Plateau Meteorology

Current Issue

28 December 2012, Volume 31 Issue 6   
  • Possible Causes of Total Ozone Depletion over the Qinghai-Xizang Plateau and Its Relation to Tropopause Height in Recent 30 Years
  • ZHOU Shun-wu;YANG Shuang-yan-;ZHANG Ren-he;LI Hui;WANG Mei-rong
  • 2012 Vol. 31 (6): 1471-1478. 
  • Abstract ( ) PDF (3646KB) ( )
  • Using the monthly total ozone data from the Total Ozone Mapping Spectrometer and the Solar Backscatter Ultraviolet Radiometer from 1979 to 2008, the total ozone depletion over the Qinghai-Xizang Plateau is revealed, and  the influences of the terrain lifting activities on total ozone are discussed. Finally, the influence of the total ozone depletion on the lifting at tropopause height of the Qinghai-Xizang Plateau is analyzed. The results suggest that there are significant seasonal differences both total ozone over the Qinghai-Xizang Plateau and its declining trend. What′s more, comparing with the same latitude but no-mountain region, the total ozone amount over the Qinghai-Xizang Plateau is lower in each month, especially from March to September. The lose is serious. In recently 30 years, the total ozone over the Qinghai-Xizang Plateau declines in each season and the decline range is larger than no-mountain region except for autumn. The strong upward movement over the Qinghai-Xizang Plateau in spring and summer is conducive to transport the low concentration ozone from troposphere to the stratosphere, resulting in the decrease of the total ozone. There are close relations between the losses of total ozone in spring and summer and the uplift of the second tropopause height in summer over the Qinghai-Xizang Plateau in recent 30 years.
  • Interannual and Interdecadel Changes of Summer Low over the Qinghai- Xizang Plateau and Its Relationship to Precipitation in China
  • XIE Qing-xia-;FAN Guang-zhou;ZHOU Ding-wen;ZHU Li-hua
  • 2012 Vol. 31 (6): 1503-1510. 
  • Abstract ( ) PDF (3868KB) ( )
  • The tendency variation of 600 hPa geopotential height fields over the Qinghai-Xizang Plateau(QXP) in the summer months (JJA) during1948-2009 were calculated based on the NCEP/NCAR data. The geopotential height field shows a increasing trend since 1948. The center was located on the low area over 27.5°-40°N, 80°-102.5°E on 600 hPa, it is defined regional average as summer  low index over the QXP. Using the Empirical Orthogonal Function (EOF) and wavelet analysis, the interannual and interdecadal changes of the summer low index over the QXP are examined. The results of temporal-spatial structures reveal that: In general, the  summer low over the QXP shows a decreasing trend since 1948. The low index has been in a low phase before  1980s, and it is the lowest in 1962 and the highest in 1979. From the 1980s to the early 21st century the low index has been in a high phase. The spatial distribution of the low index  reveals that most of the low indexes over the QXP region  increase from south to north, appears obvious zonal distribution, and its expansion coefficient shows the long-term positive trend. The analysis of the expansion coefficient shows that there is a obvious weakening change of the low in 1976. Wavelet analysis of expansion coefficients indicates that there are the periods of 1~2  and 13 years. At last, using the precipitation data from 596 stations in China, the relationship between interannual and interdecadal changes of the summer low  over the QXP and the precipitation in China is explored: When the plateau low increasing, the precipitation  in the Yangtze River and Xinjiang is more,  precipitation  in the Northeast China, North  China and South China is less.
  • Simulation Analysis on Land Surface Process at Maqu Station in the Qinghai-Xizang Plateau Using Community Land Model
  • CHEN Bo-li-;L Shi-hua;LUO Si-qiong
  • 2012 Vol. 31 (6): 1511-1522. 
  • Abstract ( ) PDF (1420KB) ( )
  • Using the Community Land Model version 3.5 of NCAR (CLM3.5) and the observed data atMaqu station in the Qinghai-XizangPlateau during June 2010 to February 2011, a single point simulation experiment has been done. The comparison of the simulated and observed physical variables such as radiationfluxes, energy flux, soil temperature and soil moisture proved that the model simulated the land surface process successfully. The simulation of the upward short wave radiation in summer is better, but bias occurs during winter. The simulation of the upward long wave radiation is good but the result is a little higher. The simulation of the net radiation is also good, the correlation coefficient of the observed value and the simulated value is 0.99 and the bias is -1.28 W·m-2. The  simulated result of the sensible heat flux is higher than the observed value in total while the simulation of the latent heat flux is good enough. The simulation of the soil heat flux is better in summer but worse in winter. A shallower of the simulated snow depth may lead to the bias. The comparison of the simulated and observed soil temperature showed that the result in summer is better than that in winter. The correlation coefficients of the six soil layers are all above 0.98, and the mean bias is -1.80 ℃. The  simulated the unfrozen water is successfully when the soil is frozen, which is a big improvement in soil moisture simulation comparing with the previous version of the CLM model. The mean correlation coefficient of the six soil layers is 0.94, and the mean bias is -0.015 m3·m-3.
  • Statistical Analyses on Characteristic and Environmental Aspect of Summer Thunderstorm over the Tibetan Plateau
  • YOU Wei-;ZANG Zeng-liang-;PAN Xiao-bin;LI Yi;AN Cheng;LI An-tai
  • 2012 Vol. 31 (6): 1523-1529. 
  • Abstract ( ) PDF (6710KB) ( )
  • Using the routing sounding and surface observation data,  the spatial-temporal distributions and isometeoric vertical profiles on thunderstorms weather over the Tibetan Plateau are analyzed in summer (from June to August) during 2000-2009. The stability index K is modified as KM index basis on these research and KM index is validated. The results show that the center of thunderstorm number is mainly located in hinterland,  southwest and east over the Tibetan Plateau. The center of thunderstorm number transfer along with months of summer from midland to southwest. The location of thunderstorm center is excursion to south and the mean frequency of  thunderstorm  numbers decrease in recently 5 years. The  thunderstorm  happened in different time over the Tibetan Plateau. The occurring time of thunderstorm in north and midland is 3~6 h early than that in the south of Tibetan Plateau. The inverse humidity occurs near ground in Lasa and Dingri district. There is the minimum value of θse on  400 hPa. In addition,  an especially unstable layer is present between 500 and 400 hPa,  and above  400 hPa,  the condition of atmosphere is stable. The validate KM index is shown that approximately 93.5% of thunderstorm occur with the KM>10 ℃ and there is no thunderstorm occur when KM<0 ℃. The KM index can predict thunderstorm on the Tibetan Plateau combined with wind,  humidity and other parameters.
  • Influence of the Different Averaging Period on Computing the Turbulent Fluxes Using LOPEX10 Data
  • LV Shao-ning|WEN Jun|ZHANG Yu|WANG Shao-ying|ZHANG Tang-tang|TIAN Hui|LIU Rong
  • 2012 Vol. 31 (6): 1530-1538. 
  • Abstract ( ) PDF (4287KB) ( )
  • The latent heat and sensible heat exchange between land surface and atmosphere can be obtained by processing the eddy covariance system observation data. However, the averaging period has essential influence on computing turbulent flux. The datasets collected from the LOess Plateau mesa region land surface process field EXperiment series (LOPEXs) have been analyzed to assess this influence. A formula named Flux Compensation (FC) has been derived for calculating the flux difference among the specified averaging periods. It shows that this formula could be applied to compensate flux loss due to shorter averaging periods and analyze the contribution from low-frequency eddies with a correlation coefficient around 0.95 compared to that directly calculated from the eddy covariance system observation data. After carefully calculations and analyses, it is concluded that the optimum averaging period for LOPEXs proved to be 30 min, and FC could also be applied to any other in-site data. It is the low-frequency eddies that cause the difference in flux with the different averaging periods. FC could be a technique in identifying optimum averaging periods and compensates the flux consumed by low-frequency eddies while keeping its high temporal resolution.
  • Mean Characteristics of Land Surface Key Parameters in Semi-Arid and Arid Regions of China in Summer of 2008
  • ZENG Jian-;ZHANG Qiang;
  • 2012 Vol. 31 (6): 1539-1550. 
  • Abstract ( ) PDF (3471KB) ( )
  • By picking 12 stations whose underlying land surfaces include grassland, cropland, orchard and forest, the climatic characteristics of land surface key parameters are investigated using the data measured from July to September 2008, provided the Northern China Observation Coordination and Integration Research in Semiarid and Arid Regions. The roughness lengths for momentum, sensible heat and water vapor, and bulk transfer coefficient, albedo, and soil thermal conductivity and diffusivity are calculated and compared within various underlying land surfaces. The results are compared with the model theoretic reference values as well. It shows that the thermal-hydrologic properties of vegetated land surface and vegetation height significantly influence some key land surface parameters, and that there is no evident relations between soil thermal conductivity and diffusivity and underlying surface types. Specifically aerodynamic roughness length and momentum drag coefficient increase with increasing vegetation height, but albedo decreases with vegetation height. The measured aerodynamic roughness length of grassland is smaller than model reference value, but it is not true for cropland and orchard. The measured momentum drag coefficient is larger than model reference value over grassland, but it is smaller than model reference value in other underlying surfaces. The measured albedo is basically lower than its model reference value although it lies between visible albedo and near-infrared albedo.
  • Study on Structure Characteristic of Southwest Vortex Accompanying with Heavy Rainstorm in East Sichuan Basin
  • JIANG Yu-hua-;DU Qin;ZHAO Da-jun;HE Yue;LI Jiang
  • 2012 Vol. 31 (6): 1562-1573. 
  • Abstract ( ) PDF (2039KB) ( )
  • Based on daily precipitation datasets from 1951 to 2008 at 54 stations in east Sichuan basin（27°-32°N， 105°-110°E）, the results of the daily precipitation statistics show that the heavy rainstorm with storm, hail and strong wind usually occurs from June to September. The high incidence area of single station rainstorm is in the Northeast of Sichuan and Chongqing. Frequent occurred area of regional heavy rainstorm is in the western of Chongqing and southeast of Sichuan. Using the observational data and NCEP/NCAR 1°×1° reanalysis data, selecting sixcases with regional heavy rainstorm processes in Yibin, Nanchong and west of Chongqing from 2007 to 2010, using the composited method, an analysis is made for the dynamic and thermal structure and moisture conditions of the influence system which promotes the occurrenceand development of Southwest Vortex (SWV). The results show that asdevelopment of SWV, the air column is warmed obviously on 200 hPa, but it turn partlycold, the convective instability is obvious. As well as a trough moves eastward on 500 hPa, the positive vorticity enhances and extends from the lower troposphere to 300  hPa and it inclines westwardlywith the height. That severe precipitation happened accompanying with the formation of upper-level jet on 200 hPa with the intersectional region of the southward strong wind and the northward one is located in 105°-107°E and 28°-30°N in the lower troposphere (low-level jet). In the mean while, the water vapor is transported from southeast to northwest significantly. The characteristic of satellite cloud image appears to be MCC, the Doppler radar echo feature is mesocycloneand ‘traineffect’ of SWV.
  • Analyses on Spatial Distribution and Temporal Variation of Atmosphere Water Vapor over Northwest China in Summer of Later 10 Years
  • LI Jiang-lin;LI Zhao-rong;YANG Jian-cai;SHI Yan-zhao;FU Jing
  • 2012 Vol. 31 (6): 1574-1581. 
  • Abstract ( ) PDF (3876KB) ( )
  • The spatial and temporal distributions of atmosphere water vapor were analyzed in  Northwest China in summer using the NCEP 1°×1° reanalysis data during the 10 years (2000-2009). The results showed that (1) the distribution of the atmospheric probable precipitation and vapor flux in Northwest China in summer of nearly 10 years were more on both sides and less in the center. The vapor flux from 700 hPa to 200 hPa was larger than that from surface to 700 hPa, but the vapor flux from surface to 700 hPa was larger than that from 700 hPa to 200 hPa in South Xinjiang basin. Vapor flux was abundant from 600 hPa to 450 hPa. (2) The convergence zone of whole vapor flux divergence has guidance for the area of precipitation forecasting. Vapor flux divergence below  and  above 700 hPa had opposite distribution phase in Northwest China besides Hexi region of Gansu Province. (3) The water vapor transport main is from westerlies which is divided into north and south on the west side of  Qinghai-Xizang Plateau, water vapor of the Bay of Bengal with the southwest wind and westerlies climbing up the Qinghai-Xizang Plateau and along its south side of transport  to the southeast of  Northwest China. The main reason of the annual change of whole layer of water vapor flux is caused to be water vapor transport capability with westerly wind. (4) Nearly 10 years, the whole layer vapor flux is increasing linearly, the annual change trends of the whole water vapor flux  basically indicate the annual trend of surface precipitation. (5) The vapor source main is from meridional transport, but zonal water vapor flux  play a decisive role for the net budget of vapor in  Northwest China.
  • Analysis on Circulation Pattern and Water Vapor Source of Heavy Precipitation in Maqu Region
  • LI Jiang-ping;DU Liang-liang;ZHANG Yu;WANG Jia-yuan;WANG Jing-song;WANG Shi-gong
  • 2012 Vol. 31 (6): 1582-1590. 
  • Abstract ( ) PDF (4964KB) ( )
  • Maqu is located in Gansu Province, lying in the northeast of the Qinghai-Xizang Plateau. It is not only the water resourceof upstream and source of the Yellow River, but also the intersection of the Qinghai-Xizang Plateau and Loess Plateau, so it is very sensitive to climate change. The researches on source of water in this region were focused on different seasons and dry/wet years. However, it is limited in the study of water source in different circulation patterns. 500  hPa circulation pattern of heavy rain in Maqu region are analyzed using NCEP/NCAR and observation precipitation data from 1967 to 2008; theHYSPLITmodel is used to study the vapor track in this region. The results indicate that:(1) The main circulation pattern of causing heavy rain is pressure trough on the Qinghai-Xizang Plateau, and that causing heavy rain is shear pattern; (2) The differences of the vapor tracks of different circulation patterns for rainstorm in Maqu region are obviously distinct, while that of the vapor tracks in one circulation pattern are not distinct in three pressure levels; the differences of the vapor tracks of different circulation patterns for rainstorm in Maqu region are not distinct, while that of the vapor tracks in one circulation pattern are obviously distinct in three pressure levels; (3) The vapor transport in Maqu is found to can be represented by the vapor transport track that forward 360 h tracing, the vapor track was dominated by southerly airstream. In conclusion, although the vapor tracks are different in circulation patterns and precipitationamount, the moisture affecting northeast of the Qinghai-Xizang Plateau comes from Indian Ocean-the Bay of Bengal and South China Sea-the Bay of Bengal.
  • Numerical Simulation of Impact of Ecological Environment Change on Lake Effect in the Source Region of the Yellow River
  • LI Zhao-guo-;LV Shi-hua;AO Yin-huan;WEN Xiao-hang
  • 2012 Vol. 31 (6): 1591-1600. 
  • Abstract ( ) PDF (4578KB) ( )
  • A three-dimensional mesoscale atmospheric model WRF is used to examine the characteristic of lake effect over Lake Ngoring in the upper reach of the Yellow River and the influence of  terrestrial environment change on the lake effect. Three groups of experiments have been simulated which include environmental improvement, status quo, degradation. The main results show: (1) From noon to nightfall in sunny summer, there is a clear lake-breeze circulation in Lake Ngoring; both sensible heat flux and latent heat flux are small over the lake in daytime, moreover, there is a strong cold (warm) lake effect over Lake Ngoring region in daytime (nighttime); the specific humidity over lake is larger than that over land in surface layer, but there is converse above it; the water vapor wall and high value areas of sensible flux can be found on land along the lake under the influence of lake breezes. (2) Environment degradation results in an enhanced lake-breeze circulation and higher water vapor wall. In addition, the difference of the boundary layer height increases between land and lake; for the different surface characteristics, the changes of sensible heat  and latent heat fluxes over land are much more than that over the lake. (3) Environment changes impact on the distributions of air temperature and specific humidity in the bottom and top of the boundary layer through the underlying surface and the lake breeze, respectively, as a result, there is a reverse trend in different heights.
  • Simulation Study of the Influence of Vegetation Fraction on Meteorological Condition in Lanzhou Using WRF Model
  • HE Jian-jun-;YU Ye;CHEN Jin-bei;LIU Na-;ZHAN Shu-ping-
  • 2012 Vol. 31 (6): 1611-1621. 
  • Abstract ( ) PDF (1335KB) ( )
  • Vegetation fraction is an important parameter in land surface model, which has obvious effect on the simulated results. The influence of a new vegetation fraction input data, deduced from the MODIS normalized difference vegetation index (NDVI) data, on the simulated surface meteorological field and energy budget in Lanzhou region using the Weather Research and Forecasting (WRF) model with the Noah land surface model (LSM) has been analyzed. The results show that: (1) The use of the new vegetation fraction data results in a decrease in surface albedo and an increase in surface emissivity in the study domain, which leads to increase in daytime and decrease at nighttime for sensible heat flux. (2) The simulated near-surface air temperature is significantly improved and the simulated wind speed is slightly improved when the new vegetation fraction data was used. (3) The increase of vegetation fraction in the new data compared to the model default value leads to the decrease of direct evaporation and near surface water vapor. (4) The planetary boundary layer height increases when the new vegetation fraction data was used, indicating the possible improvement of air quality by increasing vegetation coverage in the study domain.
  • Projection of Climate Change with Various Emission Scenarios over Huaihe River Basin in the 21st Century
  • LI Xiu-ping;XU Zong-xue;CHENG Hua-qiong
  • 2012 Vol. 31 (6): 1622-1635. 
  • Abstract ( ) PDF (1486KB) ( )
  • Using 14 GCMs from the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR4), the simulated air temperature and precipitation in the Huaihe River basin has been assessed, and their changes in the 21st century are projected. The simulation ability of 14 GCMs in simulating present climate for one single GCM is analyzed by comparing with observations for 1961-1999, and the ensemble simulation ability composed by better models selected through the Taylor diagram is analyzed as well. The results suggest that all GCMs show the good simulation ability for air temperature and precipitation over the Huaihe River basin, but most of them underestimate air temperature and overestimate precipitation. Ensemble models could improve the simulation ability, but do not show the best performance as anticipated. Although the scenarios projected by 14 GCMs vary greatly, all models project consistent increasing trends in air temperature and precipitation in  the most regions of the Huaihe River basin in the 21st century. The characteristics of annual and seasonal means, and temporal and spatial changes for air temperature and precipitation from the projection of ensemble models by 14 GCMs in 2010-2039, 2040-2069 and 2070-2099 have been investigated. The results suggest that both air temperature and precipitation would increase during three benchmark periods under the different scenarios, with scenario A2 increasing the most and scenario B1 the smallest.
  • Study on Climate Change in Mountainous Region of Shulehe River Basin in Past 50 Years and Its Effect to Mountainous Runoff
  • LAN Yong-chao-;HU Xing-lin-;XIAO Sheng-chun-;WEN Jun;WANG Guo-ya;ZOU Song-bin-;LA Cheng-fang;SONG Jie
  • 2012 Vol. 31 (6): 1636-1644. 
  • Abstract ( ) PDF (3537KB) ( )
  • The characteristic of climate change in the mountainous region of the Shulehe River basin in the past 50 years and its effect to runoff are analyzed usingthe observational data at the relationalhydrological and meteorological stations. The results show that the climate in the region has become more and more wet and warm in the past 50 years because of the influence of global warming. The mean temperature of year and every season have been presenting a rising and increasing trend in the region. The precipitation of whole year and every season except for summer also all have been  a rising and increasing trends in the region as a whole, and the annual fluctuation of precipitation variation is quite obvious, especially for theprecipitation during flood season. The mountainous runoff of the Shulehe River basin also has been  an increasing trend because the precipitation in the zones which elevation are below 3 000 m are ice and snow melt-runoff in the high elevationzones above 3 000 m areobviously increase. The reason of summer runoff increasing main is the increasingof snow and ice melt water supply from the zones above 3 000 m because the summer precipitation is not increase.
  • Impact of the Observational Environment Change on Surface Wind Speed in China
  • LIU Xue-feng-;LIANG Xiu-hui;REN Guo-yu;REN Zhi-hua
  • 2012 Vol. 31 (6): 1645-1652. 
  • Abstract ( ) PDF (2701KB) ( )
  • Using a data set of mean surface wind speed at 460 stations in the period 1971—2002 and comprehensive environmental survey data of meteorological station in China in 2007，  the effects of the observational environment change on long-term wind speed trends in China are analyzed. Based on the observational environment rating scores and wide-angles of barrier around observational surface, the stations are classified to five groups, and a comparative analysis is made to identify the differential effects of the observational environment on the surface wind speed. The results show that there are significant decreasing trends of annual mean surface wind speed for most of the non-moved stations, and the largest decrease occurs in winter, and the least change in autumn. The observation environment affecting wind speed includes many factors, but the wide-angle of barrier around observational surface is the most important factor. The decreasing trend of wind speed increases with the wide-angle of barrier around observational surfaces. The wide-angle of barrier around observational surface accounts for about one third of the observed decreasing trend in surface wind speed, but the observational environment change is not the only factor affecting the  wind speed change.
  • Analyses on a Meso-γ Scale Characteristic and Cause in Heavy Rainstorm Process in the South Border of Maowusu Sandy Land
  • JING Xi;TU Ni-ni;JING Yu;CHEN Chuang;WAN Hong-wei;HANG Xiao-jun;LI Xiao-li;KANG Lei
  • 2012 Vol. 31 (6): 1653-1662. 
  • Abstract ( ) PDF (6850KB) ( )
  • The MICAPS data, Doppler radar data and NCEP data are used to analyze the meso-γ-scale  characteristic and cause in heavy rainstorm process in the south border of Maowusu sandy land on 10-11 August 2010. The result show that, when the severe precipitation occurring, the development and enhancement of the southwesterly low-level jet, the development and maintenance of meso-γ-scale cyclone convergence on the left side of the southwesterly low-level jet are observed from velocity field of Doppler radar as well as strong echoes more than 50 dBz. Continuous decrease of barometric pressure, continuous southerly wind with maximum speed more than or close to 4.0 m·s-1 are observed during the rainstorm process. The analysis of vorticity budget show that, when the  heavy rainstorm beginning,  the dominant factors are horizontal advection and horizontal divergence terms, the vorticity budget  bellow 600 hPa in the rainstorm area, which reached 6×10-9s-2 on 800～700 hPa. Due to horizontal advection item, the  vorticity  maintained on 350～100 hPa, which reached -6×10-9s-2 nearby 150 hPa level. The analysis of apparent heat source (Q1)   indicat  that, when the   heavy precipitation beginning, the dominant factors are local chang and vertical advection  terms, Q1 forms the positive heating layer from 780 to 300 hPa; the dominant factor is horizontal advection term, Q1 forms the negative cooling layer from 300 to 220 hPa. The atmospheric thermal forcing is favorable for the ascending movement and the cloud cluster development. The accumlated distribution of apparent heat source (Q2) showed that, as the approach of heavy rainstorm occurrence, large value center  is more than 20 J·kg-1·s-1  near the upstream region of heavy rainstorm area, the Q2 is greater than 10 J·kg-1·s-1 in rainstorm area.
  • Study on Characteristic of Persistent Air Pollution in Beijing from 2000 to 2010
  • WANG Yu;HOU Qing
  • 2012 Vol. 31 (6): 1675-1681. 
  • Abstract ( ) PDF (3022KB) ( )
  • Through the air quality daily report in Beijing from June 2000 to December 2010, the characteristics of the persistent air pollution in Beijing were analyzed. The result showed that the air quality has been significantly improved in Beijing in recent 10 years. The persistent air pollution days and the exceed air quality  standard days appeared decreasing trend, but the  persistent pollution days account for the proportion of pollution days is still a large, persistent pollution has become a distinctive feature of  air pollution in Beijing. Spring is the season of the most persistent air pollution days, average 25.4 days per year. Summer is the season with minimum days of persistent air pollution, but the persistent pollution caused by wheat-straw burning often occurs in June. Distribution of persistent air pollution in Beijing can be divided into three types: Dust storm type, pollution accumulation type and  wheat-straw burning type. Distribution characteristic of the persistent air pollution effected by  dust storm is  high API in the whole  Beijing, expecially in urban area and southwest of Beijing. The distribution characteristic of the persistent air pollution of pollution accumulation type is of ‘higher in the south than north’. The distribution of  persistent air pollution of  wheat-straw burning type is  high API in the suburbs.
  • Analyses on Differences Between Cumulative Distribution Functions and Means of Topographic Indexes for Grid Cell and Individual Basin
  • XIAO Yan;DENG Hui-ping;SUN Shu-fen
  • 2012 Vol. 31 (6): 1682-1689. 
  • Abstract ( ) PDF (2803KB) ( )
  • To improve simulations of hydrological processes, the topographic-index hydrological model（TOPMODEL） has been applied to land surface models.  The simplified scheme which applies TOPMODEL to grid cells of Global Climate Model(GCM) can simplify application of TOPMODEL in land surface models. The 2°×2°  grid cell located in mountainous region of Changjiang basin and the other located in relatively flat region of Amazon basin are selected. The topographic indexes are calculated and statistical properties of topographic indexes for two grid cells are extracted using the data from digital elevation model of the Shuttle Radar Topography Mission. River basins and drainage network are extracted using the same dataset and statistics are extracted for each basin. The difference between  the cumulative distribution functions and means of topographic index for whole grid cell and for individual basin are analyzed. the cumulative distribution functions for whole grid cell and  individual basin are fitted by exponential function. The main conclusions are summarized as follows: (1) Although there are differences between the cumulative distribution functions and means for whole grid cell and  individual basin but the differences are not significant. It may be a reasonable simplification to apply TOPMODEL directly to grid cell of GCM； (2) The exponential function can fit the cumulative distribution functions well. These results provide helpful information for designing a TOPMODEL based and simplified hydrological model for use in land surface model.
  • Assessed Sounding Effect in Planetary Boundary Layer in East China in Winter
  • LI Yao-sun-;SHI Chun-e;YANG Jun;DENG Xue-liang;YANG Yuan-jian;WU Zhao-xian
  • 2012 Vol. 31 (6): 1690-1703. 
  • Abstract ( ) PDF (1783KB) ( )
  • To assess the performance of MM5 in simulating the meteorological parameters in the planetary boundary layer (PBL), Meteorological elements of PBL in east China in December of 2006 and 2007 were simulated by MM5. The simulation results were assessed objectively by the ground convention observation data and daily sounding data at Nanjing and Anqing stations at 08:00 and 20:00. Some common used statistical parameters of temperature, relative humidity, wind direction and wind speed at surface and different levels in PBL were calculated. And simulation effect of sounding in PBL before fog and during fog were assessed, respectively. The results show that: (1) the simulated temperature and relative humidity were reliable at the ground level, but the error of simulated wind speed was more. Frequency distributions of the biases between simulated and observation temperature，relative humidity and wind speed are near-normal distribution, and peak values are -1.52 ℃, 4.59% and 1.92 m·s-1, respectively. The simulation effect in daytime is better than in nighttime. (2) Take Nanjing and Anqing stations for example, the simulated sounding in PBL at 08:00 and 20:00 were acceptable, and the effect at 20:00 was better than that at 08:00. Simulation effect of temperature and relative humidity in PBL at Nanjing station was better than that at Anqing station, but wind speed at Anqing was better. (3) Take Nanjing as an example, simulation effect of temperature and relative humidity during the fog and before fog days were worse than normal, but wind speed had no significant difference. (4) The frequently of temperature inversion near surface were more than 40% in Nanjing and 30% in Anqing in winter. Temperature inversion near surface reappeared but overrated by model, and simulation effect in middle-to-upper boundary layer was not good. In addition, According the results of numerical sensitivity test, the high vertical resolution near surface was not necessary the bias of negative temperature at the ground level in modeling scheme.
  • Analyses on Cloud Physical Characteristics in a Special Rain and Snow Processes of Shandong Province in 2009
  • SHENG Ri-feng;MA Zhan-shan;OU Jian-jun;WANG Jun;GONG Dian-li;JIANG Peng;ZHOU Yu-quan
  • 2012 Vol. 31 (6): 1711-1720. 
  • Abstract ( ) PDF (1576KB) ( )
  • Based on the sounding data, CloudSat  data, automatic observational data and NCEP reanalysis data, the microphysical process,   weather situation and dynamic field of blizzard in the western part of Shandong on 11-12 November 2009 were analyzed. The major conclusions are as follow: (1)The shear line and southwest jet on 700 hPa played important roles in blizzard. The intersection of low-level southerly wind jet and cold air formed strong convergence and moisture convergence, which was conductive to the development and enhancement of the weather system. (2)The intersection of cold and warm air over snow area formed apparent energy front in horizontal and vertical directions. In the vertical direction, θse contour was intensive and a significant northward with height, which produced thermal conditions for Blizzard. (3)Before the snowfall, the invasion of cold air in low level triggered the circulation development of snow. During the severe  snow period, the appearance of cyclonic circulation on upper level enhanced transportation of southwest warm air. In the late of snowfall, the cold air strengthened and  dominate in low level, which cut off the supply of warm air, so snow gradually stopped. (4)Comprehensive analysis revealed cloud microphysical process and vertical evolution  under some dynamic conditions  using CloudSat, NCEP reanalysis data and L-band radar sounding data, Updraft can help the delivery of water vapor. At the same time, cloud droplet, ice crystal particle, snow crystal particle were better mixed, coagulated or condensated with each other. Big value zone of ice water content were consistent with the one of  vertical velocity, and the centre of number concentration of ice crystal located at the  top  of upward motion. L-band radar sounding data reflected the vertical evolution of heavy snow cloud under a certain dynamic condition.
  • Synoptic Situation and Pre-Warning of Anhui Tornado
  • YAO Ye-qing-;HAO Ying;ZHANG Yi-jun;LI Jin;LIU Gao-ping;QIU Xue-xin;YU Jin-long;LIU Yuan-yong
  • 2012 Vol. 31 (6): 1721-1730. 
  • Abstract ( ) PDF (1397KB) ( )
  • Using the historical observation data from 1960 to 2009  the climatic characteristics and in Anhui tornado  have been analyzed. The results show that the occurring frequency of tornado in Anhui Province is more than that of the east of Changjiang-Huaihe  valleys and no mountainous area from April to September. And tornadoes have obviously reduced since 1980s. Four types of synoptic situation which form tornadoes probably to have been summarized too. Through the contrastive analyses of the difference of tornado, hail and gust with thunderstorm using 20 km×20 km JMA reanalysis products, the conclusions are as follows: Before the tornado occurring, the air on the low-level  is warm and wet, sometime is wet in whole layer. Lifting condensation level is lower. CAPE main is from below 0 ℃ level. There is strong vertical wind shear in middle-lower levels and the value of storm relative helix is large. Tornado pre-warning depends mostly on velocity field from Doppler radar. The identifying characteristics of tornado are mesocycle and TVS (TVS often can be identified). The mesocycle or TVS almost is in the lowest height detected by radar. The positive/negative difference of Doppler velocity is becoming larger and its height lower during TVS evolution. And velocity difference is the largest when the tornado touches on the ground. Other influencing factor of tornado pre-warning is the distance from tornado position to Doppler radar, the ideal distance is between 20 km and 100 km.
  • Study on Quality Control of Radar VAD Wind in Data Assimilation
  • ZHU Li-juan-;GONG Jian-dong;LI Ze-chun
  • 2012 Vol. 31 (6): 1731-1738. 
  • Abstract ( ) PDF (3376KB) ( )
  • Developing the multiple iterative fitting quality control method for Velocity Azimuth Display (VAD) in order to meet the variational assimilation requirements. The radar VAD wind is mean horizontal wind at different heights with the characters of high time-frequency, suitable for applications in Numerical Weather Prediction model(NWP) and complex error source. Made good use of the VAD data in NWP, it could compensate the less wind information in the low level. However, whether  it will play a positive impact or not in data assimilation, the key problem is the VAD data quality control. In this paper, the VAD data adaptability for assimilation using the traditional quality control method is analyzed firstly. A series of comprehensive quality control is carried out for different error sources. The result shows that the VAD data has large negative bias comparing with the background. Then by diagnosing the problem, it is found that  many data do not meet the hypothesis among the raw radial velocity data used to retrieve VAD wind. In order to resolve this problem, the multiple iterative fitting quality control scheme is developed. The results show that the method could purify the data gradually to satisfy the harmonic characteristics. Compared  with the sounding data, it is more accurate than without the multiple iterative fitting quality control. Furthermore, the negative bias compared with the background is also corrected. Case and monthly continuous test reveals that the retrieved VAD data could meet the requirements of quality control for data assimilation.
  • Reanalysis on the Urban Heat Island Effect in Kunming
  • CHEN Yan;DUAN Xu;DONG Wen-jie;YANG Ming-zhu;DUAN Chang-chun
  • 2012 Vol. 31 (6): 1753-1760. 
  • Abstract ( ) PDF (1512KB) ( )
  • Using the homogeneous surface air temperatures  from 1971 through 2008, the temperature trends in Kunming region, including its four suburban counties and a real rural station of Taihua Hill are analyzed. The particularity and complexity of the urban heat island (UHI) effects with the rapid urbanization in the low-latitude plateau are studied. The results indicate that the annual mean temperatures are generally increasing despite their different amplitudes, with a descending order from Kunming, suburban counties to Taihua Hill. As for the trends of temperature, that in Kunming and its suburban counties present similar characteristics. The primary feature is that the minimum temperature trends ascend in winter and spring and the diurnal temperature range obviously descends. However, the temperature of Taihua Hill varies in a dissimilar way, with no obvious trend of the minimum temperature in all seasons and somewhat increasing trends of the maximum temperature and the diurnal temperature range. The temperature, especially the minimum temperature in Kunming and its suburban counties may have been contaminated substantially under UHI effect since late 1980s, which results in more serious assessment of UHI at Kunming than previous studies that taking stations in medium and small cities as rural ones. In the addition, both the minimum and  maximum temperatures in Kunming tend to show cold urban island features before late 1980s when taking Taihua Hill and the suburban counties as rural station, respectively.
  • Influence of Temperature Change in Southeast Guizhou on Evaporation from Evaporating Dishes
  • GU Xin-;KANG Wei-min;LONG Xian-ju;ZHANG Yan-mei-
  • 2012 Vol. 31 (6): 1761-1766. 
  • Abstract ( ) PDF (1632KB) ( )
  • Using the monthly observation data at 16 surface weather stations in Southeast Guizhou from 1961 to 2010, the impact of evaporation from evaporating dishes on meteorological elements by means of the gray correlation method was  analyzed and the Empirical Orthogonal Function Decomposition Method (EOF) was used to extract the time coefficient of the first eigenvector field. The Mann-Kendall method was used for abrupt change test and linear trend estimation, and non-linear regression method to establish mathematical models in which several quantity relationships between single of elements and the evaporation were determined. For example, the impact of temperature change on evaporation, etc. The results show that there are some correlations between the evaporation from the dishes and temperature factors, humidity factor, the energy factor, wind speed and other factors in the Southeast Guizhou region. Meanwhile, there is a obvious warming trend in the Southeast Guizhou region, and the critical period of temperature occurring abrupt change is in the middle 1990s, the and its temperature tendency rate reaches to  0.25  ℃·(10 a)-1, which had passed the significanct level at α=0.05. The evaporation from the dishes increases about 5.93%~8.04% while the temperatures increases 1 ℃, and gradually decreased from east to west. The evaporation from the dishes is  negative correlation with sea level elevation.

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