Plateau Meteorology

Current Issue

28 February 2014, Volume 33 Issue 1   
  • Characteristics of Water Vapor Distribution and Variation in Upper Troposphere and Lower Stratosphere over Qinghai-Xizang Plateau
  • 2014 Vol. 33 (1): 1-13.  DOI:10.7522/j.issn.1000-0534.2013.00074
  • Abstract ( ) PDF (1293KB) ( )
  • Using the MLS (Microwave Limb Sounder), high-spectral resolution AIRS (Atmosphere Infrared Sounder) and ECMWF (ERA-interim) data from 2005 to 2008, combined with NCEP/NCAR reanalysis data and a trajectory model (NOAA HYSPLIT), the distributions and sources of atmospheric water vapor near tropopause region over the Qinghai-Xizang Plateau (QXP) were investigated and stratosphere-troposphere exchange (STE) over the QXP was expounded. The results show that the distributions of water vapor over the QXP are characterized by a minimum over the southern QXP from March to April, and a maximum over the southern QXP from July to October near tropopause region on 100 hPa. The water vapor mixing ratios have large values in the upper troposphere over the south slope of QXP between March and April, the results suggest that transport of air masses from the troposphere to stratosphere occurs over south slope of QXP because of the orographic lifting of QXP and the westerly circulation. The low water vapor on 215 hPa over the center of the QXP (80°E90°E) is related to the sinking of dry air from the UTLS region. The water vapor over the QXP is the highest in the exuberant monsoon season between July and August and is related to the Indian summer monsoon and anticyclonic circulation, which transports water vapor to the lower stratosphere over the QXP through the upward movement of 2~4 days. The seasonal variation of water vapor mixing ratios near tropopause region (i.e., on 100 hPa) is consistent over the QXP, the east and west of QXP, the minimum value of water vapor occurs in March.
  • Verification for GRAPES_Meso Model in Eastern Qinghai-Xizang Plateau and Its Surroundings in Summer of 2011
  • 2014 Vol. 33 (1): 14-25.  DOI:10.7522/j.issn.1000-0534.2012.00175
  • Abstract ( ) PDF (977KB) ( )
  • The eastern Qinghai-Xizang Plateau and its surrounding areas, which have a character of a ladder-like topography distribution, are not only the strong signal areas for many significant weather systems upstream, but also the difficulty of many weather forecast models. In order to understand the prediction performance of GRAPES_Meso V3.1 in these areas, two forecast outputs of GRAPES_Meso V3.1 and V2.5 in  summer (from June to August) of 2011 are compared using statistical methods. The main conclusions are shown as follows: (1) Since assimilation system is upgraded, the initial fields have been greatly improved, and the mean error (ME) and root mean square error (RMSE) of various elements are reduced obviously, especially in the middle-upper levels of troposphere. According to the error-decreasing amplitude, various elements are sorted from large to small as follows: relative humidity, zonal wind, meridional wind, geopotential height, temperature. (2) TS scores of the V3.1 model, either every 6 h or 24 h accumulated precipitation forecast, are higher than that of V2.5 model, especially 25 mm and 50 mm precipitation forecast. The missed event rate of V3.1 model has improved significantly, and the average daily rainfall is better than that of V2.5 model, but it can not improve the false precipitation in the west of Yunnan. (3) The vertical-error profiles of V3.1 model for geopotential height, temperature, wind and relative humidity forecast are different with V2.5 model. V3.1 model mainly improves the whole-layer meridional wind, zonal wind and relative humidity, as well as geopotential height in middle-high-layer troposphere and temperature below 500 hPa. It is noteworthy that the geopotential height errors of V3.1 model are growing faster than that of V2.5 model and new model forecast stronger south wind than true wind in low-layer troposphere. (4) Compared forecast results in three different terrain height of V3.1 model, it is found that, in addition to the geopotential height and temperature on 700 hPa, the differences of the same element error are small in the initial moment, but gradually expand with forecast length increasing. Those show that the errors of V3.1 model are affected significantly by topography.
  • Climate Change Scenarios in the Yarlung Zangbo River Basin Based on ASD Model
  • 2014 Vol. 33 (1): 26-36.  DOI:10.7522/j.issn.1000-0534.2012.00176
  • Abstract ( ) PDF (931KB) ( )
  • The Qinghai-XizangPlateau (QXP) plays a key role on both hydrological cycle and climate for southern and eastern Asia. It is important to simulate and analyze future climate condition over the QXP to investigate the distribution and evolution trend of ecosystems, climate and water resources for southeastern Asia. Based on ASD statistical downscaling model, climatic factors including precipitation and air temperature in the Yarlung Zangbo River (YZR) basin were downscaled to meteorological stations by using the MIROC3.2_medres data. Simulation accuracy was evaluated by comparing with the outputsof ERA40 reanalysis. Future climate change scenarios in the periods of 20462065 and 20812100 were generated on the basis of ASD downscaling model. The results show that ASD can be applied to the YZR basin satisfactorily, being able to simulate the spatial and temporal patterns of precipitation and temperatureregimes, and the explained variance of temperature exceeds 90%, while the explained variance of precipitation reaches 12%~27%. Changes of annual total precipitation are not significant, the change trends are less than 5% for most of scenarios, but precipitation will become more concentrated. Precipitation in spring, autumn and winter decreases remarkably, with the largest ratio of 55.58%. Precipitation in summer, however, shows a significant increasing tendency. The largest amplitude is 30.44%. Temperature over the YZR basin will increase dramatically, the amplitude is 1.60~2.12℃ inthe middle of 21st century, and 2.34~3.69℃at the end of 21st century. It showed that water resources planning in the YZR basin will become a great challenge due to the changes of precipitation and air temperature in the future.
  • Characteristics of Climate Change of Precipitation and Rain Days in the Yellow River Basin during Recent 50 Years
  • 2014 Vol. 33 (1): 43-54.  DOI:10.7522/j.issn.1000-0534.2012.00177
  • Abstract ( ) PDF (9955KB) ( )
  • Based on the precipitation data of 143 stations, temporal and spatial variation characteristics of precipitation and rain days in the Yellow River basin during 19612010 are analyzed. The results show that: (1)Multi-year average spatial distribution characteristics of annual precipitation and annual rainy days in the Yellow River Basin is less in the North and more in the South. (2)Annual precipitation and annual rainy days change trend have effective consistency in the Yellow River basin during the recent 50 years, both decreasingly. And the reduction trend of the annual rain days is more significant. The percentage of stations of annual precipitation with negative trend is 81.8%, and the percentage of stations of annual rainy days with negative trend is 88.8%. (3)About the seasonal variation in the Yellow River basin, the precipitation and rainy days in winter appear positive trend while they present negative trends in other three seasons, especially in autumn. The negative trend stations of precipitation in four seasons passing the significance test are autumn>spring>summer>winter, and the negative trend stations of rain days in four seasons passing the significance test are autumn>summer>spring>winter. (4)The unanimous mutation of both annual precipitation and annual rainfall in the basin is 19851986, and the decrease of precipitation and rain days mainly results from the changed atmospheric circulation. For example, the above normal precipitation and rain days in 1986 are due to the stronger monsoon which enables the effectively conveying of vapor and the wind convergence in the northwest. On the other hand, after the mutation, the weaker monsoon, the lack of effective moisture transport and the anticyclonic circulation in the area from the Mongolia to Hetao may result in less precipitation and rain days.
  • Establishment and Analysis of Assimilation Dataset of Oasis-Gobi System over an Arid Region in Northwestern China
  • 2014 Vol. 33 (1): 66-79.  DOI:10.7522/j.issn.1000-0534.2013.00073
  • Abstract ( ) PDF (1115KB) ( )
  • The water-energy exchange process and land-atmospheric interaction were simulated by Weather Research and Forecasting (WRF) model version 3.1, which developed by the National Center for Atmospheric Research. The underlying surface land use and vegetation types with MODIS data and the meteorological data which were acquired in Jinta experiment during summer in 2008 were also assimilated in the WRF model. Further, the Jinta high resolution data assimilation reanalysis dataset was produced by WRF model. This dataset includes landuse types with 1 km horizontal resolution for each hour, wind, temperature, humidity and pressure at 19 levels, soil temperature and moisture at 4 levels, vegetation fractional coverage, radiation and heat fluxes on land surface from June to August 2008 over heihe river basin in Jinta Oasis. The surface pressure, temperature and relative humility were verified by observations in this study and the  cold-wet land effects′, characteristics of mean atmospheric circulation, and long-period variation of air temperature and relative humidity were analyzed by using this dataset. The result showed that the thermal difference was obviously between oasis and Gobi, and the differences of land surface temperature in the day and night time was 21 and 3℃ in oasis and Gobi, respectively. The differences of soil temperature at 10 cm depth during daytime was 17℃ at the most, and the peek value of soil temperature in oasis occurred 3 hours later than in Gobi. The averaged relative humidity in oasis was 11% lower than that in Gobi. The ‘clod island effect’ and ‘wet island effect’ could affect the atmospheric layer up to 2000 m and 1500 m height during the day, respectively. It showed that a weak  cold island effect' appeared below 500m near surface layer at night. In the upper layer over oasis, updraft appeared during nighttime and downdraft occurred during daytime on a large scale, and the maximum vertical velocity downwards could reach to -0.3 m·s-1. This reanalysis dataset could be used in further research on the long period climatic effects and characteristics of atmospheric boundary layer over Oasis-Gobi system.
  • Parameterization Scheme about Albedo Changing with Solar Altitude Angle over Different Underlying Surface in Arid Areas of Northwest China
  • 2014 Vol. 33 (1): 80-88.  DOI:10.7522/j.issn.1000-0534.2012.00168
  • Abstract ( ) PDF (608KB) ( )
  • Using the data attained by the instrument parallel experiment of Gulang Heterogeneous Underlying Surface Layer Experiment over the uniform desert land surface, a detailed analysis of observational radiations was made to value the three different types of radiation instruments (CNR4, Kipp&Zonen; PSP, Eppley; MS102, EKO) at first; and then using the data observed over western, eastern desert and cropland stations in sunny days of the basic observation, the parameterization schemes about surface albedo changing with solar altitude angle were developed by two separation methods of plus and multiplication over different underlying surface in arid areas, and their universality on different land surfaces were checked; finally, the parameterization scheme developed in this paper were compared to the several existing parameterization schemes over western, eastern desert and cropland underlying surfaces. The results show that: (1) The correlation coefficients between the radiation observed by CNR4 and the radiations observed by PSP and MS102 are more than 0.96, the difference of observational shortwave radiation is less than 6%, the difference of observational longwave radiation is less than 2%, the difference of net radiation is less than 10%; the radiation observed by PSP is more close to that observed by CNR4, the difference of them is less than 5%, while the radiation observed by MS102 is more bias to that observed by CNR4, the difference of them is less than 10%. (2) Multiplication separation is universal. (3) Compared to several existing parameterization schemes, the parameterization scheme developed in this paper is better in portraying the diurnal variation of surface albedo with solar altitude angle over different underlying surface land in the arid areas.
  • Change Features of Surface Albedo of Semi-Arid Grassland over the Loess Plateau of Middle Part Gansu
  • 2014 Vol. 33 (1): 89-96.  DOI:10.7522/j.issn.1000-0534.2012.00178
  • Abstract ( ) PDF (607KB) ( )
  • The annual variation of the surface albedo of semi-arid grassland,  and its variation characteristics under typical weather conditions over the Loess Plateau of middle part Gansu were analyzed by using the observation data of Semi-Arid Climate Observatory and Laboratory of Lanzhou University (SACOL) in the whole year of 2010. The results show that: The surface albedo of semi-arid grassland over the Loess Plateau of middle part Gansu is higher in winter half year than that in summer half year,  and the annual average surface albedo is 0.21,  which is higher than that in oasis regions,  but lower than that in the semi-arid farmlands. In addition,  weather conditions obviously have impacts on the diurnal variation of the surface albedo. In sunny days,  the surface albedo is higher in morning and evening but relatively lower at noon,  while it has little variation in cloudy days; The surface albedo firstly decreases and then increases after rainfall,  while firstly increases and then decreases after snowfall. Moreover,  the surface albedo is a little higher in dust weather than that in sunny days. Surface albedo is significantly asymmetric in sunny days,  namely the surface albedo is higher in early morning than that in late afternoon at the same solar elevation. The difference has good agreement with the variation of shallow soil moisture. The results of this study have a certain scientific value in determining the surface albedo,  verifying and improving models′ ability to simulate weather and climate.
  • Evolutive Features and Its Causes of the Wintertime Precipitation in Yunnan Province
  • 2014 Vol. 33 (1): 130-139.  DOI:10.7522/j.issn.1000-0534.2012.00180
  • Abstract ( ) PDF (903KB) ( )
  • Using the monthly observed precipitation data of 124 stations of Yunnan Province from 1961 to 2010, the monthly mean atmospheric circulation data and SST data from NCEP/NCAR reanalysis, the evolutive features of the winter precipitation in Yunnan and correspondingly atmospheric circulation anomaly and SST anomaly were studied by correlation analysis method and synthesis method. The results indicate that: （1）The winter precipitation mainly shows the consistency change mode. This mode accounts for 53% of the total variance and has significant period of 5 years or so. It also has obvious interdecadal variations. （2）The second main mode of the winter precipitation in Yunnan shows an reverse phase oscillation between the middle area, the south area and the east area of Yunnan and the west area and the northwest area of Yunnan. This mode accounts for 13.4% of the total variance and has significant period of 3 years or so. It also has obvious interdecadal variations. (3）It is founded that the wintertime precipitation in Yunnan has intimate correlation with atmospheric circulation by the correlation method. When the wintertime precipitation in Yunnan is above(below) normal, the SLP in the most of China is higher(lower), the activity of cold high near surface is more(less) frequent and the cold air is (not) easy to influence southward Yunnan Province. The height near Lake Baikal is higher(lower), the high ridge is stronger(weaker) in 500 hPa height field, so it is (not) useful to lead the cold air toward the south. At the same time, the height of the north of Bay of Bengalis lower(higher), the southern branch trough is stronger(weaker), so it is (not) useful to lead the warm and wet air toward the north. The anomalous water vapor transport from the south China sea and the Bay of Bengal converges(diverges) in Yunnan and leads to more(less) precipitation in this region. （4）Through the synthesis method, it is founded that the wintertime precipitation in Yunnan also has intimate correlation with SST anomalies. The SST difference field between the above normal years and below normal years of the wintertime precipitation in Yunnan province is similar with the distribution of SST anomaly of El Nino years: The SST in the tropical eastern Pacific is higher and the SST in the western Pacific Ocean of the east of the Philippines is lower. In El Nino years, the wintertime precipitation in Yunnan is mainly above normal. On the contrary, in La Nina years, the wintertime precipitation in Yunnan is mainly below normal. The SST anomaly in the tropical eastern Pacific may act as a potential predictor for the wintertime precipitation in Yunnan. （5）There is closely relationship between AO and the wintertime precipitation over Yunnan. When the AO index is positive(negative) phase, the wintertime precipitation over Yunnan is above(below) normal. This relationship is modulated by ENSO. In the warm ENSO phase, this relationship between AO and the wintertime precipitation over Yunnan is much close, while in the cold ENSO phase, there is scarely relationship between AO and the wintertime precipitation over Yunnan.
  • Feature Analyses of Mesoscale Convective System of a Heavy Rainfall in the Central Shaanxi Plain
  • 2014 Vol. 33 (1): 148-161.  DOI:10.7522/j.issn.1000-0534.2013.00049
  • Abstract ( ) PDF (1404KB) ( )
  • A process of brief heavy rainfall on 89 August 2007 in the central Shaanxi plain was simulated using mesoscale model WRF with high resolution. The evolution， causes and three-dimensional structure of mesoscale convective system, especially the slight structural features of three rainstorm central meso-β-scale convective system (MβCS) in the rainstorm process including three-dimensional stream field, dynamical and thermal structure were analyzed basing on model output. The results showed that the process of heavy rainstorm had tight relationship with development of a meso-α-scale vortex, in which the strong developing MβCS directly caused the three heavy rainstorm centers. MβCS showed as vortex, warm shear line and ladder trough on 850 hPa, 700 hPa and 500 hPa, respectively. The dynamical forcing of upper westerly jet right flank were possibly reason of divergent formation and strengthen, and ageostrophic wind caused by dynamical forcing was one of the reasons for the formation of rainstorm, and the ladder trough on 500 hPa played a role that carrying dry cold air inflow from the rear of rain group, which result in the strengthening of the convective instability, and the mesoscale convergence formed by the lower and ground wind in different directions and wind speed and mesoscale southwest jet and southeast jet triggered the occurrence of heavy precipitation, and the mesoscale jet disturbance was excited owing to occurrence of heavy rainfall, which played a feedback role to maintain and strengthen of rainstorm, and the barrier function of Qinling mountains and the dynamic lifting role of trumpet-shaped topography contributed to occurrence and enhancement of heavy precipitation. MβCS which bring three strong rainstorm centers had different stream field, vertical dynamical and thermal structure. The vertical structure of the stream field given as follows: the air from different directions flowed into the meso-β-scale cloud tower in middle and lower troposphere, forming different vertical circulation circles in different layers; the updraft in cloud tower had been stretched to 200 hPa or 150 hPa and then turn to horizontal movement toward both southeast and northeast directions out of the cloud tower. The vertical dynamical and thermal structure showed as. In Qishan: in middle region of the meso-β-scale cloud tower, there were a strong divergence zone above 450 hPa, weak divergence or convergence zone at the south side of the meso-β-scale cloud tower and convergence or divergence zone at the north side of the meso-β-scale cloud tower below 450 hPa; the vertical lifting movement inclined to the south, then to the north, and finally to the tropopause. The potential equivalent temperature column appeared two high-energy centers, which brought about dual unstable stratification. The temperature had a significant characteristic of vertical structure which there were two warm-corn in the middle layer and cold center in the upper and lower respectively. In the other two heavy precipitation centers in Liquan and Gaoling, the entire column of ascent movement was coupled with the strong divergence column, as well as the positive vorticity column. In Liquan, the lifting movement was a column with one strong warm center in the mid-high levels while cold in the high and low levels, which had the unstable stratification structure as ‘the saddle’ surface pressure field. In Gaoling, at the south edges of the meso-β-scale cloud tower, there were the high, energy center and frontal zone of temperature deviation below 550 hPa, saturated water vapor column below 400 hPa in middle region of the meso-β-scale cloud tower.
  • Analysis of a Brief Torrential Rain Event in Autumn in Xinjiang
  • 2014 Vol. 33 (1): 162-170.  DOI:10.7522/j.issn.1000-0534.2012.00170
  • Abstract ( ) PDF (877KB) ( )
  • Based on the data of hourly precipitation in Xinjiang and the data of FY2D Stationary Meteorological Satellite from China Meteorological Agency and the reanalysis dataset from the NCEP/NCAR reanalysis project, the mesoscale characteristic and the mechanism of a brief torrential rain event in Xinjiang are analyzed by the 25-point smooth filter methods．The results show that the temperature in Bozhou in the earlier stage is slightly higher than normal, which provide the thermodynamic conditions for the brief torrential rain event in late fall. There is a mesoscale vertical circulation cycle in Bozhou, which provides the favorable dynamic condition for the torrential rain. The position and the moving direction of mesoscale cyclone and TBB are all the same. Unsteady stratified atmosphere has great impact on the maintaining and development of the mesoscale convective cloud mass over Bozhou. Continuous moisture convergence and potential instable energy transportation in the lower layers provide enough water and energy for the lasting heavy precipitation over the rainstorm area. The effect of terrain to the heavy rain event is very important. The surface mesoscale convergence line and mesoscale depression may be the trigger system.
  • Application of Multiquadirc Interpolation in Objective Analysis of Mesoscale Meteorological Data
  • 2014 Vol. 33 (1): 171-178.  DOI:10.7522/j.issn.1000-0534.2012.00182
  • Abstract ( ) PDF (726KB) ( )
  • Objective analysis of mesoscale meteorological data has an important role in real time monitoring and diagnostic analysis. The Cressman method is very popular in meteorology.The Multiquadric method has been widely applied in geodesy, geophysics, geography and surveying and mapping problems. The Multiquadric method is compared to the Cressman method by using conventional observations and variable number of mesoscale automatic observationsto analyze the approximate extent to real data with different datadistribution and quantity.The results indicate that: The root mean squared error of the Multiquadric method is less than that  the Cressman method. The difference between these two methods gradually diminishes with the increasing number of observations for objective analysis. When the distancebetween two observations is large or few observations are used, the Cressman method  tends to produce untrue centers while the analytical field by using the Multiquadric method is more closer to observations. Multiquadric smoothing parameter  λ is regarded as a low-pass filter which screens high frequency waves and preserves large scale systems. The intensity of temperature centers gradually diminishes with increasing  λ. The multiquadric parameter c has an upper limit. When c is greater or less than the threshold, the analytical result shows different sensitivities.
  • Composite Analysis of the Evolving of Yangtze River and Huaihe River Shear Line with Heavy Rain and without Heavy Rain in Meiyu Period
  • 2014 Vol. 33 (1): 199-209.  DOI:10.7522/j.issn.1000-0534.2012.00174
  • Abstract ( ) PDF (1288KB) ( )
  • Based on the observed data and NCEP reanalysis data, with the evolution process of Yangtze River and Huaihe River shear line with heavy rain and without heavy rain was composite analyzed. The results show that reinforcement of meridional wind leads to shear line development and wind direction convergence is strengthened in the evolution process of shear line with heavy rain. In the south of shear line, enhancement of southwest wind jet stream causes wind speed convergence. West wind on 200 hPa increase to jet stream. Convergence in the low level and divergence in the upper level is dynamic mechanism. Power convective instability, bountiful water vapor transporting and intense water vapor convergence are in favor of mesoscales development in south of shear line. At the same time, different intensity of dynamic and thermal condition, correspond to different intensity precipitation in shear line with heavy rain. In culture heavy rainstorm, dynamic system is deeper, the instable energy is powerful and water vapor is more bountiful than common heavy rain. In shear line without heavy rain, the wind in low and high level of configuration isn't beneficial to precipitation development. Meridional wind doesn't increase obviously and the shear line doesn′t enhance. Without southwest jet, wind speed convergence is week. On 200 hPa, the center of jet is so far away from Jiangsu that the divergence of high level isn′t powerful. The mechanism of convergence in the lows level and divergence in the upper level is not established. Configuration of dynamic, thermal condition and water vapor transporting in south of shear line without heavy rain is adverse to mesoscale′s development.
  • Comparison among Several System Biases Calibration Methods on C-band Polarimetric Radar
  • 2014 Vol. 33 (1): 221-231.  DOI:10.7522/j.issn.1000-0534.2013.00134
  • Abstract ( ) PDF (917KB) ( )

  • Abstract: The principles of system biases calibration of horizontal reflectivity (ZH) and differential reflectivity (ZDR) on C-band dual linear polarimetric radar are introduced. Further analysis are performed by the actual data which were detected in Yunnan and Anhui Provinces with two same type mobile C-band dual polarization radars, which were both produced by Anhui Sun-Create Electronics Co, Ltd. The results suggest that, for ZDR calibration methods, sun method is difficult to actual application as the consistency between horizontal and vertical receiver are not well in the weak signal; vertical detection one need the radar antenna can be lifted to 90° elevation angle, which has some mechanical limitation; the elevation one need a very uniform rain region which is difficult to satisfy; the change of ZDR caused by ground clutter have not regularity in the statistical analysis, therefore, the clutter calibration method is also excluded from practical application; for dry snow method, the value of ZDR of dry snow do not equal 0 dB, and the 0℃ level height need to know in advance, furthermore, the data which satisfy the requirement of SNR (signal to noise ratio) are less above the height of 0℃ level, and the phase of hydrometeor is indefinable as dry snow, so there are certain limitation in dry snow method; micro-raindrop method can be explained clearly in theory, and the conclusion is convinced, which do not need special span mode, and can obtain a large number of data that satisfy the thresholds of SNR、 ZH from a scan volume, therefore, micro-raindrop method is a better one to calibrate ZDR using meteorological target. After ZDR biases corrected, the feasibility of reflectivity ZH calibration by self-consistency technique is verified. The results suggest that self-consistency method can approximately test the correctness of ZH calibration, however, while the method is used to calibrate ZH, high quality of polarization parameters are needed, and the coefficients in the self-consistency relationship need to be validated further more.
  • An Inversion Algorithm of Columnar Water Vapor Amount Derived from Sun-Sky Radiometer
  • 2014 Vol. 33 (1): 232-240.  DOI:10.7522/j.issn.1000-0534.2012.00184
  • Abstract ( ) PDF (680KB) ( )
  • An inversion algorithm was presented, which can retrieve the atmospheric water vapor content from direct solar irradiance measurements of sky-radiometer at 940 nm under clear-sky conditions. For the traditional method, the atmospheric transmissivity and total columnar water vapor content are generally calculated by radiative transfer model with accurate spectral response function of sensor through a modified Langley plot method. The constants of a and b were calculated directly by using combination of this method and measurements from sky radiometer. The constants can describe water vapor transmissivity and  not dependent on the accurate spectral response function. Meanwhile, the constants (a and b) include the seasonal variations of vertical profiles of air temperature, pressure, and moisture over observation site and may reduce the error of water vapor content retrieved from the traditional method. This method is preliminarily applied to the sky-radiometer data collected at the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) from March to August 2009. And the water vapor content during this period was retrieved. Firstly, compared the results obtained from sky-radiometer and microwave radiometer with the simultaneously radiosonde, and the validations show that the results from different methods are both reliable. Secondly, the results derived from sky-radiometer agreed well with microwave radiometer and sun photometer. The fitting slope values are 1.03 and 1.64, respectively. While the correlation coefficients are all greater than 0.95 with the relative error ranging from 2.1% to 11.3%. This method can be widely used to compute the water vapor content measured by sky-radiometer in SKYNET over East Asia.
  • Comparative Analysis on Characteristics of Circulation and Dynamic Structure in Three Types Duststorm Processes
  • 2014 Vol. 33 (1): 241-251.  DOI:10.7522/j.issn.1000-0534.2012.00172
  • Abstract ( ) PDF (1586KB) ( )
  • The cold front, Mongolia cyclone and surface inverted trough at bottom of Mongolia cold high types are the main weather systems inducing duststorm processes in North China. The characteristics of circulation and dynamic structure were comparative analysed by using observational data. The results show that the cold front type and the Mongolia cyclone type processes formed the planetary-scale trough (low) in the high-latitude area. Its separated low  developed southwards. It induced the development of cold front (or Mongolia cyclone). Their difference  was a cut-off vortex formed in the mid-lower troposphere in the Mongolia cyclone type process. On the surface inverted trough at bottom of Mongolia high process, the northwest wind stream was dominant in the mid-high latitude area. The Mongolia cold high moved southwards and encountered the northwards developed inverted trough and induced a quasi-stationary front formed there. The  duststorm appeared in south of the quasi-stationary front. In both of the cold front and Mongolia cyclone processes, a typical baroclinic structure formed in the mid-lower troposphere. In the cold front process, the cold front zone was nearly perpendicular to the surface below 700 hPa. A slope ascending air stream appeared and formed a center in the mid-lower troposphere. In the Mongolia cyclone process, an perpendicular ascending air stream column formed at the cyclone area and spread to 8~10 latitudes horizontally and to the whole troposphere vertically with the positive vorticity. In the inverted trough process, along the meridional direction an evident intersection area between the southern and northern wind appeared above 700 hPa. Below it, a positive circulation formed with its ascending branch locating in the duststorm area while its down sinking branch appearing in the cold high area.
  • Study of Squall Line Genesis with Northeast Cold Vortex
  • 2014 Vol. 33 (1): 261-269.  DOI:10.7522/j.issn.1000-0534.2013.00005
  • Abstract ( ) PDF (1266KB) ( )
  • Using the conventional meteorological data, automatic station meteorological data, satellite data, radar data and NCEP reanalysis data, the physical mechanisms and mesoscale features of severe convective weather processes under the circulation background of northeast cold vortex in recent ten years were analyzed. The squall lines occurring under the situation of northeast cold vortex were studied mainly, which result in vast thunderstorm wind, hail and other severe convective weather in Huanghuai and Jianghuai region on 3, 5 and 14 June 2009. The results show that: During the development stage of northeast cold vortex, namely with the dissymmetrical structure of temperature pressure and strong atmospheric baroclinicity, the highest probability of thunderstorm wind, hail and other severe convective weather taking place at the west, southwest, south to southeast parts of cold vortex. Under the situation of northeast cold vortex, the squall lines occurring have some conditions as follows: (1) Obvious mesoscale cyclonic circulation exits, and there is convergence line or dry line on 850 hPa, 925 hPa and surface. (2) Hydrostatic instability. The lapse rate of temperature in low and middle level is large. (3) Strong vertical wind shear. The wind strongly clockwise with height increasing; westerly jet exists on 400~500 hPa, which closely relates to the severe weather area. (4) With the development of the squall line, there is large pressure-rise center behind it. The intensity of thunderstorm high not only indicates the different developing stage of the squall line, but also refers to disastrous wind forecasting. (5) The moving path of the squall line closely relates to transfer of the convection echo, outflow border and the leading flow.
  • Forecast Method of Earth-Atmosphere Elements Binding of Heavy Rainstorm Location in Langfang Region
  • 2014 Vol. 33 (1): 270-276.  DOI:10.7522/j.issn.1000-0534.2012.00185
  • Abstract ( ) PDF (989KB) ( )
  • Based on the viewpoint of earth-atmosphere coupling, using the data of heavy rainstorm、MICAPS、surface temperature、10 cm and 20 cm soil temperatures、air temperature、water vapor pressure, pressure in Langfang region from 1980 to 2009, the distributions and changing characteristics and configuration relationship of earth-atmosphere elements and location forecast of heavy rainstorm weather processes in Langfang region were analyzed in detail. The results are as follows: (1) The heavy rainstorm mainly occurs from April to October, single-point heavy rainstorm and partial heavy rainstorm is one of the outstanding characteristics of heavy rainstorm in Langfang region；(2) Each of the rainstorm processes is a very complicated process of earth-atmosphere coupling and interaction, the heavy rainstorm through Langfang region also has the effect of landing northbound tropical cyclones which carries a large amount of water vapour and occurs on the tropical sea and includes the contribution of hydrosphere； (3) The period time of heavy rainstorm is to take place in the same period of 25, 24 and 23℃ of the surface temperature, 10 cm and 20 cm soil temperatures in Langfang region； (4) The distribution and changing and configuration characteristics of earth-atmosphere elements have important reference value for heavy rainstorm location forcast, the high spots of earth-atmosphere elements have important forecast significance for heavy rainstorm location in Langfang region； (5) On the basis of identification of rainstorm weather system, from the viewpoint of earth-atmosphere coupling, considering the distribution and configuration characteristics of earth-atmosphere elements fully, superposing and complementing the earth-atmosphere elements is the effective way for heavy rainstorm location forecast.
  • An Observational Study on Aerosol Scattering Properties in Urban Site of Hangzhou
  • 2014 Vol. 33 (1): 277-284.  DOI:10.7522/j.issn.1000-0534.2012.00186
  • Abstract ( ) PDF (2447KB) ( )
  • The variation features of the aerosol scattering coefficient in the urban area of working and living environment in Hangzhou was studied based on nephelometer and conventional meteorological date from national basic meteorological stations in 2011. The results showed that the mean value of aerosol scattering coefficient was (396.8±191.3) Mm-1 in Hangzhou. Scattering coefficient in autumn and winter were higher than in spring and summer. Atmospheric circulation, meteorological change as well as internal and external sources were the important factors in causing seasonal variations of the scattering coefficient. The diurnal variation of scattering coefficient presented a single-peak under the combined effects of boundary layer evolution, traffic emissions and human activities, the peak and valley value appeared at 08:00 (Beijing time, it is hereafler the same) and 14:00, respectively. The scattering coefficient in working days was significantly higher than that in the weekends. The most representative aerosol scattering coefficient was 238.9 Mm-1, which was calculated by fitting hours frequency distribution. The increase in haze grades leaded to the rise of scattering coefficient, which may be the direct reason for visibility degradation. Special geographical position could result in scattering coefficient interval difference in different wind direction, but the wind speed played a distinct role in diffusing and conveying aerosol scattering coefficient.
  • Character Analysis of Sea Fog in Bohai Bay from 1988 to 2010
  • 2014 Vol. 33 (1): 285-293.  DOI:10.7522/j.issn.1000-0534.2012.00187
  • Abstract ( ) PDF (593KB) ( )
  • Using meteorological and hydrological observed data from 1988 to 2010 from Platform A of Chengbei Oilfield in Bohai Bay, the climate statistics of sea fog was analyzed and the occurring mechanism was discussed. The results show that due to the dual influence of flow from sea and land, the fog days have distinct marine characteristic in spring, summer and autumn, while have continental feature in winter. 59.2% fog events happened over warmer sea surface. Among them, advection evaporation fog days were more than advection cooling fog days, which was related to the meteorological hydrological features of Bohai Bay. The most suitable wind speed for sea fog formation was 2~3 grade wind, and second was 4~5 grade wind. When the sea surface temperature were higher than that of air, more than 88% fog samples satisfied the condition of advection evaporation fog formation due to the significantly increased humidity by evaporation. But, it still has sea surface evaporation in advection cooling fog which indicated the difference between the continental surface and oceanic surface. The evaporation in the samples of advection cooling fog showed the difference between the underlying surface of continental and oceanic.

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