individual mean layer. The diagnostic verifications and forecast simulations with these schemes show that the scheme E, the internal energy conservation scheme, is superior to the others.

• INITIALIZATION SCHEMES OF THE WIND FIELD DATA IN THE FINE-MESH MODEL OVER A LIMITED AREA
• Gu Hongdao;Hu Xingfang;Yan Hong
• 1987 Vol. 6 (s1): 171-181. 
• Abstract ( ) PDF (642KB) ( )
• In order to forecast the generation and development of the weather systems over and around the Qinghai-Xizang Plateau, the initialization schemes of the wind field data have been studied. The specific formulas and steps of the schemes, which eliminate the integrated mass divergence or the wind divergences on all levels, are discussed, with emphasis on the analyses of different ways to eliminate the integrated mass divergence. The results show that the indirect elimination way which find the non-divergent component of the integrated mass flux Vψ ^(m) first and then get its divergent flux Vx ^(m) to be eliminated, can remove Vx ^(m) and retain Vψ ^(m) effectively.The use of the spiral method to solve Poisson's equation is faster than the regular method.

• A SCHEME COMPARATIVE TEST OF INITIALIZATION WITH WIND DATA FOR A LIMITED-AREA FORECAST MODEL
• Hu Xing fang;Ou Xiao yu;Gu Hong dao;Yan Hong;Han Feng
• 1987 Vol. 6 (s1): 182-191. 
• Abstract ( ) PDF (1018KB) ( )
• A study of initialization of observed wind data has been conducted recently to improve the forecast of the generation and development of weather systems over Qinghai-Xizang Plateau and its vicinity. Using the FGGE Ⅲ _b data of 1200 GMT 2 June 1979 as the initial input data, a comparative test is done for three kinds of initialization schemes, i.e., the mean nondivergence scheme, the scheme of nondivergent wind for each level and the geos trophic scheme. The statistical analysis and the map-discussion show that the forecast with the mean nondivergence scheme is superior to the others over Plateau and its vicinity. More serious loss of kinetic energy is found in the results of scheme of nondivergent wind for each level. The flow field simulated with the initial geostrophic wind is some-how noisy in the lower layers, though appears better than the others in the upper levels. Based on above analysis, we have tested a combined scheme which uses geostrophic wind at the upper layers and then repeats the whole procedure of mean nondivergence to the model atmosphere. The numerical simulation shows some improvements in the 36h forecast over Plateau.

• AN INVESTIGATION OF ONE-WAY NESTING SCHEMES FOR THE LIMITED-AREA MODEL PART ONE: REVIEW AND A PROPOSED SCHEME FOR THE C-TYPE STAGGERED MODEL
• Yan Hong
• 1987 Vol. 6 (s1): 192-204. 
• Abstract ( ) PDF (625KB) ( )
• The theory of computational physics associated v, ith the lateral boundary problem of the nested limited-area model has been reviewed in this paper at first.Then the some popular techniques for the lateral boundary treatment current available for the research models as well as the operational models are introduced briefly. Basedon the review of previous studies and the features of our model a numerical scheme is prope and for the one-way the model with C-type staggered grids. It is also discussed in this peper hew to can pare the lateral boundary sehemes to select the oprimam one.

• AN INVESTIGATION OF ONE-WAY NESTING SCHEMES FOR THE LIMITED-AREA MODEL PART TWO： A COMPARATIVE TEST OF THE DIFFERENT LATERAL BOUNDARY SCHEMES
• Li Dingming;Yan Hong;Zhang Zhengguo
• 1987 Vol. 6 (s1): 205-214. 
• Abstract ( ) PDF (587KB) ( )
• Using the nested fine-mesh model under dry and adiabatic conditions, a comparison test of different lateral boundary schemes is studied in detail, T h e differences in aspects o f the mod el s' ability, the forecast verif i-cations and the distribution of various variables due to the differences of these sc hemes are disc uss ed ? It shows t h athere is an interaction bet ween the computational modes caused by the ill-posed lateral bo und ary conditions and the model terrain?丁he errors in the lateral boundary conditions may give the influences (.o weater systems of all different scales. The nested scheme with the pseudo-radiative conditions may allow the synoptic and mes o~sc ale systems passing thro ugh the lateral boundaries, w h ic h provides more realistic b ack^gro and of large scale circulation to the f ine-mesh model without noticeable inc ons is t enc ies near the lateral boundaries ? On the other hand, other schemes have some deficiencies on the aspects o f ?, he numerical stability or the forecast accuracy.

• AN INVESTIGATION OF ONE-WAY NESTING SCHEMES FOR THE LIMITED-AREA MODEL PART THREE: A PRE LIMINARY RESULT OF THE NESTING WITH MODEL-OUTPUT
• FuErxuan;Yan Hong;Wang Qiang
• 1987 Vol. 6 (s1): 215-224. 
• Abstract ( ) PDF (894KB) ( )
• A one-way interaction nesting scheme with the model-output is introduced in this paper with the emphasis of the interpolation scheme. The forecast simulations of 24h and 48h periods without and with topograhy under dry adiabatic conditions are performed successfully. The results show that the forecast with this nesting scheme is stable. The simulation near the lateral boundary appears very smooth. The forecast of westerly jet and synoptic situation in the fine-mesh grid domain gives more detail, which improvse the simulation.

• THE FORECAST EXPERIMENTS OF LARGE SCALE PRECIPITATION
• Qian Zhengan;Yan Hong;Chen Guixun;Chen Dongwei
• 1987 Vol. 6 (s1): 225-238. 
• Abstract ( ) PDF (487KB) ( )
• By using a nested fine mesh model over complex terrain and the FGGE level Ⅲ _b dataset from 2 to 6 June 1979, a series of contrast experiments for large scale precipitation (LSP) have done in this paper. A scheme of the LSP which uses modified saturation removal method was adopted. Results of the experiments show; 1) In the runs with the different initial conditions, the 24-hour forecast is better than the 48-hour one, especially in mid-and low-lati- tudes; 2) The LSP can be set on either at each time step or once per model hour, but the former run is more reasonable in physics and gives a better forecast in rainfall than the latter run; 3) In the southreu part or in the season with high temperature and humidity, the rainfr.ll forecast is sensitive to the changes in saturation condensation ratio, Fr; 4) There are significant improYement s in the forecast of situations and flow fields in the model run with topography) 5) The somewhat improvements of the moist model run over dry one are that the LSP latent heating makes weather system moving faster, which cause the pressure fall and affect the flow fields in the lower level. The heating mainly occur in the levels from 740 to 800hPa.

• A SCHEME COMPARATIVE TEST FOR THE RADIATION PARAMETERIZATION PART ONE: SOLAR RADIATION
• He Guangbi;Wei Li;Yan Hong
• 1987 Vol. 6 (s1): 239-246. 
• Abstract ( ) PDF (504KB) ( )
• By using the diagnostic analysis of solar radiation heating in one case, a comparative study of parameterization of solar radiation has been done with three different schemes, i.e.the recurrent method, the simplified cloud classification method and Kuo-Qian's scheme(Kuo and Qian 1981,1982). Results show that the first two schemes appear to approach the original requirement (Yan, 1987). Especially, the recurrent scheme which includes more details in the sense of physics gives the most reasonable si mulation, though with a little bit more time-consuming. The solar radiation heating on the surface diagnosed with the simplified cloud classification method very close to the result ob'-.ained with the first scheme, but the heating rate of each layer of model atmosphere is not as reasonable as previous one. The advantage of this method, as expected, is very efficient in computation. Kuo-Qian's scheme is relatively simple, though the simulation under partly cloudy conditions is not very reasonable. The discussion in this comparative test gives us some useful suggestion for the further improvement of short-wave radiation scheme and its application to the model.

• A SCHEME COMPARATIVE TEST FOR THE RADIATION PARAMETERIZATION PART TWO： LONG WAVE RADIATION
• Wei Li;Yan Hong
• 1987 Vol. 6 (s1): 247-254. 
• Abstract ( ) PDF (751KB) ( )
• Based on Kuo-Qian's long- wave radiation parameterization scheme, quite a few of modifications have been made for the nested fine-mesh model, such as introducing the cloud amount parameter,designing an economic look-up table method for determining the mean area transmissivity and the intensity of flux emissivity of black body.In the model, iw is very simple ^ o choose one scheme for the mean area transmissivity from three current available methods.There fore, a series of comparative tests may be studied easily to determine i h e optimum one for the research and operational application. Three sets of comparative tests have been done in this paper:(1)Kuo9 s method with additional cloud amount parameter introduced. (2)Original Kuo's method, i,eo without the cloud amount parameter^ 3) Improved scheme for mean area transmissivity proposed by Qian,further simplified and added with cloud amount parameter in this model by Yan and et al. The computational efficiency and accuracy of the look-up t able method for determining the transmissivity and the intensity of flux emissivity of black body are also verified against the values given by the analytic formula. The results from the numerical tests are following:(1) Applicat ion of the look-up table method for long-wave radiation cooling can save computation time without losing the required numeric al accuracy*(2)Introdu-ction of the cloud amount parameter gives more realistic simulation of diababic long- wave radiative cooling in the model atmosphere.(3)The orders and horizontal distribution of long-wave radiative cooling computed with the original Kuo's scheme and tlie modified scheme (by Qian) are very coqipatible, though the latter appears more reasonable.

• A COMPOSITE ESTIMATION OF SURFACE ALBEDO AND SOIL MOISTURE CONTENT AND THEIR /MPACT 〇N THE SURFACE DIABATIC HEATING
• Yan Hong;Wei Li;Chen Yuchun;Li Suhua;Li Zuofang;Li Lanping;Hu Yihong;Qiu Li
• 1987 Vol. 6 (s1): 255-266. 
• Abstract ( ) PDF (532KB) ( )
• In order i o provide more realistic data of the surface albedo and the soil moisture content for our model, based on the current available albedo data, a comprehensive estimation has been done in the past years f vhich composites a set of data including the surface albedo and soil moist ure content for each season and year- aver age over a domain of 0°-180°E and 30°S-90°N with 2.5×2,5 deg. reso lu t io n.Then the c om par a ti ve study is made with the data from other source. Using the observed data over Plateau, by means of the statistical correlation analysis,an empiric al formula of surface albedo is found as a function of the solar zenith and the s oil moisture content near the sur -face. Fin ally, three sets of numerical tests are performed. The impact of surface albedo data on the surface diabatic heating is addressed.

• A SIMPLE AND PRAGMATIC GRAPHICS PRESENTATION SCHEME FOR DISPLAYING THE MODEL OUTPUT
• Ou Xiaoyu;Yan Hong;Chen Yuchun;Zhu Xiaoli
• 1987 Vol. 6 (s1): 267-275. 
• Abstract ( ) PDF (599KB) ( )
• A simple and pragmatic graphics output package is introduced briefly in this paper which is capable to print the horizontal contour chart, vertical cross-section,vertical circulation or flux chart for the numerical model ou put on a simple line-printer. With present available computational facility in China, it is considered as an efficient and economic method to provide graphics output for analyzing the model output in time.

• AN INTRODUCTION TO THE PROGRAM FOR DIAGNOSTIC ANALYSIS AND FORECAST VERIFICATION
• Chen Yuchun;Yan Hong;Gu Hongdao
• 1987 Vol. 6 (s1): 276-284. 
• Abstract ( ) PDF (983KB) ( )
• A program for data diagnostic analysis and forecast verification has been coded for the requirement of research as well as operational purposes. With this program, diagnostic analysis can be done for various datasets such as the data from FGGE Ⅲ _b historical tapes, The initialized data defined at the model layers and the model output during the simulations. A selection of verifications of forecast is available such as the mean square error, the standard deviation, the correlation coefficient, S1 score and difference between two fields etc. The scale-filtering codes in this program is very useful for studying the meso-scale weather system. The graphics output are also flexible for user's options. Therefore, it may be considered as a useful tool for the diagnostic analysis and forecast verification with current available computational facilities ia China.

• A PRELIMINARY RESULTS OF THE DRY ADIABATIC FORECAST BY THE NESTED FINE-MESH MODEL OVER COMPLEX TOPOGRAPHY
• Li Suhua;Yan Hong Chen;Yu chun
• 1987 Vol. 6 (s1): 285-299. 
• Abstract ( ) PDF (962KB) ( )
• Using the nested fine-mesh model and the FGGE Ⅲ _b data for 1979, dry adiabatic forecast tests (without moisture, radiation and surface process) have been done with and without the complex topography respectively. The results show that the model performances are very stable, the forecast with complex terrain is even closer to the observed than that without terrain. Further more, with the same scheme and at the same level, the simulations at higher latitudes are better than that at low latitudes, the forecast of flow fields appears to be more realistic than that of geopotential fields. On the other hand, the model is also capable to simulate some meso-scale systems, such as the cyclogenesis due to the mechanic forcing of terrain. Therefore the model performance is consistent with the basic theory of the pure dynamic effect of large-scale topography.

• PRELIMINARY ANALYSIS OF THE FORECAST TESTS WITH THREE CASES
• Li Suhua;Chen Yuchuu;Qian Zhengan;Song Jie
• 1987 Vol. 6 (s1): 300-315. 
• Abstract ( ) PDF (724KB) ( )
• Using the nested fine-mesh model and the FGGE Ⅲ _b data for 1979, 24-60h numerical forecas tests have been done with three cases which are chosen for Spring, Summer and Winter respectively. The preliminary analysis of these tesis show that the model performances are very promising, the forecast is successfully done for the major features of the synoptic evolution in these three cases, such as the reorientation of the "west-east" located trough to the normal position, the explosively moving of cold front, the large-scale trough blocking by the terrain at the upstream side of Tibetan Platau, then slowing down and splitting to two small ones, finally speeding up and enhancing again after passing through the Plateau. On the other hand, the model is also capable to forecast the South-West vortices and the associated heavy rainfall. though the forecast remains to be improved over the low latitude area and in the high troposphere.