Vol.7, NO.1, 1996

Display Method:
Performance of Parameterization of Sub-scale Physical Processes in Numerical Model and Its Effects on Typhoon Track Forecastings
Chen Dehui, Wang Shiwen, Wang Houjun
1996, 7(1): 1-8.
A new package of parameterization of sub-scale physical processes has been performed for model of typhoon track prediction at Numerical Meteorological Center (NMC), Beijing. Five cases of typhoons, which happened during the summer 1992 (ELI and JANIS), were chosen for the numerical simulations. In comparison of the results obtained by the performed physical processes schemes with those obtained by the old simpler schemes, it is shown that either in typhoon track forecasting or in typhoon intensity prediction, the new schemes are superior to the simpler schemes. In fact, the mean errors of 24 h and 48 h typhoon central forecastings are 188 km and 337 km for the new schemes, respectively, and 226 km and 446 km for the simpler schemes respectively. The mean deviation of 48 h predicted central pressures from the observed ones is 23 hPa for the new scheme, and 26 hPa for the simpler scheme.
The Interactions of Different Scale Systems in the Torrential Rain over the Changjiang and Huaihe River Valley in 1991
Yang Fuquan, Yang Dasheng
1996, 7(1): 9-18.
The filtering technique is employed to the grid data sets on 1~5, July, 1991 in the East Asian region. The atmospheric motions are decomposed into the large scale background and the mesoscale perturbation fields. Using the p-coordinate dynamic equation system for moist air, the equations including the nonlinear interactions of the different scale system over the various isobaric surfaces in the two-layer model are obtained. After simplification a physical parameter characterizing the development of the mesoscale system on the lower layer (about 700 hPa) is obtained. The development and attenuation of the system would depend upon the positive and negative of the parameter, i. e., upon the motion, vorticity and temperature fields and their interaction of various scales on the 200, 500 and 700 hPa isobaric surfaces.
Application of Potential Vorticity Theory to Analysis of Formative Mechanism of Torrential Rain
Wang Jianzhong, Ma Shufen, Ding Yihui
1996, 7(1): 19-27.
By using the concept of potential vorticity, the characteristics of potential vorticity and other corresponding physical quantities are analyzed in the process of excessively heavy rain over the Changjiang-Huaihe River basin in 1991. It is shown that the strong precipitation area is located in the lower value area of dry potential vorticity and at the warm side of negative wet potential vorticity center, and it is related directively to relative wet potential vorticity. The baroclinic part of wet potential vorticity can reflect clearly the role of wet baroclinity in the convectively instable systems. There is a stronger response to frontgenetical forcing in the atmosphere where the value of wet potential vorticity is relatively small.
Climatological Characteristics of Rapidly Intensifying Tropical Cyclones over the Offshore of China
Yan Junyue
1996, 7(1): 28-35.
The occurrence of rapid intensification (RI) of tropical cyclones (≥10 m/s in 12 h ) in the offshore of China is examined to determine the geographic and seasonal variation of these events. Eighty-four cases of rapid growth process during the period 1949~1990 were selected to study climatological characteristics. The statistical results reveal that the majority (82%) of RI occurs in July through October. Most of RI are associated with sea surface temperature ≥28℃. The changes of wind speed and central pressure of RI as well as the rate of intensifying are also estimated.
The Influences of Cloud Microphysical Parameters on Cloud Optical and Radiative Properties
Wang Hongqi, Zhao Gaoxiang
1996, 7(1): 36-44.
In the view of radiation transfer theory, the cloud optical parameters: βe, ωo and g are calculated under the different cloud droplet size distributions, and their influences on cloud reflectivity, transmissivity and absorptivity are investigated. And, the effects of inhomogeneities of cloud droplet size distribution and cloud liquid water content in the vertical direction on assemble cloud radiative properties, radiative flux density and heating rate in the cloud are also estimated.
A Method of Forecasting Tropical Cyclone Track and Intensity—SAPC Method
He Xiajing, Zeng Zong, Xu Yongguo, Wu Jiehua
1996, 7(1): 45-52.
The SAPC (stagewise analogous persistence of climate) method is used to forecast tropical cyclone track and intensity. It can effectively synthesize climatic tracks, analogous tracks and persistent tracks by using the various analogous conditions and weights. The method, which avoiding the changes of the track curvature and considering the climatic statistical results of the various tropical cyclones varying with time and location, can make a predicted tropical cyclone track and intensity according to the present situation. By testing historical data of tropical cyclones and operational forecasting, it is shown that the method is available.
Utilizing Tree Ring Chronologies to Reconstruct 300-Year Drought Days in Eastern Tianshan Mountains
Zhang Zhihua, Wu Xiangding, Li Ji
1996, 7(1): 53-60.
The major local tree ring chronology (1665~1989) in the Eastern Tianshan Mts was obtained by averaging 6 tree ring chronologies. The response surfaces of tree ring to climate indicate that growth of spruce in the Eastern Tianshang Mts is nonlinear correlated with precipitation and temperature. This interaction makes it unreasonable to reconstruct either precipitation or temperature, separately, using regression methods. Drought days during tree growth season were estimated from regression model including both temperature and precipitation which would influence tree-ring growth. The relationship between tree ring and drought days is significant. As a result, the local past drought days back to 1665 A. D. at Miquan and Fukang, Eastern Tianshan, were reconstructed based on spruce tree-ring chronologies. The results are coincided with the actual situation.
The Preliminary Study on the Efficiency of Parallel Model Computation
Yu Wei, Yan Hong, Jin Zhiyan
1996, 7(1): 61-68.
The suitability and relationship between complexity and efficiency of multiple parallel computation have been intensively studied by using the parallelized version of the limited-area fine-mesh grid-point model. The preliminary study indicates that, with suitable algorithm, the speedup can be improved by increasing the number of CPU (the number of transputers) in general. And, the efficiency of parallel may decrease with the CPUs, and increase with higher complexity. The results suggest that massively or highly parallel computer systems are most privileged for solving computationally intensive problem. In the light of its scalability the system which has the unlimited potential to provide much faster and more powerful computer resources required for further development of NWP and numerical modeling.
2-Dimensional Land-air Model with Vegetation Effect and Simulation of Climate over Semiarid Region
Jiang Ye
1996, 7(1): 69-75.
Based on the equations of energy and moisture balances, radiation transfer and thermodynamics, a 2-dimensional land-air dynamic model with vegetation effect in the entity of soil-vegetation-atmosphere is developed. Variations of heat and moisture with height and latitude are modeled. Taking account of geographic and climate features, the climatic mean fields over the northern part of Shaanxi Province are simulated with the model, thereby the simulation scheme for understanding desertification over the semiarid is presented and the preliminary computational results are obtained.
A Study of Urban and Country Fire Forecasting Model
Mao Xianmin, Liu Guifeng, Liu Sujie
1996, 7(1): 76-81.
The necessity and feasibility of developing a fire forecasting model are studied at first. Then, the relationship between the fire occurrences and wind velocity, monthly precipitation and relative humidity in liaoning Province during 1981~1990 is analyzed. From conceptual model, the factors related to fires are investigated. Finally, the quantitative fire forecasting model is developed. The forecasting results are satisfactory.
The Linear and Nonlinear Inertial-gravitational Waves Influences by CISK
Wang Yongzhong, Xia Youlong
1996, 7(1): 82-88.
By using the equations of atmospheric dynamics with polar symmetry, the linear and nonlinear CISK heating processes are investigated. Using traveling wave method and theory of qualitative analysis of ordinary differential equation, the stability of the linear and nonlinear inertial-gravitational waves with CISK process and the influence of CISK process on the intensity and width of soliton inertial-gravitational waves are discussed. The results show that linear CISK process affects not only the intensity of soliton, but also the width of the soliton, nonlinear CISK process only affects intensity of the soliton.
Abrupt Change of Drorght/Flood for the Last 522 Years in the Middle Reaches of Yellow River
Yu Shuqiu, Lin Xuechun
1996, 7(1): 89-95.
The summer dryness/wetness grades series for the last 522 years (1470~1991) in the middle reaches of Yellow River are analysed by T test. The results indicate that there are two abrupt changes with 100-year scale in this region, around 1650’s (from drought to flood) and in the early 1760’s (from flood to normal). There are also jumps of 20~30 year scale within the 100-year scale variations. It is also found that the drought/flood in the region are associated with the evolution of atmospheric active centers and the Sea Surface Temperature Index (SSTI) of the equatorial East Pacific.
Calculation of HIRS/2 Channel Transmittances by the Exponential Sum Fitting of Transmission Model
Jin Xin
1996, 7(1): 96-102.
The absorption coefficient, transmittance and weighting function of the channels of HIRS/2 depend on the temperature profile which varies with the location and/or time in turn. An improved ESFT (the Exponential Sum Fitting of Transmission) model suitable for calculating the HIRS/2 channel transmittance has been obtained by adding the instrument weighting function to the ESFT model proposed by Shi Guang-Yu. With this new ESFT model, the variations of transmittance and weighting function with the temperature can be calculated efficiently. Comparing with the exact line-by-line calculations, the results obtained show that the maximum absolute error in transmittance for CO2 channels smaller than 0.0036, and that for the H2O channel is smaller than 0.0035.
Efficient and Noiseless Data Compression of Satellite Image
Wu Lenan, Wang Dachang, Zhang Qisong, Rong Zhiguo
1996, 7(1): 103-107.
Bases on the synthetical analyses of efficient and noiseless data compression methods of satellite image, a 2D-differential pulse code modulation (DPCM) predictor along with a reflex-type entropy encoder has been utilized to compress meteorological satellite image data for various gray scales noiselessly. Higher compression rate and faster execution speed obtained by the method have demonstrated its value to practice.
Applying Helicity to Analysis of Torrential Rain over the Changjiang Gorges
Wu Baojun, Xu Chenhai, Liu Yanying, Zhou li, Wei Dongsheng, Chen Lianghua
1996, 7(1): 108-112 .
The helicity was applied to analyse a torrential rain event, which was the heaviest one during 1964~1990, occurred on July 16,1982 over the Changjiang Gorges. The results show that: (1) on the vertical section chart, there was a negative minimum center of the helicity near 300 hPa; and a positive maximum center of the helicity near 600 hPa over the heavy rain area. (2) on the 300 hPa chart, the center negative minimum of the helicity was most close to the center of the main heavy rain area, the distance between them was about 60 km
Validation of the Scheme to Estimate the Intensity of Tropical Cyclone Based on Digitized Cloud Imagery and Its Application
Fan Huijiun, Li Xiufang, Yan Fangjie, Hu Zhibo
1996, 7(1): 113-117.
The intensity of tropical cyclone (ITC) estimated by digitized cloud imagery is compared with that observed by aircraft weather reconaissance from Guam and by the wind data from the landing tropical cyclones. It is shown that the mean absolute error of this scheme is less than 3m· s-1. In the paper, the operational experiments in 1994 are given. The results show that the scheme can basically meet the needs in daily operations for analyzing and forecasting tropical cyclones.
The Relationship Between Ozone Variation in the Stratosphere over Antarctic Syowa Station and Trihydrate Condensation Temperature
Zhao Yongjing, Kong Qinxin, Wang Gengchen
1996, 7(1): 118-123 .
Based on the ozonesonde and rawinsonde data observed at Syowa station in Antarctica the relationship between the ozone variation on the isobaric surfaces of 20, 30, 50, 70, 100 and 150 hPa and nitric acid trihydrate (NAT) condensation temperature is analyzed and a general feature of ozone variation in Antarctica is given.
The Freezing Damage of Citrus of Hubei Province in 1991 and the Division of Freezing-Avoiding Cultivation
Qiao Shengxi, Wu Yijin
1996, 7(1): 124-128.
By examining the relationship between decreasing rate of orange yield per unit area in 1992 and the minimum temperature in December 1992 in various regions of Hubei Province, it is found that there is an exponential correlation. So, the relationship between the freezing damage of citrus and the minimum temperature can well be explained. By using Gumbel distribution, the minimum temperature once every 5, 10, 20, 25 and 50 years are calculated for 59 stations. Furthermore, according to various minimum temperature once in a decade indifferent regions of Hubei Province, the area-division between optimum, sub-optimum and no-optimum for planting orange in Hubei Province is given. Therefore, the scientific basic for freezing-avoiding cultivation is provided.