Current Issue

• NUMERICAL SIMULATION OF THE EVOLUTION OF RIVER VALLEY BREEZE
• Wang Hao
• 1993 Vol. 12 (1): 1-11. 
• Abstract ( ) PDF (751KB) ( )
• The evolution process and the spatial structure of river valley circulation without synoptic scale wind have been predicted by using a non-hydrostatic numerical model including the prediction of surface temperature both on land and on water body.Both valley and water body induced the circulation over a river valley.The results show that the combination of lake-land breeze and slope wind circulation produces a more complex flow pattern.The evolution of the lake-land breeze always delays that of slope wind.The topography and water body strengthen the land breeze on water body surface of river valley during nighttime,but topography confines the development of the lake breeze,and the speed of the lake breeze on the water body surface of river valley is always light during daytime.

• THE PERSISTENCE AND THE CHARACTERISTICS OF OSCILLATION OF SOIL TEMPERATURES IN DIFFERENT DEPTHS
• She Jun;Zhang Banglin;Chou Jifan
• 1993 Vol. 12 (1): 12-17. 
• Abstract ( ) PDF (392KB) ( )
• First,by using iterative EOFs expansion,the data of soil temperatures in 0.8m and in 1.6m are,retrieved,then the persistence and the characteristics of oscillation are studied.Results show that:there are durations of 3-5 months on soil temperature in 0.8 m and about 6 months in 1.6 m,significant periodic oscillations of about 12 months which attribute 24.4% and 32% to total variance on soil temperatures in 0.8m and 1.6m respectively.The spectral variance of longer periodic oscillation is higher in 1.6m than that in 0.8m.But the spectral variance of shorter periodic oscillation is lower in 1.6 m than that in 0.8 m.

• CLIMATOLOGICAL CHARACTERISTICS OF TEMPERATURE VARIATION IN LANZHOU
• Li Dongliang;Pen Suqing
• 1993 Vol. 12 (1): 18-26. 
• Abstract ( ) PDF (567KB) ( )
• The evolution characteristics of monthly mean temperature are analysed by using the monthly mean temperature data from 1951 to 1990 in Lanzhou.The main characteristics are as follows:the annual mean temperature was higher in the early fifties,then temperature dropped slowly until the sixties and the temperature rose fluctuantly in the late sixties.The temperature was the positive departure from 1985 to 1990.In recent 40 years,temperature evolution process was a warm-cold-warm processes,the temperature rpse obviously in winter and its amplitude was rather small in summer.Comparison between the temperature in the eighties and one in the fifties,the annual mean temperature rose 0.5℃ in the eighties,it rose 2.4℃ and 0.7℃ in winter and autumn,respectively and it dropped 0.3℃ and 0.2℃ in summer and spring,respectively.There are better persistence and the periodicity for the temperature variation in Lanzhou.Its variation is affected by the large-scale circulation,sunspot,urban devolopment and urban heat island effect.

• THE INFLUENCE OF GEOGRAPHY ON INTERANNUAL VARIATION OF LARGESCALE FLOW PATTERNS
• Wang Baoling;Luo Zhexian
• 1993 Vol. 12 (1): 27-33. 
• Abstract ( ) PDF (438KB) ( )
• In this paper,it is investigated that the influence of geography on interannual variation of large-scale flow patterns arised from external interannual thermal forcing and internal dynamical processes by means of low-order spectral model of barotropic vorticity equation.More than 60 numerical experiments whose integration time is larger than 30 model years are performed for every case that orographic factor is introduced into the model or not.When orographic factor is considered in the model,in certain parametric region,the computed results show that (1) the interannual variation of large-scale flow pattern can be arised from internal dynamical processes;(2) the amplitudes of flow patterns become small obviously and their periodes become long;(3) the range of amplitude-jump of flow patterns interannual variation is decreased along with gradual changes of thermal forcing parameters.

• A NEW TOOL TO ANALYSE THE PRECIPITATION PROCESS——DURATION INTENSITY FUNCTION
• Zhang Xuewen;Ma Li
• 1993 Vol. 12 (1): 34-39. 
• Abstract ( ) PDF (420KB) ( )
• In order to improve the analysis and forecast on precipitation process,we introduce a new tool to express the relationship among the precipitation area,precipitation duration and its depth.This is a bivariant function named "Duration Intensity Function".For any precipitation process,if we have enough concern data,it is not difficult to work out its Duration Intensity Function.In this paper,we gave how to get this function from the concern data and to work out the figure of this function by numerical method.We point out this function is a tool to link the entropy principle with precipitation phenomenon.

• INFLUENCE OF LAND-SEA DISTRIBUTION ON GENERAL CIRCULATION OF ATMOSPHERE
• Ma Xiaobo;Gao Youxi;Li Ci
• 1993 Vol. 12 (1): 40-47. 
• Abstract ( ) PDF (545KB) ( )
• In this paper,temperature and geopotential height (pressure) departures along latitude are calculated by using ten-year mean (1963,5-1973,4) climatic data of CFDL in USA and influence of land-sea distribution on general circulation of atmosphere is discussed.It is shown that land plays the main role,the biggest variation of influence of land-sea distribution on general circulation of atmosphere appears in the north hemisphere.The center of variation in the north hemisphere is over the Eurasian continent.The stronggest influence of land-sea distribution on general circulation of atmosphere appears in winter,and the smallest in summer.

• THREE STATISTICAL MODELS FOR THE VERTICAL DISTRIBUTION OF THE ATMOSPHERIC REFRACTIVE INDEX OVER NORTHWEST REGION OF CHINA
• Dai Tiepi;Zhang Peichang;Shen Peilu;Jiang Hangdong
• 1993 Vol. 12 (1): 48-55. 
• Abstract ( ) PDF (546KB) ( )
• In this paper,conventional radiosonde data from three representative observational stations in northwest region of China are used to establish three statistical models for the vertical distribution of the atmospheric refractive index based on the atmospheric refractive theory and the statistical approach.Results show that the current 4/3 effective earth's radius model has the lowest accuracy and can be used only below the height of 1 kilometer over the surface to guarantee sounding accuracy while the modified effective earth's radius model has the greatest accuracy.It is found that accuracy can be guaranteed by using the exponential model when below 3 kilometers over the surface.

• SYNOPTICAL AND CLIMATOLOGICAL ANALYSIS OF THE CYCLONE AND ANTICYCLONE IN THE LOWER ATMOSPHERE OVER THE EAST ASIAN CONTINENT IN JANUARY AND JUNE
• Xu Baoyu;Luo Siwei
• 1993 Vol. 12 (1): 56-66. 
• Abstract ( ) PDF (756KB) ( )
• In this paper,we have analysed the synoptical and climatological feature of the cyclone and anticyclone on the sea-level,850 hPa and 700 hPa charts in the Eurasian continent in January,April,July and October of 1976-1985.The main results are:(1) Except for Qinghai-Xizhang Plateau,the lee cyclogenesis and the windward anticyclogenesis over the Asian mountains are the same as the general rule.(2) There are five frequent centers of the low pressure whose main features are that from sea level to 700 hPa their frequencies increase rapidly.The frequent center for the west of the Qinghai-Xizang Plateau corresponds to the cut off low in the upper atmosphere which always appears and the other four centers of weak low pressures are generated by local,which always move eastward and disappear rapidly.The southwest vortex over Sichuan Province is typical one of them,which appears rare at surface (sea level) but about once a day on 700 hPa.Its frequent center is large for all four seasons in which it is larger in spring and autumn and less in summer,but vortex is stronger in summer.(3) In January on the sea level cold high over the west mountains of the Mongolia is the strongest with the largest frequecy but on 850 hPa it decreases rapidly in intensity and frequency.The smaller scale anticyclone over the region of Shanxi,Gansu and Ningxia Provinces-northeast part of the Qinghai-Xizang Plateau is the strongest with maximum frequecy.The sea level elevation of these areas approach to 850 hPa and their analysed results should be more able to represent the real situation of the surface but the analysis on the sea level chart may make more mistake due to the correction from the surface to sea level,i.e.the intensity and frequency of the Mongolian High on the sea level may not be true enough and some mechanism of pressure increase may exist around Lanzhou-northeast part of the Qinghai-Xizang Plateau.

• INDIRECT MEASUREMENT OF ARTIFICIALLY TRIGGERED LIGHTNING DISCHARGE CURRENT AND ITS CHARACTERISTIC ANALYSIS
• Zhou Zhonghua;Liu Xinsheng
• 1993 Vol. 12 (1): 67-76. 
• Abstract ( ) PDF (667KB) ( )
• Magnetostatic field at the close range of artificially triggered lightning was measured by a magnetic field antenna system.The characteristic of triggered lightning current deduced from the magnetic field antenna system is consistent with that of direct current measurement by coaxial shunt system,electric field charge measurement by slow antenna and relative luminosity measurement by photocell system.Triggered lightning for storms in Yongdeng,Gansu is initiated with the upward going negative leader,under the influence of the dominant lower positive charge of storm,which propagates upwards followed by continuous current process.The speed of leader propagation was calculated from synchronous measurements of close magnetic and electric field and also from synchronous measurements of electric field change at two stations,results being the order of 10 ⁵m/s.The triggered lightning lasts a few tens of milliseconds with the neutralized change of a few coulombs.

• EFFECT OF "COLD ISLAND EFFECT" ON ATMOSPHERIC DIFFUSION OVER OASIS IN ZHANGYE REGION
• Liu Yanxiang
• 1993 Vol. 12 (1): 77-83. 
• Abstract ( ) PDF (428KB) ( )
• In this paper,we studied the stratification characteristics of wind and temperature fields in boundary layer in Zhangye region by using the data of atmospheric environment observation in Summer of 1990.It shows that there is a inhibition effect of cold island effect in oasis on atmospheric diffusion.

• HAIL CLOUD RECOGNITION AND ITS RESULTS VERIFICATION BASED ON RADAR ECHOES DATA BY USING PRINCIPAL COMPONENT ANALYSIS
• Li Zuoyong;Liu Shaonong;Deng Xinmin;Zhang Huijun
• 1993 Vol. 12 (1): 84-89. 
• Abstract ( ) PDF (409KB) ( )
• This paper presents a comprehensive recognition formula of hailstorm cloud by using principal component analysis.The approach establishes correlation coefficient matrix of recognition indexes with historical data of radar echoes in a certain location.Then factor loads can be determined by using principal component analysis and the weights of recognition indexes are derived by load matrix and correlation coefficient matrix.Finally,the discrimination formula of hailstorm cloud is derived.The discrimination formula established based on historical radar echoes data in Chengdu by this method is applied to forecasting test of Chengdu and results verification of Luzhou.The recognition results are better than comprehensive probability method.It shows the method is suitable for hail recognition.

• ARTIFICIALLY TRIGGERED LIGHTNING AND THE CORN VARIATION
• Liu Xinzhong;Chen Mingli;Fang Guangseng;Wang Huaibin;Yuan Yi
• 1993 Vol. 12 (1): 90-94. 
• Abstract ( ) PDF (1675KB) ( )
• In this paper,the artificially triggered lightning in the maize field during the earing and flowering stages was discussed.The change of the electromagnetic field near the stroke points was measured.It was found that the rates of two earing and the earing of male flower of the maize near the stroke points and the thoroughfare of igniting wire of artificially triggered lightning in the crop field are much greater.They are 4 times and 2.8 times higher than in common one respectively.The phenomenon is the same as that of mutation induced by physical factors.If it can repeat and the mutation can inherit,it must be one of the evidence of the evolution of life in nature.

• SOME ADVANCES ON THE RESEARCH OF PLATEAU MONSOONS (A REVIEW)
• Tang Maocang
• 1993 Vol. 12 (1): 95-101. 
• Abstract ( ) PDF (544KB) ( )
• In this paper,the researches of Plateau Monsoons during the past 30 years were described.It is pointed out that Plateau Monsoon is a dominant factor for the formation of Plateau climate,that is a high effective lever transformed the heat energy to the kinetic energy over the Plateau region.The development of the Plateau Monsoon may be divided as 3 stages in the entire period of Plateau arising.

• EFFECTS OF SOLAR RADIATION AND CELL VOLTAGE ON PYRGEOMETER PERFORMANCE
• Zhou Yunhua;Xiang Yueqin
• 1993 Vol. 12 (1): 102-110. 
• Abstract ( ) PDF (550KB) ( )
• The effect of solar radiation and cell voltage uncertainties on Eppley Pyrgeometer performance is observed and discussed.(1) By means of exposing and shading the dome from the sun alternatively the effect of solar heating the KRS-5 dome is showed.During the period of noon on clear sky output of the pyrgeometer as the dome exposed is over 10% higher than the values as the dome shaded.The increase,Δ L,in pyrgeometer outputs caused by solar heating of the dome can be estimated empirically with the formula,Δ L=0.045 Q, Q is solar radiation.This formula can be used to correct the output of pyrgeometer to obtain the atmospheric radiation.(2) The effect of battery voltage uncertainty on output of pyrgeometer is studied.The error caused using of 1.5V battery instead of 1.35 V mercury cell is calculated.This error is not only dependent on the battery voltage but also the thermopile cold junction temperatures.So it can not be corrected.(3) For the deterioration of KRS-5 dome the instrument sensitivity is not often matched with the battery voltage.This is a main source caused the error in measurements.

• DATA TRANSMISSION SYSTEM BY USING WEATHER RADAR TO MEASURE RAINFALL IN BAJIAZUI RESERVOIR AREA
• Wang Zhijun;Xu Baoxiang;Su Debin;Wang Jun;Song Xinmin;Li Xiaoping;Jia Wei
• 1993 Vol. 12 (1): 111-114. 
• Abstract ( ) PDF (328KB) ( )
• Remote measurements of rainfall intensity and areal precipitation by using weather radar are a problem that meteorological scientists have researched with an effort.With the rapid developing of computer,it is possible that by using weather radar to measure rainfall intensity and areal precipitation in higher accuracy.We have used a dual linear polarization radar which was located in Baimiao radar station of Pingliang to measure rainfall in Bajiazui reservoir area and the data measured are transmitted to the Flood Prevention Office in Xifeng city by radio,then they are displaied repeatedly on color screen of computer in the Flood Prevention Office.In this paper,we introduce the potential and function of the system.