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28 October 2015, Volume 34 Issue 5   
  • Analysis on Climatological Characteristics of Deep and Shallow Precipitation Cloud in Summer over Qinghai-Xizang Plateau
  • PAN Xiao;FU Yunfei
  • 2015 Vol. 34 (5): 1191-1203.  DOI:10.7522/j.issn.1000-0534.2014.00112
  • Abstract ( ) PDF (27683KB) ( )
  • Climatological characteristics of the deep (strong deep convection and weak deep convection), shallow precipitat ionincluding their horizontal distribution, vertical structures, infrared signal characteristics, the diurnal variation and meridional movement of the precipitation mentioned above in the Plateau (QX) are investigated based on combining measurements of the tropical rainfall measuring mission (TRMM) precipitation radar (PR) and visible and infrared scanner (VIRS) from 1998 to 2007.The results show that the precipitation over QX is mainly in the form of week deep convection, which occupies 67.8% followed by the form of shallow precipitation with 26.4% and the strong deep convection with 5.8%.The average rain rates of deep precipitation for different cloud infrared radiant temperature all experience an increasing-reducing process from the storm top altitude to the ground level, while the shallow precipitation only has anincreasing process.Both the precipitation frequency peaks forstrong deep convection and weak deep convection appear at 16:00(local time, hereafter the same).While the precipitation intensities of which reach their peak at 13:00 and 18:00, respectively.Moreover, the strong deep convection has a secondary peak at 00:00.For the shallow precipitation, the precipitation frequency and intensity peaks both appear at 20:00, having the characteristicof night rain.The diurnal variation curves of radiant temperatureof deep and shallow precipitation are similar to each other, as a result, their minimaappear around 19:00.It is obvious that the strong deep convection and weak deep convection have the characteristics of eastward movement, and the week deep convection is more obvious.The shallow precipitation don' t have significant meridional propagation characteristics.
  • Summertime Thermal Characteristics over Qinghai-Xizang Plateau and Surrounding Areas and Its Relationship with Precipitation in East Asia
  • AO Ting;LI Yueqing
  • 2015 Vol. 34 (5): 1204-1216.  DOI:10.7522/j.issn.1000-0534.2014.00100
  • Abstract ( ) PDF (9469KB) ( )
  • By using the ERA-interim monthly averaged reanalysis data from 1979 to 2011 and reverse computational method,the summertime atmospheric heat source and moisture sink over the Qinghai-Xizang Plateau(QXP) and its surrounding areas were calculated.We also use REOF analysis to examine their spatial distribution and then choose five sub-regions for research.We compare the thermal characteristics of each sub-regions and analyze their relationship with the precipitation in East Asia.Our results show that heat source distribution over QXP and its surrounding areas is complicated,and its local characteristics are significant.The heat source anomalies in different regions have much obviously difference,and their relationships with East Asian precipitations are also distinct.In particular,when heating over southern QXP adjacent areas enhances, precipitations over the QXP and northern Indian will increase correspondingly.Enhanced heating over northeast QXP adjacent areas will increase precipitations of North China and neighboring regions.Increased heating over eastern QXP will make precipitations over Yangtze-Huaihe river basin stronger.Heating over southeast QXP adjacent areas increases will enhance the precipitations over Yangtze valley.Stronger heating over western QXP will lead to enhanced precipitations over South China.Furthermore, heat source anomalies in different regions have various impact on water vapor transportation and thus lead to different corresponding changes in precipitation in East Asia.
  • Structural Features and Numerical Simulation of a Thermodynamic Thunderstorm in Lhasa
  • WANG Tianyi;ZHU Keyun;ZHANG Jie;ZHOU Yunjun
  • 2015 Vol. 34 (5): 1237-1248.  DOI:10.7522/j.issn.1000-0534.2014.00054
  • Abstract ( ) PDF (9665KB) ( )
  • The numerical simulation and the structural features of a thermodynamic thunderstorm over Lhasa were studied by using the three dimensional hailstorm numerical model.The results indicate that: the occurring, aging and weakening features of the thermodynamic thunderstorm over the Lhasa area were successfully presented by this model.The updraft was relatively weak when the thermodynamic thunderstorm was just happened.The total water vapor mixing ratio reached maximum as well as the ascending velocity in the mature stage, and then it reached the extinction phase when the thermodynamic thunderstorm cells declined later.Crystal ice particles were of the highest production and of the majority among hydrometeors (ice, snow, graupel and hail particles), but the graupel particles dominated at the primary stage of the thermodynamic thunderstorm.The water vapor within the thermodynamic thunderstorm was little and appeared after the daily maximum temperature, which is the unique feature of the thermodynamic thunderstorm over the plateau.The vector wind showed a convergence in the low-level and divergence in the upper level.Instable energy is relatively small and thermal perturbation in the afternoon is the main trigger of the thermodynamic thunderstorm.The CAPE value of this thunderstorm is 186.6 J·kg-1, which is potentially instable.But because of the strong radiation in Tibet, after noon, it can turn into convective instable leading to strong convection.There is less water vapor in the thunderstorm in Tibet, which is different from the thunderstorm over plain.
  • MCC Survey and Rainfall Characteristic in East Mountain of Yunnan-Guizhou Plateau
  • YANG Jing;DU Xiaoling;QI Dapeng;LUO Xiping
  • 2015 Vol. 34 (5): 1249-1260.  DOI:10.7522/j.issn.1000-0534.2014.00060
  • Abstract ( ) PDF (8756KB) ( )
  • Take advantage of average black body temperature data of FY meteorological satellite, altitude and surface weather observations, precipitation data of 85 meteorological stations in Guizhou Province, and hourly precipitation data of township automatic observation station during 2010.Censused of mesoscale convective complexes (MCC) in the eastern mountain of Yunnan-Guizhou Plateau, counted and analyzed its spatial and temporal characteristics, strength characteristics, life history, moving path, its precipitation distribution and intensity characteristics.The results indicate that, MCC in the eastern mountain of Yunnan-Guizhou Plateau in summer used to appear from May to July, formation time is from 19:00 to 03:00 the next day, its life history are generally more than 8 hours, newborn convective clouds which formed MCC generate in 13:00-18:00, its initial source area in western of Guizhou (103°-E105.6°E, 25°-N27.5°N).Vortex in Guizhou western edge is the direct influence system which cause convective cloud occur frequently.Maximum precipitation of MCC is mainly concentrated in the northwest and the northeast quadrant, and the distance to center of MCC is less than 3 latitude or longitude.Mountain short-term heavy precipitation are occurred mainly during the mature stage of MCC, and brightness temperature below -70℃.
  • Analysis on Temporal and Spatial Distribution Characteristics of Strong Hour Rainfall Intensity in Sichuan during 2008-2012
  • ZHOU Qiuxue;LIU Ying;FENG Liangmin;NIU Junli
  • 2015 Vol. 34 (5): 1261-1269.  DOI:10.7522/j.issn.1000-0534.2014.00070
  • Abstract ( ) PDF (4590KB) ( )
  • Based on the hourly precipitation data of 1052 stations during 2008-2012 in Sichuan Province, multiple-time-scale variations of the frequency and the extreme rainfall intensity of strong hour rainfall intensity (hereafter SHRI) are investigated by using statistical diagnostic methods.And get the following main conclusions.(1) The frequency of SHRI which is more than 20 mm·h-1 reached 3537.8 times annually.Averagely the extreme rainfall intensity is more than 100 mm·h-1 per year, and it jumped in 2012.(2) The SHRI area mainly concentrated in most parts of the whole basin and the Southwest of Panxi area, and the strong precipitation with high centers are mainly located in the longitudinal steep terrain area from basin to mountain transition.The extreme rainfall intensity area also concentrated in most parts of basin and Panxi area which is more than 30 mm·h-1.Obviously there is a very close contact between rainfall frequency, extreme rainfall intensity and altitude.The windward slope of the steep terrain weakened the reduce rate of frequency and extreme rainfall intensity with higher elevation.(3) Monthly changes of frequency are more significant than monthly changes of extreme rainfall intensity.SHRI occurs most frequently in July, followed by August, at least in May.The extreme rainfall intensity is more than 100 mm·h-1 from June to September.(4) The diurnal variations of SHRI which beyond 20 mm·h-1 and 30 mm·h-1 show a single active peak during night, but the diurnal variations of SHRI which beyond 50 mm·h-1 has multiple peaks, and it happens very suddenly.Diurnal variations and active peaks also have great differences in different areas of basin.
  • Net Radiation Flux Estimated Based on MODIS Products over the Semi-Arid Loess Plateau
  • WANG Lijuan;GUO Ni;ZUO Hongchao;HU Die;SHA Sha
  • 2015 Vol. 34 (5): 1270-1278.  DOI:10.7522/j.issn.1000-0534.2014.00096
  • Abstract ( ) PDF (1772KB) ( )
  • Using the first level products of Moderate-Resolution Imaging Spectroradiometer (MODIS) and three algorithms to estimate the shortwave radiation, longwave radiation and net radiation of Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) from April to August in 2007, and further the coefficients of WKC algorithm were modified using observed data of SACOL from June to August in 2006.Compared to the observed values, the result showed that the accuracy of estimated shortwave radiation was better than longwave radiation in the satellite transit time.Based on the components of the surface radiation, the accuracy of estimated net radiation was good, and the minimum mean absolute percent error was 9.98% in the satellite transit time.The daily net radiation which obtained by using the time scale expansion method was close to the measured data, and the mean absolute percent errors were less than 25.0%.The daily net radiation which estimated based on the shortwave radiation directly was deviated from the observed value, but the correlation was good.However, the result had improvement after it was modified by the measured data of SACOL, and the deviation between the estimated result and observed one was the minimum.It was worth noting that each radiation component was can be retrieved by MODIS products directly and did not need any other auxiliary data, and accuracy of estimated net radiation was only after the modified algorithm in the satellite transit time.The biggest advantage of the algorithm which estimated net radiation based on the shortwave radiation directly was avoid the longwave radiation estimated,and the accuracy of the algorithm was better after it was modified by the observed value, but it required measured auxiliary data.So, in the case of having the ground observed data, the net radiation can be estimated by using the modified algorithm based on the shortwave radiation.In the case of absence the ground observed data, it provides an effective way to estimated the net radiation by estimating the radiation components.
  • Comparative Analysis of Relationship between Moisture Budget and Precipitation Changes among Global Significantly Wetting/Drying Regions
  • JIANG Xianling;MA Zhuguo;GONG Yuanfa
  • 2015 Vol. 34 (5): 1279-1291.  DOI:10.7522/j.issn.1000-0534.2014.00109
  • Abstract ( ) PDF (2797KB) ( )
  • Changing tendency of moisture budget (MB) of global significantly wetting/drying regions during 1948-2009 and relation between net moisture budget (NMB) and precipitation (P), as well as between precipitable water vapor (PWV) and P were analysed utilizing NCEP/NCAR reanalysis data and CRU (Climatic Research Unit) precipitation data.During the research, statistical methods, such as linear regression, lowpass filtering and correlation analysis, were used.Results show that: (1) Annual NMB over both East Asian continent (EA) and African continent (A) had an obviously decreasing trend, comparing to increasing trend over North American continent (NA).And changes of NMB were in accord with regional arid/wet changing characteristics over all of these three areas; (2) Over EA, spring, summer, autumn and annual mean MB were consistent, that was, meridional moisture budget (MMB) and NMB decreased significantly; zonal moisture budget (ZMB) showed an increasing trend.However, in winter, NMB, MMB and ZMB all increased; (3) Over NA, MB in summer, autumn and winter had a similar trend to annual MB, that was, MMB and NMB increased, but ZMB decreased; only in spring, MMB decreased, but ZMB increased; (4) Over A, ZMB and NMB in all the four seasons reduced, and changes of ZMB dominated that of NMB in this region; and different to annual variation, MMB in spring and summer decreased; (5)In recent decades, over EA and A, with reduction of seasonal and annual P, NMB and PWV in the same period reduced, along with correlation coefficients between NMB and P, as well as between PWV and P, being significant.Over NA, along with the increase in seasonal and annual P, NMB also increased with correlation being significant.It is noteworthy that PWV and P weren't in coincident over NA.Its mechanism is still unclear, which requires an addition of numerical models or other methods for further study.
  • Relation of Spring Dust-Storm Activities in Northern China and Changes of Upper Westerlies
  • LI Xue;LIU Xiaodong
  • 2015 Vol. 34 (5): 1292-1300.  DOI:10.7522/j.issn.1000-0534.2014.00067
  • Abstract ( ) PDF (4599KB) ( )
  • Based on the strong sandstorm sequence datasets produced by the National Meteorological Information Center and the NCEP/NCAR reanalysis data from 1954 to 2007, the connection between sandstorm activities in northern China (northward to 30°N) and changes of high-altitude westerly jet in East Asia was investigated.The results of correlation analysis show that the positively correlation is exist between the frequency of spring sandstorm in the northern China and the changes in the high-altitude westerly jet axis position which is significant at α=0.01, with the correlation coefficient of 0.36, and the relationship exists both at the interannual and interdecadal time scales.The location of jet axis has northern (southern) movement during the years of more (less) sandstorm activities, compared with the normal year.The sandstorm activities exhibit a decreasing trend from 1954 to 2007, and the high-altitude westerly jet axis moves southward systematically at the same time.Further analyses shows that the sandstorm activities is impacted by the position changes of high-altitude westerly jet axis.When position of upper westerly jet axis on 200 hPa moves southward in spring, the westerly in the northern boundary between China and Mongolia (70°-E120°E, 42.5°N-52.5°N) becomes weaker, on the one hand, which lead to the surface wind in the dust source region decrease through the momentum downward transport, and constrain the power of sandstorm to break out; on the other hand, it reduces the wind shear and baroclinicity, limiting the generation of ground cyclones, finally leading to less sandstorm activities.
  • Analysis on Mechanism of Mesoscale Rainstorm Triggered by Quasi-Stationary Dryline in Boundary Layer
  • WANG Xiaoling;WANG Haiyan;WANG Shanshan;WU Cuihong;ZHANG Pingping
  • 2015 Vol. 34 (5): 1310-1322.  DOI:10.7522/j.issn.1000-0534.2014.00056
  • Abstract ( ) PDF (13627KB) ( )
  • NCEP GFS reanalysis data with the satellite,radar,automatic station and synthetic diagnosis method were used to analyze ten mesoscale rainstorms triggered by quasi-stationary in boundary layer.The results showed that this type rainstorm often happened in warm area, having strong instability energy the rainstorm center was small and stable while the precipitation time was longer.Generally, it's rainfall intensity was between 30 mm and 50 mm.The dynamic mechanism can be drawn as follows.Positive vorticity advection on 500 hPa extending to rainstorm area, enhanced cyclonic vorticity in boundary layer, positive vorticity advection column developed.Meanwhile, with the development of northerly significant flow in boundary layer, dry and wet advection enhanced at two sides of dry line respectively, dry air was involved in wet air, produced local frontogenesis, and small perturbation were produced due to dipole distribution of positive and negative temperature advections in boundary layer, lead to ascending motion enhancing.The average air flow was consistent with the moving direction of the convective system, high temperature and humidity instability region was located in the upper reaches of the convective system, so the convective motion of the system is obviously backward propagation, the new convection monomer linear and followed by the same position, lead to the train effect, conducive to the precipitation in the same place long time maintenance.The rainfall region was discovered that wet tongue tip on the south side of the dry line in boundary, and close to warm moist side of the zero line of temperature and humidity advection.
  • Multiscale Features of Climate Change for Temperature of Centurial Weather Stations over Southeast China during Latest 139 Years
  • LIANG Ping;CHEN Baode
  • 2015 Vol. 34 (5): 1323-1329.  DOI:10.7522/j.issn.1000-0534.2014.00058
  • Abstract ( ) PDF (2134KB) ( )
  • Basing on annual temperature data of five century observatories over southeast China and 3 sets of global surface temperature data including HadCRUT3, GISSTEMP and 20th Century Reanalysis, by using of EEMD (Ensemble Empirical Mode Decomposition), a new method to process time series with instability and nonlinearity, the multi-timescale features of climate change for temperature of weather stations with Shanghai as a representative over Southeast China during 1873-2011 and the global consistency of those features are analyzed.Results suggest that temperature of century observatories over southeast China for the time period of 1873-2011 show long-term warming trend and multi-quasi-cycle oscillations with multi-timescales including interannual, decadal, and multi-decadal variability.The long-term warming trend component does leading contribution to trend of observatory temperature change over more than 100 years.But for the period of latest 50 years, the multi-decadal oscillation with quasi-64-year period does more contribution than the long-term trend component.Two distinct warming period (represented by 1930's-1940's and 1990's-early 2000's) during 1873-2011 show most significant correlation with quasi-64-year oscillation.Meanwhile, the long-term warming trend and interannual-decadal oscillation with 6~16-year periods also exert impacts on the distinct warming periods.Quasi-64-year oscillation also plays a fundamental role in periodic transformations for trends of temperature change during the hundreds of years.The above multi-timescale characteristics of temperature change of century observatories have significant global consistency.The quasi-64-year oscillation makes significant contributions to trend variation of annual temperature over north hemisphere.In comparison to long-term warming trend component, the quasi-64-year oscillation of annual temperature of north hemisphere is in closer association with change rate for temperature of centurial observatories.Atlantic Mutidecadal Oscillation may be a factor for modulating the quasi-64-year oscillation of air temperature of centurial weather stations and its global consistency.
  • Study on Diagnosing Three Dimensional Cloud Region
  • Cai Miao;Zhou Yuquan;Ou Jianjun;Liu Jianzhao;Cai Zhaoxin
  • 2015 Vol. 34 (5): 1330-1344.  DOI:10.7522/j.issn.1000-0534.2014.00061
  • Abstract ( ) PDF (12232KB) ( )
  • Cloud mask and relative humidity (RH) provided by Cloudsat products from 2007 to 2008 are statistical analyzed to get RH Threshold between cloud and clear sky and its variation with height.A diagnosis method is proposed based on reanalysis data and applied to three-dimensional cloud field diagnosis of a real case.Diagnostic cloud field was compared to satellite, radar and other cloud precipitation observations.Main results are as follows.Cloud region where cloud mask is bigger than 20 has a good space and time corresponding to the high value relative humidity region, which is provide by ECWMF AUX product.Statistical analysis of the RH frequency distribution within and outside cloud indicated that, distribution of RH in cloud at different height range shows single peak type, and the peak is near a RH value of 100%.Local atmospheric environment affects the RH distribution outside cloud, which leads to RH distribution vary in different region or different height.RH threshold and its vertical distribution used for cloud diagnostic was analyzed from Threat Score method The method is applied to a three dimension cloud diagnosis case study based on NCEP reanalysis data, and the diagnostic cloud field is compared to satellite, radar and cloud precipitation observation on ground.It is found that, RH gradient is very big around cloud region and diagnosed cloud area by RH threshold method is relatively stable.Diagnostic cloud area has a good corresponding to updraft region.The cloud and clear sky distribution corresponds to satellite the TBB observations overall.Diagnostic cloud depth, or sum cloud layers distribution consists with optical thickness and precipitation on ground better.The cloud vertical profile reveals the relation between cloud vertical structure and weather system clearly.Diagnostic cloud distribution correspond to cloud observations on ground very well.Precipitation on ground usually can be observed at deep-developed cloud area.The time series of cloud vertical structure evolution at single point is well consistent with local radar and surface cloud and precipitation observations.In summary, diagnosis of three-dimensional cloud field and its distribution by relative humidity threshold from the reanalysis data are in good agreement with the development and movement of cloud precipitation and weather systems.It can be well applied to weather, climate and weather modification research.
  • Study of Model Error Correction on Summer Temperature in China Based on the Method of Combine with Dynamic and Statistical
  • SU Haijing;FENG Guolin;YANG Jie;WANG Qiguang
  • 2015 Vol. 34 (5): 1345-1356.  DOI:10.7522/j.issn.1000-0534.2014.00069
  • Abstract ( ) PDF (7580KB) ( )
  • By using climate trend coefficient analysis the variation of observed and model predicted China summer temperature in the past 30 years.The dates come from NCEP/NCAR daily reanalysis date and National Climatic Center monthly models temperature date.Through empirical mode decomposition method fitting the raise trend of observed temperature and remove the trend in the context of global warming.Combined with systematic error correction and seasonal prediction method-statistical method of combining power to analysis the trend on the impact of summer temperatures forecast.The results show that: most of the area in China has a significant increase trend in summer temperature in last 30 years.In most areas the climate trend coefficient get through 0.01 significance level.But mode temperature almost have no change in trend in last 30 years, there is obviously inadequate for global warming.In order to avoid this kind of model simulation of observed temperature the overall trend is insufficient to predict effect and the effect of the optimal predicted results.Using the empirical mode decomposition method can effectively fitting and remove the trend of observed temperature.When forecasting the temperature we remove the trend first and add the trend in the last.Trough tests find that the method can significantly improve the result compare with direct forecast result in most area.And solve the problem of forecast result is lower than observed result.All the results show that it is necessary to remove the observed temperature increase trend in numerical prediction model results in post-processing.
  • Study on Severe Convective Weather Forecast Method Based on Approach Concept
  • ZENG Mingjian;ZHANG Bei;WU Haiying;WANG Wenlan;SHEN Yun;ZHANG Bing;ZHOU Jialing
  • 2015 Vol. 34 (5): 1357-1368.  DOI:10.7522/j.issn.1000-0534.2014.00143
  • Abstract ( ) PDF (2319KB) ( )
  • Based on proximity principle,the 2668 strong convective weather processes including regional thunderstorm,gale,hail,tornado and short-term heavy rainfall in Jiangsu province from February to September 2000-2010 were matched up with 56 kinds of convective parameters about thermal,dynamical,energy and vapor,etc.which were calculated by 1°×1° NCEP FNL analysis data.So the eigenvalue of convective parameters of different kinds of strong convective weather in different month as the reference sequence can be yielded by statistics.At the same time,the corresponding convective parameters deduced from 10 km resolution,hourly output of the mesoscale model were regarded as comparison sequence.Then,with the relative deviation fuzzy matrix skill,the weight allocation was conducted on the bias of eigenvalue and climatic value and self-stability of convective parameters in different month.At last,using fuzzy mathematics and gray theory,methods about economics,a series of approaching degree indexes were introduced and constructed from the perspective of the approaching degree among sequences,and acquired better forecasting effects in real-time strong convective weather forecast.
  • Numerical Study of Background Cloud Condensation Nuclei Effects on the Intensity of Idealized Tropical Cyclone
  • YANG Yuhua;CHEN Baode;WANG Bin;WANG Xiaofeng;ZHANG Lei;WANG Ping;XU Xiaolin;HUANG Wei
  • 2015 Vol. 34 (5): 1379-1390.  DOI:10.7522/j.issn.1000-0534.2014.00095
  • Abstract ( ) PDF (5385KB) ( )
  • By making use of the Weather Research and Forecasting (WRF) model in which the newly updated Thompson microphysics scheme was implemented, three idealized numerical experiments were conducted under different atmospheric background conditions (clear air, polluted air and severe polluted air) to examine the impact of background aerosol concentration on tropical cyclone (TC) intensity.The new Thompson microphysics scheme took into account the influence of aerosol acting as CCN and IN, which is called “Aerosol-aware” scheme.The results showed that, during the stage of early development, the simulated TC intensity was the weakest, middle and strongest for server polluted, polluted and clear air conditions, respectively.While with forecasting time increasing, the differences of TC intensities among three experiment tended to be indistinctive.The increased aerosol had little influence on total precipitation amount, rather than delayed the timing of rainfall occurrence in TC area, nevertheless, a significant impact on the spatial and temporal distribution of the simulated precipitation was found.The cloud droplet number concentration in the TC developed under server polluted conditions are much higher than that under clean conditions, which, combined with dynamical and thermal process, can result in a large difference in the hydrometers and their conversion for different simulations.More latent heat release in the outside of TC under server polluted conditions led to a weaker horizontal pressure gradient, and as a result, a reduced intensity and increased size.Moreover the weakening of the TC was also related to its spiral rain band development.With development of the spiral rain band, a cold pool formed and invaded into the eye wall, resulting in a reduced intensity.The experiment results would suggest that aerosol-aware” Thompson microphysics scheme should be reasonably persuasive in the description of “indirect effect” of aerosols on precipitation process.
  • Mesoscale Characteristic Analyses on Severe Convective Weather Process at Yuxi in Yunnan
  • AI Yongzhi;YANG Chuanrong;LI Rui
  • 2015 Vol. 34 (5): 1391-1401.  DOI:10.7522/j.issn.1000-0534.2014.00068
  • Abstract ( ) PDF (10787KB) ( )
  • By using routine sounding data, NCEP/NCAR reanalysis data, automatic weather station observation data and T639 numerical model forecast data, a strong convection weather process occurred in Yuxi in 9-10 June 2013 is diagnosed.The results show that this strong convection weather process was caused by the interaction of the warm-wet flow coming from southwest and the cold air from north guided by the northwest flow behind trough, occurred in the north of the middle Yunnan Province.The direct impact systems of this process are shear line in the lower troposphere, surface mesoscale convergence line and the cyclone type convergence center.Convergence of the water vapor from the Bay of Bengal in Yunnan attributes favorable vapour condition to this process.Analysis shows that there is a good corresponding relationship in the mesoscale severe convective cloud band, surface mesoscale convergence system and the discontinuous band of the convective available potential energy (CAPE).The location where the mesoscale convective band generate and develop is essentially consistent with the surface convergence line which formed early.The convective cell is more easily to get strengthened and developed on the large value area of the discontinuous band of CAPE.Thus the comprehensive analysis of surface flow field and high-resolution distribution of CAPE have a certain indicative significance to the short-term weather forecast of the severe convective weather.
  • Study on Shear Snowstorm by Ingredients-Based Methodology
  • YANG Chengfang;ZHOU Xuesong;LI Jing;MENG Xiangui
  • 2015 Vol. 34 (5): 1402-1413.  DOI:10.7522/j.issn.1000-0534.2014.00108
  • Abstract ( ) PDF (9567KB) ( )
  • The process of snowstorm responsible for complicated precipitation type and distribution from 20 to 21 January 2013 is examined using conventional observation,NCEP/NCAR and radar data by IM(Ingredients-Based Methodology).The results can be briefed as follows.To begin with cooperation of two high trough,low level shear,and surface front and reverse trough caused the snowstorm.In the second place,the snowstorm depended on four favorable ingredients,including plenty vapor from two southwestward and southeastward flows,strong vertical velocity by low level shear,optimal Precipitation efficiency with appropriate temperature (-15~-14℃) and low temperature.Meanwhile,low longitudinal shear attached importance on the second precipitation center.Besides,the heaviest snowfall occurred while southwest wind in mid-high level and southeast wind got most powerful.Last but not least,with regard to precipitation phase,because of difference of temperature advection in low troposphere,temperature in low level especially 1000hPa and surface is key factor.Temperature under 925 hPa must be analysized particularly when 2 m temperature is at about 1℃.And complex terrain can affect precipitation phase,too.
  • Analysis on Rare Snowstorm in West of Southern Xinjiang
  • YANG Xia;ZHANG Yunhui;ZHAO Yizhou;MA Chao;ZHAO Fenghuan
  • 2015 Vol. 34 (5): 1414-1423.  DOI:10.7522/j.issn.1000-0534.2014.00063
  • Abstract ( ) PDF (12097KB) ( )
  • Based on the data of FY-2E Stationary Meteorological Satellite from China Meteorological Agency(CMA), Doppler radar products, the reanalysis dataset from the NCEP/NCAR reanalysis project and convention observation, the caused mechanism of a rare snowstorm event in the west of southern Xinjiang was analyzed.The results show that the rare snowstorm occurred on the background of central Asia trough to south cutting cortex low.The favorable configuration of three jet streams in snowstorm is similar as in rainstorm.It is unusual that the low-level jet's speed exceeds 20 m·s-1 in winter.The formation time of low-level jet earlier than the high-level jet 12 hours plays an important role in the snowstorm.Favorable configuration about the jet streams of higher southwest and lower east to provide the power and water condition for the snowstorm.Water vapor source payments calculation analyses show that there are three parts of water vapor sources, the first is thick central Asian vortex itself carry water vapor form southwest airflow, the second is by east of airflow water vapor concentration and convergence form southern basin on middle low level, the third is conveying the relay water vapor that warm-moist from the coastal margin of southeast China.The water vapor transmission from the east airflow is more than others.The two meso-β-scale cold clouds are the main systems for the severe snowstorm.The mesoscale cloud enhanced in local is the direct effect of heavy snow.The main radar echo during the snowstorm is stratiform cloud.In local place the radar echo intensity gradient is large and has the short-term weak convection characteristic.
  • Analysis of the Severe Convective Weather Caused by Long-Live Cold Vortex in Inner Mongolian
  • MA Suyan;HAN Jingwei;SI Qin;CHANG Yu
  • 2015 Vol. 34 (5): 1435-1444.  DOI:10.7522/j.issn.1000-0534.2014.00098
  • Abstract ( ) PDF (9087KB) ( )
  • Using the conventional detection, satellite images, T-log P and NCEP reanalyzes data (horizontal resolution 2.5°×2.5°), under the background of a cold vortex from 8 to 18 on June 2012, the route of the cold vortex and the cause of the severe convective weather in different areas of Inner Mongolia were investigated.The results show that: (1) the reasons for cold vortex's turning west were cold air from West Siberia and the transportation of vorticity to the back of the vortex.Turning west of the cold vortex is the main reason of long duration of the cold vortex, the rainstorm and continuous severe convective weather.The east region of Inner Mongolia was located in a tongue of high of potential temperature and its high gradient.(2) In the northeast of Inner Mongolian,severe convective weather happened when meso-micro scale convective systems strongly developed and consolidated,and maximum rainfall intensity happened when TBB(gradient of TBB)obviously decrease(increase), the ascending motion and water vapor convergence in the vertical direction of the windward slop were strengthened by terrain, which offer conditions for rainstorm.(3) In the southeast of Inner Mongolian,merging of several meso-micro scale convective systems continually lead the deep moisture air to the southeast of Inner Mongolian,and the water vapor was convergent strongly in the vertical direction.There also existed dry intrusion in the southeast, which provided instable condition for the severe convective weather.Low level jet and low level shear were the dynamic factor of the severe convective weather.The severe convective weather happened under the ascending branch of secondary circulation.
  • Analysis on a Severe Convection Triggered by Gust Front in Yinchuan with Radar Data
  • HU Wendong;YANG Kan;HUANG Xiaoyu;JI Xiaoling;MU Jianhua;WANG Min;YANG Jianling;ZHENG Xiaohui
  • 2015 Vol. 34 (5): 1452-1464.  DOI:10.7522/j.issn.1000-0534.2014.00099
  • Abstract ( ) PDF (21670KB) ( )
  • Based on the data of Yinchuan Doppler Weather Radar (CINRAD) and Automatic Weather Stations, using radar meteorological methods, diagnosis of a retro-propagating storm occurred at 19:00 July 18 2010 is conducted.The results show that: (1) The general configuration of weather systems, CAPE, CIN and LFC values are favorable for severe convection triggering and developing.Three gust fronts converged and triggered new severe convections.(2) The processes of gust fronts genesis, evolution, maturation, collision, decease and new storm-triggering are monitored by CINRAD, and the detail of 3 gust fronts and downburst is revealed.Descending of high reflectivity region and decreasing of the intensity in base reflectivity and high values in radical velocity before the downburst are of importance for disastrous gale warning.(3) All the 3 gust fronts experienced 3 stages of rapid increase, mild growth and turning decrease in length, and there is a similar trend in width.The propagations of gust fronts were affected by underlying surface especially the urban friction and result in velocity fluctuation.After gust fronts collision it took 18-30 min for the triggered convection to evolve into well mature, and so a precious leading time for accurate warning is provided.(4) Based on analysis of weather background, it can be expected to find out the clues to forecast the new convection genesis about 1 hr ahead by monitoring gust fronts changes in detail with radar data.The radar data is the key to trace the gust fronts, surface jet, downburst and triggered storms and it plays a crucial role in severe weather watching.
  • Two Clouds Merger Cases Observation by Dual Linear Polarization Radar
  • HUANG Yong;WU Linlin;FENG Yan;ZHAI Jing;LIU Huijuan;YUAN Ye
  • 2015 Vol. 34 (5): 1474-1485.  DOI:10.7522/j.issn.1000-0534.2014.00057
  • Abstract ( ) PDF (9233KB) ( )
  • Clouds merger is a common phenomenon in convective weather.And the conformation, dynamic character, effective for precipitation of merging process had been found from a lot of observational facts.However, the micro-physical progressed and characters cloud only been researched by numerical simulate.For the purpose to find out the micro-physical characters of clouds merging data of dual linear polarization radar at Shouxian station were analyzed and two clouds merger cases were researched on early July 2008.As the results shown, only several merging processes of small echo blocks have be found in in the region of convective clouds merging in satellite imagery.With merger of echo blocks, the reflectivity, radial velocity and specific differential propagation phase shift are all raised.As to differential reflectivity, the strong centers are moved to the joint of two blocks at the initial stage.Then two centers are combined into a new center, and a negative center is appeared symmetrically.Furthermore, there are rain drops fields at the joint during the period of echoes merging.And only in the merger process, which is initial form the low layer, the quantity of ice partial could be increased.
  • Effect of Distribution Characteristic of Space Charge on Propagation Behavior of Intra-Cloud Lightning Discharge
  • TAN Yongbo;LIANG Zhongwu;SHI Zheng;ZHU Junru
  • 2015 Vol. 34 (5): 1502-1510.  DOI:10.7522/j.issn.1000-0534.2014.00064
  • Abstract ( ) PDF (2846KB) ( )
  • Based on the existing stochastic lightning parameterization scheme, a thundercloud charge structure was set up in the paper and two-dimensional fine-resolution lighting discharge simulations were performed to quantitatively investigate the effect of distribution characteristic of space charge in thunderstorms on propagation behavior of intra-cloud lightning discharge.The results show: (1) The screening charge layer at top of thunderstorm and the lower positive charge region will constrain the vertical propagation range of positive and negative leaders of intra-cloud lightning that are triggered between the main positive and negative charge regions.Thereby, the channels of intra-cloud lightning can only propagate in a certain vertical range and tend to propagate horizontally in the end.(2) The increase of charge density or distribution range of charge region both will increase the channel length of intra-cloud lightning, but in different way.The charge density increases the channel length mainly by increasing the channel branches near high charge density center, and they have a nonlinear relationship, while the distribution range increases it by extending the horizontal propagation range of channels, and they have a linear relationship.(3) The increase of charge density of charge region will increase the number of branches of intra-cloud lightning channel, especially near the high density center, which makes the fractal dimension of intra-cloud lightning channel show a trend of increase, while the bi-level branched channel of intra-cloud lightning will never be changed.The increase of distribution range of charge region will do not affect the fractal dimension of intra-cloud lightning channel.