Vol.2, NO.4, 1991

Display Method:
Determination of Thermal Diffusivity of Soil and Its Application
1991, 2(4): 337-345.
In this paper, field measured values of soil temperature in four different soil conditions were used to calculate the apparent diffusivities by use of six methods, and the characteristics of every method and the quantity and quality of data required for calculating the thermal diffusivity of soil were analysed. These results show that four of the six methods (i. e. Amplitud, Phase, Arctangent and Logarithm) provide explicit equations for thermal diffusivities. These explicit equations only need a few measurements of soil temperature, and the calcutations are very simple, but the calculating results are erratic. Although numerical and harmonic methods must use implicit equations to calculate the apparent thermal diffusivities and need a great number of soil temperature data, their estimations are steady and reliable. The temperature gradients of soil simulated by the apparent thermal diffusivities under four different soil conditions were consistent with the field measurements, the standard diviation was less than 0.043. In this paper, that the harmonic method was also used to calculate the heat flux of four soils is with great satisfaction, as compared with the field measurements.
Numerical Simulation of a Cyclone over the Jianghuai Area and Its Mesoscale Systems
1991, 2(4): 346-354.
Fritsch-Chappell’s one dimensional cloud model is introduced and incorporated into 11-layer primitive equation model. The convective parameterization scheme proposed by Kuo (1995) is also incorporated into the model used in this paper. The difference between the two schemes is compared each other in simulating a mesoscale convective process occurred over the Jianghuai area on 12 May 1982. The two numerical simulations indicate that this one dimensional cloud model is better than Kuo’s scheme. This investigation indicates that the mesoscale cyclone is the weather system occurred in planetary boundary layer. The interaction between mesoscale cyclone convection makes the cyclone develop. But in the early period of convection, the development of cyclone is limited by influencing of downdraft and cumulus momentum transport and mixing. When convection comes to depress, the mesoscale cyclone develops
Influence of Ocean-continent Distribution in the South Part of Asia on the Formation of Asian Summer Monsoon
1991, 2(4): 355-361.
By using the numerical experiment, the influence of thermal contrasts between Africa and Arabian Sea, Indian Subcontinent and Bay of Bengal, Indochina Peninsula and South China Sea on the formation of Asian summer monsoon are studied. The results show that not only the thermal contrast between Asia continent and its surrounding ocean influence the summer monsoon formation, but the thermal contrasts between subplanetary scale ocean and continent mentioned above can also influence the structure of summer monsoon. The velocity centers of southwest monsoon over the Arabian Sea, Bay of Bengal and South China Sea and their cross-equator currents are produced by the effect of thermal contrast.
The Effects of Flow Patterns over the Northwest Pacific on Typhoon Tracks
1991, 2(4): 362-368.
Based on the analysis of wind field in the troposphere over the Northwest Pacific, the effects of the environmental flow—patterns on typhoon tracks have been examined. For seven categories of normal tracks of typhoons, the anticyclonic circulation of the subtropical high over the Northwest Pacific is believed to be the key circulation feature directly affecting the typhoon tracks. The circulation features in the westerlies, especially, distribution and variation of the upper–level westerlies play an important role in controlling the different tracks. The analysis further indicates that typhoons tend to move along the axis line of warm area of deep tropospheric layer in the direction of the thermal wind.
Determination of the Earth Surface Type by Using the AVHRR Data From NOAA
1991, 2(4): 369-374.
A method of determining the type daylight scene viewed by each resolution element of AVHRR is presented. The specification of the scene types is restricted to five categories: cloud, vegetation, non-vegetation land, ice/snow and water. The routine processing range is 10°—60°N, 75°—150°E. And, the output products were compared with the satellite cloud images at the same time. The results indicate that the method is sufficiently sensitive
Analysis of Chemical Compositions of Cloud Water and Rain Water During the Plum Rains Period in Shanghai
1991, 2(4): 375-384.
During the plum rains period of June-July, 1986, the pH values of cloud water and surface rain water were measured in Shanghai, and their chemical compositions were also analysed. These results indicate that: (1) The acidification of rain water is caused by sulphates in Shanghai; (2) The rain acidity is related to its chemical compositions. In cloud water and rain water with higher pH values (pH≥6.00), Ca2+ content is the highest, and with pH<5.00, SO content is the highest; (3) The acidification of altostratus (As) precipitation is mainly due to washout process below the cloud, and the rain acidity of nimbostratus (Ns) is mainly due to rainout process in the cloud. Further, the acidification of cloud water in Ns may be affected not only by the local air pollutants transported upward but also by the distant air pollutants through the advection transportation
The Spacial Dissipative Structure Solutions Excited by Unstable Disturbance of Benard Thermal Convection
1991, 2(4): 392-400.
In this paper, by means of the critical perturbation method, the formation of the stable solutions of spatial dissipative structure of Benard thermal convection, by incorporating the nonlinear forcing terms into the system after destruction of its equilibrium state, is examined. The results show that when the parameters are suitable values, the vertical and horizontal velocities, temperature change with the height, and the distribution of streamline on X–Z cross-section are basically consistent with the experimental results. The solutions have the characteristic of the supercritical bifurcations
Evolution of the Early Rice Yield in China and its Prediction Methods
1991, 2(4): 401-407.
Based on the data of yield and painting area of early rice from ten provinces of China, the spatial distribution and historical variation of rice production were analyzed. By using fuzzy classification method, the planting areas of ten provinces (city) can be divided into four parts. According to the harmonic analysis, the quasi-biennial fluctuation and its multiple periods were found; and the influences of temperature and precipitation on early rice yield were analyzed by use of regression integral method. During the period of experimental prediction operations from 1987 to 1990, the better results were obtained synthesizing the methods of the harmonic analysis, atmospheric model, temperature-precipitation model experts system.
Diagnostic and Comparative Analysis of the Atmospheric Entropy Changing Fields of Typhoon Heavy Rain Process
1991, 2(4): 408-415.
With the aid of the atmospheric entropy balance equation, the diagnostic and comparative analyses of the entropy reduction motion under the action of the negative entropy flow during the typhoon heavy rain have been conducted. The results are as follows: (1) The large-scale heavy rain caused by typhoon corresponds with intense and negative entropy change. So it is better than the conventional synoptic method to resolve the heavy rain areas. (2) The interaction between synoptic systems of the mid and low-latitude belts can be clearly represented in the confluence of negative entropy changes which provide a sign of the intense and hard rain processes or hardstorm rainfall affected by the typhoon far from rain area. (3) It can be explained by the equation of entropy density variation that the genesis and development of synoptic system in the rain area are associated with the physical process of the atmospheric entropy reduction resulted from precipitation. (4) The effect of atmospheric entropy divergence, especially in mid- and upper-levels, on the occurrence and maintenance of heavy rain is as important as heating, even more important.
A Study of Cross-equatorial Flow into South Indian Ocean in the Lower Troposphere During the Winter
1991, 2(4): 416-422.
The cross-equatorial flow that comes from the Northern Hemisphere into the South Indian Ocean in the lower troposphere during the winter has been investigated using grid point wind data at 850 hPa and the data geopotential height field at 500 hPa during 1980—1987. It points out that there are four channels of cross-equatorial flow coming from the Northern Hemisphere near the equatorial area from 35°E to 135°E and they are characterized by considerable annual and interannual variations. The four channels of cross-equatorial from mainly come from the northeast monsoon of continental of continental cold highs ranging from Arabian peninsula through East Asia, the intensity of flow depends on the northeast monsoon activities
A Multiple-layer Weighted Mean Steering Method of the Typhoon Track Forecast
1991, 2(4): 434-439.
According to the calculation and analysis of many cases, four sets of regression equations of typhoon track forecast, which are derived from the weighted mean steering flows of the pressures from surface to 500 hPa and surface to 300 hPa levels, are established. The forecast experiments show that the equations have better prospect for predicting for predicting typhoon tracks in middle and lower latitudes. The bases and results of the forecast method are discussed in detail in the paper.
An Analog Method of Phase Space for Long-range Forecast
1991, 2(4): 440-444.
By way of the calculation of fractal dimension D, a phase space with d-dimensions (d=INT (l+D)) is established using a time series. Then, the analog theory of statistical forecast is applied to the phase points of phase space, and it is hypothesized that the mode of state at the nearest phase points after evolution time T is equal to each other. A lot of trial studies based on the hypothesis show that the forecast accuracy of anomaly sign can reach 60%—70%, and the relative error is generally less than 8%