Current Issue

• Some Remarks on the Predictability of Atmospheric Processes
• BIAN Jian-chun;YANG Pei-cai
• 2003 Vol. 22 (4): 315-323. 
• Abstract ( ) PDF (381KB) ( )
• From the view of nonlinear theory,the three types of atmospheric motions issued by von Neumann(1955) are re-explained,and it is pointed out that in the prediction of atmospheric processes there exist two kinds of uncertainties-uncertainties in initial conditions and uncertainties in external forces,which become the studied objects of the first kind prediction and the second kind of prediction,respectively.In this paper,the objectivity in the predictability of atmospheric processes is emphasized.Owing to the complexity of atmospheric motions and the limitation of observation skill and knowledge of human being,the predictabilities of atmospheric processes can only be estimated.For example,the upper limit of daily weather is estimated to be about two weeks.The sources of prediction errors-the uncertainties in initial conditions and the imperfectability of prediction models are analyzed,and it is emphasized that the essential reason of prediction error growth is the chaotic character of atmospheric motions.

• Numerical Experiment for Effect of the Reference Atmosphere and Mass Conservation Scheme on Monthly Forecast in Climate Model
• LUO Mei-xia;CHEN Jia-bin;ZHANG Dao-min
• 2003 Vol. 22 (4): 324-328. 
• Abstract ( ) PDF (268KB) ( )
• In order to evaluate the ability of the reference atmosphere and the atmosphere mass conservation scheme to improving monthly forecast in the spectral climate model of national climatic center.The above-mentioned schemes are introduced to the spectral climate model respectively.For the cases on 1 and 10 July 1992,we have performed up to 30-day integrations for each scheme.Then predicted monthly mean heights are compared with the observations.Furthermore the effect of different schemes on anomaly correlation coefficient(AC) and the root mean square error(RMS) of heights are discussed.The results show that monthly mean forecast quality can be improved in both schemes mentioned above,but the improvements in the reference atmosphere scheme are more obvious than that in the atmosphere mass conservation scheme.

• An Improved Scheme to Deal with Non-Simultaneous Doppler Radar Observation during Three Dimensional Wind Field Retrieval
• LIU Shun;QIU Chong-jian
• 2003 Vol. 22 (4): 329-336. 
• Abstract ( ) PDF (462KB) ( )
• The MANDOP three dimensional wind retrieval method is modified.A new scheme is added to deal with non-simultaneous weather Dopplerradar observation.In the new scheme,assuming that wind field evolution is linear during retrieval period.Two three dimensional wind fields at the beginning and the ending of two volumes scan are retrieved.Hence the retrieved variables are consistent with the observed variables in objective function.The scheme is tested by simulated datasets and supercell storm observation.Results show that the new scheme can improve wind retrieval.

• Climatic Characteristics of Annual Sand-Dust Storm Days in Northern China and Its Response to Surface Sensible Heat in Spring of Qinghai-Xizang Plateau
• LI Dong-liang;ZHONG Hai-ling;WEI Li;Lü Lan-zhi
• 2003 Vol. 22 (4): 337-345. 
• Abstract ( ) PDF (1088KB) ( )
• 185 conventional meteorology observation stations data of the annual sand-dust storm days from beginning to 2000 were selected,and then the climatic characteristics of sand-dust storm in northern China and its response to the abnormal sensible heat of surface over Qinghai-Xizang Plateau in the spring of recent 50 years were analyzed.The results show that the sand-dust storm days have a better spatial coherence in general.There are five sand-dust sources in Gansu corridor,southern rim of south Xinjiang basin,Alxa plateau,Eerduosi plateau and Hunshandake sandlot.By comparing with the interdecade variability of the sand-dust storm days in recent 50 years of China,the negative trend is found.The numbers of sand-dust storm days in 1990's are the least during the recent 5 decades.From the end of 20 century to the beginning of 21 century,the sand-dust storm days have an obvious increasing trend in China.The further research shows that the sand-dust storm days in China have well relation with the surface sensible heat in spring of Qinghai-Xizang Plateau.When the EOF1 mode of the surface sensible heat over Qinghai-Xizang Plateau in spring occurs,the sand-dust storm days in northern China is obviously more than normal year.

• The Structure of Atmospheric Boundary Layer over Valley City and Its Transfer Ability
• ZHANG Qiang;Lü Shi-hua;ZHANG Guang-shu
• 2003 Vol. 22 (4): 346-353. 
• Abstract ( ) PDF (1030KB) ( )
• Using the data including wind speed,wind direction,temperatureand humidity of atmospheric boundary layer observed with tethered balloonin fieldexperiment of Lanzhou that is supported by "study on atmosphere pollution and its countermeasureof Lanzhou city" which is a Gansu province-Chinese Academy of Science joint researchproject,as well as temperature in surface layer observedbyAutomatic Meteorological Station(AMS) and surface global radiationgotten by formal meteorology station,the structuresof wind speed,wind direction,temperatureand humidity of atmospheric boundary layerare analyzed,the dynamic ruleof character,intensity and distribution of inversion maintaining in daytimeand nightare revealed,and the environmental factors of forming the special inversion in Lanzhou valleyare pointed out.Finally,the characteristicsof the bulk stability of atmospheric boundary layer and Froude numberunder condition of present local microclimate and terrain ofLanzhou cityare given out,and from this the transfer abilitiesof atmosphericboundary layer by turbulence motion and horizontal advectionin Lanzhou city are discussed.

• A Study on Scattering Properties of Aerosol Particle over Xigu District of Lanzhou
• HU Bo;ZHANG Wu;ZHANG Lei;CHEN Chang-he;FENG Guang-hong
• 2003 Vol. 22 (4): 354-360. 
• Abstract ( ) PDF (1584KB) ( )
• The atmospheric aerosol scatteringcoefficientand its relation to air pollution were analyzed by using the Integrating Nephelometer and PM ₁₀ data in Xigu district of Lanzhou cityfrom January 31 to February 3,2002.The results show that the daily variation of partical scatteringcoefficient(λ=550nm) presents a curve of bi-peaks,the maximum value appears at 11:00~12:00 and 22:00,respectively.The range of scatteringcoefficient variesfrom 1.34×10 ^-4 to 3.3×10 ^-3m ^-1.The concentration of PM ₁₀ and scattering coefficient have a high correlationcoefficient( r≥0.8).The variation of particle scattering coefficient is the same as that of the concentration of PM ₁₀.

• The Nonlinear Kelvin Travelling-Wave Solution with Orographic Slope
• ZHU Hong-wei;CAI Qi-fa;ZHANG Ming
• 2003 Vol. 22 (4): 361-364. 
• Abstract ( ) PDF (1669KB) ( )
• The nonlinear Kelvin travelling-wave solution with orographic slope is shown in this paper.Suppose that the orographic slope is invariable along the mountain range orientation but is variable across it,then analytic solution of the model is obtained,which is favourable for further understanding coastally mountain-trapped wave.Here the solution is compared with typical solution,where lateral boundary is perpendicular and bottom boundary is horizontal surface.It is found that wave speed and perturbation amplitude of the former is smaller than the latter;it is also analogous in some ways to the case of real coastally mountain-trapped wave in Wuyi Mountain of southeast China.

• Real-Time Attenuation Correction for Weather Radar Reflectivity Factor
• ZHAO Heng-xuan;CHEN Zhong-rong;ZHOU Feng
• 2003 Vol. 22 (4): 365-370. 
• Abstract ( ) PDF (2040KB) ( )
• Based on the method of signal processing and the format of output data which are adopted by modern weather radar,this paper presents two real-time attenuation correction algorithms suitable for the attenuated radar reflectivity factor,which are,respectively,the basic correction algorithm and the reference target correction algorithm.And the strong and weak points of the algorithms are discussed by comparison between the simulation results produced by the two algorthms respectively.It is also described that the blind range attenuation A( r ₀) and the radar system error Δ C make an impact on the true reflectivity factor.

• Dry and Wet Climatic Changes of Western China in Recent 300 Years
• LI Yi-lin;XU Yuan;QIAN Wei-hong
• 2003 Vol. 22 (4): 371-377. 
• Abstract ( ) PDF (1009KB) ( )
• The ice core and the tree ring proxy data are employed to analyze the temporal and spacial characteristics of dry and wet climatic changes in western China in recent 300 years.The results show that in whole western China,the dry and wet climatic changes appear a significant quasi-70 year period changes.In most of the region,the quasi-30 and quasi-110 year periods are fairly significant as well.Before the year 1850 and according to the quasi-70 year period,the eastern part of the Tibet Plateau and Xinjiang region almost are in the same dry and wet phases.They can be classified into one humidity belt.Namely both humidity belts,the Xinjiang and the western part of the Plateau,have a dipole relationship.But after that year,the Xinjiang changes gradually into the simultaneous phase with the western part of the Plateau,but it is not as good as the relationship between Xinjiang and the eastern part of the Plateau again yet.In other words after the year 1850,the western part of the Plateau and Xinjiang are grouped into the same humidity belt,not the eastern part of the Plateau again,now both the west and east of Xinjiang construct a new dipole.Up to recent decade,it is likely to appear that the western and eastern parts of the Plateau change into a simultaneous phase and a new dipole is constructed with Xinjiang.But because of the boundary effects of the wavelet transform,the reliability can be doubted.Anyhow,the drift of the dipole relationship among above three regions is very interesting,it is likely the drift of climate.In the situation of quasi-110 year change,the main part of the Plateau and the Hua mountain compose one humidity belt,before the year 1850 period,the Plateau and Xinjiang take fairly the same phase;after the climatic abrupt change of the end of 19th century,the north part of the Plateau and Xinjiang show a relationship of dipole.on quasi-30 year period scale,the phase of the Plateau and Xinjiang are almost identical.

• Variational Characteristics of Some Parameters and Factors during Dusty Weather in Spring of Dunhuang
• SHEN Yan-bo;SHEN Zhi-bao;DU Ming-yuan;WANG Wan-fu
• 2003 Vol. 22 (4): 378-384. 
• Abstract ( ) PDF (997KB) ( )
• Using the observational data of Dunhuang from "Japan and China joint project on aeolian dust experiment on climate(ADEC) impact",the variation of two dusty parameters-Dust Concentration Index(DCI) and Particle Number concentration( N( d)) and the relations of friction velocity( u*),wind speed( u) and dust outbreak from ground surface in spring of 2001,2002 were analyzed.It concludes that the threshold DCI of common dusty weather is 0.2 and the threshold DCI of dust storm weather is 0.4;the thresholdfriction velocityis about 0.5 m·s ^-1 at desert and 0.3 m·s ^-1 at oasis and the thresholdwind speed is about 7 m·s ^-1 at desert and 3 m·s ^-1 at oasis.The difference of threshold friction velocity at desert and oasis results in that the occurring frequency of the dusty weather at oasis is more than that at desert.Last,it means that the total dust particle number concentration N( d>0.5 μm) is proportional to u _* ² approximatively.

• A Study on Convective Characteristics and Formation Mechanism of Precipitation over Upper Reaches of Yellow River
• ZHAO Shi-xiong;DELI Geer;TU Duo-bin
• 2003 Vol. 22 (4): 385-392. 
• Abstract ( ) PDF (466KB) ( )
• The generality and particularity of convective function for rainfall in each kind of clouds were further explained using the radar echo data,surface observation data and rain particle spectrums data over the upper reach area of Yellow River from June to september 1997-2000.Through the case study of rain particle spectrum evolution,we preliminary infer that the microphysical processes of rainfall in cloud probably have two formation mechanisms of warm rain and cold rain,but the warm rain mechanism play an important part in precipitation development of cloud.The above-mentioned facts may be the important reason of frequent rainfall in Qinghai-Xizang Plateau

• A Study on Air Pollution,Visibil ity and General Circulation Feature
• ZHAO Qing-yun;ZHANG Wu;WANG Shi-gong
• 2003 Vol. 22 (4): 393-396. 
• Abstract ( ) PDF (185KB) ( )
• The correlation between the pollution and the atmospheric visibility in Lanzhou are analyzed by using the pollution and the visibility data(July 2000-June 2001).Using the visibility data(1980-2000),the visibility and the general circulation features are analyzed,and the forecast equations of the visibility are made.The results indicate that the visibility shows apparent daily variation,the interannual variation shows increasing trend.The visibility in 1990's is better than that in 1980's.The pollution index is correlated to the visibility negatively.

• Climatic Analysis of Mean Temperature in Qinghai Province
• ZHU De-qin;GAO Xiao-qing;TANG Mao-cang
• 2003 Vol. 22 (4): 397-400. 
• Abstract ( ) PDF (201KB) ( )
• Using the "regression analysis on difference" and supposing that the temperature( T) is a linear function of height above sea level( h),latitude( φ) and longitude( λ),the distributing characteristics of annual mean temperature residual error(Δ T),the annual variety of Δ T,the temperature difference( T ₇- T ₁) and the cause of Δ T formed are analyzed.According to the curve of Δ T in those representative stations,we discussed the reason that high and low temperature formed in Qinghai Province.The results show that the temperature is higher in west part of Qinghai than that of in east part during the whole year,the distribution of temperature difference( T ₇- T ₁) increases with latitude,the annual temperature difference( T ₇- T ₁) is low,but the diurnal temperature differenceis high near the turbulence detached line in east part of the plateau.Qinghai Lake is a warm resource in winter,but is a cold resource in summer.The lake is the minimal region of annual temperature difference( T ₇- T ₁),and the diurnal temperature differencein lake region is lower than that of around.

• Time and Space Characters of Congeal in Guizhou and Circulation Features Analyses
• XU Dan;LUO Xi-ping
• 2003 Vol. 22 (4): 401-404. 
• Abstract ( ) PDF (189KB) ( )
• By using the congeal index of 47 meterological stations of Guizhou from 1951 to 1996,the field distribution feature of congeal index and the evoluting rule of time coefficient were analyzed,and the first time coefficient and 500 hPa height correlation field distribution were analyzed as well.Based on the change of the first time coefficient,the five serious and light congeal years in the last 46 years were determined.Using the composite method,the distribution feature of winter 500 hPa average height in the serious and light congeal years were analyzed.The results show that the most significant differences occured over the Europe and Asia areas.When 500 hPa geopotentical height anomaly in winter is with the positive(negative) in the north and the negative(positive) in the south,the congeal in Guizhou is serious(light).

• An Improved Method MOS Forecast Based on Circulation Characteristics
• QI Ming-hui;XIAO Zi-niu;YAN Hong-ming
• 2003 Vol. 22 (4): 405-409. 
• Abstract ( ) PDF (949KB) ( )
• A new method of forming MOS(Model Output Statistic) forecast factors to improved prediction accuracy was given in this paper.The result show that the method can significantly improve the MOS forecast skill for precipitation and temperature of 32 stations in Yunnan.But the MOS forecasts for precipitation are more skillful than that for temperature in Yunnan.At the same time,the test display prediction accuracy of MOS is sensitive to the forecast factor select.And considering circulation background and making a optimal forecast factors is very important to improve the performance of MOS forecast.

• Interannual Variation of Indian Monsoon and Summer Flood/Drought over Tibetan Plateau
• ZHOU Shun-wu;JIA La
• 2003 Vol. 22 (4): 410-415. 
• Abstract ( ) PDF (915KB) ( )
• Based on the NCEP/NCAR reanalysis data and the sea surface temperature anomaly(SSTA) of U.K.Meteorological Office,200,850 hPa composite wind fields and SST anomaly pattern of India Ocean for five more and less rainfall years over the Tibetan Plateau are analyzed.It is found that there are obvious differences in the Indian Ocean high,low level wind fields and sea temperature field at the same period and before it between more and less rain years.Namely Indian Peninsula maitains west(east) wind anomaly at 850 hPa composite wind fields;West Indian Ocean-the coast of East Africa,south(north) wind anomaly;Arabia Sea and the Bay of Bengal,anticyclonic(cyclonic) anomaly circulation wind fields in the Plateau more(less) rainfall years.Indian Peninsula maitains east(west) wind anomaly at 200 hPa composite wind field;South Asia high,strong(weak),the coast of Somali,south(north) wind anomaly.It means that the Indian summer monsoon is strong(weak).Indian summer monsoon anomaly has good relation to the zonal distribution pattern of SSTA.When summer SSTA appears the pattern with cold(warm) in the west and warm(cold) in the east,summer monsoon is strong(weak) and Plateau precipitation is obviouly more(less) than usual.The results show that the summer rainfall over Tibetan Plateau is closly related to Somali cross-equatorial flow(SSCI).SSCI is found to reflect well the interannual variation of summer flood/drought over Tibetan Plateau.

• Analysis on High and Low Temperature Weather and General Atmospheric Circulation in Ningxia
• CHEN Nan;CHEN Yu-ying;PENG Wei-geng
• 2003 Vol. 22 (4): 416-421. 
• Abstract ( ) PDF (262KB) ( )
• The temporal-spatial characteristics of high and low temperature weather were analyzed by using the 40-year daily data of maximum and minimum temperatures at 24 weather stations of Ningxia.At same time,a diagnostic analysis on the abnormal characteristic of atmospheric circulation of more or less years in high and low temperature weather were carried out using the data of NCEP/NCAR during 1979-1999.The result showed that the intensity and position of polar vortex,the intensity and position of continental and subtropical highs were obviously different from each other during the more or less years of high and low temperature weather in Ningxia.On the contrary,the temperature fields show an opposite distribution.

• Primary Study on Strong and Very Strong Dust Storm Trend in Hexi Passageway
• DONG An-xiang;BAI Hu-zhi;LU Deng-rong;FENG Jian-ying
• 2003 Vol. 22 (4): 422-425. 
• Abstract ( ) PDF (182KB) ( )
• A study on climate variation of strong and very strong dust storm in Hexi Passageway from 1955 to 2000 is presented.The analyzed results show that the strong and very strong dust storm has mainly decreased since 1955,but increased in the late 1990s.Its trend was more in the 1950's and 1970's,normal in the 1960's,less in the 1980's and the least in the 1990's.Its climatic jump occurred in later 1960's and around 1980.

• Analogue Method of Aerological Temperature and Pressure Fields of Spring Hailfall's Short-Range Forecast in Guizhou
• XU Bing-nan;ZHOU Ying
• 2003 Vol. 22 (4): 426-430. 
• Abstract ( ) PDF (957KB) ( )
• By using the analogus coefficient critical value of 08:00 500 hPa temperature and pressure field and 700 hPa temperature field,spring regional short-range weather forecast model of hailfall in Guizhou is established,the prediction model is established with 427 hailfall days and 484 non-hailfall days,it is determined monthly analogus prediction index,consequently they have very largely statistical reliability.Prediction model acuracy for sample period is 66%.The forecasting results in 1999 and 2001 indicate that this method is efficient.