Plateau Meteorology

Current Issue

28 June 2016, Volume 35 Issue 3   
  • Study about a Process of MCC Converting to MCV on Qinghai-Xizang Plateau
  • DING Zhiying;WANG Yijie;LIU Ruixiang
  • 2016 Vol. 35 (3): 561-573.  DOI:10.7522/j.issn.1000-0534.2016.00020
  • Abstract ( ) PDF (18669KB) ( )
  • With WRF(ARW)model and 3DVAR system,using ATOVS satellite data from the National Centers for Environmental Prediction as observation field,a direct assimilation test and numerical simulation is done about the conversion process of MCC to MCV on the Qinghai-Xizang Plateau in July 22-23,2013.First,do assimilation test with AMSUA,AMSUB and HIRS3 data,and test results showed that:different sensor data assimilation have different effects; multiple sensor data assimilation isn't better than a single data results; cycling assimilation effectively improve the strength and location of the simulated MCV.After cycling assimilation with AMSUB data,analysis on the process of MCV shows that mesoscale eddies and heavy rainfall occurred in wet isentropic surface subsidence area.Altitude positive MPV1 superimposed lower positive temperature,weakened convective instability,induced cyclonic circulation,making the development of cyclonic vorticity and precipitation.And the latent heat of condensation of water vapor further exacerbated wet isentropic tilt,making vertical vorticity further development.Meanwhile,by the influence of water vapor in the process of heating,the gradient of equivalent potential temperature weakened,and baroclinic term also declined,so the total MPV increases.In addition,the comparison results of the differences between east and plateau MCV showed that the latter had larger vorticity in low-layer due to the heating effect of the Qinghai-Xizang Plateau.
  • Dynamic Downscaling Simulation of Extreme Temperature Indices over the Qinghai-Xizang Plateau
  • XIAO Linhong;GAO Yanhong;CHEN Fei;XU Jianwei;LI Kai;LI Xia;JIANG Yingsha
  • 2016 Vol. 35 (3): 574-589.  DOI:10.7522/j.issn.1000-0534.2016.00039
  • Abstract ( ) PDF (45628KB) ( )
  • To produce high-resolution climate simulations over Qinghai-Xizang Plateau(QXP)for studying extreme temperature indices,a dynamic downscaling experiment(WRF2 for short)has been performed over East Asia based on WRF coupled with Noah-MP,forced by ERA-Interim(ERA-Int).Compared with grid observation data,the performance of ERA_Noah-MP in simulating extreme temperature indices over the QXP has been evaluated.To investigate the impacts of the land surface model and the boundary conditions on the simulated extreme temperature indices.Different land surface models(Noah LSM)and boundary conditions(CCSM)are used to run two other dynamic downscaling experiments(WRF1,WRF3 for short),which have the same model configurations with WRF2 except for the land surface models and the boundary conditions.The results show that the basic features of the spatial patterns of all extreme temperature indices over the QXP can be finely reproduced by WRF2.The centered pattern correlation coefficients of WRF2 compared to observation for most extreme temperature indices are above 0.77 and the simulation of the length of growing season performs best.But simulations for extreme temperature indices suffer from systematic biases to a certain extent,On the whole,a cold bias exists in the simulations of WRF2,especially in winter.WRF2 can simulate the observed inter-annual variations well,and can reproduce the warm trend of extreme temperature indices.However,due to the impacts of the boundary conditions,climatic tendency rates of extreme temperature indices for WRF2 exist negative deviation.In spite of being forced by the different boundary conditions,the two experiments coupled with the same land surface model reproduce the similar spatial distributions of extreme temperature indices under current model configurations; between two land surface models tested,WRF1 produced significantly larger cold bias.This difference between two experiments is caused by the different reproduction between two Land surface models for snow cover and snow melting process,bare soil albedo over QXP,which lead to a higher surface albedo in Noah LSM compared with Noah-MP.However,the boundary condition has more influence on climatic tendency rates of extreme temperature indices compared with the land surface model,and thus the climatic tendency rates of WRF3 are close to observation.
  • Vertical Structure and Variation Characteristics of Wind Field in Low-Level Atmosphere in the Southeastern Margin of Qinghai-Xizang Plateau
  • DONG Baoju;LI Jian;SUN Jihua;XU Anlun;SU Jinlan
  • 2016 Vol. 35 (3): 597-607.  DOI:10.7522/j.issn.1000-0534.2015.00041
  • Abstract ( ) PDF (12278KB) ( )
  • In order to further understanding long-term variation of low-level wind field over the mountains region of the Qinghai-Xizang Plateau,based on the observational data of boundary layer tower and wind profile radar in Dali region of the southeastern margin of the Qinghai-Xizang Plateau from 2008 to 2012,the vertical structure and variation characteristics of wind field were analyzed.The results show as follow:Firstly,wind speed and wind direction frequency in the low-level atmosphere varied with height.Wind force scale was 2 level and prevailing winds were east winds between 2 m and 400 m height.It indicated that wind speed and wind direction measured with boundary layer tower and wind profile radar was continuous.Secondly,vertical wind speed changed with season,which its value was greater in winter than that in summer.The diurnal variations of wind speed at different height were different,that is to say,the diurnal variations of wind speed displayed one peak below 20 m and two speaks between 100 m and 1500 m height,and were not evident above 2000 m height.The monthly variations of wind speed showed one speak below 20 m and above 1500 m height,and showed two speaks between 100 m and 1000 m height.Finally,the zonal winds below 600 m height appeared a daily cycle of east wind and west wind.The meridional winds were south winds all the day between 2 m and 20 m height,and were south winds from afternoon to sunset and north winds form night to next morning above 100 m height.
  • Impacts of Freeze/Thaw Processes on Land Surface Energy Fluxes in the Permafrost Region of Qinghai-Xizang Plateau
  • GE Jun;YU Ye;LI Zhenchao;XIE Jin;LIU Chuan;ZAN Beilei
  • 2016 Vol. 35 (3): 608-620.  DOI:10.7522/j.issn.1000-0534.2016.00032
  • Abstract ( ) PDF (3661KB) ( )
  • Permafrost is ubiquitous on the Qinghai-Xizang Plateau.Soil freezing/thaw processes change the surface condition,which significantly influences the material and energy exchange between land and atmosphere.Observational data of land surface processes from the National Basic Research Program of China‘The response of desertification over Tibet Plateau to global changes'at Beiluhe during 2014-2015 were used in this paper.The permafrost is divided into four stages based on the daily maximum and minimum soil temperature at 5 cm depth,i.e.the thawing stage,the compLEtely thawed stage,the freezing stage and the compLEtely frozen stage.Characteristics of the seasonal and diurnal variations of surface sensibLE heat flux(Hs),latent heat flux(LE), ground soil heat flux(G0)and Bowen ratio at different freeze/thaw stages are analyzed and the impacts of freeze/ thaw processes on land surface energy fluxes and energy partitioning are investigated.The results show that: the transition of soil freeze/thaw stages has remarkabLE effect on the seasonal variations of Bowen ratio and G0.Bowen ratio decreases and G0 changes from positive to negative at the beginning of the compLEtely thawed stage and conversely when the soil starts to freeze.The impact of freezing process on the trend of Hs and LE is not obvious but Bowen ratio increases significantly.Thawing process LEads to the reduction in Hs and increase in LE,which makes Bowen ratio decrease obviously.The diurnal variation of Hs is similar during different stages.The diurnal variation of LE is related to the near surface soil water content and its diurnal variation.Due to weak diurnal variation, the higher soil water content LEads to larger LE during compLEtely frozen and thawed stages.LE is constrained during the freezing and thawing stage by the combined effects of the large diurnal variation of soil water content and the out-of-phase changes of soil water content and Rnet.Influenced by freeze/thaw processes,the diurnal variation of G0 is weak during the freezing stage.
  • Influence of Snowfall on Soil Temperature and Moisture in Source Region of the Yellow River during Different Freezing and Thawing Stages
  • BIAN Qingyun;LYU Shihua;CHEN Shiqiang;WEN Lijuan;LI Zhaoguo;PAN Yongjie;FANG Xuewei
  • 2016 Vol. 35 (3): 621-632.  DOI:10.7522/j.issn.1000-0534.2016.00029
  • Abstract ( ) PDF (3658KB) ( )
  • As two integral parts of the cryosphere,snow cover and frozen soil both have important impacts on climate system,and the interaction between them makes it complicated to analyze the their influences on climate change in areas where snow cover and frozen soil coexist.In order to investigate the influence of snow cover on the thermal regime and hydrological process of frozen soil,different soil freezing and thawing stages was divided into soil freezing stage,frozen stage and thawing stage by soil temperature data observed from October1, 2013 to May 31,2014 in source region of the Yellow River,then the effects of snowfall on soil temperature and moisture were analyzed in each stage.During soil freezing stage,the ground surface net heat flux decreased during the snowfall day and the following sunny days(with snow cover),which resulted in an obvious increase of the soil daily minimum temperature at depths of 5 cm and 10 cm and led to a rise of the soil daily minimum temperature at depth of 20 cm to above 0 ℃.This could delay the soil freezing process at the depth of 20 cm.During soil thawing stage,the ground surface net heat flux decreased during the snowfall day.As a result,the soil daily minimum temperature at depths of 5 cm and 10 cm dropped to below 0 ℃ and thus prolonged the process of soil thawing at these layers.In the snowfall process of the soil freezing and thawing stages,snow cover could not only change the soil moisture by thawing,but also change soil moisture by influencing soil temperature.During soil frozen stage,snow cover had an effect on soil temperature,but it had little effect on soil moisture.During the soil freezing-thawing,compared to the change of soil moisture caused by soil freezing and thawing,the change of soil moisture caused by snow thawing is smaller.
  • Dissimilarity Analysis between Scalars over Farmland Surface in Jinta Oasis
  • ZHANG Shan;ZHANG Yu;WANG Shaoying;SHANG Lunyu;SU Youqi
  • 2016 Vol. 35 (3): 633-642.  DOI:10.7522/j.issn.1000-0534.2016.00037
  • Abstract ( ) PDF (2970KB) ( )
  • Monin-Obukhov(M-O)similarity theory is an important theoretical basis of the study of the atmospheric surface layer turbulence.Since the surface is always heterogeneous at different scales and in different degrees, temperature(T)is not similar to humidity(q).In order to investigate the dissimilarity of temperature and humidity at different scales and to further understand the turbulent transport process above Jinta Oasis farmland, the data for three heights(3.33,8.41,16.60 m)in sunny day from the“The Oasis System Energy and Water Cycle Field Experiment”over Jinta Oasis farmland was used, which was conducted from 23 May to 18 June in 2005.Firstly, the correlation coefficient of temperature and humidity for every 30-min runs was calculated.Secondly, the frequency distributions of |rTq| in different wind directions and different wind velocity,and the probability distributions of stability with different correlation coefficients for three heights in daytime were analyzed.Thirdly, the spectrum of the correlation coefficient and relative transfer efficiency with Fourier transform under six kinds of correlation coefficient cases(rTq > 0.6,0.3< rTq <0.6,0< rTq < 0.3,<-0.6,-0.6< rTq <-0.3,-0.3< rTq <0)and three kinds of stability conditions (unstable ζ <-0.05,near-neutral -0.05 < ζ <0.05,stable ζ > 0.05) were analyzed in the frequency domain.The results show that the scalar similarity is larger with the lower wind speed at the low level and with the wind speed is between 2 ~-4 m·s-1 at the top level.With the stability closing to near-neutral conditions, the scalar similarity is decreasing.RTq(n)and λn is approximately to a constant in the frequency domain 10-2 < n < 10-1 and 10-1 < n < 100,respectively.With the |rTq| decreasing, the corresponding peak frequency of RTq(n)is decreasing,and the relative transfer efficiency is also decreasing,i.e.,the transfer efficiency of water vapor is increasing,which are caused by the inhibition of heat advection of oasis-desert on heat transport.
  • Evaluation of Monthly Air Temperature from Two Reanalysis Datasets in Mongolia
  • WANG Tianye;WU Tonghua;LI Ren;XIE Changwei;ZOU Defu;QIN Yanhui;YU Wenjun;WANG Weihua
  • 2016 Vol. 35 (3): 651-661.  DOI:10.7522/j.issn.1000-0534.2016.00033
  • Abstract ( ) PDF (1694KB) ( )
  • Under the scenario of global warming,the air temperature has changed significant in the mid-high latitude regions of North Hemisphere.The climate in Mongolia plays an important role in the East Asia climate system.However,the unavailability of meteorological observations in Mongolia handicapped the understanding on the climate changes in this country.Reanalysis products,surrogates for large-scale observations,have been increasingly applied to assess climate impact in the past two decades because they are designed to estimate the state of real atmosphere and land surface characteristics.In order to evaluate the applicability of the JRA-55 and the ERA-interim products of air temperature in Mongolia,this study compared them with the observations of 18 metrological stations in Mongolia from January 1,1987 to December 31,2006.High correlations with an average of 0.99 indicate that the two datasets could capture the annual cycle very well.However,the average root-meansquare error(RMSE)of 2.5℃ and 2.3℃ for JRA-55 and ERA-interim respectively,reveals that they could not be applied directly for the individual sites.The biases can be mainly attributed to the altitude differences between ERA-Interim grid points and stations.An elevation correction method based on monthly lapse rates is limited to reduce the bias for all stations.After the calibration,the biases in all seasons except the winter were largely reduced.Furthermore,the seasonal and annual trends of the reanalysis data of air temperature were analyzed and compared with those of the observations.The results indicated that the two kinds of reanalysis monthly air temperature data in Mongolia agree well in the quality.The biases of ERA-interim are smaller than JRA-55,while JRA-55 can effectively capture the variability of air temperature.
  • Interannual and Interdecadal Anomaly Features of Siberian High and Their Impact on Winter Temperature of China
  • LAN Liuru;LI Dongliang
  • 2016 Vol. 35 (3): 662-674.  DOI:10.7522/j.issn.1000-0534.2016.00022
  • Abstract ( ) PDF (5614KB) ( )
  • Based on the NCEP/NCAR reanalysis data and air temperature data of the 160 stations in China,by using harmonic analysis,correlation analysis,singular value decomposition and others,the interdecadal and interannual anomaly features of winter Siberian High(SH)and their impact on winter temperature of China are investigated.The results are as followings:(1)On the interdecadal time scale,SH became weak and shrank after the late 1960s,with its east edge retreating to the west and its south edge backing up north.Since the 21st century, the area of SH has a trend of expansion.On the interannual timescale,the area of SH gets the maximum interannual variance.(2)The interannual variability of the intensity and area as well as the east edge of SH have gone up since the beginning of 21st century.On the interdecadal timescale,starting around 1975,the interdecadal variability of the whole SH feature variables all turned smaller than before.(3)SH in colder winter years of China is more powerful,along with the expansion to the east and south,the corresponding anomaly pattern like EU positive phase in the 500 hPa height field and the enhanced Eurasian ridge play a key role in the development of SH,and vice versa.When SH strengthens and enlarges with its frontiers sweeping eastward and southward on interannual timescale,then the intensity of SH makes the most impact,leading to the cold winter in most parts of China,especially in the South,and vice versa.However for the interdecadal scale,the area of SH has the greatest influence on winter temperature.When the SH becomes strong(weak)and expands eastward(retreats westward),the temperature in the land to the north of the Yellow River turns lower.(4)When there are great(small)variations in the interannual intensity and area of SH,and the interannual variability of its east edge and south edge is at low(high)level,as a result,the interannual fluctuation of temperature in most parts of China is sharp(gentle).On the interdecadal scale,When all the SH feature variables'interdecadal variability increases(declines),consequently the interdecadal undulation of winter temperature in north and northeast China gets large(small),while the interdecadal fluctuation of winter temperature in the south is reduced(increased).
  • Change Properties of Summer Extreme Precipitation Events and Temperature and Associated Large-Scale Circulation in China during 1960-2009
  • CHEN Jinming;LU Guihua;WU Zhiyong;GU Shixiang;HE Hai
  • 2016 Vol. 35 (3): 675-684.  DOI:10.7522/j.issn.1000-0534.2015.00072
  • Abstract ( ) PDF (7821KB) ( )
  • Climate simulations have suggested that a greenhouse-gas induced global warming would also lead to a moistening of the atmosphere and an intensification of the mean hydrological cycle.Such a change can contribute directly to changes in regional precipitation climate,so there is an ongoing interest in the possible relationship between temperature and extreme precipitation events(EPE).The relationship between summer temperature and extreme precipitation events was studied using Singular Value of Decomposition(SVD)method based on the daily precipitation and temperature data of the 610 meteorological stations in China and NCEP/NCAR reanalysis data from 1960 to 2009,the difference of their corresponding change in atmospheric circulation was also analyzed.Results show that there exists a significant correlation between EPE and temperature in China that a positive correlation in northwest and southern areas but a negative correlation in the northeast to southwestern areas.Abrupt summer temperature and EPE change both emerged around 1992,an abnormal continental cyclonic circulation whose center in Mongolia existed in 850hPa wind fields during pre-mutation(1960 1992),however, abnormal continental cyclonic circulation translated to anticyclonic circulation during later mutation(1993-2009).This abnormal cyclonic(anticyclonic)would strengthen(weaken)the cold air invasion southward,resulting in higher temperature of the later mutation.During pre-mutation,western and southern China were respectively influenced by abnormal western and southwestern water vapor transportation,water vapor was abnormal divergence and resulted in less EPE.However,northeast to southwest areas were affected by abnormal southwestern water vapor transportation,water vapor was abnormal convergence and leaded to more EPE.The situation was just opposite after mutation.
  • Spatial and Temporal Characteristics of Soil Temperature at 1.6 m Depth in Mainland of China from 1981 to 2000
  • GAO Na;GAO Xiaoqing;YANG Liwei;ZHOU Ya
  • 2016 Vol. 35 (3): 685-692.  DOI:10.7522/j.issn.1000-0534.2016.00002
  • Abstract ( ) PDF (2521KB) ( )
  • Soil thermal conditions have a significant impact on weather and climate change.The temperature in soil is an indicator of the thermal condition.It represents a change in the underlying heat storage.It is very necessary to do some researches about the soil temperature.In this paper,some characteristics of soil temperature at 1.6 m depth of the whole country are discussed.The soil temperature data observed from 157 observatories at 1.6 m depth from 1981 to 2000 has been used.The FCM method was applied to study the similarities and differences of all observatories.As a result,when longitude,latitude and soil temperature of each station are concerned,all observations are classified into four types of clusters.They are thecool area with T1.6 ≤9 ℃ including northeastern China and Qinghai-Xizang Plateau,the warm area with T1.6≥18 ℃ including the southern China and the middle and lower reaches of the Yangtze River region,the secondary cool area with 9 ℃ ≤T1.6 ≤15 ℃ mainly including the northwestern China,and the secondary warm area with 15 ℃ ≤T1.6 ≤18 ℃ mainly including Huai River basin and its around,respectively.Then,the EEMD(Ensemble Empirical Mode Decomposition)was used to study the quasi-periods and nonlinear trends of the four-type areas.It shows that all areas have similar quasi-periods of 1.5 and 4 years in monthly soil temperature anomaly at 1.6 m depth.The nonlinear trends of the four types of clusters have played in two ways:the constantly warming way(in the cool and secondary cool areas)and the warming after cooling way(in the warm and secondary warm areas).The warming rate has been amplified with time,especially after 1990,and this warming is something like to be accelerated.
  • Aridity Characteristic in Middle and Lower Reaches of Yangtze River Area based on Palmer Drought Severity Index Analysis
  • WANG Wen;XU Zhili;CAI Xiaojun;GAO Jing
  • 2016 Vol. 35 (3): 693-707.  DOI:10.7522/j.issn.1000-0534.2015.00011
  • Abstract ( ) PDF (8889KB) ( )
  • To evaluate the ravages of a drought in middle and lower reaches of Yangtze River area,a farther modified Meteorological Drought Severity Model was developed based on the Palmer Drought Severity Model.The conventional precipitation and temperature data in 90 stations were used as basic data(1961-2012)to establish the Palmer drought index in middle and lower reaches of Yangtze River,with this modified index we have calculated the monthly drought index for 90 stations in the middle and lower reaches of Yangtze River area,we compared with the situation of drought and waterlog recorded in documents and analyzed the characteristics of the drought and waterlog.It is found that the farther modified Palmer Drought Severity Model can reflect the severity of meteorological drought comparatively and be consistent with the actual onset time,duration time,the severity of droughts and floods and regions where droughts and floods occur,it is sensitive to droughts and flood;there is a marked interannual variation of drought in the middle and lower reaches of Yangtze River area and the drought has duration of three months;Interdecadal variation is obvious in Summer while weaker in Winter; Drought often happened in west and north of Anhui,north of Zhejiang and northwest of Hunan in summer and autumn,extreme drought mostly happened in Fuyang,Ningguo,Hengyang,Chenzhou,Cixi,Dinghai and Badong in autumn.
  • Characteristic Analysis on Two Regional Rainstorms at Guanzhong in Early Summer
  • ZHANG Yabin;MA Xiaohua;RAN Lingkun;HOU Jianzhong
  • 2016 Vol. 35 (3): 708-725.  DOI:10.7522/j.issn.1000-0534.2015.00014
  • Abstract ( ) PDF (15060KB) ( )
  • NCEP 1°×1° reanalysis data,conventional observation data and satelite data are used to analyse characteristics of circulation pattern,physical field and Temperature of Black Body(TBB)for two early summer rainstorms at Guanzhong from 2 to 3 June 2006(the‘0602')and on 25 May 2013(the‘0525’)with midsummer case comparison.Results show that:before early summer rainstorms happen,Tibetan High is weak and located obviously southward,which cause morphology and location changes of 200 hPa Jet north to rainstorm are small.At the same time,wind longitudinal gradient at the south side of 200 hPa Jet increases significantly.During early summer rainstorm there are no impacts of West Pacific Subtropical High and remote typhoon,meanwhile,westerlies influence systems at upstream and surrounding area are different,which lead to vapor transportation and convergence at low levels are significantly weaker than midsummer cases and different distributions.Stability of high pressure around China eastern continent on 850 hPa is contributed to duration of southeast vapor transportation to rainstorm area.Early summer rainstorms happened under potential stable stratification and warm and moist air climbe northward along the low level cold air.Isentropic surface tilted northward with height increasing along rainstorm centre and it exist energy front genesis and symmetric instability.Moist Potential Vorticity (MPV)anomaly appear over rainstorm area.Meanwhile,vertical difference between deeply positive MPV at mid-high levels and shallowly negative at low level increases.MPV above 300 hPa increase significantly.Zonal vertical circulations about 300 km east to early summer rainstorms contribute to upward movement maintaining.The maximum of vertical velocity,central height and unstable energy near high energy ridge at low level during early summer rainstorms are obviously lower than midsummer cases.Total helicity significantly increased zone is indicative to early summer rainstorm beginning.Zero line between positive and negative helicity area is near the north boundary of early summer heavy rain,meanwhile,positive helicity increasing center is near the north boundary of rainstorm.There is a significant negative helicity area north to Guanzhong.Positive helicity range and strength near Guanzhong are obvious small and its center moving and increase area are relatively south with midsummer case comparison.Meanwhile,locations of positive helicity centers in vertical direction are relatively dispersive.Early summer rainstorm clouds are large and have complex structure,which mainly composed of northern shield shaped cloud corresponding significant anticyclonic region at high level and southern belt cloud region at low level.TBB centers are higher than -60 ℃ and cloud top are lower than those of midsummer cases.Early summer rainstorm mainly located near the convergence area of north and south clouds and strong belt echo rather than TBB central or large gradient areas.
  • The Classification Statistics on Summer Precipitation in Beijing using Vertical Sounding Radar
  • HUANG Yu;RUAN Zheng;GUO Xueliang;HE Hui;JI Lei
  • 2016 Vol. 35 (3): 745-754.  DOI:10.7522/j.issn.1000-0534.2015.00038
  • Abstract ( ) PDF (5132KB) ( )
  • In order to analyze the characteristics of different types of precipitation in mid-latitude regions,the precipitation data have been divided into shallow convection,shallow stratiform,deep convection,deep stratiform and transition five types of precipitation based on spectral parameter(echo intensity,velocity,spectral width)of wind profile radar.The shallow convection and shallow stratiform precipitation belong to the category of warm rain,and the deep convection,deep stratiform and transition precipitation belong to the category of cold rain.In this paper,author classified and analyzed the characteristics of precipitation weather process in Beijing Yanqing during 2012 and 2013 summer(from May to October)with the above-mentioned classification scheme.The results show that,warm rain is an important part of precipitation in Beijing summer,accounted for 26%,its precipitation proportion takes 17%;cold rain accounted for 74%,the precipitation proportion takes 83%.A majority of the precipitation in Beijing summer is transition precipitation(47%),followed by stratiform precipitation,accounted for 43%,the lest is convection precipitation,takes 10%;the greatest contribution of precipitation is convection precipitation,followed by transition precipitation,the lest is stratiform precipitation.Characteristics of all types of precipitation are summarized: the variation of spectral parameters in shallow stratiform precipitation with altitude is not obvious,the whole trend smooth relatively;the variation of shallow convection is fiercer than shallow stratiform,it increases obviously at 3 km,and the number of precipitation data is increasing rapidly with altitude descent;spectral parameters of deep convection precipitation are distributed widely,especially the spectral width,is broader than that of other types,besides,the high value area is also exist in high altitude;deep stratiform precipitation echo presenting a uniform bright band distribution,velocity and spectral width comes out a strong gradient feature near zero layer;transition precipitation possess characteristics of both convection and stratiform precipitation,the echo distribution is similar to deep convection precipitation, but the distribution of velocity and spectral width is similar to deep stratiform precipitation.With the classification statistics on summer precipitation in Beijing,it can have a deeper understanding in precipitation system in Beijing,improving the prediction accuracy and working efficiency of weather modification.
  • Multiple-Radar Data Assimilation of a Squall Line with SVD-En3DVar
  • WANG Yueya;SHAO Aimei
  • 2016 Vol. 35 (3): 755-766.  DOI:10.7522/j.issn.1000-0534.2015.00109
  • Abstract ( ) PDF (9047KB) ( )
  • The effectiveness of using a three-dimensional assimilation method based on the forecast-ensemble and singular value decomposition(SVD-En3DVar)to assimilate real Doppler radar observations is investigated by applying the technique to a squall line case occurred on June 14,2009 over Jiangsu Province of China.The assimilation and forecast experiments are conducted with the Weather Research and Forecasting(WRF)model.The impact of the localization parameters in SVD-En3DVar on assimilation skill is also examined and the identical assimilation experiments are performed with WRF 3DVar as a comparison.The experimental results show that the SVD-En3DVar method has the ability to assimilate Doppler radar data effectively.The SVD-En3DVar method is slightly sensitive to horizontal localization parameter for the convective-scale weather system.In this squall line case,the horizontal localization radius of about 50 km can achieve the best prediction of composition reflectivity;The radar data assimilation both using the SVD-En3DVar and WRF 3DVar all improves the prediction of reflectivity,and the SVD-En3DVar method outperforms WRF 3DVar.Compared with observed reflectivity, the predicted reflectivity with using SVD-En3DVar can capture the structure and evolution of the squall line well.
  • Isentropic Potential Vorticity Analysis of Typhoon‘Utor'
  • LI Huijin;HUANG Mingce;QIN Changliu
  • 2016 Vol. 35 (3): 777-787.  DOI:10.7522/j.issn.1000-0534.2015.00044
  • Abstract ( ) PDF (5372KB) ( )
  • The Isentropic Potential Vorticity(IPV)theory is used to Typhoon ‘Utor’ which seriously impacted the southern China in 2013.The result showed that: during the activity of ‘Utor’,the upper-level high Potential Vorticity(PV)over the top of the circulation center transported downward with typhoon movement,and the intensity and position of upper-level high PV transmission downward were close related to typhoon intensity and moving direction changed,the performance are typhoon movement generally along the long axis direction of the IPV distribution,PV increased in upper-level,the central pressure decreased,the intensify strengthen.The upper-level high PV transported downward,the dynamic tropopause descended and led to a cyclone circulation in front of the PV anomaly area,resulted in generating vortex or cyclone,and impactied typhoon movement.The cyclone circulation had a positive feedback on the upper-level PV,that was advantaged to typhoon.Because of the positive influence of the upper-level high PV transmission downward to typhoon intensity,and the high PV air around was transported,and the cold air moved southward in later period,the tropical cyclones generated at Bay of Bengal and the northwest Pacific,at the east of Taiwan,totally,three high PV streams transported into ‘Utor’ from east,west and north.As a result,‘Utor’ strengthened quickly in the early stage,developed again when it moved into South China Sea,maintained for a long time after landing.
  • Structure Feature and Momentum Budget Analysis of a Gust Front in Shanghai Region
  • YUE Caijun;YUAN Zhaohong;TAO Lan;CHEN Guomin;DAI Jianhua;TAN Jianguo
  • 2016 Vol. 35 (3): 788-799.  DOI:10.7522/j.issn.1000-0534.2015.00019
  • Abstract ( ) PDF (16811KB) ( )
  • There is a gust front occurred in Shanghai region during 13-14 on July 2012.Based on Doppler radar data,automatic weather station data and outputs from WRF model simulation,the structure feature of gust front was analyzed,and the cause of gust front translation speed was studied on the basis of the momentum budget method.The results are as follows:(1)The weather phenomena of gust front is obvious,such as pressure rising, wind direction inversing,wind speed increasing,temperature and dew-point temperature dropping and so on,along with instantaneous heavy rain.It is noted that above weather phenomena don't occur at the same weather station synchronously.(2)The evolution of gust front and its influence process on Shanghai are simulated successfully by WRF model.However,the moving speed of the simulated gust front is slower than that of the observation.( 3)There is a cold pool at the back of gust front,lying below 2 km,with negative perturbation pressure above cold pool.Meanwhile,perturbation west wind in the 2~3 km air cloumn downloads into cold pool.The intensity of cold pool affects the counterpart of gust front directly,and momentum with downloading wind not only drives cold pool directly but also affects the genesis of gust front and its intensity.(4)The analysis of momentum budget shows that vertical advection and pressure gradient force are the primary contributions to the zonal translation of gust front,which discloses the cause of gust front translation quantitatively.
  • Analysis on the Difference of Airflow Structure of Three Ocean-Effect Snowstorms in Shandong Peninsula
  • SUN Dianguang;HUANG Benfeng;XUE Yanbo;LIU Xueping
  • 2016 Vol. 35 (3): 800-809.  DOI:10.7522/j.issn.1000-0534.2015.00017
  • Abstract ( ) PDF (35713KB) ( )
  • Using Yantai Doppler radar data and observational station data,the airflow structure of three oceaneffect snowstorms occurred in Shandong Peninsula on 3-4 December 2005,4-5 December 2008 and 3-4 January 2010 were analyzed.The results show that a distinct,low-level convergence zone(coastal front)formed along the coast as winds over the ocean became north-northeasterly while winds over land remained northwesterly.But the intensity of airflow was obviously different,one structure was that the value of northwest wind was obviously higher than the value of north-northeast wind(TypeⅠ),another structure was that the value of northnortheast wind was obviously higher than the value of northwest wind(TypeⅡ).For type Ⅰ,radar products show that the initial echo generated in east Bohai sea,strengthened moving to south-east direction,the right side of echo band weaken while the band reached the land,the left side of echo band developed along the coast as a result of coastal front convergence zone and formed a remarkable‘train effect'.For type Ⅱ,radar products show that the initial echo generated in the central part of Bohai strait,strengthened moving to south-east direction, the right side of echo band developed along the coast as a result of coastal front convergence zone,while the left side of echo band weaken gradually.The cyclone on the sea area to the east of Shandong Peninsula determined differences between the north-northeast airflow intensity and the northwest airflow intensity.
  • Evaluation of the MODIS Aerosol Products and Analysis of the Retrieval Errors in China
  • WANG Hongbin;ZHANG Lei;JIAO Shengming;ZHANG Zhiwei;ZHU Yuying;ZHU Chengying
  • 2016 Vol. 35 (3): 810-822.  DOI:10.7522/j.issn.1000-0534.2015.00043
  • Abstract ( ) PDF (4524KB) ( )
  • By using sunphotometer(AERONET)data as ground truth,the MODIS AOD from both Terra and Aqua in China were evaluated.The error sources of retrieval algorithm were investigated and analyzed.The results show that:(1)Xianghe,Yulin,Shouxian,Hefei,Hong Kong and Taiwan sites MODIS AOD accuraciesare better than other sites.We compared Terra and Aqua AOD data separately to AERONET data,and found no significant differences.(2)MODIS AOD at Xianghe,Taihu,SACOL,Beijing,Xinglong and Chen-Kung_Univ sites was selected for detailed analysis.As compared to other sites,MODIS AOD at Xianghe site shows much closer to the 1:1 line,and higher correlations(0.96 and 0.97 for Terra and Aqua,respectively).In addition,72% and 65% of the MODIS retrievals of the comprehensive data set lie within the expected error for Terra and Aqua,respectively.MODIS AOD was overestimated,and can be revised using the intercept of the fitted line at Taihu and Beijing site.At SACOL,the relationship between Terra and Aqua MODIS AOD and AERONET AOD is poor;with the correlation coefficient is 0.66 and 0.77,respectively.MODIS C005 AOD products precision is higher than Deep Blue AOD product precision at SACOL.(3)Error analysis shows error mainly from surface reflectance relationship inaccurate,at Xianghe and SACOL.At Taihu and Beijing sites,retrieval errors may be due to effect of both surface and aerosol model.The majority of cases have low cloud fraction and there is no significant bias,however,MODIS overestimates AOD when cloud fraction is higher.
  • Measurement Bias and Mosaics Analysis for X Band Doppler Radars
  • WU Chong;LIU Liping;WU Haitao
  • 2016 Vol. 35 (3): 823-833.  DOI:10.7522/j.issn.1000-0534.2015.00052
  • Abstract ( ) PDF (16187KB) ( )
  • Three X band weather radar developed by Institute of Atmospheric Physics,Chinese Academy of Sciences was the first time used to the multi-radar network test in Jiangsu province from June,2013.Based on the observation data from this network and nearby CINRAD,the detecting capability of X band Doppler radar is analyzed and its attenuation bias is corrected.Through 3D mosaics system from Chinese Academy of Meteorological Science,the networking data is used to explore the operational supplement of X band weather radar for CINRAD.Results indicated that:(1)the ground clutter,blockage,and attenuation have negative effect on the data quality of X band Doppler radar,and preliminary quality control has been applied.(2)From the contrast of echo structures and vertical profiles,the X band radar data is improved through the quality-control method of ground clutter suppression and attenuation correction.And this radar network including 3 radars can get rational precipitation echoes within 60 km,and reflect the precipitation characteristic exactly.(3)After inputting X band radar network and CINRAD data into 3D mosaics system,the echo structure of output data is continuous,with lower smoothing effect and wider radar coverage.The X band radar could be an efficient supplement for CINRAD at low altitude.
  • Model Study of Relationship between Updraft Core and Graupel Non-inductive Charging Regions
  • WANG Fei;ZHANG Yijun;ZHENG Dong
  • 2016 Vol. 35 (3): 834-843.  DOI:10.7522/j.issn.1000-0534.2015.00009
  • Abstract ( ) PDF (2477KB) ( )
  • Using a 3-D charging-discharging cloud resolution model,an isolated thunderstorm was simulated based on the sounding data in Beijing for investigating the spatial relationship between the updraft core(where the updraft speed Wmax >5 m·s-1)and the Graupel Non-inductive Charging Region(GNCR)when the maximum updraft speed was greater than 5 m·s-1.The characteristics of updraft in GNCR were also analyzed.The results showed that the GNCR was mainly distributed within and around the updraft core.The non-inductive charging processes in the GNCR always had a Relatively High Charging Efficiency(RHCE)with the absolute value greater than 0.1 nC·m-3.Even when the updraft of the cell reached peak,graupel in the region of updraft center can still obtain charge through the non-inductive charging processes.But too strong updraft speed was disadvantageous for appearance of More Efficient Non-inductive Charging Efficiency(MENCE),which absolute value was greater than 0.5 nC·m-3.In this simulation case,the RHCE almost appeared only when the maximum updraft speed was higher than 5 m·s-1.The regions with RHCE were usually distributed in the regions with the updraft speed range from -4 m·s-1 to 28 m·s-1.Although the area with MENCE would extend wider and its position would be closer to the updraft center while the maximum updraft speed became stronger,the center of the area with MENCE never overlapped with the updraft center,and always appeared in the region with the updraft speed less than 20 m·s-1.Additionally,the height of updraft speed center was approximately coincident with the height of inverted temperature.It could be used to separate the regions where graupels obtained negative and positive charges respectively through the non-inductive charging processes in operation in the future:during most of the time the updraft core existing,graupel in the regions near or above this height will obtain negative charge dominantly, graupel in the regions beneath this height will be charged by positive charge.

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