Current Issue

• A NUMERICAL SIMULATION OF CHARACTERISTICS OF LAND-SURFACE PROCESS UNDER INTERACTION OF OASIS AND DESERT IN ARID REGION
• ZHANG Qiang;ZHAO Ming
• 1998 Vol. 17 (4): 335-346. 
• Abstract ( ) PDF (483KB) ( )
• Using the developed two-dimensional mesoscale model of soil-plant-atmosphere continuum, the characteristics of land surface process and energy transport under interaction of oasis and desert are simulated. The results of the simulation test are not only used partly to test and verify the observational results of land surface process, but also to remedy the defects of the observation results. The diural variation of soil water and physical variables of leaves surface, the spatial distribution of surface energy budget, and the characteristics of land surface process are further obtained. The range and extent of the influence of oasis on the downstream desert are recognized to a certain extent.

• THE RADIATIVE CHARACTERISTICS OF ATMOSPHERIC DUST OBSERVED FROM SATELLITE
• WEI Li;SHEN Zhi-bao
• 1998 Vol. 17 (4): 347-355. 
• Abstract ( ) PDF (338KB) ( )
• The method for estimating planetary albedo and outgoing longwave radiation at the top of atmosphere by using of NOAA11-AVHRR data was decided. The AVHRR data set obtained from 10 times NOAA 11 satellite just overpassing the HEIFE area in March to May, 1991 were analysed. The results show that AVHRR data is available for studying the influence of atmospheric dust on the radiative energy budget in the earth-atmosphere systerm. The reflectances of AVHRR visible and near infrared channels, and the brightness temperature difference between the channel 3 and 4 are sensible to the atmospheric dust:the backscatter and planetary albedo of the earth-atmosphere systerm are increased with the increasing atmospheric turbidity, but the outgoing longwave radiation at the top of atmosphere is decreased, which seems depended on the surface temperature.

• ANALYSIS OF TURBULENT CHARACTERISTICS IN ATMOSPHERIC BOUNDARY LAYER OVER THE QINGHAI-XIZANG PLATEAU
• MIAO Man-qian;CAO Hong;JI Jing-jun
• 1998 Vol. 17 (4): 356-363. 
• Abstract ( ) PDF (356KB) ( )
• The meteorological exploration data collected from the Qinghai-Xizang Plateau are used to analyse the variation of bulk transport coefficient C _D and C _H. The results show that the values of C _D and C _H are much higher on the Plateau than those on plain area, and the daily ranges are also higher, while the dynamical roughness lengths are almost the same. The main reason seems that the Qinghai-Xizang Plateau is located in inland, large variation of air temperature caused strong daily variation of atmospheric stratification. Secondly, complicated terrain enhances mechanical turbulent movement. The boundary layer height over the Qinghai-Xizang Plateau is also higher than that on plains.

• SOME COMPARTIVE ANALYSES OF PRECIPITATION OVER NORTHWEST CHINA DROUGHT AREA AFTER THE QINGHAI-XIZANG PLATEAU HEAVY- AND LIGHT-SNOW YEARS
• WU Tong-wen;QIAN Zheng-an;LI Pei-ji;SONG Min-hong;MA Xiao-bo
• 1998 Vol. 17 (4): 364-372. 
• Abstract ( ) PDF (332KB) ( )
• To analyze the relationship between the winter and spring accumulated snow over the Qinghai-Xizang Plateau(QXP) and the subsequent precipitation over NW China Drought Area(hereafter the NWCDA),a comparison analysis between the QXP accumulated snow depth feature and surface thermal condition as well the May~September precipitation over the NWCDA in heavy and light snow years has been conducted,utilizing the accumulated snow depth,rainfall,departure index of surface air temperature and subground temperature during the period of 1957~1990. The main conclusions are:(1) There is weak inverse correlation between the QXP accumulated snow depth in winter and spring and the following May~September rainfall over the NWCDA in heavy and light snow years.(2) There exists clear difference between the QXP accumulated snow depth feature and surface thermal condition in early winter of heavy and light snow years.(3) From the abnormality of the QXP surface themal condition in early winter, the prediction of following May~September precipitation over the NWCDA can be made.

• COMPUTATION OF NET RADIATION OVER THE QINGHAI-XIZANG PLATEAU IN WINTER UNDER SNOW COVER
• CAO Mei-sheng
• 1998 Vol. 17 (4): 373-380. 
• Abstract ( ) PDF (281KB) ( )
• Based on the charts of snow depth over the Qinghai-Xizang Plateau monitored by SMMR,the evolution of snow albedo with its depth and the algorithms of climatic computation on the components of radiation balance, which were summed up based on the data measured at the heat sources observation stations on the Plateau from September 1982 to August 1983, the surface net radiation over main of the Plateau was calculated at temporary and spatial resolution on dekad and 0.5°×0.5° latitude-longitude cell, respectively, for November to February during 1978/1979 to 1986/1987. The results show that it will be altered from positive to negative in December, while the monthly mean of sunshine percentage is 73 and the snow cover percentage over 60.

• RESEARCH ON DROUGHT AND FLOOD INDICES IN THE NORTHWEST CHINA
• ZHANG Cun-jie;WANG Bao-ling;LIU De-xiang;CAI Zhong-lan
• 1998 Vol. 17 (4): 381-389. 
• Abstract ( ) PDF (290KB) ( )
• By use of the monthly precipitation data of 83 sampling meteorological stations in the Northwest China from 1961 to 1990,the anomalous percentage of precipitation, the standard variable of precipitation and the Z-index were tested and compared with each other. Grades of flood/drought for Z-index were again determined, the modified Z-index was recognized to be optimum for differentiating station flood or drought in the Northwest China. On this basis, flood and drought differentiating indices were given for the Northwest China.

• ANALYSIS ON TURBULENT CHARACTERISTICS IN THE ATMOSPHERIC SURFACE LAYER AND SOME EXPLORING IN THE APPLICATIONS OF DIFFUSION MODELING
• LIU Heng;JIANG Wei-mei
• 1998 Vol. 17 (4): 390-396. 
• Abstract ( ) PDF (248KB) ( )
• The intensities, correlation, scales and spectra of velocity components of turbulence in the surface layer atmosphere in the suburb of Beijing are investigated using the data from an u, v, w anemometer at the height of 47m and 120m. Based on the observations, some questions in the application of the diffusion model in the atmospheric environment pollution are discussed. The results indicate that under certain conditions the supposing:(1) σ _u=σ _v;(2) σ _u, σ _v, σ _w are constant;(3) T _EU≈ T _EV is reasonable.

• A STUDY ON THE CHAOTIC CHARACTERISTICS OF THE ATMOSPHERIC BOUNDARY LAYER TURBULENCE OVER OASIS AND DESERT IN HEIFE AREA
• GAO Zhi-qiu;WANG Jie-min
• 1998 Vol. 17 (4): 397-402. 
• Abstract ( ) PDF (222KB) ( )
• The characteristic quantities describing chaos in respect of correlation dimension, Lyapunov exponents and Kolmogorov entropy are calculeted and analyzed by means of the horizontal wind( u) data observed at Zhangye and Desert stations. Results show that the atmospheric turbulence is a chaotic motion over oasis and desert regions, some conclusions are given and discussed.

• THE ANALYSIS OF THE DISCHARGING PROCESSES OF TRIGGERED LIGHTNING FLASHESⅡ. PROCESSES BETWEEN THE RETURN STROKE
• YAN Mu-hong
• 1998 Vol. 17 (4): 403-411. 
• Abstract ( ) PDF (371KB) ( )
• In this paper, the characteristics of the discharge processes between the return stroke of artificially triggered lightning flashes were analysed by use of electrical field, current data, and digital photographic obtained with a high-speed CCD camera system(frame rate 1 000F/s). The results show that "Non-continuous current stage" was a important condition for triggered the dart-leader and the subsequent return stroke. The " M" component between the return stroke can falled into three kind of "the positive slow breakdown"、"negative slow breakdown" and "positive fast breakdown",especially "positive fast breakdown" can triggere the subsequent return stroke. The results also show that the electric field change wave of the Non-standard dart-leader namely "even change wave" depend on the branches structure of the lightning channel namely non-uniformity of the charge distribution close by the lightning channel.

• OBSERVATION AND ANALYSIS OF INFLUENCES OF ARTIFICIALLY TRIGGERED LIGHTNING ON CHARACTERISTICS OF THUNDERSTORM
• ZHANG Yi-jun;YAN Mu-hong;QIE Xiu-shu;ZHANG Hong-fa;DONG Wan-sheng;LIU Xin-sheng
• 1998 Vol. 17 (4): 412-419. 
• Abstract ( ) PDF (292KB) ( )
• The ground electric field, precipitation and radar data were analyzed and the influences of artificially triggered lightning on characteristics of thunderstorm were discussed. The results indicate that electric characteristics of thunderstorm may be influenced by artificially triggered lightning. For this thunderstorm, there was not any lightning during 20min and electric field on the ground was reduced after two artificially triggered lightning. The precipitation increased after artificially triggered lightning and maximum value of precipitation lag the artificially triggered lightning by a time of about 6min. From the radar data, we know that higher Z _H areas moved from middle to bottom of thunderstorm and higher Z _DR areas with maximum value of -1.6dB moved toward the bottom of thunderstorm after artificially triggered lightning. The reason which caused these changes were discussed.

• A SYNOPTIC CLIMATOLOGICAL ANALYSIS OF ATMOSPHERIC GRAVITY WAVES IN THE MIDDLE PART OF GUIZHOU
• ZHAO Cai;TIAN Ying;ZHOU Tao
• 1998 Vol. 17 (4): 420-426. 
• Abstract ( ) PDF (258KB) ( )
• Using continuous data detected by single detector for 16 months since 1994 and the dynamic spectrum analysis method, a synoptic climatological analysis of activities of atmospheric gravity waves(AGWs) in the middle part of Guizhou province were made. The results show:(1) AGWs in winter-spring are stronger than that in summer-autumn obviously;(2) The characteristic of diurnal variation of AGWs is that the waves with longer periods are stronger in midday and the waves with shorter periods are stronger in midnight;(3) The characteristics of distribution of AGWs spectra are that the strength of waves with periods 140~160min and shorter than 20min are weaker, the strength of waves with periods 50~60 min and longer than 320min are stronger;(4) The main factors which influence on strength of AGWs are activities of cold air and severe convections;(5) The pressure waves produced by atmospheric tide are also reflected in the long period spectrum band of AGWs.

• RESEARCH OF FLOOD/DROUGHT FORECAST AND COMPOSITE FORECAST METHODS FOR THE SEASON AND YEAR IN SHAANXI PROVINCE
• WANG Yu-xi;TIAN Wu-wen;YANG Wen-feng;LI Zhi-jia;DONG Ya-fei;YANG Yue-juan
• 1998 Vol. 17 (4): 427-436. 
• Abstract ( ) PDF (336KB) ( )
• Flood/drought is the main climitic disaster in Shaanxi province. As a matter of experiences in weather forecast,forecast factors are selected,precipitational characters are analysed and flood/drought indicatrixes are detemined by analysing geographical environment,climitic background,turning pattern and abrupt variation of large scale weather,solar activity and astronomical factor. Finally, using artificial nervous unit network,Chebyshev polynomial and variance analysis etc.. A composite forecast method forecasting the season and year flood/drought in Shaanxi province is found. By test forecast in 1994, accurate rate reaches to 83.3 percent and good effect is obtained.

• INFLUENCE OF THE SOIL WATER CONTENT ON THE ESSENTIAL ELEMENTS TO CONSTITUTE THE YIELD OF WHEAT IN THE LOESS PLATEAU REGIONS
• DENG Guo-lun;WAN Xin;DENG Zhen-yong;FANG De-biao
• 1998 Vol. 17 (4): 437-442. 
• Abstract ( ) PDF (201KB) ( )
• The relationship between the soil water content from the jointing of wheat to the heading and numbers of grains of every ear of wheat is the closest in the dry farming regions of the Loess Plateau. The relationship between the soil water content from the stages that wheat is in the milk to milky maturity and the weight of all grains of every ear is also the closest. Wheat is easily influenced by environment factors for two periods mentioned. The influence of the base soil water content before sowing of seeds on yield of wheat is evident. In the wake of wheat growing up, the soil water content in deep layer will play an important role.

• THE INFLUENCES OF WINTER-SPRING'S AIR TEMPERATURE CHANGE ON GRASSLAND PRODUCTIVITY IN HAIBEI AT QILIAN MOUNTAIN
• LI Ying-nian;ZHANG Jing-hua
• 1998 Vol. 17 (4): 443-446. 
• Abstract ( ) PDF (159KB) ( )
• Grass production of Alpine Meadow is highly negatively correlated with winter-spring air temperature of Haibei at Qilian mountain. The rising of winter-spring air temperature leads to the decrease of grassland production, and this is maily because that the rising of winter-spring air temperature makes winter frozen layer thinning and soil water lossing seriously. At the beginning of nutritional growing period,faced with the most severe "drought" pressure and deficient natural precipitation in North China, the requisite water for grass growing and developing are limited, and the rise of grassland production is ultimately limited. analysing the winter-spring air temperature by EOF, a regression model is set for the effects of air temperature on grass production. The regression results show that the fitting rate is relatively high, the results of prediction for 1995 show the model's erros is small,and the effect is very good.