Current Issue

• Numerical Simulation of Effect Qinghai-Xizang Plateau on Drought in Northwest China
• WANG Yong-qing;CHEN Lian-shou;LUO Zhe-xian
• 2002 Vol. 21 (6): 529-535. 
• Abstract ( ) PDF (312KB) ( )
• The synchronous NCEP/NCAR summer reanalysis data are verified by comparing with the intensive observation boundary layer wind speed and direction of TIPEX at Damxung station indicate a distinctive phenomenon that there exists and low in the south modon of pressure field in Qinghai-Xizang Plateau boundary layer.The drought formation of on the northeast side of Qinghai-Xizang Plateau has been studied by introducing stationaryheat force and transient heat force,which determined by continuos evolution of sensible heat flux(May 31 to June 4,1998).The main results are there exist(1) advection transportation of to upstream anticyclone vortex through westerly basic flow,(2) southerncyclonic energy dispersion,(3) anticyclon system intesifying caused by Qinghai-Xizang Plateau heat forcing.

• The Relationship between the Summer Monsoon Circulation in East Asia and ENSO Cycle
• CHEN Yue-juan;ZHOU Ren-jun;JIAN Jun
• 2002 Vol. 21 (6): 536-545. 
• Abstract ( ) PDF (413KB) ( )
• The variation of East Asia summer monsoon circulation in different periods of ENSO cycle has been analyzed by using meteorological data from NCEP/NCAR and sea surface temperature data from NCAR. The normalized relative intensity, correlation and difference between the circulation of each year and the mean circulation are calculated and their relation with SST anomalies are discussed. The results show that there are obvious annual and decadal changes in East Asia summer monsoon circulation, and there are quiet good negative correlation between the normalized relative intensity of the summer monsoon circulation and SST in East Equatorial Pacific. Especially, the negative correlation between the summer monsoon circulation and SST in March and April is best. The northward extended latitudes of the south wind component at 850 hPa and the meridional circulation in East Asia summer monsoon region in June and July in the cool period of Nino1+2 SST is much different from those in the warm period of Nino1+2 SST. The meridional wind bigger than 2 m·s ^-1 extends more northward and the upward flow of monsoon circulation in the cool SST period and East Asia summer monsoon is stronger in cool SST period then that in warm SST period.

• The Energy Budget of Surface-Tropospher System over Qinghai-Xizang Plateau
• SHEN Zhi-bao;CHENG Tian-tao;WANG Ke-li
• 2002 Vol. 21 (6): 546-551. 
• Abstract ( ) PDF (253KB) ( )
• By using the results of the radiative energy budget calculated by CRM/CCM3,we studied the seasonal characteristics of the radiative energy budget in earth-troposphere system over the Qinghai-Xizang(Tibet) plateauin winter and summer,the relationship of the radiative energy budget in earth-troposphere system and in earth-atmosphere system,and compared them with that over the plain in the eastern china and the arid region in the north-western china.The cloud radiative forcing and the effects of surface snow-cover on the radiative energy budget in winter,and the contributions of the radiative heating and surface sensible heat flux on the atmospheric heat source over the plateauin summer were discussed.

• The Air Temperature Change in the Past 2000 Years Simulated Using Solar Activity Indices
• WANG Zhong-rui;GAO Xiao-qing;TANG Mao-cang
• 2002 Vol. 21 (6): 552-555. 
• Abstract ( ) PDF (180KB) ( )
• The Chinese temperature change in the past 2000 years was simulated using the sunspot number and the sunspot cycle length.The trend of simulated temperature,especially in the past 700 years,basically consists with that in the previous studies.In addition,the temperature change over the Northern Hemisphere in the past 120 years is also simulated.The results indicate that the solar activity is the basic factor influencing the temperature change over 10 year time scale,and the action of greenhouse gas may not be overlooked in the past 10 years or more.

• Impact of Plateau and Cold Air on SHWP and Rain Belt Summer in 1998 and 1991
• SONG Min-hong;QIAN Zheng-an
• 2002 Vol. 21 (6): 556-564. 
• Abstract ( ) PDF (500KB) ( )
• The 500 hPa Subtropical High over the West Pacific(SHWP) is one of the members of summery monsoon systems in Eastern Asia,it has the important influence on the main rain belt in China summer.In this paper to seek the forecast precursors for medium-and short-range forecast of the SHWP moving southward and northward suddenly,the impacts on the SHWP moving southward and northward and associated rain belt of the Qinghai-Xizang Plateau(QXP) vortexes moving eastward,the 100 hPa Southern Asia High(SAH) moving southward and northward,as well as the cold air invading from the North have been analyzed,utilizing the daily weather maps from June to August in 1998 and 1991,and the observational data from the Second Meteorology Science Test on the QXP,and the daily averaged gridded reanalysis data(e.g. u, v, h) on 2.5°×2.5° from NCEP/NCAR.The main conclusions are as follows:1) If the air-column thickness between 300 and 500 layers over the eastern QXP is greater than or equal to 392 gpdm,then the QXP vortexes moves eastward out of the QXP,and the southwest vortexes occurs and moves eastward,as a result,the SHWP moves southward and the rainstorm belt occurs in mid-and lower reaches of Changjiang River in the future.2) Both the eastern section of SAH ridge line and the west section of the SHWP ridge line have the same trend of moving southward and northward.But the former is much more stable and changes three days ahead.We can predict the moving of SWHP and the associated rain belt.3) If there are the cold air invading in North China and more than 2 m·s ^-1 positive and negative south wind anomaly on 850 hPa occurring Changjiang River,the rainstorm belt occurs easily in the transition band of the positive and negative anomaly of the south wind,especially on the negative anomaly side.It makes the SWHP more stable.4) Certainly,the combined consideration will be needed in real forecast,and the first priority will be given to the SAH moving and the north cold air invading.

• Decrease of Arctic Sea Ice and Its Relationship with the Sea Surface Pressure and Temperature in High Latitude
• FANG Zhi-fang;GUO Yu-fu;QIAO Qi;FANG Jin-huai
• 2002 Vol. 21 (6): 565-575. 
• Abstract ( ) PDF (434KB) ( )
• Using the Arctic sea-ice data during the period 1953-1998,the sea level pressure in North Hemisphere,and the temperature in 22 stations of North-East China,we analyzed interannual and decadal climatic changes with statistical method.The results are as follws:(1) Obvious reduce of the sea-ice extent was appeared in high latitude.In latitude band to the north of 60°N,the variance of the tendency term is larger then 50% of total variance,and larger than period variation.(2) Since 1990,the sea-ice extent decrease was suddenly appeared in the Barents Sea,Greenland Sea,Lablador Sea and to the north of 50°N.The Arctic sea ice is very sensitivity to climatic variation of the warm in the world.(3) There exist period variation about 11~15 years in the high latitude ocean,but the sea ice decrease trend is dominant scale.The variance of decrease tend is larger than the period variation in he high latitude ocean,therefor the sea-ice extent decrease is main character in sea-ice variation during the 46 years.(4) The variance tend of the SLP to the north of 40°N was decreased.The obvious reduce was appeared with AO index.There exist a significance deference since 1990.(5) Corresponding to the SLP decrease,the temperature evidently increases in North-East China.(6) The Arctic Oscillation has an effect on the sea-ice extent in the Barents Sea,Greenland Sea,Lablador Sea,and the temperature in North-East China.When the Arctic Oscillation is stronger than normal,the sea-ice extent in the Barents Sea and Greenland Sea will be larger,the sea-ice extent in Lablador Sea will be smaller than normal,the temperature in North-East China will obviously be decreased.

• The Influence of Typhoon on Subtropical High Location and Intensity
• LI Chun-hu;HUANG Fu-jun;LUO Zhe-xian
• 2002 Vol. 21 (6): 576-582. 
• Abstract ( ) PDF (287KB) ( )
• The test is 6-group time integral in total 4~5 model day for studying the influence of typhoon on subtropical high location and intensity using a shallow water model.The results show that the interactions between typhoon and subtropica1 high strengthen subtropical high and move it westward,by which potential theories lie in statistic relationship between typhoon action and drought over the east part of northwest China is discussed.

• A Simplif ied PDF for Computing Regional Mean Flux over Heterogeneous Surface and Its Appl ication
• LIU Jing-miao;WANG Ji-jun;DING Yu-guo
• 2002 Vol. 21 (6): 583-590. 
• Abstract ( ) PDF (390KB) ( )
• A simplified probability density function(PDF) which is applied to description surface heterogeneity is presented in this paper.The PDF may be directly used in LSPM to carry out the numerical experiment of the land-air physical exchange over subgrid scale area,and the accuracy of the calculated flux is not influenced by this simplified method.Thus,the method has certain generality.But,only a symmetrical simplified PDF distribution is researched in this paper.The cases for calculations of net flux of infrared radiation over the heterogeneous land surface are virified by using the simplified PDF.

• Application Potential of Polarization Radar in Weather Modification
• WANG Zhi-jun;CHU Rong-zhong
• 2002 Vol. 21 (6): 591-598. 
• Abstract ( ) PDF (353KB) ( )
• It is impotent that understanding the parameters of size,density,type and moving of hydrometeors and the process of microphysics change of these hydrometeors within clouds in real-time for weather modification,because these parameters and process reveal the different evolution stages of cloud and precipitation,and they are very useful for estimating the potential increase precipitation of cloud and correctly select the area and time of artificial seeding.It provide the basis for raising effect of weather modification.According to the successful application examples of polarization weather radar,the application problem of the polarization weather radar in weather modification was discussed and especially the methods of identify the type was introduced,density of hydrometeors and monitor the microphysics change process within clouds and estimating the effect after artificial seeding.These methods will be useful for developing ourselves polarization weather radarand raising application level of weather modification in our country.

• Contrast Analysis of April General Circulation between More and Less Sandstorm Years in Ningxia
• Peng Wei-geng;Chen Nan
• 2002 Vol. 21 (6): 599-603. 
• Abstract ( ) PDF (224KB) ( )
• The characteristics of April mean general circulation between more and less sandstorm years in Ningxia are compared with each other.The results show that the intensity of the pole eddy at 500 hPa and the latitudinal west wind in North China are stronger in more sandstorm years and weaker in less sandstorm years.Also the longitudinal general circulation is stronger in more sandstorm years and weaker in less sandstorm years in April.Furthermore,the anomaly of geopotential height on the north side of West Pacific subtropical high in more sandstorm years is contrary to that of the less sandstorm years.It shows that the sandstorms in North China including Ningxia maybe have important relations to low-latitude circulation.

• Characteristics of Vertical Distribution of Urban Heatisland Effect in Kunming City
• ZHANG Yi-ping;HE Yun-ling;MA You-xin;LIU Yu-hong LI You-rong;DOU Jun-xia;GUO Ping
• 2002 Vol. 21 (6): 604-609. 
• Abstract ( ) PDF (289KB) ( )
• Using the vertical measurement data of urban and suburb in kunming which located at low-latitude plateau,the characteristics of vertical distribution of city climate at low-latitude plateau city were analyzed.Through comparing analyses,the primary results are as follows:The findings indicate that urban heat island lie in not only near the ground but also upper atmosphere,the intensity of night(influenced height＞ 50 m) go beyond daytime(influenced height＜ 50 m),near the ground exceed upper atmosphere.In urban area,the air temperature decrease with height increasing in daytime and temperature at night is inversion distribution,the center of urban heat island shifts with height increasing.This distribution would have an effect on the diffusion of urban contamination,architecture design and energy saving.

• Correlation Analysis of East Asia Summer Monsoon Circulation Anomaly Index and Land-Sea Temperature Difference
• ZHANG Hong-mei;DONG Wen-jie;WEI Zhi-gang
• 2002 Vol. 21 (6): 610-614. 
• Abstract ( ) PDF (294KB) ( )
• Using 0.8 m monthly soil temperature over China and NCAR sea surface temperature data,the land-sea temperature difference of China with the East Asia summer monsoon circulation anomaly index were analyzed initially.The correlation analysis between the East Asia summer monsoon circulation anomaly index and the land-sea temperature difference is notable.And there is distinguished heterogeneity of temporal-spatial distribution of annual variation trend,the distinguished differences exist in correlation distribution in various area.Dynamic analysis further proved the effect of the land-sea temperature contrast on the East Asia Summer monsoon.

• The Characteristics of Ultraviolet Radiation and Its Physiology Effect on the Plants in the Area of Haibei Alpine Meadow of Qilian Mountain
• LI Ying-nian;WANG Wen-ying;ZHAO Liang;ZHAO Xin-quan;CAO Guang-min;SHI Sheng-bo
• 2002 Vol. 21 (6): 615-621. 
• Abstract ( ) PDF (295KB) ( )
• The diurnal and seasonal varying characteristics of solar ultraviolet radiation and the ratio( η) of UV to total radiation during the plant growing season were analysed by observed radiation data in the area of Haibei alpine meadow of Qilian mountain in 2000.Ultraviolet radiation was higher in this area.The instant maximum ultraviolet radiation was 77 W·m ^-2,thetotal maximum ultraviolet radiation in a day was more than 1.8 MJ·m ^-2,the accumulated ultraviolet radiation in a month was 41.620 MJ·m ^-2(May) under the real weather condition;the total accumulated ultraviolet radiation was 218.651 MJ·m ^-2 during the plant growing season(from April to October).The ultraviolet radiation had obvious diurnal and seasonal changing pattern in this area.The diurnal variation of ultraviolet radiation showed as a single peak curve which was related with the total radiation change caused by the change of sun's altitude.The change of η in a sunny day was higher in the morning,lower in the afternoon,average value was 0.048;whereas the change of η in a cloudy day was higher from 13:00 to 14:00,lower in the morning and night,and changed obviously with the change of cloudy amount.The η in a overcast day was higher than that in a sunny day. η was higher in the prior plant growing period,lower in later plant growing period and the average η was about 0.052.Owing to the strong UV effect,the soluble sugar,starch and non-structural carbon-hydrate component quantity of root,stem and leaf of several main plants were higher and showed as the rapidly increase after the sun rise;plant root,stem and other organs were thicker and stronger.The plant physiology adaption and its structure chinging made the alpine meadow plants had obvious functional mechanism and morphological structure against cold conditions in alpine meadow under the influence of stronger ultraviolet radiation.

• Analyses on Potential Air Water Resources over Northeast Qinghai in Spring
• DE li-ge-er;HUANG Yan-bin;LI Lun-ge
• 2002 Vol. 21 (6): 622-627. 
• Abstract ( ) PDF (244KB) ( )
• It is very important to know and master the status of atmosphere vapor in operation of artificial precipitation enhancements.The principle of dynamical meteorology is used to calculate the vapor transportation,convergence and divergence in spring over northeast Qinghai,the total vapor content and liquid water are observed by the microwave radiometer.The calculated result shows that the input of vapor in northwest Qinghai is more than output,and the vapor about 83 percentcan pass the area and then move out Qinghai,and it has bigger potential water resource.From the liquid water content,though the vapor content is less than the area of plain,but the liquid water content is more than that one.Otherwise,according to calculations of tatal cloud condensation water and precipitation efficiency from the third dekad of March to the first dekad of May 1997,the atmospheric total condesation water is obtained to be 284×10 ⁸t,but actual precipitation is about 34×10 ⁸t,the average precipitation efficiency is 0.12.If precipitation efficiency rised 1 percent,precipitation would increase about 2.5×10 ⁸t,these have good artificial precipitation potential

• Study on Short-Range Climatic Prediction Models of Summer Server Drought and Flood in Guizhou
• XU Bing-nan
• 2002 Vol. 21 (6): 628-631. 
• Abstract ( ) PDF (169KB) ( )
• Short-range climatic prediction factors of summer server drought and flood in Guizhou were analysed.The forecast signal of summer sever drought and flood using different combinations of the East Asian and North American troughs in spring obtained five main prediction factors.The two short-range climatic prediction models of summer sever drought and flood in Guizhou are established using the forecast signal and prediction factors.The model forecast results of independent sample in 1997-2000 are satisfactory.

• Correlation Analyese between Atmospheric Stratification Factors and Ground Lightning Activities in Pingliang Convective Storms
• ZHANG Cui-hua;ZHANG Yi-jun;QIE Xiu-shu;WANG Huai-bin
• 2002 Vol. 21 (6): 632-636. 
• Abstract ( ) PDF (231KB) ( )
• Statistical analyses are made of morning sounding data and ground flash data from June to August 1997 and 1998,the latter was obtained with a 3-station lightning direction finder network installed in Pingliang.The results show that there is good correlation between total ground flash number of convective storm and environmental stratification factors.Atmospheric instability,ambient temperature at altitude with residual instability of 5℃ and mean relative humidity in the middle layer are important factors,which affect the ground flash frequency of storm,therefore can be used for lightning activity forecast.