Current Issue

• Influence of the Mechanical and Thermal Forcing of Tibetan Plateau on the Circulation of the Asian Summer Monsoon Area
• WANG Tong-mei;WU Guo-xiong;WAN Ri-jin
• 2008 Vol. 27 (1): 1-9. 
• Abstract ( ) PDF (1350KB) ( )
• The NCEP/NCAR reanalysis data were used to study the seasonal variation of thermal condition over Tibetan Plateau(TP), and its mechanical and thermal forcing on the atmospheric circulation over the surrounding regions, particularly for the tropical Asian monsoon circulation. Results show that the TP mechanical effects on the circulation, is the strongest in winter, get reduced in spring. The mechanical forcing result in a winter pattern of lower atmosphere deviation circulation, characterized by the cyclonic/anticyclonic circulations over the south/north of the TP, which is called the "TP Dipole Mode". Following northward shift of the westerly and transition of total heating of TP from negative to positive in April, the cyclonic deflection circulation in the southern TP becomes stronger and moves northward gradually, and becomes a typical summer cyclonic circulation patterns over the whole TP in June. To the southern TP, the TP mechanical and thermal forcing result in Indian-Burma trough all the time over the Bay of Bengal, and thus, lead to a stronger sensible heating on the Indian Peninsula than that over the Indochina Peninsula, and a stronger latent heating on the Indochina Peninsula than that on the Indochina Peninsula. The variation of Indian-Burma trough exhibits a semi-annual periodic feature. The maximum strength of Indian-Burma trough in the early February and August correspond to the strongest of the winter mechanical and summer thermal forcing, respectively. The analysis of the tropical meridian wind shows that the TP thermal forcing before the monsoon onset is very important, particularly for the persistent rainfall in early spring in South China, and occurrence of the earliest Asian monsoon onset in the eastern of the Bay of the Bengal and the latest in the Indian Peninsula.

• Estimation of Precipitation Latent Heat in Rainy-Season over Qinghai-Xizang Plateau
• LI Dong-liang;LIU Miao;WANG Hui
• 2008 Vol. 27 (1): 10-16. 
• Abstract ( ) PDF (1349KB) ( )
• The data of this paper includes two parts, one is the monthly average data of Outgoing Long-wave Radiation(OLR) from June 1974 to December 2005, which is observed by the National Oceanic and Atmospheric Administration(NOAA) satellites, there are altogether ninety-one grid points in the regions of 75°~105°E and 25°~40°N and the horizontal resolution ratio is 2.5°×2.5°Lon./Lat.. Another is the monthly rainfall data of ninety-three conventional meteorological station of the Qinghai-Xizang Plateau during the period of 1961-2005. On the basis of the relationship between rainfall and OLR and the partition of climatic zone, the mathematic model is established in each zone and grid, which is used for estimating the monthly rainfall, and then estimating the monthly precipitation latent heat year by year from 1961 to 2005. It shows that the annual average rainfall is 401.5 mm and the latent heat is 18.55×10²⁰J in the eastern part of the Qinghai-Xizang Plateau, which has some increase in recent 45 years, and the increasing rate is 0.218×10²⁰J/10a, that is to say, it will increase 1.2 percent in each decade.Furthermore, the total latent heat and its variability of the Qinghai-Xizang Plateau have a little greater than the eastern part.

• Evolution Features of East Asian General Circulation and Mechanism during Transition Season between Autumn and Winter
• KUANG Xue-yuan;ZHANG Yao-cun;LIU Jian
• 2008 Vol. 27 (1): 17-25. 
• Abstract ( ) PDF (1935KB) ( )
• The general circulation differences of the transition season between autumn and winter, altogether with the transition time differences at various levels are analyzed by using NCEP/NCAR reanalysis data. The results show that the thermal effect of the Tibetan Plateau is not only the key factor for the onset of East Asian monsoon but also the trigger to the circulation transition from autumn to winter due to its quick decreasing of surface temperature.The southward retreat to the south of 35°N of the East Asian subtropical westerly jet axis(EAWJ) and intensified EAWJ center over the western Pacific Ocean is the signal of the establishment of the winter circulation pattern. Comparison of the surface heat flux between the Tibetan Plateau and Yangtze-Huai River basin indicates that the sharp decreasing of the surface sensible heat flux over the Tibetan Plateau far exceeds the increasing of the net long-wave radiation, which leads to the corresponding dropping of surface air temperature. It is known that the sensible heating mainly works at low level, so the response of high level atmosphere to its change is 2~3 pentad lagged through thermal adapting mechanism.However, the sudden decreasing of latent heat is the main thermal feature for Yangtze-Huai River basin.The effect of the latent heat can reach the atmosphere at high level, which is responsible for the consistency of atmosphere at high level and low level.

• Mechanism Analysis of the Influence of Atmospheric Moist Potential Vorticity on Anomalies of Precipitation over Yangtze-Huaihe River Basins in Summer
• ZHANG Yan-xia;QIAN Yong-fu;ZHAI Pan-mao
• 2008 Vol. 27 (1): 26-35. 
• Abstract ( ) PDF (1938KB) ( )
• Based on the ERA-40 reanalysis data at GMT 00:00 during 1958-2001, the difference of moist potential vorticity(MPV) and its components in more and less years of protecipitation are analyzed.The results show that:(1) both MPV and MPV1 are affected by the variation of convective stability, which is mainly induced by the discrepancy of the moisture vertical gradient;(2) relative MPV and MPV2 are mostly caused by the vertical vorticity and vertical shear of zonal wind as well as the meridional shear of warm and moist airflow, respectively. Additionally, MPV1 and MPV2 are used to investigate the atmospheric property of 850 hPa over Yangtze-Huaihe River basins.The result indicates that the atmospheric convective(baroclinic) instability weakens(strengthens) in recent 50 years.

• Modeling of Near Surface Energy and Characteristic of Boundary Layer in the Northern Tibetan Plateau
• LI Mao-shan;MA Yao-ming;Lü Shi-hua;HU Zeyong;Ishikawa Hirohiko;MA Wei-qiang;SUN Fang-lin;SONG Min-hong
• 2008 Vol. 27 (1): 36-45. 
• Abstract ( ) PDF (1874KB) ( )
• Using the NCAR MM5V3.7 atmosphere model coupling NCAR LSM land surface model and 2002 CAMP/Tibet IOP data,the numerical simulation experiment in the northern Tibet was carried out. The results of simulation were consistent with that of observations on the mesoscale or single station. Potential temperature profile is lower than that of the observed; the convective layer height is higher than that of the observed. We need adjust the scheme of land surface process and physics process parameterization to improve the climate model simulations over northern part of Tibet.

• Synthetic Analyses on Environmental Conditions of an Abrupt Heavy Rainstorm on the Northeast Side of Tibetan Plateau
• JING Xi;LI Dong-liang;LI Ming-juan;BI Xu;HE Wen-bin;JING Yu;DU Ji-wen
• 2008 Vol. 27 (1): 46-57. 
• Abstract ( ) PDF (2030KB) ( )
• Using the routine synoptic charts, satellite cloud image, conventional physical factors field, surface energy ratio and moist potential vorticity, an abrupt heavy rainstorm in Xi'an on afternoon of 29 June, 2004 is comprehensively analyzed.Conclusions are drawn that the cold air moving from west and east led to energy accumulation near surface level in Guanzhong.Low energy ratio tongue formed of eastern cold air movement on surface chart triggered the abrupt rainstorm.The weak southwest stream in lower-troposphere on the eastern side of Tibetan Plateau before rainstorm caused high energy and geopotential instability in rainfall area. The simultaneous rapid development of southeast and south stream in boundary layer provided abundant water vapor for the abrupt heavy rainstorm in 12 hours.Southwesterly jet on 300 hPa coupled with south wind and southeast stream below 850 hPa, and its coupling with northwest stream behind the ladder trough created a double secondary circulation, which supplied the rainstorm with continuous strong ascending motion. On wet barotropic field, mesoscale β convective instable core formed in lower-troposphere, wet barotropic field coupled with wet baroclinic field, ∂θ_se/∂p changed with height, and favorable situations for rapid development of mesoscale cyclone was obviously built up in lower-troposphere, which are also important factors for the rainstorm achieving strong ascending motion in very short period of time.On satellite cloud image, it appears that the low-mid westerly cloud system interacts with subtropical cloud system, where the mesoscale β convective cell rapidly develops near the intersection.

• A Comparison Study on Snow Cover of the Conventional Meteorological Observation and Its Variational Tendency in Qinghai Region
• LEI Jun;FANG Zhi-fang
• 2008 Vol. 27 (1): 58-67. 
• Abstract ( ) PDF (948KB) ( )
• Based on the monthly snow depth and snow day of the conventional meteorological observations at 44 stations in Qinghai region, a comparison study about character of variation between snow depth and snow day is carried out. It is found that the snow depth and snow day have a better relation and reflect the tendency variation of snow cover congruously in Qinghai region. It shows that the snow cover had decreased in summer and autumn since 1960's. Although in winter and spring the snow cover had increased from 1960's to early 1990's, but it had rapidly decreased from middle 1990's to early 21st century.In winter, snow depth and snow day all show that the variation tendency is obvious, especially in the area among Tanggula mountain-Bayanhar mountain-A'ny maq n mountain in 32.5°~35°N, 95°~102°E.But in spring there is a reverse tendency in west and north Qinghai region.According to analyzing several snow data synthetically, it is found the winter snow is more than multi-year mean in 1964, 1975, 1993, 1995, 1998 and less in 1963, 1965, 1969, 1997, 2003. The spring snow is rich than multi-year mean in 1977, 1982, 1987, 1989 and 1990 and less in 1969, 1979, 1985, 1999, 2001. The correlation coefficient field shows that snow depth and snow day have best relationship in winter and conventional snow dataset in northeast and southeast of Qinghai region in spring should be used cautiously.

• Simulation and Analysis of Heavy Snowfall in the Hexi Corridor with WRF Model
• TAO Jian-hong;ZHANG Xin-rong;ZHANG Tie-jun;JI Hui-min
• 2008 Vol. 27 (1): 68-75. 
• Abstract ( ) PDF (1735KB) ( )
• Numerical simulation is made with the new generation numerical model-WRF(Weather Research and Forecast) on a heavy snow process happened in the Hexi Corridor during 13~16 March 2005. It is clear that the WRF model can make good simulation about the snowfall distribution.Main conclusions are as follows:(1) The appropriate collocation of cold front of surface, shear of lower-level wind field and upper-level jet enhances the development of vertical circumfluence.(2) There is the maximum convergent 600 hPa, and the divergent is above 500 hPa when the heavy snowfall is happened.With the beginning of the snowfall, the mesoscale synoptic system fades gradually.(3) There is intense mesoscale ascending motion in the whole snowfall process, and the ascending motion between 500~400 hPa is the strongest.(4) The westerlies(especially 600 hPa) supports enough water vapor to the area of snowfall.

• Maintenance Mechanism of the Scandinavian Pattern in Its Positive Phase during 2000/2001 Winter and Its Influence on the Weather over the Northern Part of China
• BUEH Cholaw;SHI Ning;JI Li-ren
• 2008 Vol. 27 (1): 76-83. 
• Abstract ( ) PDF (1604KB) ( )
• The maintenance mechanism of the Scandinavian pattern(SCA) in its positive phase, which prevailed in 2000/2001 winter, is investigated in terms of the energy dispersion of Rossby wave and barotropic feedback forcing due solely to high-frequency transient eddies. The possible impact of this pattern on the weather and climate of the northern part of China is analyzed as well.The upstream portion of this pattern, which covers the region extending from the North Atlantic to the Scandinavian peninsula, is primarily driven and maintained by high-frequency transient eddies and partly sustained by the energy dispersion in association with the Rossby wave propagation. The downstream part, which locates near Lake Baikal, manifests itself as a result of an almost pure downstream propagation of the Rossby wave packet.The maintenance of this pattern causes a cold air accumulation over the west and central Siberia and, a cold advection in the westerly to the south.Consequently, the northeastern China and part of North China suffered from the cold weather. It also causes an abundant snowfall over North Xinjiang, eastern part of Inner Mongolia and northeastern China. The eastward extension of the Atlantic jet and the associated enhancement of the baroclinic eddies may be regarded as a precusory signal of the strong snowfall event of North Xinjiang, eastern part of Inner Mongolia and northeastern China.

• Relationships between Climatic Anomaly in Arid Region of Centre-East Asia and Sea Level Pressure Anomaly in the Last 100 Years
• WANG Jin-song;CHEN Fa-hu;JIN Li-ya;GUO Jiang-yong
• 2008 Vol. 27 (1): 84-95. 
• Abstract ( ) PDF (1613KB) ( )
• Based on the grid data of precipitation, temperature in arid region of centre-east Asian(ARCEA) and North Hemispheric sea level pressure(SLP) during 1901-2002, the relationships among the precipitation, temperature and SLP in winter and summer are analyzed, respectively.And the composited analysis of SLP anomaly field is investigated for the representative anomalous years of precipitation and temperature. The results show that when SLP is kept higher over the NW Pacific and the Arabian Sea in winter, the precipitation is more and air temperature is high in ARCEA in winter. In spring when the Aleutian low and its southern part' west Pacific subtropical high are intensive, the summer precipitation in ARCEA is more.As SLP in ARCEA itself is kept lower in spring, the temperature of ARCEA has higher in summer. The notable impact of spring SLP anomaly on the climate change in ARCEA has guiding significance in climatic prediction.In addition, the negative(positive) SLP anomaly is in extratropical zonal(low latitude) when the ARCEA has abnormal more precipitation and higher temperature in winter.The positive SLP anomaly is in ARCEA when it has abnormal more precipitation. The positive SLP anomaly mainly located in North of India peninsula, the west part of ARCEA is negative and east of it is weaker positive SLP anomaly.The results also show that it is easy to occur these climatic types that more precipitation/higher temperature(less precipitation/lower temperature) in winter and more precipitation/lower temperature(less precipitation/higher temperature) in ARCEA in summer.

• Analysis for the Influence of Cold Air Mass on Two Cases of Plateau Vortex Moving Out of the Tibetan Plateau
• YU Shu-hau;GAO Wen-liang;XIAO Yu-hua
• 2008 Vol. 27 (1): 96-103. 
• Abstract ( ) PDF (1110KB) ( )
• Through the two cases of Plateau vortex moving out of the Plateau during 12~20 August 1998 and 12~14 July 2003, the baroclinic of vortex and temperature advection are studied. The results are as follows:(1) Tole Plateau vortex moved out of the Plateau mainly due to northeast lasting invasion of cold air flow and the Nomhon Plateau vortex moved out of the Plateau mainly due to northwest cold air invasion to the vortex area before the west wind trough.(2) Plateau vortex moves out of the Plateau when there is strong baroclinic condition above 600 hPa in vortex pole and also with strengthened baroclinic condition on 500 hPa in eddy area.But Tole Plateau vortex baroclinic condition in vortex pole and strengthened baroclinic condition on 500 hPa in eddy area are all weaker than the Nomhon Plateau vortex.Tole Plateau with north cold and south warm conditions is stronger than the Nomhon Plateau vortex.(3) Plateau vortex is mainly controlled by the cold air advection in the eddy area and moves out of the Plateau when the west cold air advection is stronger than the east;the enhancement of the cold flux in west area will accelerate the development of the Plateau vortexes and will be good to the lasting time of the Plateau vortexes to the east of the Plateau. By influence of the shear line, the moving out of the Plateau Tole votex's west region strong cold air advection is weaker than the Nomhon vortex which is influenced by the west wind trough.And the cold air advection area of Tole vortex moving out of the Plateau is bigger than the Nomuhong vortex.

• Warming and Drought Response of Autumn Climate over Loess Plateau to Global Warm
• WANG Yi-rong
• 2008 Vol. 27 (1): 104-112. 
• Abstract ( ) PDF (1766KB) ( )
• To better look at the warming and drying response of autumn climate over Loess Plateau of China to globe warming, the climate changes over Loess Plateau of China have been analyzed using the climatic element in recent 69 years(from 1937 to 2005). The results show that the warming and drying climate trend in autumn is significant in all seasons, which became warmer and drier in autumn over the Loess Plateau. So the total rainfall and low cloud trend were down; air temperature, evaporation, sunshine time, ground soil temperature were up.The mostly character of the warming-drying climate response were same consistent; the response sensitivity area was in the middle of the Plateau.In last 70 years(1937-2005), the rainfall evolvement appear two inflexion points, and the temperature appear two abrupt changes. These changes have better relation with the subtropical high and the Qinghai-Tibet high. On evolvement of decade time scale, there is remarkable 20~30 year periods in rainfall, and no more than 70 years in the temperature.

• Analysis of Numerical Simulation on Extreme Precipitation in China Using a Coupled Regional Ocean-Atmosphere Model
• WANG Zhi-fu;QIAN Yong-fu;LIN Hui-juan
• 2008 Vol. 27 (1): 113-121. 
• Abstract ( ) PDF (1169KB) ( )
• Extreme weather and climate events have received more and more attention in recent years, due to the often large losses of human life as well as a tremendous increase in economic losses caused by them. Based on the 40-year(1958-1997) precipitation data simulated by a coupled regional ocean-atmosphere model system(P-σ RegCM9-POM), by defining the 90th percentile as the threshold of extreme precipitation for each grid, the characteristics of the summer extreme precipitation events in China simulated by the model are studied. Results show that the coupled regional ocean-atmosphere model system has the ability to produce the spatial distribution of the climatic mean extreme precipitation threshold, which is characterized by several large value centers including south China, the Yangtze-Huaihe River valley, north and part of northeast China. Also the trends in the intensity and frequency of extreme precipitation are captured. The summer extreme precipitation and extreme precipitation days significantly increase in the middle reaches of Yangtze River, some parts of southwest China and the lower reaches of Yangtze River, and decrease significantly in Midwest, some regions of north and northeast China. But they decrease in large part of the lower reaches of Yangtze River, which is opposite to the observational result. This may be caused by the difference in the peak values of the daily precipitation between the first few model years and the later years. Using the EOF(empirical orthogonal function) method, the temporal and spatial variation of the extreme precipitation events is studied. The first EOF pattern exhibits a main feature that the anomalies of the parameters of the extreme precipitation events over the areas south of Yangtze River are opposite to that over the coastal region of south China, and the areas north of Yangtze River;and this variation is featured as an interdecadal variation. While the second pattern shows that the anomalies over northwest and part of southwest China are opposite to that over other regions, and that it changes interannually. The time correlation and space correlation methods are used to investigate the ability of the coupled regional model to capture the properties of extreme precipitation. The analysis shows that the model can basically simulate well the closely correlated relation between each two of the extreme precipitation, the total rainfall in summer, and the extreme precipitation days.

• Numerical Study on Concentration Distributions of Sulfur Compounds and Their Budgets over East Asia in the Springtime
• ZHONG Chang-qin;ZHANG Mei-gen;ZHU Ling-yun
• 2008 Vol. 27 (1): 122-127. 
• Abstract ( ) PDF (1009KB) ( )
• A coupled regional chemical transport modeling system is applied to investigate the time spatial variations in sulfur dioxide and sulfate aerosol concentration over East Asia, especially to illustrate transport and chemical conversion of sulfur dioxide on 9~12 April, when the Happo, Oki and Hedo sites in Japan and part of the Japan Sea experienced a high sulfur dioxide episode revealed in the observations.Analysis of model results shows that the emissions from the Miyakejima volcano located to the south of Tokyo, Japan, had a strong impact on sulfur dioxide and sulfate aerosol concentration distributions over Japan islands and the surrounding areas, and were the dominant contributor to the high sulfur dioxide episode over the observation sites and the Japan Sea. Sulfur budgets for March 1 to April 30 indicate that the gasphase and the aqueous phase had the same importance in oxidizing sulfur oxide, and about 42% sulfur compounds(≈25% in sulfur dioxide) emitted in the model domain was transported out, while about 57%(≈35% by wet removal processes) deposited in the domain.

• Analyzing the Theoretic Retrieval error of Temperature Profiles from HIRS/3 Data
• HUANG Jing;ZHANG Yan-wu;QIU Chong-jian
• 2008 Vol. 27 (1): 128-134. 
• Abstract ( ) PDF (1148KB) ( )
• Using the HIRS/3 infrared simulation data and NCEP reanalysis data, the global distribution character of the theoretic temperature retrieval error is analyzed by combining the SVD and EOF method. The results show that the error distribution and the latitude had some relations. The absolute retrieval error in mid-high latitude regions is bigger than that in low latitude regions, while the relative error is smaller than the low latitude regions. The results of relative error reflect the poor retrieval ability in low latitude regions. And the occurrence of megarelief, for example Qinghai-Xizang Plateau, has some effect on the retrieval results.

• Analysis and Numerical Simulation of the Role of Spectral Shape Parameter for Two-Moment Bulk Microphysics Scheme
• ZHAO Zhen;LEI Heng-chi
• 2008 Vol. 27 (1): 135-142. 
• Abstract ( ) PDF (1653KB) ( )
• In bulk microphysics scheme, the size distribution of each hydrometeor category is often described by a gamma distribution law n(D)=N₀D^αexp(-λ^D). Two-moment scheme generally treat intercept N₀ and slope λ as prognostic parameter while holding spectral shape parameter α constant. The role of the spectral shape parameter α is investigated by examining its effects on sedimentation and microphysical source/sink terms. A stratiform precipitation in Northwest China is simulated by using the PSU/NCAR mesoscale model(MM5) with a new double-moment explicit microphysics scheme. Various rain water spectral shape parameters, α_r, is introduced for the model simulation experiments. It is found that the model simulation results are generally in agreement with the theory analysis and there are differences between surface precipitation and cloud macroand micro characteristics for various rain water spectral shape parameter α_r.

• The Radiation Characteristic of a Lightning Return Stroke Channel
• ZHANG Hua-ming;YUAN Ping;Lü Shi-hua;OUYANG Yu-hua
• 2008 Vol. 27 (1): 143-147. 
• Abstract ( ) PDF (516KB) ( )
• Spectra of lightning return strokes had been obtained by Slit-less spectrograph in Shandong. Channel temperature and electron density are calculated according to the information of lightning spectra. The radiation mechanism of lighting channel is analyzed.Pinch effect of lightning channel plasma is discussed,and from this pinch spot is deduced as the main radiant point of X-ray in the process of lighting.The differences between lightning channel and plasma channel produced by laser in the atmosphere is discussed.

• A Efficient Jacobian Algorithm for Radiative Transfer Models of Atmospheric Remote Sensing
• GUAN Li;LI Jun
• 2008 Vol. 27 (1): 148-152. 
• Abstract ( ) PDF (1450KB) ( )
• Using the high spectral resolution infrared sounder radiance measurements, fast and accurate calculations for radiative transfer model(RTM) and its Jacobian is needed in order to inverse the radiances or brightness temperature(BT) for atmospheric profiles or assimilate the radiances in Numberical Weather Prediction(NWP) in near real time.Linearization of radiative transfer equation(RTE) is the key in physical retrieval of atmospheric temperature and moisture profiles from infrared sounder observations. In this paper, one fast and accurate method is described for computing the Jacobians, namely from linearized RTE(LR method).The methods are independent of RTMs, only atmospheric transmittances are required in the efficient Jacobian calculations. The NAST-Ⅰ OSS(NAST-Ⅰ: National Polar-Orbiting Operational Environmental Satellite System Airborne Sounder Testbed-Interferometer Instrument, OSS: Optimal Spectral Sampling) RTM model and numerical method are used for testing the computations.The derived Jacobians are compared with the linear model that OSS RTMs and numerical method provided. The results show that Jacobians from the fast computations are very close to that from the true linear model, while the fast methods takes only 0.5 T_B calculations.

• Statistical Downscaling of Future Temperature Change in Source of the Yellow River Basin
• ZHAO Fang-fang;XU Zong-xue
• 2008 Vol. 27 (1): 153-161. 
• Abstract ( ) PDF (1656KB) ( )
• Direct outputs of climate change simulation from general circulation models(GCMs) are inadequate for the assessment of land-surface impact on regional scale. Statistical downscaling technique is proposed as one of the tools to establish the relationship between the mesoscale GCM output(frequently atmospheric circulation data) and sub-grid-scale surface variables(such as precipitation), under the assumption that the GCM output are more reliable than the latter. After analyzing both advantage and disadvantage of the statistical downscaling technique and its applicability, the daily maximum and minimum temperatures were downscaled from GCM grid to local area using the Statistical Downscaling Model(SDSM) in this paper. In order to analyze its reasonability, a resolution with the grid of 2.5 in latitude and 3.75 in longitude in source of the Yellow River was selected and the 30-year daily temperature series at 7 stations were used. First, a statistical transfer function between the large scale predictors and the local temperature was established by using the SDSM. Then, the transfer function was validated by using individual observed data. Finally, the temperature scenarios for future periods(2020s, 2050s and 2080s) were estimated using the validated transfer function from output of the HadCM3 SERS B2 at 7 stations. On the basis of above analysis, the temperature scenarios for the whole source of the Yellow River was developed by using the Kriging interpolation in ArcGIS. The results show that the downscaled maximum temperature quickly increase, and the average scenarios for the future periods are 1.34, 2.60 and 3.90℃, respectively. However, the average change of daily minimum temperature is relatively unconspicuous, and the scenarios for the future periods are 0.87, 1.49 and 2.27℃, respectively. The scenarios for different months and seasons are quite different. The scenarios for the maximum temperature are remarkable in spring and autumn, and the scenarios for the minimum temperature are distinct in summer and autumn.

• The Changes of Flood-Drought in Chongqing Urban Area during the Past 100 Years
• LI Yong-hua;GAO Yang-hua;TANG Yun-hui
• 2008 Vol. 27 (1): 162-168. 
• Abstract ( ) PDF (991KB) ( )
• Using Z index as classification of drought-flood intensity and based on the precipitation data in Chongqing urban in the past 100 years, the frequencies of years and four seasons of flood-drought have been analyzed and their change features have also been studied based on tendency analysis and MESA and wavelet ways. Results show that the frequencies of flood-drought of years and four seasons exceed 25% in Chongqing urban and flood-drought disasters are high frequency. The varieties of flood-drought contain staggered features and the characteristics of interannual variability are obvious in some period of time using the polynomial fitting and MESA ways. In a word, the features of interdecadal variability are in evidence in year and summer but those of interannual variability are obvious in other three seasons. The signals with different scales have stronger local features in time-frequency distributing in Chongqing urban in year and four seasons. Their phases are difference with different scales and they are more complex while the scales are small. The variety features of flood-drought indexes in year locate flood phase with both large and small scales, but they locate drought phase in summer in recent years. The probability of drought disaster is high frequency in summer but that of flood disaster in other three seasons during the future period of time.

• Application of a New Downscaling Model to Winter Temperature and Rainfall Prediction over Guizhou
• YAN Xiao-dong;WU Zhan-ping;MA Zhen-feng;GU Shu-hong;YAN Hua-sheng
• 2008 Vol. 27 (1): 169-175. 
• Abstract ( ) PDF (1101KB) ( )
• Based on 500 hPa geo-potential height field from CGCM model output, the observed precipitation data of Guizhou in winter, and NCEP/NCAR reanalysis data(500 hPa), the prediction skills and effects of winter precipitation and temperature were studied by using the downscaling method. The results show that: The first, from the point of statistical-dynamical downscaling, the relationship between season-scale general circulation and regional rainfall or temperature was obtained, which has obvious dynamical background and weather signification. The second, 20-year and 2-year reforecastes show that the relationship is reasonable. The third, to the prediction rate of precipitation of Guizhou in winter is about 70 percents, and the temperature is about 65 percent. Moreover, through after temperature inversion equation revising, its forecast rate reaches about 67%. In extremely unusual year, the prediction rate of precipitation waves small, but the temperature is great. According to this method, the precipitation and temperature trends in winter of Guizhou in 2005 was prospected finally.

• Relation of Summer Rainstorm and West Pacific Ocean Subtropical High Circulation in Southeast Part of Guizhou Province
• CHI Zai-xiang;BAI Hui;HUANG Hong;GONG Xue-qin;NIU Jun-mei
• 2008 Vol. 27 (1): 176-183. 
• Abstract ( ) PDF (723KB) ( )
• hrough the generalized analysis of main impact systems, the various element field and the terrain characteristics of the local rainstorm in southeast Guizhou in summer of 1996-2005, the result show that, first, 9 time local rainstorm are closely related with the position change of west Pacific subtropical high(WPSTH), and the southwest air flow of the SPSTH circulation turn into jet stream, which transports the massive water vapor and the instability energy. And then the strengthened function of special advantageous terrain creates the local rainstorm. According to the rainstorm area, we have divided it into four kinds of types, namely west rainstorm, eastern rainstorm, south rainstorm and middle rainstorm, but the southern rainstorm and the middle rainstorm have the mid-and low-level low vortex shear line coordination.

• Contrast Analysis of Two Typical Heavy Precipitation Weather Cases along Qilian Mountain
• YIN Xue-lian;GUO Jian-hua;DONG An-xiang;CHENG He-ping;CAO ling;LIU Xiu-lan
• 2008 Vol. 27 (1): 184-192. 
• Abstract ( ) PDF (1014KB) ( )
• Using the synoptic meteorology and dynamics methods, the circulation background, mcro-and small-scale weather systems, dynamic mechanisms and orographic features, as well as artificial precipitation stimulation of two typical region heavy-rainstorm weathers along Qilian Mountain were compared and analyzed. It is found that there are similar and different at two rainstorm processes, namely, shear convergence, low-level jet, and relative and stable circulation situation are a key of regional rainstorm occurring along Qilian Mountain, the special orography and geomorphology, artificial precipitation stimulation provided the favorable conditions for increasing precipitation of Qilian Mountain region.

• Diurnal Changes of Micro-Climate in Haibei Alpine Wetland in the Qilian Mountains
• LI Ying-nian;WANG Qin-xue;DU Ming-yuan;ZHAO Xin-quan;ZHAO Liang;XU Shi-xiao;GU Song
• 2008 Vol. 27 (1): 193-201. 
• Abstract ( ) PDF (1390KB) ( )
• Based on the measured data, diurnal changes of micro-meteorology in Haibei alpine wetland in 2004 were analyzed in this paper. The results were as follows: The maximum and minimum instantaneous values of diurnal averaged variations of radiation and the components of heat energy balance were observed at the noon and sunrise, respectively. The maximum and minimum values of the surface long-wave effective radiation were observed at the noon and sunset in a day, respectively. The surface surface albedo showed the variations of the "U" type in a day, which was lower in daytime than in morning and evening. Its diurnal minimum values in January and July were 0.68 and 0.12, respectively. The other parameters of micro-meteorology, such as moment flux, vertical wind speed, horizontal wind speed, friction velocity, were hight in the afternoon and low from night to morning in a day. The vertical wind speed ascended in a whole day in October, while descended in nighttime in other months, especially in winter. The Haibei alpine wetland had the strong heat source in summer, while became weak in the cold season. The soil temperatures of Haibei alpine wetland smoothly varied because its surface was covered by water for a long time. The period of soil temperature below 0℃ at the depths of 40 cm was less than two months, and that of 60 cm above 0℃ was all the year, which meant the seasonal frozen layer was thin.

• Application of Wind Energy Simulation Toolkit(WEST) to Wind Energy Numerical Simulation of China
• ZHANG De;ZHU Rong;LUO Yong;YU Wei;WANG Cheng-hai
• 2008 Vol. 27 (1): 202-207. 
• Abstract ( ) PDF (696KB) ( )
• The Canadian wind energy simulation toolkit(WEST) is applied to making wind atlas of China. Comparing with the observation data, the stations which simulation relative error less than 20% are mostly located in the eastern and the costal area of China, but the stations which relative error lager than 60% are mostly located in the high-lying western China. It is found that the WEST has more accurate distribution of wind energy resources in mid-east China with low-lying than in the western plateau of China. It shows that the climatic background classification and the atmospheric boundary layer parameterization schemes of WEST are needed to be modified.

• Modelling the Temporal and Spatial Variabilities of Precipitation in Zulihe River Basin of the Western Loess Plateau
• ZHAO Chuan-yan;FENG Zhao-dong;NAN Zhong-ren
• 2008 Vol. 27 (1): 208-214. 
• Abstract ( ) PDF (1270KB) ( )
• Zulihe River, located in the west-central Chinese Loess Plateau, is one of major tributaries draining to Yellow River. Zulihe River basin is characterized by continental climate. Therefore, water is scarce resource. Precipitation is considered as the only source of water(i.e., input) and varies both temporally and spatially in the study area. Understanding the temporal and spatial variations in precipitation are fundamental to quantitatively assess the possibility and the paths of ecological restoration and its hydrological effects. To accomplish this understanding, we first evaluate interpolation method commonly used to estimate areal precipitation in order to choose the appropriate model. In the study, we evaluated five methods such as multiple regression model, inverse distance weighted interpolation, Kriging interpolation, spline interpolation, and Trend surface interpolation. The results indicated that the trend surface model is the best one to estimate precipitation in the study area. Then the trend model was adjusted by regression model because trend model was neglect of topographic effect on precipitation. We found the adjusted model had higher accuracy than trend model. The temporal and spatial distributions of precipitation were estimated by combing trend surface interpolating model and regression model. Lower precipitation values are registered in the low valleys of Zulihe River. Higher precipitation values appear in the mountain regions. Annual mean precipitation increases 20 mm by increase of 100 m altitudes. Generally the precipitation decreases from the south to the north.

• Classifying Types of Vegetation Remote Sensing Based on Growing Law in Shaanxi Province
• LI Deng-ke;GUO Ni
• 2008 Vol. 27 (1): 215-221. 
• Abstract ( ) PDF (1227KB) ( )
• The differences between types of vegetation represent as not only the dissimilarities of their spectrums, but also of their growing laws. Vegetation grows in a cycle of a year. Difference types of vegetation respectively has its developmental rhythm or special growing law in this cycle. NDVI is the indicator of growing status of vegetation. It is a idea method to express growing law of vegetation by NDVI time sequence curve in a year. Therefore, the types of vegetation can be classified using NDVI time sequence. Sixty-nine time's MODIS images included Shaanxi Province with fine weather in 2004 had been collected to calculate NDVI. Unsupervised classification model had been run with monthly composite NDVI data set gained by MCV. Classification result was combined and interpreted under GIS according to former maps of vegetation types, land use, agricultural zone and so on. NDVI time sequence curves of vegetation types had been analyzed. It is proved that the classification result can factually reflect regional distributing of vegetation, the diversities between the curves of classifications were obvious and classifiable, growing law of the types of vegetation can be figured.

• A Operational System of Landslide Disaster Forecasting and Warning Based on WebGIS Technique
• SHAN Jiu-sheng;WEI Li;BIAN Xiao-geng;ZHANG Yi-zhi;LIU Xian-yao;LIU Xiu-fen
• 2008 Vol. 27 (1): 222-229. 
• Abstract ( ) PDF (2129KB) ( )
• Eight landslide disaster monitoring stations have been established in the regions where geological disaster took place frequently since 2004. Using the observation and analysis of the statistic data as well as the principle of landslide stability, we finally mastered the principle of how landslide took place on account of the continuous rain at the hilly land in the east of China. The study makes it clear that weather or not the rain conduce landslide not only depends on the real time precipitation rainfall, but also has relevance to the previous volume from weather process, however the influence of daily rainfall is absolutely different. In the saturation condition, the stability of landside is related with the ratio of the total pressure of interstitial water to the total uplifting pressure besides the weight of the Landslide strips. Based on the experiment and statistics, the model of Landslide disaster forecasting and warning with the very critical precipitation rainfall has been founded. By combining the Web-GIS technology with the spatio-temporal forecast of Landslide disaster, the real time system has been established by which the products of the Landslide disaster forecast are automatically promulgated. It is prove to be effect in the forecast service in the last years for successfully promulgating forecast and warning several times by which there are several hundreds of people and more than thousand million of property survived.