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28 October 2014, Volume 33 Issue 5   
  • Impact of Heat Source over Qinghai-Xizang Plateau and Its Surrounding Areas on Rainfall in Sichuan-Chongqing Basin in Summer
  • CENG Sixian;GONG Yuanfa;LAI Xin
  • 2014 Vol. 33 (5): 1182-1189.  DOI:10.7522/j.issn.1000-0534.2013.00122
  • Abstract ( ) PDF (3254KB) ( )
  • Using the NCEP/NCAR reanalysis data and observed daily rainfall from gauge stations, analyze the relationship between atmospheric heat source (hereafter called <Q1>) over the Qinghai-Xizang Plateau(QXP) and its surrounding areas and precipitation in the Sichuan-Chongqing basin in the summer has been studied in this paper, The result shows that: when the heat source (hereafter called <Q1>) over the areas that from the eastern of the QXP via the Yangtze River Basin to the Bohai Bay and its surrounding areas and from the Bay of Bengal to the Indo-China Peninsula are weakened, lead to the cool air over the high latitude and the warm air over the low latitude convergence over the west of Sichuan-Chongqing basin, thereby, most moisture was transported to the west of Sichuan-Chongqing basin, convergent and ascend lead to the rainfall occurred in this region, and the circulation over the east of Sichuan-Chongqing basin is unfavor the moisture convergent in this region, lend to the flood in the west and drought in the east; reversely, when the <Q1> over the areas that from the eastern of the QXP via the Yangtze River Basin to the Bohai Bay and its adjacent region, and from the Indo-China Peninsula to Philippines and its surrounding areas across the South China sea, and the northwest in China and the Mongolia and its adjacent areas are strengthened, lead to the cool air over the high latitude and the warm air over the low latitude convergence over the east of Sichuan-Chongqing basin, thereby, most moisture was transported to the east of Sichuan-Chongqing basin, convergent and ascend lead to the rainfall occurred in this region, and the circulation over the west of Sichuan-Chongqing basin is disadvantage for the moisture convergent in this region, lend to the flood in the east and drought in the west.
  • Contrast of Circulation Pattern Related to More and Less Spring Snow Cover over Qinghai-Xizang Plateau
  • TANG Hongyu;LI Xifu;LI Dongliang
  • 2014 Vol. 33 (5): 1190-1196.  DOI:10.7522/j.issn.1000-0534.2013.00125
  • Abstract ( ) PDF (3336KB) ( )
  • Using the daily snow observation data in 1961-2007 at 68 meteorological stations on the Qinghai-Xizang Plateau(QXP), the variation of spring snow cover day on the QXP and the circulation background of the anomalous spring snow cover year are analyzed, and the spring snow cover impact on the northern hemisphere circulation in summer is revealed. The results show that though in the years when spring snow day are fewer or more than normal, 500 hPa height fields in Eurasia all exhibit the circulation pattern with ‘two trough a ridge’ in the mid-high latitude regions, the position and anomaly extents in the more and less frequency snow cover years are obviously different. In spring, when the Iceland low is strong (weak), the Mongolian high is strong (weak), and the Indian low is weak (strong), the spring snow cover over the QXP is more (less) frequency. Whether for summer circulation in the northern hemisphere or summer climate in China, number of spring snow cover days on the QXP is an important influence signal. It has a close linkage with the main atmospheric activity centers in the northern hemisphere and the main atmospheric circulation systems impacting the climate in China in summer. When spring snow cover is more (less) frequence over the QXP, it appears that in summer the blocking high is more (less) easily developed in East Asia, while the west Pacific subtropical high is less (more) easily to be shifted with southward in the northwest Pacific. Such kind of relationship is an important indicator for short-term climate prediction in China.
  • Cause Analysis on Typical Abnormal Year of Water Vapor in the Upper Troposphere over Qinghai-Xizang Plateau
  • LI Minjiao;ZHANG Xueqin;XIE Chengying
  • 2014 Vol. 33 (5): 1197-1203.  DOI:10.7522/j.issn.1000-0534.2013.00111
  • Abstract ( ) PDF (4176KB) ( )
  • The variation of water vapor in the upper troposphere over the Qinghai-Xizang Plateau (QXP) plays an important role in the stratosphere-troposphere water vapor exchange. So the Atmospheric Infrared Sounder (AIRS) observations combined with NOAA global sea surface temperature (SST) observations, NCEP/NCAR reanalysis data and 74 circulation parameters from NCC are adopted to investigate the causes of the typical abnormal year of water vapor in the upper troposphere over the Tibetan Plateau during 2003-2011 from the aspect of ocean-atmosphere coupling. Analysis indicates that the ENSO events could be regarded as an indicator for the amount of water vapor in the upper troposphere over the QXP. And the water vapor in the upper troposphere increased (decreased) in summer when an El Nio (La Nia) event occurred in previous year. The atmospheric circulation anomaly forced by SST anomaly was the direct reason for the increase of the upper tropospheric water vapor over the QXP in 2010. The geopotential height in the upper troposphere became high in the summer of 2010, the blocking situation of East Asian region developed and the western Pacific subtropical high (WPSH) became stronger and extended westward, which were conducive to the transport of water vapor from the Western Pacific and the South China Sea to the QXP. In addition, the maintaining of the abnormal anticyclonic circulation over the QXP and the continuous converging of cold and warm air enhanced the upward transport of water vapor, leading to the anomaly of water vapor in the upper troposphere over the QXP in 2010.
  • Numerical Simulation and Potential Vorticity Diagnosis of an Eastward Moving Southwest Vortex
  • LIU Xiaoran;LI Guoping
  • 2014 Vol. 33 (5): 1204-1216.  DOI:10.7522/j.issn.1000-0534.2013.00151
  • Abstract ( ) PDF (13320KB) ( )
  • By using non-hydrostatic mesoscale WRF (Weather Research Forecast) model, an eastward moving southwest vortex process producing heavy precipitation is simulated in high resolution. The simulation is triple nesting with the highest resolution of 5 km. The results show that the WRF model successfully simulate the area and movement of heavy precipitation caused by the southwest vortex. The southwest vortex establishes on 850 hPa firstly, and then develops upward to 700 hPa after 9 h. There is convergence, positive vorticity, potential vorticity in the lower troposphere both in newborn and mature stages of the Southwest Vortex. And the strong vertical movement, positive vorticity and potential vorticity can significantly strengthen to the upper troposphere (300 hPa). The water vapor flux divergence has good indication to strength and movement of the heavy precipitation. The potential vorticity diagnostic analysis shows that vertical configuration of the diabatic heating term is contrary to that of vertical flux divergence term. The diabatic heating term caused by the release of latent heat is beneficial to the growth of low-level potential vorticity and inhibition of the growth of high-level potential vorticity. The latent heat is in favor of the generation and development of the southwest vortex.
  • Abnormal Features of Asian Summer Monsoon Circulation and Its Effects on Chinese Rain Band in 2010
  • BAO Yuanyuan;KANG Zhiming
  • 2014 Vol. 33 (5): 1217-1228.  DOI:10.7522/j.issn.1000-0534.2013.00099
  • Abstract ( ) PDF (12843KB) ( )
  • The main rain band in the summer of 2010 has the obvious features of highly concentrated periods and areas, high intensities with extremely serious floods occurring in central and southern region of the Yangtze River and South China in June, extremely serious floods in Huaxi and Northeast China from middle July to August respectively. By using NCEP/NCAR reanalysis data and NOAA OLR, SSTA data, the influence of summer monsoon circulation on the rain band and the mechanisms for the abnormal features of summer monsoon circulation are analyzed. The results show that in the whole summer Western Pacific Subtropical High (WPSH) is stronger and more northward, South Asia High(SAH) is stronger and eastward, southwest monsoon is weaker and more westward. Both WPSH and SAH are markedly southward in June and northward from middle July to August. The efficient allocation of monsoon circulation leads to the rare torrential rain and floods. The positive SSTA in equatorial Indian Ocean and near Indonesia results in stronger convection, stronger heat resources and higher temperatures in the middle and upper atmosphere over there and weaker north-south temperature difference in South Asia even in the case of less snow cover and stronger heat resource over Tibet Plateau and higher temperature over southern Asian continent. The strong resources over Indonesia and nearby promote a strong and southward WPSH in June by sinking force effect and negative vorticity increase at the north side. From July to August, convection and heat resources over South China Sea and Philippines increase rapidly with SST, SAH strengthens and maintains northward due to strong heat resources over the Qinghai-Xizang Plateau and strong latent heat released by strong precipitation in Huaxi at the northwest side of WPSH, such factors are advantageous to a strong WPSH with northward ridge and westward west ridge point. Correlation analysis confirms the influence of SSTA on WPSH and SAH.
  • Comparative Analysis of Precipitation Difference over Yunnan Influenced by Bengal Bay Storm in Autumn
  • XU Meiling;LIANG Hongli;DUAN Xu;CHEN Xiaohua
  • 2014 Vol. 33 (5): 1229-1239.  DOI:10.7522/j.issn.1000-0534.2013.00123
  • Abstract ( ) PDF (9491KB) ( )
  • Based on the data of tropical storm over northern Indian Ocean from the Guam Joint Typhoon Warning Center, NCEP/NCAR reanalysis data, daily precipitation data at 125 stations in Yunnan, two cases of strong Bengal Bay storm in autumn were selected, then their moving tracks and influence on precipitation over Yunnan were comparatively analyzed. It was showed these two cases with nearly the same intensities, moving track and landing position were difference. During their influence period, the intensity and range of precipitation over Yunnan were obviously different. The difference of south Asian high position on 200 hPa and steering flow resulted in various of moving track and landing position of Bengal Bay storm; the interaction of Bengal Bay storm with cold air was a critical mechanism to heavy rainfall generating in Yunnan; the moving of southwester areas at lower layer on the east side of Bengal Bay storm also played an important role in the formation of precipitation, on the one hand, it transported a large number of water vapor and energy into Yunnan, on the other hand, wind velocity convergence on gale areas was helpful to maintain necessarily dynamics condition. With the influence of the western ridge point of the western Pacific subtropical high on 500 hPa and intensity of southwesterly at lower layer, water vapor transport, intensity of convergence and maintenance time were various, different pattern in circulation at upper and lower layer caused the significant differences in dynamic structure, vertical motion and so on, while these were important reasons of various precipitation distribution generating in Yunnan with two storms.
  • Preliminary Study on Heavy Rainfall in Yunnan in Early Summer Initiated by Bengal Bay Storm
  • LIANG Hongli;XU Meiling;LU Aimin;DUAN Xu
  • 2014 Vol. 33 (5): 1240-1250.  DOI:10.7522/j.issn.1000-0534.2013.00076
  • Abstract ( ) PDF (7667KB) ( )
  • Based on JTWC, NCEP/NCAR reanalysis data and variational assimilation of TRMM, the activity of cold air and its impacts on Bengal Bay storm heavy rainfall in Yunnan in early summer from 2000 to 2010 were diagnosed. It was showed that Bengal Bay storm initiating heavy rainfall over Yunnan in early summer both landed at the southeast of Bangladesh, north centre coast of Burma, among them about 78 percents of heavy rainfall appeared after Bengal Bay storm landing. Except for eastern edge, the subtotal areas of Yunnan were easy to be affected by Bengal Bay storm. While there was cold air acting, the intensity of heavy-hard rain was stronger and range was wider. The evolution of circulation was closely related to storm heavy rainfall areas. Further discussion showed without cold air, southerly enhanced significantly, and the wind speed maximum sloped northward with height, vertical wind shear was small, moist layer was deep, convective instability occurred by storm warm-wet air was the important reason for heavy rainfall over western Yunnan, moreover topographic forcing also played an important role. Otherwise, while cold air acting, there was an intensive belt of θse sloping northward at the beginning of heavy rainfall, warm-wet storm clusters tilt upward-slided along southern isentropic surface, whereas there was dry-cold air in the middle-low troposphere at the side of north, they met at tilt isentropic surface, ascending motion areas sloping northward was bias to warm-wet region, during heavy rainfall periods, cold air changed more dry-cold, compared with the beginning, ascending motion was more stiff. In the aspect of moist potential vorticity, there was high MPV1 downloading to precipitation area along tilt isentropic surface at upper layer of the north side of southern Yunnan, the forcing of down-sliding cold air strengthened the upward-sliding of warm-wet air, meantime, negative center of MPV2 downloaded along intensive belt of θse from high troposphere and invaded low troposphere at the north side of heavy rainfall areas, warm-wet air met with dry-cold air at middle-low troposphere, then conditional symmetric instability generated, which resulted in heavy rainfall over central Yunnan and the south areas.
  • Comparative Analysis of Surface Energy Fluexes over Sino-US Semi-Arid Land
  • LI Shan;AI Likun
  • 2014 Vol. 33 (5): 1262-1271.  DOI:10.7522/j.issn.1000-0534.2013.00107
  • Abstract ( ) PDF (4473KB) ( )
  • To study the long-term climate trends and the characteristics of land-atmosphere interaction in the semi-arid regions, is conducive to the understanding of drought formation mechanism. It provides scientific basis for the effective organization of the orderly human activities, alleviation the process of drought and improvement of the ecological environment in arid and semi-arid region. The surface flux is the most critical factor in the land-atmosphere interaction. In order to analysis and understand the land-atmosphere interaction in semi-arid region, this paper proposes to start from the analysis of the exchange of the surface fluxes by analyzing the practical observation data in the two typical semi-arid region of China and Northern America. The analysis result shows that the sensible heat flux is the minimum in winter,followed by summer, then spring or autumn. The sensible heat flux is generally higher in seasons with high net radiation and low soil moisture. Data collected by the monitoring stations in the north of 40°N indicates that latent heat flux is larger in seasons with much precipitation. From 1979 to 2008, the 30 years witnessed the drying out of climate in semi-arid regions in eastern and northeastern part of China. As time goes, this trend is expected to continue. According to the monitoring stations in Northern America, long-term changes of resonating heat go hand in hand with temperature changes while latent heat and precipitation are in good consistency. Interannual variability of sensible heat flux in semi-arid regions of Central America is significantly affected by temperature changes and the average soil moisture content. There is a positive correlation between the interannual change of latent heat flux and that of rainfall. Besides, latent heat flux is also influenced by temperature change.
  • Extensional Study and Application on Vertical Helicity
  • YUE Caijun;CAO Yu;LI Xiaofan
  • 2014 Vol. 33 (5): 1281-1288.  DOI:10.7522/j.issn.1000-0534.2013.00115
  • Abstract ( ) PDF (5234KB) ( )
  • Vertical helicity (termed as Hp) consists of vertical velocity and vertical vorticity, reflecting vertical advection of vorticity. Until now, vertical velocity can't be obtained directly by observations, which leads to calculate vertical helicity inconveniently. It is well known that Q vector is taken as an advanced tool for diagnosing vertical motion, and when vertical velocity in atmosphere has wave-like feature, there is proportional relationship of divergence of Q vector and vertical velocity, i.e., ▽·Q∝ω(ω is vertical velocity in p-coordinate), in other words, the divergence of Q vector can estimate vertical motion indirectly. The Q vector is drawn into study on helicity first time in this paper, specifically, a new type of vertical helicity (termed as HQ) is constructed on the basis of Q vector divergence and vertical vorticity. HQ is an extensional form of Hp, and they have the same physical meaning and similar diagnostic feature. The intrinsic difference between HQ and Hp is that the vertical velocity needed not to be given before calculating HQ. On some degree, the genesis of HQ firstly realizes organic fusion of the two advanced tools of helicity and Q vector, meanwhile, the diagnostic ability of HQ will be improved along with the developing of Q vector theory. The application of HQ to a typical Changjiang-Huaihe Meiyu front cyclone torrential rainfall shows that HQ has a good reflecting ability to synchronous precipitation intensity, occurring region and their inhomogeneities, and discloses the characteristics of vertical vorticity advection tilting northwards with height over torrential rainfall area. Further analysis indicates that there is obvious positive vertical vorticity and convergence of Q vector divergence preserving over precipitation area, and there is a good corresponding relationship between convergence region of Q vector divergence and occurring region of precipitation. HQ is the synthetic manifestation of roles from Q vector divergence and vertical vorticity, however, the three dimensions spatial distributional feature of HQ has more similar to counterpart of Q vector divergence with respect to vertical vorticity, which displays HQ relating more closely to Q vector divergence.
  • Study of Influence of Aerosol on Atmospheric Visibility in Guanzhong Region of Shaanxi Province
  • LI Xingmin;DONG Zipeng;CHEN Chuang;DONG Yan;DU Chuanli;PENG Yang
  • 2014 Vol. 33 (5): 1289-1296.  DOI:10.7522/j.issn.1000-0534.2013.00116
  • Abstract ( ) PDF (3237KB) ( )
  • To further study the influence of air pollution on atmospheric visibility, using the products of aerosol optical depth(AOD) of MODIS, the observed visibility data at 43 meteorological stations, and measured AOD using CE318, wind speed, relative humidity and visibility data at Jinghe in Xi'an, the relationship between the distribution of MODIS/AOD and visibility, the relationship between MODIS/AOD and the days of visibility less than 10 km in autumn and winter, and the relationship between MODIS/AOD and visibility under different wind speed,relative humidity, have been analyzed. The results show the distribution of MODIS/AOD is correspond well with the distribution of visibility. The correlation coefficient of MODIS/AOD and visibility at 08:00 in winter and spring is better than other seasons. While the correlation coefficient of MODIS/AOD and visibility at 14:00 is better in summer and autumn. Air particulate pollution is the most important factor which causes lower visibility in autumn and winter except precipitation. When Ångstrom range from 0.8 to 1.2, aerosols impact on visibility distinctly. The deterioration of visibility caused by air polluted is closely related with relative humidity, higher relative humidity causing more visibility decline. When wind speed is lower, particles in air accumulate easily and lead to visibility deterioration. When wind speed is higher, air pollutants diffuse easily and the visibility improve quickly. Estimating visibility using AOD must consider the influence of relative humidity and wind speed on them.
  • Structure Analysis of a Snowstorm with Low-level Eastern Wind in Shanxi Province
  • ZHOU Jinhong;MA Hongqing;SUN Shaoxiong;QIAO Jinhai
  • 2014 Vol. 33 (5): 1305-1314.  DOI:10.7522/j.issn.1000-0534.2013.00087
  • Abstract ( ) PDF (10898KB) ( )
  • Based on conventional surface and sounding observation data, NCEP 1°×1° reanalysis data, a snowstorm structure with low-level eastern wind in Shanxi Province from 28 to 29 November 2011 is researched. The results are following: (1) This weather process is developed by the joint influence of upper westerly trough, shear lines in lower level, ground return-flow and inverse trough. The northeaster wind occurs from 925 hPa to 850 hPa upper Shanxi about 18 h before the snowstorm, the northeaster wind occurs on surface in Shanxi about 12 h before the snowstorm, and it is strong during the snowstorm; The low-level northeaster wind is cold and dry before the snow, and it is a wet-cold pad during the snow. (2) The water vapor of this snowstorm comes from the southwest water vapor emerging in southuest China and transport northward, this emerging southwest flow comes from the southwest wind in the front of South Westerly Trough and the turning of east flow in Beibu Gulf which comes from Western Pacific, then it is combined with the southwest flow in the front of the westerly trough. The heavy snow occurs in the area of south wind of the wind convergence on 700 hPa where is on the northwest of the vapor flux center and has dense isolines. (3) The heavy snow accompanies with the deep wet layer, the obvious vapor flux convergence under 500 hPa and strong updraft current upper 800 hPa in the troposphere upper Shanxi area, under 800 hPa it has obvious downdraft current which is caused by the low-level eastern wind. (4) The westerly jet on 300 hPa moves eastward and goes down southward among the heavy snow, Shanxi is located on the right of the jet's entrance region and occurs strong divergence, which impels the development and maintenance of the inverse trough of the Great Bend of the Yellow River on surface, and may cause stronger updraft current in the area of heavy snow.
  • Verification on Surface Wind Speed of Three Global Circulation Models in China
  • HE Xiaofeng;ZHOU Rongwei;SUN Yihan
  • 2014 Vol. 33 (5): 1315-1322.  DOI:10.7522/j.issn.1000-0534.2013.00093
  • Abstract ( ) PDF (3288KB) ( )
  • In order to meet the user's needs for high-precision wind power forecast, many organizations are using mesoscale model to forecast high-resolution wind field in the area of interest. The forecast fields of global circulation models, which are used as the background fields of mesoscale model, have an important impact on the forecast results. So wind speed forecast accuracy is very important. In order to compare performance of different global circulation models, firstly, WRF model was used to downscale the forecast fields of ECMWF, GFS and T639 model in the whole China with 10 km×10 km horizontal resolution in four typical months. Then observation wind speed of 400 wind masts and forecast results at 70 m height were contrasted. The results show that: (1) From the average verification results of four typical months in the full wind segment, ECMWF was slightly better than GFS, and T639 was slightly the worst. If averaging three forecasting wind speed, the best ensemble prediction result can be obtained. (2) The plane distribution of wind speed forecast error was similar, and the forecast error in Inner Mongolia, Northeast and parts of coastal area was less, while the error in inland area was bigger, especially it was worst in plateau and complex terrain area. (3) As by verification results of four wind speed segment of forecast wind speed indicated that in (0, 3] m·s-1 and (3, 15] m·s-1 segment TS score of ECMWF field was slightly better, in (15, 25] m·s-1 segment the TS score of GFS field was best, and in bigger than 25 m·s-1 segment ECMWF field had obvious advantages. (4) In the wind segment of (3, 15] m·s-1, the forecast wind error are almost 35%. But ECMWF was slightly better than the GFS, and GFS was slightly better than T639. (5) There was 55.5% wind masts where ECMWF had the best wind forecast performance, the percent of GFS was 24.8%, and the percent of T639 was 19.7% in the wind segment of (3, 15] m·s-1.
  • Numerical Simulation of the Rainstorm Process in Ya’an Based on WRF Model
  • WU Ze;FAN Guangzhou;ZHOU Dingwen;MU Ling
  • 2014 Vol. 33 (5): 1332-1340.  DOI:10.7522/j.issn.1000-0534.2013.00084
  • Abstract ( ) PDF (7046KB) ( )
  • A rainstorm process in Ya'an on 21 August 2010 was studied using numerical simulation conducted by the WRF model. Comparison the simulated results and the fact demonstrates that WRF model could well simulates the spatial and temporal distribution of the precipitation process. Diagnostic analysis of this rainstorm using high spatial and temporal resolution simulation data were done. The result shows that: The blocking effect of the Tibetan Plateau makes the warm air along southwest of the subtropical high continuously transport to the basin, and a cyclonic circulation center forms over Ya'an region on 700 hPa. Strong upward motion was shown in the center of heavy rainfall in the main precipitation period from low-level to senior, and it maintains high-level divergence, low level convergence, high altitude negative vorticity and low altitude positive vorticity in the storm center. With the development of heavy rain, continuous enhancement of positive vorticity in the troposphere provides pretty favorable dynamic conditions for the generation and maintenance of a rainstorm. The wet air over the middle and lower troposphere, the strong transportation of moisture and the high and low level configuration of moisture flux divergence provide adequate moisture conditions. The atmospheric stratification of the lower troposphere is unstable, and the middle is a neutral, so this kind of potential instability supply thermal conditions for the occurrence of convective weather, and it is conducive to the formation of the heavy precipitation process at the same time.
  • Impact of Differences Between the NCEP and ECMWF Reanalysis Data on Solar Radiation Simulation
  • PENG Jida;CHENG Xinghong;SUN Zhian;SHEN Yanbo;LIANG Hong
  • 2014 Vol. 33 (5): 1352-1362.  DOI:10.7522/j.issn.1000-0534.2013.00098
  • Abstract ( ) PDF (3782KB) ( )
  • Global, diffuse and direct radiation were simulated by WRF-SES2 radiation model system in Beijing urban area based on ECMWF and NCEP reanalysis data in January, April, July, and October 2010. The differences of solar radiation was put emphasis on simulation using the two kinds of reanalysis data and impacts of differences of total cloud amount on radiation simulation. The results showed that:(1) Simulated values of global radiation in most of times are larger than the observed values and those of scattered radiation are smaller; simulation values of total cloud amount are less than the observed values; errors distribution scopes of direct radiation are larger than global and scattered radiation. (2) In general, simulated errors of global, direct, diffuse radiation based on EC data in most of periods are less than those based on NCEP data because simulation errors of microphysical quantities of cloud using EC data are less than those with NCEP data. (3) Simulation effects of global radiation in January and April are better, those in October take second place, those in July are worse. Namely average absolute errors in January and April are smaller and distribution scopes of simulation error are narrower, falling in between -50 W·m-2 and 200 W·m-2. Simulation effects of direct radiation are better in January, followed by those in April and October and results in July are worse. Those of scattered radiation are better in January and October, followed by those in April and July. (4) Simulation accuracy of global, direct and diffuse radiation were obviously affected by simulation effects of cloud amounts in initial fields. When sky is cloudy and rain falls, simulated errors of solar shortwave radiation based on EC data and NCEP data are large and data assimilation in the initial field and corrections are required. We will improve simulation of solar shortwave radiation in the future research using data assimilation method, more accurate the atmospheric radiative transfer model, advanced cloud parameterization schemes and effective correction methods.
  • Heat Source over ‘Fishtail’ Type Topography Effects on Tianshan Mountain Regions Precipitation Systems and Water Resources
  • GUO Yudi;XU Xiangde;CHEN Weimin;WEI Fengying;CHEN Aijun
  • 2014 Vol. 33 (5): 1363-1373.  DOI:10.7522/j.issn.1000-0534.2013.00120
  • Abstract ( ) PDF (12214KB) ( )
  • From the point view at the role of the apparent heat source over the area of Tibetan Plateau and which connected with Tianshan Mountain, the relationship between the heat source over the area of Tibetan Plateau and which connected with Tianshan Mountain and the atmospheric water cycle, as well as the cloud-water resource in the Tianshan Mountain regions were investigated, using the satellite data, the monthly National Centers for Atmospheric Prediction and the National Center for Atmospheric Research (NCEP/NCAR) reanalysis with a resolutions of 2.5°×2.5° and 1°×1°, respectively, together with the Climatic Research Unit (CRU)precipitation data, in order to achieve the investigation on the changes of atmospheric water cycle structure in Tianshan Mountain regions in terms of diagnosis on column water vapor, moisture transport, the correlated vector and the apparent heat source. The spatial-temporal distribution of the summer half year rainfall and its variation was also analyzed. The results show that: The large parts of precipitation and column water vapor over region of Tianshan Mountain are concentrated over its west part. The analysis on the vertical structure of apparent heat source and sink of water vapor also revealed that the rich cloud-water resource is well consistent with the apparent heat source over Tibetan Plateau fishtail type topography. We further analyzed the integrate image of the long distant moisture source, which formed the rich cloud-water resources over the area of Tibetan Plateau and which connected with Tianshan Mountain using the methods correlated vector analysis between the apparent heat source over this region and the column water vapor transport. The results indicated that the atmospheric moisture is mainly come from the South Atlantic Ocean, the Bay of Bengal and the Arabian Sea and the northern Arctic Ocean. A 12-year cycle is obvious for the water vapor, precipitation, and the apparent heat source over "fishtail" type topography. From the 1950s to nowadays, the cycle of apparent heat source over "fishtail" type topography is ahead of 3~4 years compared to the changes of column water vapor. However, the column water vapor changes appeared in advance 3~4 years in contrast to the precipitation over this region, and after that, with an advance in 1~2 years. The interannual variation of cloud-water resources represented, to some extent, the response mechanism of the regional atmospheric moisture cycle structure to the apparent heat source over fishtail type topography.
  • Impacts of Spring Mascarene High on Air Temperature over Northeast China in Summer
  • ZENG Yuxing;FENG Guolin;ZHAO Junhu;SHEN Baizhu
  • 2014 Vol. 33 (5): 1374-1382.  DOI:10.7522/j.issn.1000-0534.2013.00078
  • Abstract ( ) PDF (6462KB) ( )
  • Based on the monthly average data of air temperature at 26 stations in Northeast China and the NCEP/NCAR monthly reanalysis data of wind spead and geopotential height from 1951 to 2011, the impacts of Spring Mascarene High (SMH) in summer air temperature over Northeast China are studied. The results show that SMH is positively related to the summer temperature over Northeast China. In a stronger SMH year, Northeast China region is controlled by the deep high-pressure system in summer, which lead to the divergence and sinking of air flow and the decreasing of total cloud amount, which cause the air temperature in this region is higher than the conventional year. On the contrary, when the SMH is weaker than the conventional year, Northeast China region is controlled by the low-pressure system in summer, the cold air in high-latitude and the warm air flow in low-latitude are converged in this region, which cause the increasing of total cloud amount, and the air temperature is lower than the conventional year. In addition, the SMH anomaly can cause in the middle of the Indian Ocean SST anomaly, and continue until the summer and further strengthen, the meridional teleconnection wave train which is vitalized by the summer Indian Ocean SST anomaly on 200 hPa zonal wind field have effect on 500 hPa geopotential over Northeast China, which can be used for explain the variation of air temperature in this region. Besides, SMH can also enhance summer Somali Jet and cross-equatorial flow at 80°E, which thereby enhance the convective activity in surrounding areas of the Philippines, then intensify the subtropical northwestern Pacific high, and make it extend southwestward, which also contribute to the change of air temperature over Northest China.
  • Mechanisms of Local Explosive Development of a Radiation Fog Event
  • WU Bingui;MA Cuiping;CAI Ziying;YU Lei;ZHAO Na;QU Xaiolei
  • 2014 Vol. 33 (5): 1393-1402.  DOI:10.7522/j.issn.1000-0534.2013.00066
  • Abstract ( ) PDF (11680KB) ( )
  • An explosive fog event was analysed which occurred in the coastal area of north-eastern Hebei Province(the Leting meteorological station as representative) and the Tianjin area from 21 to 22 December 2010, based on the observations obtained from the 255 m meteorological tower located in Tianjin, the NCEP reanalysis data with the spacial resolution of 1°×1°, and the automatic meteorological monitoring data adjacent to the railway. The results indicated that: The explosive fog episode in Leting is the presence of the atmospheric moisture convergence near the shear line, along with the cold air inflow in the front of a short-wave trough, and long-wave radiation cooling in the evening. The explosive thickened fog in Tianjin region is directly caused by invasion of a frontal weak cold air of the secondary cold front at lower atmosphere. In addition, the fog dissipation is due to strong cold air which is acompanied with the cold frontal passage. During the fog event, it's moist and clod in near surface layer, warm and dry in the upper boundary layer. In addition, the surface air temperature increases slightly prior to the fog intensification during the overall cooling tendency, which is an effective indicator of the explosive development of fog.
  • Influence of Sand-Dust on Solar Radiation in the Hinterland of Taklimakan Desert
  • JIN Lili;HE Qing;LI Zhenjie;Ali Mamtimin;MIAO Qilong
  • 2014 Vol. 33 (5): 1403-1410.  DOI:10.7522/j.issn.1000-0534.2013.00061
  • Abstract ( ) PDF (2908KB) ( )
  • In order to reveal the essential feature of radiation in extreme arid region of Northwest China, using the global radiation, direct radiation, diffuse radiation and meteorological data in the Tazhong station(in Taklimakan desert hinterland, 83°39'E, 38°58'N), the characteristics of atmospheric transparency coefficient, influence of sand-dust on solar radiation were analyzed by the statistical methods. The results show that: The coefficient of atmosphere transparency is better from October to December than other months, but it's worse in spring and summer. The index of the atmosphere transparency P2 is the most (least) in clear day (sand storm day). The global radiation is more than 1000 W·m-2 in clear day, dust day and sand blowing day, while, it is up to 700 W·m-2 in sand storm day at most. The diffuse radiation is partly less than 400 W·m-2, mainly between 100 and 200 W·m-2 in clear day. It is less than 600 W·m-2 in dusty day mostly. The direct radiation is reduced by dust aerosol. The probability are 41.2%, 72.5%, 78.1% and 100% when direct radiation is less than 200 W·m-2 during clear day, dust day, sand blowing day and sand storm day. The diffuse radiation is gradually concentration high value with the sand of the atmosphere is increased. The variation of every radiation is big in dusty day. The daily curve (value) of diffuse radiation is similar to the global radiation, which is reduced by dust aerosol is the same as the direct radiation. That suggests the atmosphere transparency is closely related to the global radiation, diffuse radiation and direct radiation.
  • Application of CINRAD Mosaic Products on Artificial Hail Suppression
  • DUAN Yiping;LIU Shoudong;LIU Liping;MA Jianli;YE Xiaofeng;WANG Guanhua
  • 2014 Vol. 33 (5): 1426-1439.  DOI:10.7522/j.issn.1000-0534.2013.00139
  • Abstract ( ) PDF (5836KB) ( )
  • On basis of the distribution characteristics of reflectivity mosaic of China new generation weather radar (CINRAD), six indexes are suggested to identify hail cloud during hail suppression by artificial means, which include composite reflectivity (CR), echo top (ET), maximum reflectivity of ET (MET), vertical integrated liquid (VIL), density of VIL (VILD), and gradient of VIL (GVIL), respectively. Some indexes are calculated depending on storm cell identification and tracking (SCIT), form the fuzzy logical method to identify the suppression area. The results indicate that the method of three-dimensional hail recognition experiment are applied multiple hail fall alone in Beijing and Jiangxi. To contrast the hail observation data, calculation of the accuracy are greater than 77% the false ratio is below 26%, empty ratio below 22% through multiple example. Consider the portfolio reflectance characteristics of three-dimensional shape distribution of fuzzy logic method can well identify most workable hail cloud, tracking simulation effect is good, is conducive to effective application in figure hail proof operation. The hail clouds which need to be suppressed by artificial means can mostly be identified according to the characteristics of reflectivity mosaic and fuzzy logical method. The method has a better tracking effect and a promising application in hail suppression.
  • Pseudo-Color Composite for Polarimetric Radar
  • CHENG Zhoujie;WEI Ming;ZHU Yaping;LIU Xianxun;QI Linlin;NING Yinghui
  • 2014 Vol. 33 (5): 1448-1456.  DOI:10.7522/j.issn.1000-0534.2013.00088
  • Abstract ( ) PDF (4880KB) ( )
  • Pseudo-color composite technique has widely used in satellite remote sensing applications. Polarimetric radar can give more measurements that make the use of color composite technique in radar possible. Based on three S-band polarimetric radar measurements (reflectivity factor Zh, differential reflectivity factor Zdr and linear depolarization radio LDR), a method for color composite is given. According their respective measure range, Zh, Zdr and LDR are scaled to 0~255 linearly as the RGB channel data to form RGB image. Comparing shows that within all the combinations, the image formed by LDR, Zh and Zdr as R, G, B channel respectively can take on more abundant information, which not only retains the reflectivity structure characters, but also implicates the properties of the polarimetric measurements from different colors, and has more comfortable visual effect. For different type of hydrometeors, composite color is calculated according to their radar measurements range, and the qualitative analysis show that there is distinct difference between each two colors of given hydrometeors type, which favors the visual distinguishing. Case studies based on RHI and PPI data show that reflectivity structures are retained in the composite image, and the distribution of hydrometeor types implicated form colors is reasonable. The types of radar echoes can be easily estimated from this composite image, and the proposed color composite technique can be used in polarimetric radar operational applications.