Current Issue

• THREE-PHASE CLOUD EXPLICITY PRECIPITATION SCHEME AND MESOSCALE NUMERICAL SIMULATION FOR GENERATED CAUSE OF THE "96.1" SNOWSTORM
• DENG Yuan-ping;CHENG Lin-sheng;ZHANG Xiao-ling
• 2000 Vol. 19 (4): 401-413. 
• Abstract ( ) PDF (539KB) ( )
• The analysis of generated cause for the "96.1" snowstorm event over Qinghai-Xizang Plateau was conducted using weather observational data.The results indicated that the European blocking high collapsed,the cold trough transformed from transversal into upright,the southwards invading cold and dry air flow behind the trough and the northwards intensive southwest warm-wet air flow coming from the Bay of Bengal and the Indian peninsula were converged over northeastern part of Qinghai-Xizang Plateau while a mesoscale shear line was formed and persistent developed.This shear line was main mesoscale weather system of producing the "96.1" snowstorm over Qinghai-Xizang Plateau.A mesoscale model and simulation system was developed through incorperating an ice phase cloud microphysics process parameterization and a three-phase cloud explicity precipitation scheme.The genesis and development as well as evolutive structure of a mesoscale shear line associated with the "96.1" snowstorm over Qinghai-Xizang Plateau were basically successful simulated under the condition of using conventional observational data.The results showed that the developed and improved mesoscale model and simulation system is suitable for numerical simulation research of the genesis,development and structural evolution of mesoscale system over Qinghai-Xizang Plateau of possessing complex topography and underlying surface.Spacetime evolution of simulated streamline field and physical fields revealed that the spacetime evolutive consistence of the convergence line of the streamline field with the shear line associated snowstorm showed the expression of the mesoscale system overQinghai-Xizang Plateau that is essential important by using streamline field possesses.An important mechanism of the genesis and development for the snowstorm shear line was that the divergence on upper levels was more intensive than convergence on lower levels and a dynamic coupling of positive vorticity zone with convergent zone.The intension and persistence of vertical ascending motion was a necessary condition of vapor condensation and snow formed by freezing.The deep,thick,wet tongue and moist convection instability supplied abundant moisture source and thermal instability condition.The superposition of the deep,thick,wet tongue and the convergent zone as well as the ascending motion was an intensive coupling structure for the formation and persistence of the snowstorm.The roughly consistence between the snowstorm zone and precipitation with that of the observational analysis showed the threephase cloud explicity precipitation scheme is basical reasonable.

• A COUPLED OCEAN AND ATMOSPHERE MODEL AND SIMULATION EXPERIMENT IN THE SOUTH CHINA SEA AREA
• Lü Shi-hua;CHEN Yu-chun;Peter C Chu
• 2000 Vol. 19 (4): 415-426. 
• Abstract ( ) PDF (644KB) ( )
• A regional coupled ocean-atmosphere model is developed and used to research regional climate change and sea-air interaction over the South China Sea area.The atmospheric model performs the time integration simultaneously with ocean model.The sea surface temperature has been transferred from ocean model to atmosphere model and wind stress heat flux has been transferred from atmosphere model to ocean model.The model has conducted 3-month time integration from May to July in 1995.The coupledmodel gives us a more realistic ocean circulation field than that from a pure ocean model with COADS wind stress and heat flux data as external forcing,and well-presented ocean current circulation and middle scale sea-air interaction in South China Sea area.

• CONTRIBUTION OF THE ATMOSPHERIC OSCILLATIONS TO THE GLOBAL SURFACE PRESSURE SYSTEM
• 2000 Vol. 19 (4): 427-434. 
• Abstract ( ) PDF (341KB) ( )
• The features of near surface atmospheric circulation are usually analyzed based on the sea level pressure fields.The prominent patterns of the sea level pressure appear as the atmospheric oscillations.There are four major oscillations in global near surface atmosphere,they are North Atlantic Oscillation(NAO),North Pacific Oscillation(NPO),Southern Oscillation(SO) and Antarctic Oscillation(AO).The contribution of four atmospheric oscillations to the global monthly mean sea level pressure variance is studied,and it is found that the ratio percent of variance explained by four oscillations is different for various areas.More variance is accounted for over the lower zonal belts than over higher latitudes,and more variance is explained over Southern Hemisphere than that in Northern Hemisphere.In boreal summer(June,July and August),the variance of global sea level pressure explained by the four oscillations is 38.6%,in boreal winter is 45.9%.In some areas,such as eastern Asia,there are gaps of explanation of pressure.For these regions,other factors play more important role in the climate change,the atmospheric circulation systems such as the seasonal atmospheric centers of action and monsoon should be paid more attention.

• THE NUMERICAL SIMULATION STUDY WITH THREE DIMENSIONAL ELECTRIFICATION MODEL-PRELIMINARY SIMULATION VERIFICATION
• SUN An-ping;YAN Mu-hong;ZHANG Hong-fa;HUANG Mei-yuan
• 2000 Vol. 19 (4): 435-440. 
• Abstract ( ) PDF (241KB) ( )
• In this investigation we compare the results of the three-dimensional dynamicalelectrified model simulation of the July 19 Cooperative Convective Precipitation Experiment(CCOPE) case study cloud against the actual observations with respect to the cloud's electrical characteristics,as deduced from the data of two aircrafts.It is found that the 3D model reproduced the basic microphysical,charge and electric field structure of the cloud on a time scale similar to that observed.The comparability of the modeled and observed values of the field strength and charge within the thunderstorm is directly related to the proximity of the aircraft to the main active core of the cloud.The character of the some microphysics appears to be well modeled,at least at the time of observation,even if some values simulated are little high than that observed.Finally,a few problems related to the model are advanced and discussed.

• THE ANALYSIS ON THE EVOLUTION OF EARTH SYSTEM BEFORE THE FLOODS IN YANGTSE RIVER AND YELLOW RIVER
• TANG Mao-cang;GAO Xiao-qing;LIU Yan-xiang;GUO Wei-dong;WANG Zhong-rui
• 2000 Vol. 19 (4): 441-449. 
• Abstract ( ) PDF (365KB) ( )
• After analyzing the characteristics of seismic fields in the early stage of 14 flood years of Yangtse River,Huaihe River,Yellow River and Haihe River,it is found that there were earthquakes happening in southeast part of Qinghai-Xizang Plateau,in mid-latitude zone of Eurasia and in east part to Taiwan.When earthquake happened in the hotspot region of China,India and Burma,floods occurred in Yangtse River and Huaihe River;the earthquake in the conjunction area among Sichuan province,Qinghai province and Gansu province corresponds to the flood in Yellow River and Huaihe River.The direct cause is the strong development of geothermal vortex in the region,which located at the cross point of several "Isogonic Equidistant Geothermal Vortex Families",it is the result of sympathetic vibration.The facts in 1954 and in 1982 were analyzed in detail as examples.It was discovered that there is a quasi-half-year rhythm of strong thermal pulse in the hotspot region in the conjunction of China,India and Burma.And it was compared with the self organizing phenomenon in atmospheric convective boundary layer.

• THE BASIC CHARACTERISTICS OF HEAVY SNOWSTORM PROCESS AND SNOW DISASTER DISTRIBUTION IN EASTERN PASTORAL AREAS OF QINGHAI-XIZANG PLATEAU
• ZHOU Lu-sheng;LI Hai-hong;WANG Qing-chun
• 2000 Vol. 19 (4): 450-458. 
• Abstract ( ) PDF (342KB) ( )
• The 26 weather stations in eastern pastoral areas of Qinghai-Xizang Plateau have appeared 1 689 heavy snowstorm weather processes in the past 30 years.In terms of our standard,snow disaster occurred 410 times totally.By means of statistic analysis,we concluded some preliminary time-space distribution characteristics of heavy snowstorm processes and snow disaster.The results show that Jiuzhi was the frequent center of heavy snowstorm processes and snow disaster,while Qingshuihe was the high value center of snow disaster and disaster-forming.The probability of disaster-forming reached to 80.3% in the later winter,but only 14.3% in the spring.As a result,tomake an impact on snow disaster is getting more and more serious because of the significant increment of heavy snowstorm processes and precipitation,particularly,it becomes more frequent since 1990's.

• DYNAMIC DIAGNOSES OF THE GENESIS AND DEVELOPMENT FOR MESOSCALE SHEAR LINE DURING "96.1" SNOWSTORM,Ⅱ:DIAGNOSES OF DIVERGENCE AND ITS VARIABILITY
• ZHANG Xiao-ling;CHENG Lin-sheng
• 2000 Vol. 19 (4): 459-466. 
• Abstract ( ) PDF (317KB) ( )
• The divergence and its variability during "96.1" snowstorm were diagnosed using the output data of the improved and developed mesoscale model(MM4),in which a three-phase cloud explicit precipitation scheme has been introduced.The results showed that structure and evolution of divergence field with an intensive lower-level convergence and upper-level divergence were related to the genesis and development of the mesoscale shear line and snowstorm.By calculating the divergence equation,it indicated that the centers and their belts of the negative divergence variability in the lower-level was formed and developed before that of the convergence with the strength and region of heavy snowfall 12 hours later.

• VERIFICATION OF NCEP SURFACE HEAT FLUXES OVER QXP AND ITS APPLICATION TO SUMMER PRECIPITATION FORECAST
• SONG Min-hong;WU Tong-wen;QIAN Zheng-an
• 2000 Vol. 19 (4): 467-475. 
• Abstract ( ) PDF (343KB) ( )
• The Qinghai-Xizang Plateau(hereafter QXP) has an important effect on weather and climate over its neighbor regions.In order to get a new,long-time sequence of the QXP surface heat source intensity data,firstly,the NCEP NCAR monthly 2.5°×2.5°Lat./Lon.gridded surface heat fluxes over the QXP were verified by comparison with the observed data.Secondly,the space distribution characteristics of the QXP surface heat source intensity(hereafter QXP SHSI) were analyzed by the EOF analysis technique.Finally,the impact of the QXP SHSI on Chinese summertime precipitation has been analyzed utilizing the NCEP/NCAR reanalysis data and the observed precipitation data.The main conclusions are as follows:(1) NCEP NCAR reanalysis surface heat fluxes over the QXP can represent the realistic QXP SHSI annual and inter-annual variability.Therefore,the data is useful.(2) The variability of the QXP SHSI has great space variation.(3) There are negative correlation between the early spring and summer SHSI over Northwest QXP and summer precipitation over south part of Xingjiang.The same things are true for between the SHSI over Northeast QXP and the precipitation over Gansu Corridor and between the SHSI over Southwest QXP and the precipitation over mid-and lower reaches of Changjiang River.

• THE LFP DISTRIBUTION AND PROPAGATION FEATURES OVER QINGHAI-XIZANG PLATEAU AND ITS VICINITY IN SUMMER OF 1998
• XU Guo-qiang;ZHU Qian-gen
• 2000 Vol. 19 (4): 476-486. 
• Abstract ( ) PDF (538KB) ( )
• Using NCEP reanalysis day-to-day data in 1998,the LFP(low frequency precipitation) distribution and propagation features over Qinghai-Xizang Plateau in the summer of 1998 are investigated.Results show that both LFP and its variance have noticeable contribution to total rainfall and its variance respectively in the target region.So it is practical important to research distribution,occurrence developing and migration of LFP over the highland.LFP to the east(south) of Qinghai-Xizang Plateau marches mainly west ward(north ward),but to the south very few travels into Qinghai-Xizang Plateau.Mid-and southern-and southeast of the highland may be original area of LFP developing over Qinghai-Xizang Plateau.Upper level LF(low frequency) divergence is a significant factor that influences genesis and propagation of LFP.The migration direction of the LF divergence is essential the same as the LFP.

• LIGHT-ABSORBING PROPERTIES OF AEROSOLS IN THE ATMOSPHERIC BOURDARY LAYER OVER CHINA
• HUANG Shi-hong;LI Zi-hua;YANG Jun
• 2000 Vol. 19 (4): 487-494. 
• Abstract ( ) PDF (381KB) ( )
• Based upon the sampling technique of ambient particles,we had measured absorption coefficients of aerosols at the ground level of 23 stations in China and given out their distribution.The results show that the absorption coefficients of ABL aerosols form 10 ^-6 to 10 ^-3m ^-1 are high(low) in north(south) with a pronounced high center at the Sichuan Basin and Guizhou Province.Distributions of the absorption coefficients and the mass concentration are significantly uniform with a 0.74 correlation coefficient.Furthermore,fine particles have more light absorption than coarse particle.

• THE CHARACTERISTICS OF ROUGHNESS LENGTH FOR HEAT AND ITS INFLUENCE ON DETERMINATION OF SENSIBLE HEAT FLUX IN ARID ZONE
• JIA Li;WANG Jie-min;HU Ze-yong
• 2000 Vol. 19 (4): 495-503. 
• Abstract ( ) PDF (332KB) ( )
• The roughness for heat(by the way of excess resistance κ B ^-1) over desert and Gobi sites have been calculated in HEIFE area.It was found that the range of κ B ^-1 at individual sites were large.A test of the utility of the excess resistance based on the calculated κ B ^-1 showed that ignoring of this resistance which came from the difference between the roughness length for heat and momentum will result in largely overestimation for sensible heat flux.A preliminary conclusion can be drawn that it would be unproper to take the hypothesis of z _0m= z _0h when estimating sensible heat flux using a resistance-type method.

• CORRELATION BETWEEN CLIMATE CHANGE OF ICE-CORE ON QINGHAI-XIZANG PLATEAU AND LOESS-PALAEOSOL SEQUENCE,MARINE ISOTOPE STAGE
• PANG Jiang-li;HUANG Chun-chang
• 2000 Vol. 19 (4): 504-511. 
• Abstract ( ) PDF (333KB) ( )
• The trend of climate change and main climate change events,obtained from icecore on Qinghai-Xizang Plateau of China during late Pleistocene,marine isotope stage and loess-paleosol sequence on the Loess Plateau of China are well compared.The climate change are characterized by 40 Ka and 20 Ka period and they are also well comparable to solar radiation change of midhigh latitude in the Northern Hemisphere during the late Pleistocene.The data obtained from icecore indicates that climate changes from warm to cold is gradual and from cold to warm is rapid,the coldest climate is about 23 Ka during the late Pleistocene.However,the data obtained from marine isotope stage and loess-paleosol sequence indicates that climate change from warm to cold is rapid and from cold to warm is gradual,the coldest climate is about 18 Ka.

• THE OBSERVATIONAL STUDIES ON CHARACTERISTICS OF MICROCLIMATE IN HAIBEI ALPINE MEADOW REGIONS OF QI-LIAN MOUNTAIN
• LI Ying-nian;SHI Sheng-bo;CAO Guang-min;YANG Yong-gang;SHEN Zhen-xi
• 2000 Vol. 19 (4): 512-519. 
• Abstract ( ) PDF (295KB) ( )
• The gradient observation data of microclimate measurement in a shorter period were analysed.The results are as follows:(1) The total solar radiation,net radiation,reflected global radiation,PAR and UV radiation have diurnal variation with high and low values,and the highest values have appeared at 14:00.All radiation have the same trends.The radio of net radiation,PAR,UV radiation to total solar radiation are 58%,20%,36%,and 14%,respectively.(2) The variation of heat flux in soil is lower,the variation in daytime is higher than that in the night.At the time from 07:00 to 17:00,the thermal energy is transferred from soil surface to deeper soil,and it is transferred from deeper soil to surface soil at the other times.The variations of G, H and λE is relative stable,they are about 20%,38%,42%,respectively.(3) In Haibei alpine meadow regions at Qilian mountain,the soil-air temperature varied very extremely in horizontal and vertical directions at the exact range;but at the another levels,the variation is relative stable.The inversion layer of atmosphere usually occured from 20:00 to next day 11:00.(4) The wind velocity has a stronger diurnal variation and short-term change.At the vertical direction,the wind velocity has an obvious time distribution.

• ANALYSES ON MONTHLY MEAN TEMPERATURE AND ANOMALOUS DISTRIBUTION OVER QINGHAIXIZANG PLATEAU IN WINTER AND SUMMER
• LI Sheng-chen;TANG Hong-yu;MA Yuan-cang;ZHANG Ji-nong
• 2000 Vol. 19 (4): 520-529. 
• Abstract ( ) PDF (381KB) ( )
• In this paper,utilizing the data of monthly mean temperature over Tibet(15 stations) and Qinghai(38 stations) in winter and summer and EOF & REOF analysis methods,the features in temporal and spatial distribution of winter and summer temperature over the Qinghai-Xizang Plateau and their change tendencies have been analysed.The results show the contribution of the first ten leading RPC accumulation variance of the summer &winter temperature fields can reach 90%.Whether winter or summer,the air temperature has the feature that the speed is slow and disappearing is fast over Qinghai-Xizang Plateau.After the temperatures were related,the unusual sensitive fields of thewinter temperature can be divided into north-,southeast-,boundary- and the midand west-patterns;the ones of summer temperature,into northeast-,east-,south-,the basin and west-patterns.The winter and summer temperature fields over the Plateau are heavily influcuced by not only the topography,underlying surface condition,but also the synoptic systems in winter and summer.Usually in the anomaly distribution,the westerly trough in winter and the Plateau surface thermal depression and Indian monsoon in summer may play an importand role.In the time tendency of Plateau temperature fields,the winter temperature have had warming trend in all Plateau;the same thing is true for summer temparature,especially for Northeast-,South- and West-Plateau.