Plateau Meteorology

Current Issue

28 December 2013, Volume 32 Issue 6   
  • Statistical Analysis of Shearline Activity in QXP and Its Influence on Rainfall in China in Recent 13 Years
  • 2013 Vol. 32 (6): 1527-1537.  DOI:10.7522/j.issn.1000-0534.2012.00149.
  • Abstract ( ) PDF (2420KB) ( )
  • Using the daily rainfall data,  500 hPa synoptic map of 08:00 and 20:00 (Beijing time) and the Qinghai-Xizang Plateau(QXP) vortex and shearline yearbooks from 1998 to 2010, the activities of the plateau shearlines in the winter and  summer-half years, and their influences on the rainfall in China, are analyzed with the statistical and synoptic methods. The results show that the plateau shearlines are mostly quasi-zonal shearlines during the summer  and the winter half-year and eastern shearlines are the majority. The winter half-year plateau shearlines  mostly appear in March and April, and one fifth of them can move out of the QXP in the month. The plateau shearlines in winter half-year are less and are about one fifth of the whole year number. But  quasi-zonal  shearlines with 24 h lifetime and quasi-longitudinal shearlines with 12 h lifetime can lead to middle event snow or rain in the QXP and nearby provinces. Especially the  quasi-zonal  shearlines with 24 h lifetime not only lead to the medium snow or rain in  and near to the QXP, but also influences the far from the QXP and lead to medium- and heavy-rain there. Longer lifetime the plateau shearlines have in summer half-year, larger region and intensity of precipitation in and near to the QXP  happens. Those quasi-longitudinal  in the summer half-year with 24 h lifetime can cause the rainstorm in the QXP, medium rain in Gansu Province and little rain in Sichuan basin and Yunnan Province. And in more than half of the year,  the shearline can cause medium or severe  rain in Shanxi, Henan, Shanxi, Chongqing and Guizhou at least once a year. The  quasi-zonal  plateau shearlines, which last for more than 48 h, can cause  rainstorm in the QXP,   medium or severe rain in Gansu Province, the heavy rainstorm in Sichuan Basin and little rain in Yunnan Province. And in most of the year, one to three times the shearline can cause  rainstorm or more in Guizhou, Hubei, Shanxi and Chongqing, some even can cause  rainstorm or heavy rainstorm in Anhui, Jiangxi, Gangxi, Guangdong and Henan.
  • Numerical Study of Influence of Sensible Heat Anomalies in Summer over Qinghai-Xizang Plateau on Rainfall in Sichuan-Chongqing Regions
  • 2013 Vol. 32 (6): 1538-1545.  DOI:10.7522/j.issn.1000-0534.2013.00028
  • Abstract ( ) PDF (5285KB) ( )
  • In recent years, researches pointed out that the thermal anomaly of Qinghai-Xizang Plateau (QXP) has considerable influence on the precipitation over the Yangtze River Basin, and the previous studies were mainly focused on the middle-lower Yangtze River area. Here, the ICTP Regional Climate Model (RegCM3) were used to analyze the influence of  sensible heat anomalies in summer over QXP on the rainfall in Sichuan-Chongqing areas, and reveal the mechanism behind the phenomena in details. In the control test, the original sensible heat (E1) was used, and the 0.5 times and 1.5 times of plateau heat transfer coefficient were used for the two designed sensitive schemes (E2 and E3), respectively. The experiment results show that: The sensible heat anomalies can cause the changes of the South Asian high and the subtropical high system through the thermal process of adaptation. When the QXP sensible heat in summer decreases (increases), the South Asia high decreases (increases) and shifts westward (eastward) and northward (southward). The corresponding 500 hPa west Pacific subtropical high shifts northward (southward) and eastward (westward). The change of the warm center in upper troposphere and the south Asian high lead to adjustment of the atmospheric circulation in the low lever and change of the water vapor transport, and eventually lead to precipitation anomaly in the Sichuan-Chongqing areas. A cyclonic differential circulation occurs in the eastern plateau for both schemes E2 and E3. When the sensible heat decreased, the center of the cyclonic difference circulation is located in the center of the basin, and westerly air flow occurs in the south of the Sichuan-Chongqing areas, which blocks the water vapor transport from the southwest, and therefore the precipitation in south Sichuan-Chongqing areas decreases. Moreover, the center of the cyclonic differential circulation is located in the eastern  basin, which conductive to the increase of precipitation in the eastern  basin.
  • Numerical Experiment of Terrain Effect of Vortex Rainstorm Process on East Side of Qinghai-Xizang Plateau
  • 2013 Vol. 32 (6): 1546-1556.  DOI:10.7522/j.issn.1000-0534.2012.00150.
  • Abstract ( ) PDF (6923KB) ( )
  • Because of the terrain model and  real terrain have different degree of deviations, and the terrain on precipitation plays an important role. Using WRFV3.1 model, the influence of topography on the numerical model forecast effect was analyzed as to an heavy precipitation in Sichuan basin on 20-22 July 2008 through the meteorological station elevation changing the model grid point terrain height method and introduction of the more realistic terrain model. The results show that the more real terrain in model is introduce to increase the intensity of precipitation, location and occurring time of severe precipitation center are improved; the ascending motion and cyclonic shear in middle and lower troposphere increased significantly,  the vortex position is improved, which result in the improvements of  severe precipitation location and occurring time. The changing of single point of terrain height cause the above meteorological elements have changed than the surrounding areas. The variation of meteorological element is more remarkable with the increasing of terrain height change in model. The more real terrain makes the characteristics of the humidity increasing, height decreasing and temperature increasing are more significant. Variations of meteorological elements are in favor of low value system strengthening and precipitation intensity increasing after the topography change. The change of single point of terrain height cause a slight deviation of initial local meteorological elements, the deviation further increases with integration time.  The regional pattern, in order to ensure the integral stability of the model，  the real terrain height is introduced through some key points to improve the prediction effect， especially a terrain processing idea of precipitation prediction.
  • Temporal-Spatial Distribution and Evolution of Surface Sensible Heat Flux over Qinghai-Xizang Plateau during Last 60 Years
  • 2013 Vol. 32 (6): 1557-1567.  DOI:10.7522/j.issn.1000-0534.2012.00151
  • Abstract ( ) PDF (6685KB) ( )
  • Using the analyzed surface sensible heat flux (SHF) grid data provided by NECP/NCAR, the basic temporal-spatial distribution and evolution features of surface SHF over Qinghai-Xizang (Tibetan) Plateau (QXP) had been systematically investigated during the period 1950-2010 based on moving t test and wavelet analysis. The influence factors of surface SHF variation were analyzed using different data. Meanwhile, the influence of surface SHF change on Asia summer monsoon was discussed. The result shows that the annual average surface SHF is positive in most parts of QXP, accounting for QXP being a heat source. The average value of the surface SHF over  QXP merely appears a weak negative value in the winter. And it is positive in the rest seasons, that is, heat flux's translated from ground to atmosphere. The surface SHF presented weak downward trend in the spring and summer during the last 60 years, but not significantly. However, prominent downward trend appeared in the annual mean change, winter and autumn, and annual mean sensible heat flux has weakened by 0.49 W·m-2·(10a)-1, autumn and winter for 0.94 and 0.50 W·m-2·(10a)-1, respectively. The spatial distribution of linear trend had seasonal and regional differences. During the period from 1970 to 1981, the downtrend of surface SHF is extremely remarkable on  QXP due to the abrupt climate change around 1969. There are negative correlation between SHF and air temperature, positive correlation between SHF and wind speed and surface temperature, no obvious relationship with precipitation over QXP. Furthermore, there are positive (negative) correlation between the weakening (strengthening) of SHF and Asian summer monsoon. Therefore, its significance variation may affect Asian summer monsoon to some extent at the interannual scale.
  • Study on Vertical Structure of Several Meteorological Elements in Mount Qomolangma Region
  • 2013 Vol. 32 (6): 1568-1579.  DOI:10.7522/j.issn.1000-0534.2012.00152.
  • Abstract ( ) PDF (9173KB) ( )
  • The spatio-temporal variation of several meteorological elements at Dingri station of the north slope of Mount Qomolangma were investigated across the board in the vertical, in terms of temperature, wind speed, and humidity. The data applied in this study included one year (2007) worth of twice-per-day radiosonde sounding data (08:00 and 20:00, Beijing time). The height of various tropopause types was calculated according to tropopause criteria developed by the World Meteorological Organization (WMO). Particularly, good appreciation of climatic features in this region was obtained: The temperature dropped down to the lowest at 18 km above sea level. Compared with the relatively lower wind speed in summer and the prevailing northeasterly, the wind speed in other seasons was much greater and the dominant wind direction changed to westerly. In addition, there was a humidity inversion at lower atmosphere layer all year round, whereas water vapor mixing ratio was relatively higher in summertime from surface to 8 km above sea level, consistent with the well-known precipitation peak in this region. Furthermore, the first tropopause can be seen all year round and single tropopause appeared in summer and multi-tropopause took majority in winter. The first tropopause  and the second tropopause  varied inversely with temperature at the first tropopause,  whereas the third tropopause  kept constant with varying temperature, which was possibly due to the fact that the third tropopause was located in the stratosphere.
  • Objective Identifying Method of Qinghai-Xizang Plateau Vortex Using NCEP/NCAR Reanalysis Dataset
  • 2013 Vol. 32 (6): 1580-1588.  DOI:10.7522/j.issn.1000-0534.2012.00153
  • Abstract ( ) PDF (2403KB) ( )
  • The application of reanalysis data to identify plateau vortex over the Qinghai-Xizang Plateau using NCEP/NCAR reanalysis data in 2009 is discussed. Based on geopotential height field and wind field, the plateau vortex recognition standard is defined by requirements including closing vortex, acreage, continuity, location, vertical structure and cyclonic shear. The plateau vortex objective identifying method is discussed using the knowledge of meteorology and computational-geometry. A new intensity index of the plateau vortex is defined as the difference between the minimum geopotential height of the central plateau vortex and the average geopotential height of the environment flow of plateau vortex. The maximum motion distance and minimum vector difference between environment flow vector and plateau vortex motion vector are combined to join the plateau vortex continuous motion tracks. 53 plateau vortexes are identified in all. The features of initial location, seasonal distribution, intensity, life period, and motion tracks of plateau vortex are analyzed using the recognition dataset. The objective identifying (OI) result is compared with the dataset of ‘The Yearbook of Plateau Vortex and Shear Lines in 2009’(YB). The comparison shows that OI′s plateau vortex track is consistent with YB′s except April and October which are the switching seasons; Part of the plateau vortex positions has major differences?more than 10 longitude/latitude. The OI′s plateau vortexgenesis location is more western than the YB′s, and the OI's plateau vortex track shows more meticulous details than the YB′s. The objective identifying method can analyze the plateau vortex activity objectively and quantitatively and also can reduce the burden for the plateau vortex analysis work from the artificial reading weather maps work of analyzing plateau vortex.
  • Application of JICA Comprehensive Observation and Satellite Data in Three-Dimensional Cloud and Humidity Construction over Qinghai-Xizang Plateau
  • 2013 Vol. 32 (6): 1589-1596.  DOI:10.7522/j.issn.1000-0534.2012.00154
  • Abstract ( ) PDF (5364KB) ( )
  • Clouds and humidity can contribute to heating or cooling in the Earth’s radiation budget and their vertical distributions play key roles in determining diabetic heating profiles of the atmosphere. The knowledge of clouds and humidity over the Qinghai-Xizang Plateau is key component in the hydrological cycles. They are helpful for evaluating the roles of clouds and humidity in climate changing and can improve the cloud and precipitation simulation in climate models downstream. The information from JICA Tibetan comprehensive observation and FY-2C satellite infrared and visible images are incorporated into LAPS (Local Analysis and Prediction System) to construct three-dimensional cloud and humidity data. According to data inserted into LAPS, four schemes have been designed to analyze the role of each data in cloud analysis. Four schemes are: (1)Scheme 1: Only NCEP relative humidity data is inserted into cloud analysis of LAPS to derive three-dimensional cloud amount; (2) Scheme 2: Inserts Tibetan observation data on the basis of scheme 1; (3) Scheme 3: Inserts satellite data on the basis of scheme 1; (4) Scheme 4: Inserts both  observation data and satellite data on the basis of scheme 1. Analysis of horizontal and vertical distribution of three-dimensional cloud amount indicates that JICA Tibetan observation data gives some information of cloud base and cloud amount for the lower atmosphere. Satellite infrared brightness temperature and visible reflectance provide information of cloud top height and cloud amount in the upper atmosphere. Inserting both  observation data and satellite data can obtain more accurate cloud amount. Three-dimensional specific humidity data is produced through inserting GPS total precipitable water data which from JICA Tibetan comprehensive observation into LAPS model. Specific humidity distributions after and before inserting GPS total precipitable water are compared and indicates that GPS total precipitable water can correct the humidity in the lower part of atmosphere over the Qinghai-Xizang Plateau.
  • Analyses on Temporal-Spatial Distributions and Synoptic Characteristics of MCC in China
  • 2013 Vol. 32 (6): 1597-1607.  DOI:10.7522/j.issn.1000-0534.2012.00141
  • Abstract ( ) PDF (8806KB) ( )
  • The temporal-spatial distributions and synoptic characteristics of MCC in China were studied by means of FY-2C satellite cloud image data and MICAPS data in 2005-2011. The obtained results are as follows: MCC in China mainly occurs in four different regions, MCC occurred in  Yunnan, Guizhou, Guangdong and Guangxi regions is more than other regions. MCC in China occurs from May to August, June is the peak period, 57% of the total number, July is next, 28% of  the total number. The night (from 19:00 to 06:00 of the next day) is advantageous to MCC genesis and development, the midnight （from 00:00 to 03:00） is the most advantageous to MCC genesis and development. MCC occurs mostly with heavy rain and above of precipitation and has characteristics of stable and less moving distance generated in situ. Taking the circulation situation on 200 hPa or 150 hPa as the classification criteria, MCC in China may be divided into six different circulation types: Anticyclonic circulation development type of 200 hPa short wave trough in the eastern Qinghai-Xizang Plateau, eastward development control type of Tibetan high center on 200 hPa, 200 hPa mesoscale anticyclonic circulation development type on the south side of northwest jet zone, 200 hPa airflow branch divergence type on the northeast side of North China high, 200 hPa current branch divergence type on the east of Tibetan high.
  • Temporal and Spatial Characteristics and Influence Factors of Low Cloud Amount over China in 1951-2009
  • 2013 Vol. 32 (6): 1608-1616.  DOI:10.7522/j.issn.1000-0534.2012.00142
  • Abstract ( ) PDF (6223KB) ( )
  • Based on the surface monthly low cloud amount observation data of 360 surface stations in China in 1951-2009, and using GIS interpolation and t-test methods, the characteristics of the temporal and spatial distributions of the low cloud  amount were analyzed, and relationships of other climate factors and low cloud amount were discussed. Using the linear tendency estimate methods, the climatic trends of the low cloud amount were studied. The results show that the annual average low cloud amount in China decrease with the latitude increasing， while the cloudy regions locate in  Sichuan, Yunnan and Guizhou regions, and the less low cloud regions are locate in the northern drought region. The average low cloud amount overall are decreasing at rate of about 0.3% ·(10a)-1， moreover there are the significant differences in the decadal, seasonal and regional variations. In the arid area， semi-arid area， moist area, Northeast area， Qinghai-Xizang Plateau and Southwest area， the average change rates of low cloud  amount are  -0.18, -1.5, -0.19, 0.25, -1.20  and -0.37%·(10a)-1, respectively. Correlation analysis show that there is a positive correlation among low cloud cover and precipitation, relative humidity, the maximum snow depth, and negative correlation between evaporation and temperature; low cloud amount change lags the solar activity cycle, but the difference between different areas of low cloud amount change and climate factor is larger, which provide the basis for the projections of climate change.
  • Study on Improvement of Moist Q Vector Interpretation Technique
  • 2013 Vol. 32 (6): 1617-1625.  DOI:10.7522/j.issn.1000-0534.2012.00155
  • Abstract ( ) PDF (1975KB) ( )
  • A kind of moist Q vector interpretation technique applied to quantitative precipitation forecast (QPF), specifically, based on wind, temperature and dew-point temperature output by numerical prediction model, the vertical velocity can be obtained by solving the Omega equation whose forcing term is moist Q vector divergence, then the rain amount can be calculated by combining vapor, whereby dynamic interpretation method of QPF is produced. The moist Q vector interpretation technique will be improved by using the revised moist Q vector consisting of convective vapor condensational potential heating besides synoptic scale stable vapor condensational heating and by considering the roles of orographic lifting and surface friction. The modified moist Q vector interpretation technique (termed as QMVIP) is applied to Eastern China regional mesoscale numerical prediction model (which is based on WRF V3.1 and hereafter termed as WRF), and the QPF effect of QMVIP is verified with comparison to the counterpart of WRF from June to September 2010. The results of forecast statistical verification in 72h show that the test scores (TSs) and forecast accuracy of QMVIP forecast are higher than the counterparts of the WRF in the context of the rain with intensity over 0.1 mm·(24h)-1, 10.0 mm·(24h)-1 and 25.0 mm·(24h)-1, on average by 8\^61%, 17.65% and 29.57% respectively for TSs and by 8.44%, 6.49% and 1.88% respectively for accuracy, meanwhile, the false-alarm and miss rates of QMVIP forecast are lower than those of the WRF, on average by 16.79%, 15.05% and 10.74% respectively for false-alarm and by 9.75%, 3\^78% and 10.48% respectively for miss-alarm. Furthermore, for the rain with intensity over 50.0 mm·(24h)-1, TS is increased by 65.04%, accuracy is almost the same and miss rates are decreased by 12.94%, while false-alarm is increased by 12.67%. Therefore, QMVIP technique improves QPF effect in comparison to WRF on the whole. Finally, the further perfection of QMVIP technique and the improvement of operational QPF effect are discussed constructively.
  • Comparative Analysis on Abnormal Circulation in Spring in Extreme Drought Year of Yunnan
  • 2013 Vol. 32 (6): 1665-1672.  DOI:10.7522/j.issn.1000-0534.2012.00143
  • Abstract ( ) PDF (4293KB) ( )
  • Using the NCEP/NCAR reanalysis data  from 1961 to 2010, the difference of atmospheric circulation in spring between the extreme drought and rainy years (from March to April) in Yunnan were analyzed. The results show that the characteristis of atmospheric circulation in rainy spring are different from that of in spring of drought year. In the extreme drought years, it is negative anomaly in the region of the north of 40°N but positive in the region  of the south of 40°N on 500 hPa geopotential height field. The south branch trough and  Siberian high pressure are weak in the extreme drought year. The atmospheric circulations are characteristic of strong westerly and zonal circulation on 700 hPa in the Eurasia mid-latitude. There is an abnormal anticyclone over the Bay of Bengal and the South Peninsula, which lead the sinking motion in the troposphere. In the rainy years, it is positive anomaly in the region of the north of 38°N but negative of the south of 38°N on 500 hPa geopotential height field. The atmospheric circulations are characteristic of weak westerly and meridional circulation on 700 hPa in the Eurasia mid-latitude. The south branch trough and Siberian high pressure are strong in the rainy years. There is an abnormal cyclone from north of  South Peninsula to Yunnan, which lead the ascending motion in the troposphere. Water vapor transportation over Yunnan comes from the vapor transportation of south branch westerly and  water vapor transportation of west Pacific subtropical high external vapor transportation. Both of the two water vapor transportation are weak, resulting in the reducing of the vapor content   over Yunnan in the extreme drought years. On the other hand, the convergence of those two branch vapor transportations are strong, especially stronger in the  of water vapor western Pacific subtropical high external, increasing the content of the water vapor in the rainy year. The weak cold air, the sinking air flow and the weak convergence of water vapor flux, which lead to the poor dynamical conditions and weak water vapor transportation, are the reasons of extreme drought in Yunnan. The AO index  is negative correlation of the temperature in Yunnan in spring but positive correlation of the precipitation. In the negative phase of AO index, the temperature is higher and the precipitation is less in Yunnan, the spring drought is obviously, which is helpful to  the development of extreme drought.
  • Influences of Snow Cover of the Northern Hemisphereon Precipitation of Yunnan Province in May
  • 2013 Vol. 32 (6): 1712-1719.  DOI:10.7522/j.issn.1000-0534.2012.00160
  • Abstract ( ) PDF (4677KB) ( )
  • With the data of snow cover provided by National Oceanic and Atmospheric Administration/National Environmental Satellite Data and Information Services, Arctic Oscillation, wind field reanalyzed provided by NCEP/NCAR and the precipitation of Yunnan Province from 1973 to 2009, the relationships between the northern hemispheric snow cover in spring and the precipitation in Yunnan Province were analyzed. The study found that there is a closely relationship between spring snow cover in hemisphere and precipitation in Yunnan Province, when the northern hemisphere snow cover area increases, the precipitation in western of Yunnan Province is less, more in eastern Yunnan Province, which presents a parting space characteristic. The physical process that abnormal the precipitation in May in Yunnan caused by anomaly snow cover in the northern hemispheric as follows: When the spring snow cover in hemisphere increases, the AO presents negative phase distribution characteristic and abnormal east wind in middle latitude, the western region in Yunnan Province was controlled by the anticyclone, the precipitation was less, while the northern of Yunnan Province was influenced by the warm and wet southeast air flows of subtropical high peripherals, precipitation was more. The correlation between anomaly spring snow cover in the northern hemisphere and the precipitation in May in Yunnan Province keeps good continuity, therefore, the early anomaly spring snow cover in northern hemisphere can be used as a strong signal factor that affect the precipitation in Yunnan Province and make use of in the later precipitation short-term climate prediction.
  • Variation Features and Impact of High Temperature in Sichuan during Last 50 Years
  • 2013 Vol. 32 (6): 1720-1728.  DOI:10.7522/j.issn.1000-0534.2012.00161
  • Abstract ( ) PDF (3943KB) ( )

  • Abstract: Based on the daily temperature data of 141 stations in Sichuan from 1961 to 2010, variation features of the high temperature and the impact were analyzed. The results show that, from 1961 to 2010, the occurrence time of the first high temperature day in Sichuan had shifted to an earlier date with a speed of every 10 years ahead of 1.2 d, and the occurrence time of the last high temperature day had shown a postponed trend of every 10 years to defer 1.8 d. The high temperature days showed a significant increasing trend of every 10 years to increase 0.7 d, and the longest continuous days of the high temperature also showed a significant increasing trend, with an increase of 0.3 d every 10 years. For the whole Sichuan Province, during the past 50 years, the southern part of Sichuan Basin is the region where the high temperature days and the intensity showing the most significant increase trend, and the area of the western and central part of the Basin is the second obvious region. Since the 1990s, to the southern region of the Basin, the significantly increased and enhanced high temperature weather and obvious reduced precipitation had led to more frequent high temperature and drought disaster with more seriously affect; To the western and central region of the Basin, the obvious increased and enhanced high temperature weather and signicantly reduced precipitation had led to a grim regional water resources situation.
  • The Regional and Spatiotemporal Characteristics of Sunny Sunshine Duration in Southwest China during Recently 46 years and Its Formation Reason
  • 2013 Vol. 32 (6): 1729-1738.  DOI:10.7522/j.issn.1000-0534.2012.00162
  • Abstract ( ) PDF (5033KB) ( )
  • Using the data set of sunshine duration at 93 stations in Southwest China during recently 46 years, the regional and spatiotemporal characteristics and its formation reason were analysed. The results show that: (1) The sunny sunshine duration in Sichuan Basin is lower than other places; and the highest value is  in central mountainous area. The sunny sunshine duration in summer is higher than in winter, and the lowest value in winter in Sichuan Basin can be down to below  5 h·d-1. (2) The variation of sunny sunshine duration in recent 46 years revealed an obvious decline trend, and the trend coefficients in annual average, summer and winter are -0.82, -0.86 and -0.79, respectively, passed the significant level at 0\^001. (3) The variation of sunny sunshine duration in different cities is consistent with the regional averaged, and the decline extent of sunny sunshine duration in big cities is larger than that in medium and small cities; the annual mean regressive coefficients are -0.25, -0.19 and -0.08 h·d-1·(10a)-1. (4) The variation of sunny scattered radiation is similar to sunny sunshine duration at big cities in Southwest China, and the correlative coefficients of annual average, summer and winter are -0.726, -0.818 and -0.555, passed the significant level at 0.001. (5) Similar to sunny sunshine duration, the distribution of aerosol index over Southwest China also shows that the value in Sichuan Basin is higher than that in other places, and there is an increasing variation trend, which leads to the increased sunny sunshine duration. （6）There is a good simultaneous correlation between the variation trend of sunny sunshine duration and GDP in Southwest China.
  • Characteristics of Cloud Chart and Environment Field on a Heavy Rain Process in Shanxi Province
  • 2013 Vol. 32 (6): 1747-1757.  DOI:10.7522/j.issn.1000-0534.2012.00163
  • Abstract ( ) PDF (5060KB) ( )

  • Abstract: The characteristics of cloud chart and environment field on a heavy rain process in Shanxi Province in July 2011 was analyzed  using satellite data, automatic station data, L Brand data, and conventional observation data. The results showed that: (1)This heavy rain occurred under the background of two trough and one ridge on 500 hPa, subtropical high stability, and an anticyclone on 200 hPa. High energy, high humidity, divergence at high and convergence at low, and strong ascending motion were the basic environment characteristic of initial generation of cloud cluster, but there is a great difference among dynamic and thermal structure, intensity, and mesoscale environment that lead to the development of cloud cluster a later period. Four area of heavy rain caused by different property of cloud, and there is a great difference between precipitation property and characteristics. (2) L brand showed that disappear of cloud layer, lower of cloud top height, enlarge of humidity thickness, lower of congeal height, lower of 0℃ layer, and disappear of temperature inversion layer were indication of forming of MCC. (3) Diagnosis physical quantity showed that there were main information of development of MCC: Low-level jet stream as narrows, a branch of jet was disappear, and northwesterly jet high was weaken,  northwesterly wind at low was strengthen at the same time. Atmosphere instability was enlarge. Water vapor was enlarge suddenly, and air pressure was strengthen continually in warm area south of frontal surface. (4) Forced by humidity front, MCC is formed by development of convective cloud cluster near humidity center since invasion of dry and cold air.
  • Numerical Simulation of SO2 in Chengdu-Chongqing Economic Area (Sichuan)
  • 2013 Vol. 32 (6): 1758-1764.  DOI:10.7522/j.issn.1000-0534.2012.00146
  • Abstract ( ) PDF (7745KB) ( )
  • In order to analyze  the distribution of atmospheric pollution which is caused by the emissions of SO2，using the third models of  Community Multiscale Air Quality model, the emission of SO2 in the Chengdu-Chongqing Economic Area in April, July, and October of 2009 was numerically simulated, and the spatial-temporal distribution and change trends, at the same time, briefly analyzed the causes of the SO2.  The result shows that the correlation coefficient between daily simulation and observation of SO2 is 0.445, high SO2 concentration values appear  in the three areas, i.e., Neijiang-Zigong-Luzhou-Yibin area, Deyang-Chengdu-Meishan area and Guang′an-Dazhou area. The simulation value is less than the monitoring value around all the cities, the maximum value of  the simulated average annual concentration of  SO2 appearsin Neijiang city, it is 13.4 μg·m-3, and the minimum value of one appears in Mianyang, it is 1.76 μg·m-3. The change discipline of the seasonal concentration of SO2 is winter>autumn>spring>summer, respectively. The maximum value  of SO2 concentration occurs in winter whereas the minimum value occurs in summer. The maximum area of SO2 concentration always appears in Luzhou and Neijiang, the maximum value appears in Meishan.
  • Numerical Simulation on Meteorology Condition of Pollution in Xining
  • 2013 Vol. 32 (6): 1765-1773.  DOI:10.7522/j.issn.1000-0534.2012.00145
  • Abstract ( ) PDF (8652KB) ( )
  • The unsteady three-dimensional Lagrange puff transport model CALPUFF was used to simulate the pollution meteorology condition and diffusion regulation in Xining. The result shows that CALPUFF model well simulate the pollution level and variation trend in Xining, the simulated and monitored results have a good consistency; high pollution days appear from October to March in next year. When it is in the higher pollution, the wind speed is small in Beichuan and Huangshui river valley because of the terrain influenc, so it is not beneficial to diffusing the pollution. In the typical meteorology condition, because of the wind field influencing,  the pollution isn′t also beneficial to diffusing, additionally, inversion layer or the temperature varying with the height is not apparent at altitude of 450 m, the mixed layer height is in 100～400 m, which is not conducive to pollutant in vertical direction, lead to pollution accumulating in the valley zone. The concentration distribution about pollution in spring, autumn, winter and the valley direction are consistent generally in Xining, which appear the ‘十’ shape distribution, PM10 and NO2 is mainly distribute the west of Xining and Beichuan river valley in summer, but SO2 don′t affect to Beichuan river valley, the values of pollution average density is winter>autumn>spring>summer.
  • Cause Analysis on the Phase Transformation of Precipitation in Shanxi in Spring
  • 2013 Vol. 32 (6): 1787-1794.  DOI:10.7522/j.issn.1000-0534.2012.00165
  • Abstract ( ) PDF (4800KB) ( )
  • Based on the NCEP reanalyzed data, conventional observational data and automatic meteorological observing station data, the evolution of the phase transformation of precipitation happened in  spring from 31 March to 2 April 2011 was analyzed. The results show that, there are three strong wind belts, which are the northeast wind belt on  850 hPa, the southwest wind belt on  700 hPa and the northwest on  500 hPa. The characteristic of the flow configuration in this weather process is the clockwise rotation of the three strong wind belts along with the increase of height. The incursion of cold air making the temperature of intermediate and low-level atmosphere decreased and the reducing of the height of 0℃ atmospheric layer are the main reasons of the change in precipitation phases. The warm shear line on  800 hPa is the boundary of the snow and the rain which goes south with the shear line. There are solid precipitation on the north of the shear line, liquid precipitation to the south and mixed precipitation nearby the shear line. The temperature of 4℃ on 850 hPa is the critical value of the precipitation phase transformation for the stations which are in the north of Shanxi Province or at an altitude of 1000 meters at least in the central and south of Shanxi Province, while the temperature of 0℃ on 925 hPa is the critical value for the stations which are under the altitude of 1000 m in the central and south of Shanxi Province.
  • Characteristics and Countermeasures of Urban High Temperature in Chongqing City 
  • 2013 Vol. 32 (6): 1803-1811.  DOI:10.7522/j.issn.1000-0534.2012.00167
  • Abstract ( ) PDF (2617KB) ( )
  • Based on the daily temperature data measured at Shapingba weather station in Chongqing city from 1951 to 2011, the characteristics of urban high temperature in the past 61 years was analyzed. The influence factor and mitigation measure were also discussed. The results showed that in the past 61 years the annual average temperature in Chongqing city mainly experienced three stages of warmer period, colder period and warmer period. Its change tendency was first fall and then rise and the general trend was warming with a tendency of 0.8℃·(100a)-1. The warming trend of annual average minimum temperature change was the most evident, its tendency reached 1.4℃·(100a)-1. The warming trend of average temperature in summer was not evident. Combined with the change of annual average temperature, it was lagged. The change trend of the high temperature days had been ‘low-high-low-high’, and gradually consistent with global warming in recent years. The urban high temperature of Chongqing had some characteristics such as the high temperature days was many, the annual variability of the high temperature days was great, the duration of high temperature was long, the appearance time of first high temperature day in every year was early, the appearance time of high temperature days spanned a long time and the high temperature days were centralized. The urban high temperature of Chongqing was determined by the geographic environment and basic character of regional climate first, influenced by the big background of global warming, and aggravated by the urban heat island. There were some measures to reduce the influence of urban high temperature, such as strengthening the work of urban planning to increase natural ventilation, protecting and utilizing river valley breeze and mountain valley breeze, attaching importance to the city virescence, increasing water area, controlling the density of population and atmospheric pollution, reducing the release of man-made heat, developing the work of spray rain and fog to reduce temperature and then adjust microclimate of Chongqing city.

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