Current Issue

• Surface Latent Heat Flux Characteristics over Tibetan Plateau and Circulations of Summer Precipitation Anomalies in South Xinjiang
• YANG Liang-mei;ZHANG Qing-yun
• 2007 Vol. 26 (3): 435-441. 
• Abstract ( ) PDF (1292KB) ( )
• The surface latent heat flux characteristics over Tibetan Plateau and circulations of summer rainfall anomalies in South Xinjiang are diagnostically investigated using the NCEP/DOE reanalysis data and the precipitation data of 225 stations in China from 1980 to 2004.It has been found that west(east) south Asia high is stronger than normal,westerly jet tends to north(south),Iran high moves to north and east(south and west),and western Pacific subtropical high moves to south(north) in drought(flood) year of South Xinjiang.There exits a vertical circulation with descending(ascending) motion anomaly over North Tibetan Plateau and South Xinjiang,and Ferrell circulation strengthens(weakens) in drought(flood) year of Xinjiang.From winter-spring to summer the latent heat variations over Bengal Bay,Tibetan Plateau and South Xinjiang are reverse between drought and flood years of South Xinjiang.There is obvious positive correlation between summer rainfall in South Xinjiang and latent heat over North Plateau.

• Study on Numerical Simulation and Occurring Mechanism of "5.31" Heavy Rainstorm in Hunan in 2005
• LI Feng;YANG Ke-ming;MAO Dong-yan;ZHANG Fang-hua;XU hui
• 2007 Vol. 26 (3): 442-452. 
• Abstract ( ) PDF (2329KB) ( )
• Meso-scale system and its triggering,maintaining mechanisms of "5.31" heavy rainfall in Hunan in 2005 are studied and diagnosed by used of NCEP 6 h reanalysis data with resolution 1°×1° and simulation data from MM5.The results show that the best collocation of high-low layer jet and establishment of their coupling pattern provide favorable environment conditions for the rainstorm occurring.The meso-scale systems occur in south of Chongqing and west of Hunan Province to move to Hunan with its developing,which strengthen unstable dynamical field so as to boost convection.Southerly warm and moisture airflow abruptly strengthen is key for onset of heavy rainstorm.Pump from high layer and both latent heat and sensible heat from weak rainfall that occurred before the heavy rainstorm are very important for convection start and development.Additionally,the complicated terrain in Hunan is also crucial for startup of heavy rainstorm.South hill slope lead south wind slide to Hunan along low layer,west mountain mostly uplift airflow,which is one of reasons that heavy rainstorm happened.Whereas,the sensitivity experiment shows that the uplift of terrain is not necessary for the rainstorm startup,it is propitious to enhance vapor transport and surface meso-scale system which converge became mainly trigger mechanism when southerly mountain are removed.The rainstorm event is lied on the system development,terrain may impact rain shape and its amount,windward(leeward) hillside gradient increase lead to rainfall enhancing(weakening),contrarily,windward(leeward) hillside gradient decrease lead to rainfall weakening(enhancing).

• Estimating Moisture Profile Using Integrated Water Vapor
• LIU Xiao-yang;MAO Jie-tai;LI Cheng-cai;WANG Mei-hua
• 2007 Vol. 26 (3): 453-459. 
• Abstract ( ) PDF (798KB) ( )
• This paper presents a moisture profile model based on the statistic properties of radio soundings over China from 1986 to 2001.According to the model,the profile of specific humidity to air pressure follows the power law above atmospheric boundary level,and the linear law within the boundary level.Detailed validations are presented by comparing the monthly mean profiles to those of radio soundings and NCEP data during the period of November 2004 to October 2005.Results show that the model disintegrated specific humidity profiles consist with the profiles of soundings and NCEP data.The more the height near the surface,the more the error of the model.For 1 mm integrated water vapor,the maximum bias of disintegrated specific humidity are less than 0.055 g·kg^-1 and 0.1 g·kg^-1,respectively,comparing with the specific humidity of NCEP and sounding near surface.Similarly,the estimation of the specific humidity profile from microwave radiometer integrated water vapor has the maximum bias 0.83 g·kg^-1 at the sounding hours during the period of November 2004 to April 2005.

• Anomalous Mositure Sources for the Severe Precipitation over North China during Summer
• LIANG Ping;HE Jin-hai;CHEN Long-xun;LI Wei
• 2007 Vol. 26 (3): 460-465. 
• Abstract ( ) PDF (1634KB) ( )
• Using the daily NCEP/NCAR reanalysis data and observed rainfall data in China in 1980-1997,the features of rainstorm over North China in summer are analyzed.The sources of moisture contributing to rainstorm are examined with particular reference.The results show that the high value center of locates approximately over the one of climate rainfall.Correlation analyses between the moisture transport flux of rainstorm over North China and other regions,the day to day variation and anomaly of the moisture transport during the period of rainstorm find that the moisture tranport from the west Pacific through the South China Sea play an important role in the occarrence of rainstorm over North China, while the moisture transport from the Bay of Bangle enhances the rainstorm to some extent.

• The Middle-Upper Circulation Analyses of the Plateau Vortex Moving Out of Plateau and Influencing Flood in East China in Recent Years
• YU Shu-hua;GAO Wen-liang;GU Qing-yuan
• 2007 Vol. 26 (3): 466-475. 
• Abstract ( ) PDF (1657KB) ( )
• Using the NCEP reanalysis data,the middle-upper troposphere moving east activity characteristics of the Plateau vortex that induced severe rain storm and flood in different regions of China are analyzed in 1998-2004.Results show that there are four synoptic types for the Plateau vortex moving out of the Plateau,they are Plateau vortex of north trough and south vortex type,Plateau vortex on shear line,Plateau vortex in shear stream field and Plateau front of the west wind trough.And the relationships between the moving out of the Plateau vortex and the cold air at 500 hPa,the position of the Subtropical High,the south Asian High and the westerly jet stream are revealed.The common character of them had been pointed out and the strong signals of the moving out of the Plateau had been pick up.All these had presented scientific witness to the prediction storm rainfall induced by the Plateau vortex.

• Characteristics of Summer Water Vapor Transportation in Sichuan Basin and Its Relationship with Regional Drought and Flood
• JIANG Xing-wen;LI Yue-qing;LI Chun;DU Jun
• 2007 Vol. 26 (3): 476-484. 
• Abstract ( ) PDF (1628KB) ( )
• Using the observational data in summer from 1981 to 2000,the water vapor transportation characteristics over Sichuan basin in summer are analyzed,especially in typical drought and flood years.The results indicate that the water vapor over Sichuan basin in summer mainly originates from Tibetan Plateau,Bay of Bengal and South China Sea.When the West Pacific Subtropical High(WPSH) shifts northward and westward,the southeast wind outside of it can bring the water vapor in South China Sea to the west of Sichuan Basin;the water vapor from Bay of Bengal and Tibetan Plateau are held up and only can stay in the west of Sichuan basin.So anomalous water vapor converges in the west of Sichuan,and diverges in the east.These lead to flood in the west of Sichuan and drought in the east.By contrast,when the WPSH shifts southward and eastward,the southwest water vapor outside of it cannot extend to the west of Sichuan basin,only can extend to the southeast,but the water vapor from Bay of Bengal and Tibetan Plateau can extend to the east.So it forms anomalous water vapor convergence in the east of Sichuan basin and divergence in the west,and brings to drought in the west and flood in the east.

• Effects of Climate Change on Lake Acreage in Naqu Region
• ZHUO Ga;YANG Xiu-hai;TANG Hong
• 2007 Vol. 26 (3): 485-490. 
• Abstract ( ) PDF (479KB) ( )
• Using the conventional meteorological observation at Naqu station etc from 1960 to 2004,along with the dataset of China-Brazil earth resource satellite and US land satellite,the climate changes of some lake regions in the middle-and eastern-Naqu areas in the recent 45 years and effect of climate changes on lake acreage since 1980's were analyzed.On the basis of above,the fitting equation for lake acreage was estabilished through the corresponding relationship between climatic factors and lake acreage.The results show that the precipitation,air temperature and surface temperature in the lake drainage area have been increased in the recent years,but the evaporation,sunshine duration,maximum depth of snow,maximum depth of frozen soil appear to gradually decrease trend.These factor variations have obvious linear relation with the increasing of lake acreage.The estabilishing regression equation based on climatic factors could well fit the variation of lake acreage.

• The Application of Artificial Neural Network to Short and Mid-Range Temperature Forecast in Tibet
• MA Xue-kuan;PUBu CiRen;TANG Shu-yi;LIN Zhi-qiang
• 2007 Vol. 26 (3): 491-495. 
• Abstract ( ) PDF (299KB) ( )
• According to the meteorological data of 32 stations in Tibet from November 2003 to October 2005,based on the interpretation of numerical forecasting products of ECWMF,T213 and so on,an artificial neural network model is constructed with dynamic learning rate BP algorithm to forecast daily maximum/minimum temperature from one day to seven days.The results show that the neural network model has preferable adaptive learning and non-linear mapping abilities and its forecast results can satisfy the precision requirement for real-time forecast,which has good referenced value in short and mid-range real-time operational forecast of extreme temperature.

• The Space-Time Variation Analyses of Air Temperature over the Qinghai-Xizang Plateau in Warm and Cold Seasons
• YANG Yu-feng;JIANG Hao;NIU Fu-jun;ZHAO Hong-yan
• 2007 Vol. 26 (3): 496-502. 
• Abstract ( ) PDF (830KB) ( )
• Based on the data of monthly surface air temperature over the Qinghai-Xizang Plateau during 1974-2003,the space-time variation characteristics during warm and cold seasons are analyzed.The results are as follows.In the warm season,the air temperature can be divided as three subparts: The west subpart is about to the west of 85°E,and the Northeast one(ie,to the east of 85°E and the north of 33°N) and the southeast one(to the east of 85°E and the south of 33°N).In this three parts,the western high temperature area,Chaidamu one and southern Tibet one are very clear.In the cold season,the air temperature clearly shows two parts as warm area in the south and cold area in the north with the boundary near 32°N.The space distributions of air temperature in warm and cold seasons show same warming trend in decade scale,and obviously over north of the Qinghai-Xizang Plateau.In the warm season over north of the Qinghai-Xizang Plateau,the air temperature clearly rises with a long-time increase trend as 0.035℃/a at Wudaoliang station.In the cold season over south of the Qinghai-Xizang Plateau,the air temperature clearly rises with a long-time increase trend as 0.060℃/a at Lhasa station.For the interannual variation of air temperature,there are consistent variations in the whole of the Qinghai-Xizang Plateau in warm and cold seasons.The obvious high value center is in the river source area,and means it is the key area for the climate variation.The air temperature in warm and cold seasons make consistent long time variation trend as rises in 30 years but different in recent 10 years.However,there are decrease trend in warm season and strong increase trend in cold season.

• Contrast Analysis of the Asia-Europe Heat Wave and Its Atmospheric Circulation
• SUN Guo-wu;TANG Xu;LIU Xin-wei;LIANG Ping
• 2007 Vol. 26 (3): 503-510. 
• Abstract ( ) PDF (1249KB) ( )
• The heat wave in the Northwest China,Southern China,Europe and India and their corresponding atmospheric circulation are analyzed using the data of the radiosonde stations and 500 hPa geopotential heights from the National Meteorological Center and NCEP/NCAR reanalyzed data.It is shown that the westerly ridge superposes on subtropical on 500 hPa in south-north directions and the high on upper levels superposes on subtropical on lower levels,that the broad and deep highs cause the sinking motion and heat source centers and the heat wave in the northwest China and Europe.However the heat wave in southern China and India are associated with activity of the subtropical high and summer monsoon.

• The Variation Characteristics and Estimating Model for Ultraviolet Radiation in Beijing
• HU Bo;WANG Yue-si;LIU Guang-ren
• 2007 Vol. 26 (3): 511-518. 
• Abstract ( ) PDF (807KB) ( )
• The variation characteristics of ultraviolet radiation in Beijing city are analyzed based on observed data from April 2004 to June 2005.The daily,monthly and yearly variation characteristics of ultraviolet radiation are same as those of broadband solar radiation.The ratio of ultraviolet radiation to broadband solar radiation varies from 0.02 to 0.04.The ratio is a constant values of 0.03 under clearly sky condition.The ratios are 0.04 and 0.02 in rainy day and dust day,respectively.Dependence of ultraviolet radiation on the atmospheric clearness index is analyzed.An experiential estimating model based on the relationship of the global broadband hemispherical transmittance(K_s) and optical air mass(m) is developed to calculate ultraviolet radiation in all sky conditions.The estimation equation developed in this study can be used to calculate ultraviolet radiation from broadband solar radiation with a relative error within 10% in Beijing.

• Research on the Dynamics Factors Influencing Development of Inertial Gravity Waves
• QIN Wei-jian;SHOU Shao-wen;LI Qi-tai;WANG Yong-qing;PENG Jiang-liang
• 2007 Vol. 26 (3): 519-524. 
• Abstract ( ) PDF (376KB) ( )
• Through the detection we find that the atmosphere gravity waves,as displaying significant behavior law,are stronger in winter-spring than in summer-autumn,with abrupt weaken/strengthen in May/October,and more vigorous at the night than during daytime,especially those of the short-periods when without distinguished weather process.The waves of 40~80 min periods are the strongest of all on a time average basis.Using the parameterization of cumulus convection and expansion of Taylor equation,the isolated wave solution is derived from the nonlinear KdV equation of inertial gravity waves(IGWs) under the conditions of baroclinic atmosphere and cumulus convection heating for explaining the features of IGWs according to observation records.The results show that the IGW's strength is increased with growing of the vertical wind shear and that the jet stream is the most important IGW's source and the prime cause that the IGW is stronger in winter-spring than in summer-autumn.The Asian jet stream southward shift in October and northward jump in May is the cause of IGW abrupt strengthening in October and weakening in May,respectively,while underside the jet stream is excited the strongest IGW.Normally,the strength of IGW is proportional to the absolute vorticity,the buoyancy frequency(N²) and the frequency of IGW,which may be regard as the reasons why the IGWs are stronger in the night than in daytime when without distinguished weather process and why the strength of IGW with 40~80 min periods is stronger than that with 140~160 min periods.The strength of IGW is also proportional to the nonlinear cumulus convection parameter b and Coriolis parameter f.

• Contrast Analyses of Simulation Results in Heihe Basin Utilizing the Different Resolution DEM Data
• LIU Wei;GAO Yan-hong;RAN You-hua;CHENG Guo-dong
• 2007 Vol. 26 (3): 525-531. 
• Abstract ( ) PDF (484KB) ( )
• The detail land surface characteristic fields are the basic element in the land surface modeling and the distributed hydrologic modeling,in which the DEM data is an important factor.The 30" resolution topography data made by U.S.Geology Survey is world wide used in the numerical land surface model and distributed hydrology/ecology model.It could describe terrain distribution well large scale.While it could not describe terrain detail on small scale in some compler topography region,such as the Heihe River Basin(HRB) locates at Northwest China,where the heterogeneous is possess.At firstly,the 30 m resolution DEM data is compared with the USGS data in the HRB.In order to evaluate the modeling performance of the high-resolution DEM data of the HRB,the 30 m DEM data in Heihe river basin was re-sampled to 30 "resolution and compared to the global 30" DEM data made by USGS.Then the two data sets were used in atmospheric modeling.The atmospheric elements in Heihe river basin in June 2003 were simulated and results were analyzed,the following conclusion are obtained.DEM play an important role in air pressure,soil and air temperature field and precipitable water from the spatial correlation coefficient either between element and Dem fields or there changes.DEM has some impact on monthly precipitation amount at some extent.It could get more accurate simulation of air temperature and wind direction using Heihe data than USGS data.While,there is no obvious improvement in precipitation simulation.

• Simulations of Aerosol Diffusion and Distribution in Urban Atmospheric Boundary Layer over Complex Terrains in Winter
• ZHENG Fei;ZHANG Lei;ZHU Jiang;WANG Hui
• 2007 Vol. 26 (3): 532-540. 
• Abstract ( ) PDF (1552KB) ( )
• Focused on the diffusion properties of urban aerosol in winter,the paper develops and applies the WRF model,simulates the aerosol diffusion and distribution over urban atmospheric boundary layer in winter,through a case analysis,discusses the characters of aerosol diffusion and distribution on boundary layer structure of Lanzhou area over a complex terrain domain in winter.The model system is integrated the WRF model with the comprehensive ABL model in which the radiative effect and the diffusion of urban aerosol particles are considered.The primary character is that the aerosol has two high value centers which are under 100 m,center concentration is about 0.6~3.0 mg·m^-3.The center concentration decreases upwards and only has 0.02 mg·m^-3 at 1000 m.Under the joint influence of the emission source strength,source height and meteorology field,aerosol concentration varies greatly according to height and time in day time and its variation is 1.0 mg·m^-3.Aerosol transmission diffusion height can reach 600~800 m in day time.The simulated aerosol concentration profiles on the representative spots demonstrate the highest concentration and the most extensive vertical diffusion range at noon.These results correspond with the former observation of the smog layer height and the turbidity.At night,aerosol concentration varies weaken according to height and time,aerosol transmission diffusion height is 400~500 m and its variation is 0.05 mg·m^-3.

• Impact of Pollutant Concentration on Aerosol Optical Depth in Ürümqi
• LI Xia;REN Yi-yong;WU Yan;HU Xiu-qing
• 2007 Vol. 26 (3): 541-546. 
• Abstract ( ) PDF (603KB) ( )
• Ürümqi city,located in northwestern semi-arid area of China,is well known for its serious air pollution.In this article,aerosol optical depth(AOD) was retrieved from observation measured by sun photometer CE318 from April on 15 2002 to March on 15 2003.There were two principal kinds of air pollutants in Ürümqi,namely PM₁₀ and SO₂.Combining AOD and air pollutant concentration such as PM₁₀ and SO₂,the relationship between these elements was discussed.The research results showed that the monthly mean AOD changed in the way consistent with pollutant concentration changing year around.The correlation coefficients between AOD and daily and monthly means of PM₁₀ were 0.4227 and 0.5993,respectively;correspondingly,that ones between AOD and SO₂ were 0.3212 and 0.8168,respectively.The correlation coefficient between monthly mean concentration of SO₂ and monthly mean sulfation rate was very high with the value of 0.8430,which means concentration of SO₂ made great contribution to AOD.It was possible for concentration of SO₂ to evaluate AOD to a certain extent.

• Comparison of Two Methods of Assimilating Doppler Radar Wind Data
• YANG Yi;QIU Chong-jian;GONG Jian-dong;DENG lian-tang;XI Shuang
• 2007 Vol. 26 (3): 547-555. 
• Abstract ( ) PDF (1002KB) ( )
• The comparison of two methods of assimilating Doppler radar wind data based on WRF 3D-Var is presented.The first method is afforded by WRF 3D-Var 2.0 in which Doppler radar radial velocity observations are directly assimilated.The second methods are to assimilate the horizontal wind retrieved from Doppler radar data by using a two-step variational methods.Both methods are tested with a heavy rainfall case that occurred in the region of Huaihe River on 5 July 2003.Results show that the analyzed wind contains more mesoscale information.The threat scores with radar wind data are higher than the experiment without radar data assimilation.The predicted results are also verified with reflectivity observations.Both methods show positive impacts on the short-range forecasting for about 6 hours.However,the second methods that assimilated retrieved wind gives better forecast than the first method does.

• The Current and Electromagnetic Field in the Initial Stage of an Artificial ly-Triggered Lightning
• YANG Jing;QIE Xiu-shu;ZHANG Qi-lin;ZHOU Yun-jun;FENG Gui-li;KONG Xiang-zhen;ZHANG Ting-long;XIAO Qing-fu;ZHANG Guang-shu;WANG Huai-bin
• 2007 Vol. 26 (3): 556-562. 
• Abstract ( ) PDF (583KB) ( )
• A magnetic field measuring system of close lightning was developed.Synchronous data of the current and close electromagnetic field of the triggered lightning with 1μs time resolution have been obtained in Binzhou,Shandong Province during the summer of 2005.the characteristics of the current and close electromagnetic field in the initial stage (IS) of a triggered lightning are examined in detail.The triggering technique was a kind of classical one,but with an about 5 m Nilong at the bottom of the wire.The results show that the current of the discharge between the lower end of the wire and the lightning rod is about 720A.The corresponding electric and magnetic field of the first stroke at 60 m is 0.38 kV ·m^-1 and 11.26 μT,respectively.Further analysis show that the time interval between adjacent pulses in the stage of upward positive leader (UPL) varying from a minimum of 18.0 μs to a maximum of 25.0 μs.The geometric mean (GM) of the UPL peak current and charge transferred is 23.0A and 84.3 C with the rang es of 16.9~41.0A and 57.8~141.0 μC,respectively.At a distance of 60 m from the lightning channel the electric field of the UPL varies from 8.7 V ·m^-1 to 28.2 V ·m^-1 with a GM of 16.7 V ·m^-1 and magnetic field from 0.116 T to 0.544 μT with a GM of 0.3 μT.The relationshI_p between peak current I p (A) of the UPL and of the associated peak magnetic electric field B (μT) at 60 m can be fitted as I_p=61.9B+2.56.

• Analysis on Circulation Characteristics of Meiyu Rainstorm in the Lower and Middle-Reaches of Changjiang River during June 1999
• LONG Xiao;CHENG Lin-sheng;WANG Wen
• 2007 Vol. 26 (3): 563-571. 
• Abstract ( ) PDF (1801KB) ( )
• Using the objective analysis and intensive observation period data,the large-scale features of Meiyu front associated with intense rainfall in low-and middle-reaches of the ChangJiang River in June 1999 are studied.The results are as follows:(1)The total precipitation has a west-east distribution and is concentrated within a narrow rainband,the southern and northern boundary of rainband is clear during Meiyu period of 1999.(2)The maintaining of westerly flow which come form the Bay of Bengal and southwest flow which around along the northwestern periphery of the western Pacific subtropical high provide favorable large-scale condition for the Meiyu front rainstorm.The presence and maintaining of upper-and lower jet provide favorable lifting mechanism,at the same time the character of neutral convective instability stratification provide favorable instability mechanism in the low and middle levels.(3)The convergence of moisture is obvious in the low level of troposphere over the area of Meiyu front.The transportation of moisture mainly come from the Bay of Bengal and the western Pacific ocean,and then monsoon trough in South China Sea is a moisture transport channel from tropic sea to China mainland and has important effect in moisture transportation to Meiyu front zone.(4)Two cores appeared in high levels of troposphere which corresponding to the upper westerly-and easterly-jet in the cross-section of spatial averaged zonal wind u;the cross-section of spatial averaged meridional wind v dominates the southerly under 400 hPa and the northerly above 400 hPa;the potential instability stratification locates on northern and southern sides of Meiyu front zone,which are restricted by the downdraft and the instability energy could not be released,and then in these areas have not intense rainfall.

• The Lows over the Bay of Bengal in Early Summer and Beginning Time of Rainy Season of Yunnan Province
• LIU Yu;ZHAO Er-xu;HUANG Wei;ZHU Yong;YANG Shu-qun
• 2007 Vol. 26 (3): 572-578. 
• Abstract ( ) PDF (773KB) ( )
• The lows over the Bay of Bengal in early summer(April 21~May 31) from 1961 to 2006 were studied,which usually affect the beginning time of the rainy season in Yunnan.The result shows that the lows are roughly originated from the ranges of 9°~12°N and 88°~91°E.After starting out from the source,the lows affected Yunnan Province through two paths which correspond to the strong or weak South Asia high,respectively.There is a significant negative correlation between the frequencies of the lows and the beginning time of the rainy season in Yunnan,if the convection activity in the prior March near the Indochina Peninsula is strong(weak),it will be advantageous(disadvantageous) to establishment of the low system.A negative correlation also shows between the lows over the Bay of Bengal in early summer and the prior SST near the southern Indian Ocean,if the SST decreases(increases),it is(is not) helpful to develop the convection activity and to form the low system.

• The Urbanization Effect in Northwestern China and Its Contribution to Temperature Warming
• FANG Feng;BAI Hu-zhi;ZHAO Hong-yan;YANG Su-hua
• 2007 Vol. 26 (3): 579-585. 
• Abstract ( ) PDF (625KB) ( )
• Using the surface temperature data of 27 urban observation stations and 65 country contrastive stations over Northwestern China during 1961-2000,the urbanization effects on different scale cities were checkup.The results showed that there were two sorts of urbanization effects,namely positive and negative effects,and the urbanization effects ranged from -0.41℃ to 0.69℃ during 1961-2000,the urbanization effects contribution to temperature warming ranged from 5.3% to 27.7%.The intensity and stability of urbanization effects nearly related with the city size.In general,the big cities had the biggest intensity and the highest stability,middle cities followed it,small city had the least stability and its intensity easily changed with temperature fluctuating.Moreover,the urbanization effects were different during different periods,the average urbanization effect over Northwestern China in 1961-2000 was 0.02℃,-0.01℃ in 1981-2000,and 0.24℃ in 1991-2000.As a whole,the urbanization effects have a little influence on temperature warming over Northwestern China,the dominant fact on temperature warming was still naturally environmental changes.

• Relationship between Seasonal Variations of Climate in Lanzhou and the Urban Development in the Last Forty Years
• LI Zhuo-lun;WANG Nai-ang;YA Jing;LIU Tao;ZHI Meng
• 2007 Vol. 26 (3): 586-592. 
• Abstract ( ) PDF (549KB) ( )
• Through the ways of urban-suburb comparative method the influence of the urban development of Lanzhou on urban climate change in forty years is analyzed,especially the relationship between the urban climate change in different seasons and urban development are investigated.The population and the urban climate change in Lanzhou as two independent variables research the influence of population increase on the extent of the urban climate change using the regression analysis method.The result shows that the thermal island of Lanzhou in winter was almost caused by man-made heat.In other seasons,thermal island was also caused by man-made heat,but underlaying surface could change it,too.Man-made heat could cause the arid island,but it wasn't the main factor.

• A Algorithm Identifying Convective and Strariform in Mixed Precipitation and Its Application to Estimating Precipitation
• ZHONG Ling-zhi;LIU Li-ping;GU Song-shan
• 2007 Vol. 26 (3): 593-602. 
• Abstract ( ) PDF (898KB) ( )
• An algorithm identifying convective and stratiform based on the radar reflectivity has been developed and tested using the data of Wenzhou.The convective and stratiform regions are separated on the basis of the intensity and sharpness of the peak value indicate by the centers of the convective regions.This algorithm is operated below 3 km high above the ground so that to avoid the problem of underestimating the stratiform precipitation.Test in Wenzhou on the data of September 11,2005 shows that this algorithm performs accurately.The result is applied to estimating precipitation in a severe weather.It shows that both the convective and stratiform regions take an important role in the precipitation,especially the convective regions,and the stratiform ones significantly contributed to the rainfall amount and duration.

• Analyses on Operation Conditions of Rain and Snow Enhancement in Spring and Winter of Gansu
• YIN Xian-zhi;ZHANG Qiang;DING Rui-jing;XU qi-yun;NIU Guo-qiang
• 2007 Vol. 26 (3): 603-608. 
• Abstract ( ) PDF (533KB) ( )
• In order to meet the need of rain and snow enhancement operation,the annual variation of some meteorological factors tightly closed to precipitation in spring and winter were analyzed,meanwhile the relation between four circulation patterns,cloud systems favoring for rain and snow enhancement were revealed.According to these results,the climatic background in favor of rain and snow enhancement were also pointed out.

• Analyses on Major Effect Systems and Typical Atmospheric Circulation Triggering Mountain Torrential Disasters in Chongqing
• WANG Zhong;CHEN Yan-ying
• 2007 Vol. 26 (3): 609-614. 
• Abstract ( ) PDF (532KB) ( )
• Through the statistically analyzing the typical atmospheric circulation and major effect systems of 31 regional rainstorm cases occurred in Chongqing,the major results can be summarized as:(1) the mountain torrential disasters in Chongqing mainly come from landslides,local mud-rock flow and flood in the brooks produced by the heavy precipitation;(2) the typical local storm mainly occurs from May to September,and the most cases happen in July;(3) befor the occurrence of the most rainstorm,the patterns of two ridges with one trough(occupying 52% in the total cases) or two troughs with one ridge(occupying 42% in the total cases) are located in the high latitude;(4) plateau trough(plateau shear),plateau eddy,subtropical high,southwest eddy,low-level jet and surface cold front,et al.,are the major effect systems.

• The Dynamical Diagnosis of Snowstorm over North China in December 2004
• ZHAO Gui-xiang;CHENG Lin-sheng;LI Xin-sheng
• 2007 Vol. 26 (3): 615-623. 
• Abstract ( ) PDF (1498KB) ( )
• Based on the products of the mesoscale numerical model MM5 and surface observational data,the dynamical diagnosis of snowstorm over North China during December 20~22,2004 has been analyzed in this paper.The results showed that this snowstorm was directly related to the mesoscale shear line.The diagnosis of vorticity showed that the evolution of positive vorticity area was closely related to the movement towards the east,development,and lifting towards the north.The positive vorticity center can predict the snowstorm in advance.The vertical profile of the vorticity and divergence showed that collocation of vorticity field and divergence field was benefit to the development of snowstorm shear and form and maintaining of snowstorm.The diagnoses of moisture potential vorticity and vorticity variability showed that the intensity of vorticity variability was closely related to the conditional symmetric instability on the mid-low high.The negative center of moisture potential vorticity from low to high levels was one of the important reasons causing vorticity variability and storm increasing.The vorticity variability more accurately reflected physical mechanism of the snowstorm shear than the vorticity.

• Diagnostic Analysis on a Snowstorm Event Occurred of Xinjiang in Fall
• HUANG Hai-bo;XU Hai-rong
• 2007 Vol. 26 (3): 624-629. 
• Abstract ( ) PDF (1011KB) ( )
• Based on the conventional meteorological data combined with diagnostic analysis,a snowstorm event occurred in Urumqi of Xinjiang Province on 28 September 2003 is studied.The results show that:(1) Dramatic changes of the central-Asia atmospheric general circulations caused by the oscillations of Iran subtropical high in both the east-west and south-north directions make the large-scale background condition of the snowstorm.(2) The strong upward motion induced by the upper southwest jet and the strong interaction between the synoptic-scale systems in the lower troposphere are the important dynamical factors.(3) The dry cold air intrusion contributes to the formation and maintenance of the dry level,which makes the accumulation of water vapor and instable energy possible,enhances the convective instability during the development of the rain/snow process,are favoured for the formation,development and enhancement of the heavy rain/snow.

• Analyses on Climate Characteristic and Variation Rule of Rainstorm in Ningxia in Recent 44 Years
• DING Yong-hong;WANG Wen;CHEN Xiao-guang;ZHENG Guang-fen;SHAO Jian;JI Xiao-ling
• 2007 Vol. 26 (3): 630-636. 
• Abstract ( ) PDF (846KB) ( )
• By selecting the meteorological observed data of 24 stations in Ningxia and using the methods of resultant,Lepage test and Mexihat wavelet,the climate characteristics,the rules of interannual and interdecadal changes,the abrupt and period of rainstorm occurring in Ningxia were analyzed.The analyzed result shows that: after the 1990's,although there was extreme climate event of rainstorm,the climate characteristics of rainstorm in Ningxia didn't obviously change,meanwhile it exist the new features of beginning earlier,ending latter,obviously reduced in main flood season and increased in middle-east regions.There is the rules of interannual and interdecadal changes,and it has unconspicuous descend trend in the whole.Except for two years that could be considered abrupt not very significant in July 1972 and 1994,there were no other abrupt years.It also has period and quasi-period change characteristics in July,August and flood season in different time scales.

• A Preliminary Method Drought and Flood in Hetao Area in Spring and Summer Seasons Forecasted Using Winter Di-qi Map
• LIU Miao;TANG Mao-cang;LI Dong-liang
• 2007 Vol. 26 (3): 637-640. 
• Abstract ( ) PDF (373KB) ( )
• Comparing with the analyzed results of the precipitation anomalous percentage in spring(March~May) and in summer(June~August) of 1954-2005 and the corresponding winter Di-qi phase of 9 stations in Hetao area, the Di-qi phase can be divided 5 types:(1) Big vortex,(2) Small vortex,(3) The Hetao area at the edge of geothermic(cold) vortex,the East and West part of which is opposite(E-W opposite),(4) The Hetao area at the edge of geothermic(cold) vortex,the North and South part of which is opposite(E-W opposite),(5) The scale of Di-qi phase is very small(Phase in disorder).It is found that the Big vortex is the stablest,which results in the stability of more rain in geothermic vortex or less rain in cold vortex in Hetao area in spring and summer.While it's less stable of small vortex than big vortex,so when forecasting precipitation in summer we can refer to the Big vortex.The Hetao area is in the midst between geothermic vortex and coldly vortex where the phase is E-W opposite,so it can forecast the precipitation be normal in Hetao area in spring and summer.When the phase is N-S opposite or in disorder,we can not forecast precipitation accurately.

• Study on Climate Effect of Forest Band in Shanghai Suburb
• HE Fang-fang
• 2007 Vol. 26 (3): 641-648. 
• Abstract ( ) PDF (766KB) ( )
• Based on the analyese of temperature,humidity,evaporation,radiation synchronization observation data near forest and non-forest bands in model weather pattern in winter and summer in Shanghai suburb.The results showed that daily range of air temperatur near forest band were higher than that of the non-forest band,the daily range of air temperatur and the forest-leeward were higher than that of the forest-windward.The daily evaporation amount of the near forest band was smaller than that of the non-forest band,the average daily relative humidity near forest was higher than that of the non-forest.The scatter radiation near forest was lower than that of the non-forest,the reflection radiation near forest was higher than that of the non-forest,the difference of the total radiation and was involved in seasons and serried extent of the forest leaves.The difference of net radiation was mainly rest with the difference of the total radiation and the reflection radiation in the daytime,the difference of the net radiation was rest with forest and the difference of ground temperature between near forest and the non-forest at the night.

• A Study on Bad Visibility over Foggy Section of Freeway in Nanling Mountainous Region
• WU Dui;ZHAO Bo;DENG Xue-jiao;BI Xue-yan;FAN Shao-jia
• 2007 Vol. 26 (3): 649-654. 
• Abstract ( ) PDF (449KB) ( )
• Using the data from October 2003 to March 2005,such as minutely visibility,temperature,humidity,wind direction and wind speed from five visibility meters and three automatic meteorological stations located at Yunyan foggy section over Nanling mountainous region in north of Guangdong Province of freeway which is from Beijing to Zhuhai,the visibility character of the foggy section is studied.The results show the frequency of fog in January is the highest in whole year,the day numbers over half of January can occur fog,next is March,the lowest is in July.The fog days from the November to May next year occupy over 80% of all year round,forming obvious foggy season.The diurnal variation of heavy fog exist over foggy section of freeway in Nanling mountainous region,the frequency of the fog is the highest in the morning in a day,the lowest in the afternoon,but the range of the diurnal variation is obvious smaller compared to that of radiation fog,revealing temperature drop resulting from radiation cooling is not the main cause for the fog forming over foggy section of freeway in Nanling mountainous region,although the radiation cooling has the enhancing effect on fog forming in some extent.There are plenty of coagulate nuclei in the foggy section,but the forming of heavy fog need condition of relative higher humidity,at least reaching over 91% in Nanling mountainous region.In foggy area when the wind speed is as high as 5.2 m·s^-1,the fog still can occur.Over 90% occurrence of fog is under condition of the wind speed less 3 m·s^-1,and almost half about 2 m·s^-1.It is obvious different from the light wind condition of the forming of radiation fog.The topography has big influence on the forming of the heavy fog,the occurring frequency of fog in the windward side is higher than that in the leeward side.