Plateau Meteorology

Current Issue

28 June 2014, Volume 33 Issue 3   
  • Seasonal Variation of Turbulence Characteristics over Alpine Meadow Ecosystem
  • CHEN Yungang;ZHANG Yu;WANG Shaoying;SHANG Lunyu;XIONG Jiansheng;SHEN Xiaoyan
  • 2014 Vol. 33 (3): 585-595.  DOI:10.7522/j.issn.1000-0534.2014.00044
  • Abstract ( ) PDF (4519KB) ( )
  • The relationships between normalized standard deviations of wind velocity components, temperature, water vapor, CO2 and stability parameters z/L, and their seasonal variation characteristics in the frame of Monin-Obukhov similarity theory(MOST) were investigated. The turbulent data were collected from an homogeneous, flat and open grassland of the northeast edge of Qinghai-Xizang Plateau in 2010. The results show that normalized standard deviation of wind velocity components generally meet 1/3 power law. σu/v*、 σv/u* and σw/v* increase along with the increase of |z/L|. Under near neutral condition(|z/L|<0.05), normalized standard deviations are approximate constant, and σu/u*>σv/u*>σw/u*σ. The normalized standard deviation of the horizontal wind velocity decreases with increase of aerodynamic roughness Z0m, and σw/u* does not have obvious seasonal variation, which can be regarded as a constant on the whole. Under unstable conditions, the normalized standard deviations of temperature, water vapor and CO2 in relation to z/L satisfy the similarity law, which decrease along with the increase of |z/L|. Under near neutral condition, σq/q*>σc/C*>σT/T*. The seasonal variations of σT/T*, σq/q* and σc/C* mainly depend on the seasonal change of characteristic scale T*, q* and C*, which increase with the increase of turbulent fluxes. Compared with the latent heat and CO2 flux, sensible heat flux has evidently reverse seasonal tendency, with minimal season variety and minimum value in summer. Accordingly, the extent of annual variation σT/T* is relatively small and maximum value is in summer, while σq/q* and σc/C* have reverse seasonal tendency.
  • Structural Analysis of Heavy Precipitation Caused by Southwest Vortex Based on TRMM Data
  • JIANG Lujun;LI Guoping;MU Ling;KONG Liang
  • 2014 Vol. 33 (3): 607-614.  DOI:10.7522/j.issn.1000-0534.2013.00094
  • Abstract ( ) PDF (3980KB) ( )
  • The horizontal and vertical structure of a heavy rain system caused by southwest vortex happened in the eastern part of Sichuan and the western part of Chongqing on 17 July 2007 has been studied by using tropical measure mission data. The results indicate that: The heavy rain system was consisted of a main precipitation cloud and several scattered precipitation clouds, which was convective precipitation and characterized by high precipitation intensity and wide precipitation range. Although the number of convective rains is less than the stratiform rains, convective rains contribute much more rainfall to the total than stratiform rains for the stronger rainfall rate of convective rains. The rainfall intensity spectral distributions of convective rains mainly occurred in 1~50 mm·h-1, the rain rate of almost 90% of the stratiform rains concentrated 10 mm·h-1 below. In vertical, the rain top of heavy precipitation system can reach to 16 km from the surface. The most precipitation rate occurred in the atmospheric 2~6 km above the ground and the distributions of precipitation rate in both vertical and horizontal was inhomogeneous. The coalescence growth progress of cloud drop play an important role in the lower troposphere to precipitation. Whether for the stratiform or the convective precipitation caused by southwest vortex, the precipitation under height of6 km contributed most, in different heights, the contribution of total precipitation was inversely proportional to the height.
  • Analysis on Evolution Characteristics of Three Plateau Shearlines and Their Effect on Precipitation
  • HE Guangbi;SHI Rui
  • 2014 Vol. 33 (3): 615-625.  DOI:10.7522/j.issn.1000-0534.2013.00023
  • Abstract ( ) PDF (13352KB) ( )
  • In order to reveal the characteristics of the dynamics, thermal dynamics and the water vapor, cloud system and precipitation characteristics for plateau shear lines and to further understand the evolution mechanism of shear line, the evolution characteristics and effects on precipitation of the plateau shear line in different times and at different development stages have been analyzed by selecting three cases of plateau shear line that occurred on 19-22 May 2008, on 1-3 July 2007 and on 19-21 September 2009 respectively as well as adopting MICAPS data, NCEP 1°×1° reanalysis data, FY-infrared temperature data, etc. The results show that: (1) While winds on both sides of the shear line weaken, especially north wind, the shear line process tends to weaken. The strength of cold and warm air affects the position of shear line. Shear lines in early summer and midsummer are northerly situated while those in late summer are southerly situated. (2) During shear line process, there is positive vorticity, convergence and ascent movement in coordination with the shear line. While the shear line is disappearing, the convergence belts weaken ahead of the positive vorticity belts. There are multi centres of positive vorticity and convergence around the shear line, which may be relative to the plateau vortex activities. The characteristics of positive vorticity centers moving eastwards are obvious for midsummer and late summer shear lines, and the convergence ascent areas are more eastern situated and the motion is stronger than that for early summer shear line. (3) There are band areas or block areas of TBB<-20℃ nearby the shear line. During the shear line maintaining, TBB values further reduce. There are multi-centers of TBB low values for midsummer shear line at maintaining stage and late summer shear line at initial stage, which shows that convective activities are stronger. (4) The east and south slopes of the plateau are areas with congregated unstable energies due to terrain blocking and heating. The characteristics of high temperature and high humidity energy are obvious in near-surface layer around the shear line in midsummer. Early summer shear line brings about stable and small precipitation which is in patch form while the characteristics of unstable convective precipitation are obvious for midsummer and late summer shear lines. The distribution of precipitation, which is in band form around the shear line, is larger and intensities are stronger. (5) The shear lines on 500 hPa are also water vapour congregated band. The conglomeration of vapor and instability energies, and positive vorticity transmitting eastward and convection developing over the shear line are important mechanisms that lead to heavy precipitation.
  • Interpolation of Temperature Data in Northern Qinghai-Xizang Plateau and Preliminary Analysis on Its Recent Variation
  • HUANG Rong;HU Zeyong;GUAN Ting;SUN Genhou;YANG Yaoxian;LIU Huolin
  • 2014 Vol. 33 (3): 637-646.  DOI:10.7522/j.issn.1000-0534.2014.00027
  • Abstract ( ) PDF (1735KB) ( )
  • In order to obtain complete sequences of temperature data, an optimal pairing segmented interpolation method was established in this paper to recover the missing temperature data of objectiive sites (NewD66/D66, D105, Amdo and BJ) according to the temperature relationships between the objectiive sites and reference sites(D66/WDL, D110, MS3478 and MS3608). Furthermore, the recent temperature variations of objective sites were analyzed based on the obtained temperature data of objective sites. Firstly, the analysis shows that the temperature varaitions of objectiive sites are consitent with those of their corresponding reference sites, and that the temperature differences between objective and reference sites are large in winter while small in summer, which is the basis of optimal pairing segmented interpolation method. Then, the analysis indicates that the interpolation result is more acceptable in summer than that in winter, and the result in D66 site is best among all objective sites but that in D105 is relatively poor. The analysis also indicates interpolation values become more and more similar to observation values with time scale becoming larger and laeger because of the fact that interpolation error is approximately normally distributed, and the less acceptable interpolation result is mainly due to the facters such as substantial drop of temperature, precipitation, high wind speed and significant changes of wind direction events. Finally, the analysis based on complete temperature data of the four objective sites shows that the differences between maximun and minimun monthly average temperatue is greatest in NewD66 site while smallest in Amdo, that the average temperature of recent years is highest in BJ site and lowest in D105 site, that BJ site locates in seasonal frozen area, while the other three sites are in permafrost area. Over the last more than ten years, annual averages of temperature appear a growing trend in four obejective sites, and the trend in BJ and NewD66 is, by contrast, more obivious than that in D105 and Amdo sites.
  • Similarity-Area-Ratio Method for Determining Similarity of Atmospheric Data
  • HE Dengxin;SHAO Aimei
  • 2014 Vol. 33 (3): 658-665.  DOI:10.7522/j.issn.1000-0534.2013.00103
  • Abstract ( ) PDF (4164KB) ( )
  • The common similarity method describes the difference of data samples in terms of an average. It can suffer from the effect of several extreme sample factors. For this reason, a new similarity method called similarity area ratio is developed to determine the similarity in a global view. In this method, the non-dimensional variables are generated by using a normalization procedure on atmospheric data. The threshold in the criterion of similarity is estimated from the analysis on the distance of samples. And the similarity degree is determined by the ratio of the area where the distance between sample factors is less than the threshold to total area of sample factors. The data including temperature, height, and wind at 00:00 UTC in the winter from 2001 to 2011 is used to test the validity and efficiency of the similarity-area-ratio method. The results show the range of non-dimensional variables is consistent with each other. It is helpful to build a combined criterion of similarity that combines many atmospheric elements at all pressure levels. Different from the results from Hamming distance and correlation coefficient, the similarity sample selected by the similarity-area-ratio method is optimal. However, this similarity is not better than the other two similarity methods in high-latitude region. The long-term predictions based on these above three similarity methods are performed with monthly mean temperature data from 1948 to 2013 to further test their efficiency. The results show that the similar sample selected by these methods is same for some references. The frequency of the best forecasts with similarity-area-ratio method is higher than that with the other similarity methods.
  • Experiment of Surface-Layer Wind Forecast Improvement by Assimilating Conventional Data with WRF-3DVAR
  • ZHANG Feimin;WANG Chenghai
  • 2014 Vol. 33 (3): 675-685.  DOI:10.7522/j.issn.1000-0534.2012.00198
  • Abstract ( ) PDF (4538KB) ( )
  • Using WR-F3DVAR assimilation system, add the perturbations with the method advanced by Evenson at initial time to generate disturbance type initial fields and assimilate conventional observation data (including radiosonde observation and conventional ground observation), comparing the improvement effects of the whole atmosphere for initial and forecast fields with WR-F3DVAR system, the forecast effects of the local atmosphere for near-surface wind was also verified. The results show that: Compared to the GFS forecast directly, assimilation of conventional data improves initial fields, especially for wind and temperature fields in lower layer compared with the initial fields produced by FNL data; The initial fields produced by FNL data and assimilation of conventional data have the different valid forecast time at different pressure levels, the forecast effects of wind and temperature are improved within 36 h at lower pressure level (1000 hPa), on 500 hPa and 200 hPa, the valid forecast time of wind and temperature is 36 h and 12 h respectively; No matter FNL data or assimilation of conventional data, the forecast improvements of near-surface layer wind are only within 36 h, this implies that the forecasting effects of variables as wind, which changes greatly in short time, may improve remarkably if assimilating data that close to variables itself in spatial and temporal.
  • Analysis of Applicability of Three Drought Indices for Drought Events in Southwest China
  • XIONG Guangjie;WANG Shigong;LI Chongyin;SHANG Kezheng;MA Yuxia;ZHUANG Shaowei
  • 2014 Vol. 33 (3): 686-697.  DOI:10.7522/j.issn.1000-0534.2013.00007
  • Abstract ( ) PDF (5362KB) ( )
  • Based on the monthly precipitation and temperature data at 18 stations in Southwest China from January 1951 to December 2011, the applicability of the Relative Moisture Index, SPI and SPEI were studied. The monthly Relative Moisture Index, SPI and SPEI at time scales of 3, 6 and 12 months for the 18 stations in Southwest China in the past 61 years were calculated. Referencing to historical data of past drought disasters in Southwest China, the comparative study of characterizing drought events at different time scales was done using Mann-Kendall and correlation analysis methods. The results show that: (1) The SPEI not only can grasp precipitation and evapotranspiration which are two important determinant effects of drought, but also is well applicable to characterizing drought events at time scales of 3, 6 and 12 months in Southwest China in the past 61 years. (2) The SPI is applicable to characterizing drought events at time scales of 6 and 12 months, but it is inferior in description to the SPEI at time scales of 6 months. And it is applicable to characterizing drought events at time scales of 3 months both in spring and autumn. (3) The Relative Moisture Index is applicable to characterizing drought events at time scales of 12 months in some meteorological stations. It is applicable in the summer half year to characterizing drought events at time scales of 6 months. It is applicable to characterize drought events at time scales of 3 months in both spring and summer.
  • Analyses of Simulation Result in Loess Plateau by WRF Model with Two Reanalysis Data
  • MA Chenchen;YU Ye;HE Jianjun;CHEN Xing;XIE Jin
  • 2014 Vol. 33 (3): 698-711.  DOI:10.7522/j.issn.1000-0534.2014.00038
  • Abstract ( ) PDF (8237KB) ( )
  • WRF is one of the most widely used numerical weather prediction models, for which reanalysis data provide initial and lateral boundary conditions. Different reanalysis products may affect WRF simulation results differently. Taking Loess Plateau as research area, two WRF experiments (NCEP/WRF and ERA/WRF), using surface observation data and sounding data, taking NCEP and ERA-Interim reanalysis as initial and boundary conditions, respectively, were conducted to evaluate the influence of different reanalysis products on WRF simulations. The results indicated that both experiments can accurately reproduce the diurnal variation of 2 m temperature, 2 m relative humidity and surface temperature, with ERA/WRF giving better results than NCEP/WRF. Due to the complex terrain in the studied area, model performance for 10 m wind speed was poor. Both experiments cauld approximately simulate the diurnal variation of radiation components and ground heat fluxes. The deviation from observations mainly appeared at noon. Both experiments captured the variation of potential temperature and specific humidity in the atmospheric boundary layer well with correlation coefficient higher than 0.8. However, the performance for wind speed was not as good, with correlation coefficients of 0.63 and 0.60, respectively, for NCEP/WRF and ERA/WRF experiments. NCEP/WRF performed better than ERA/WRF in the atmospheric boundary layer.
  • Response of Soil Water Content and Soil Thermal Conductivity on Precipitation in Loess Plateau
  • JIA Dongyu;WEN Jun;ZHANG Tangtang;XI Jiaju
  • 2014 Vol. 33 (3): 712-720.  DOI:10.7522/j.issn.1000-0534.2014.00049
  • Abstract ( ) PDF (2340KB) ( )
  • Regional precipitation is the main cause of the soil water content variation in the climate system. The response of soil water content on the precipitation was analyzed using the datasets of soil water content and precipitation during 2005-2010, and soil water content datasets collected in August of 2010 in the Baimiao mesa of the Pingliang Loess Plateau. The accumulated soil water content at 10.0, 20.0 and 40.0 cm soil layers, and the response of soil water content at 20.0 cm soil layers to the local precipitation are especially considered. The results show that: (1)The variation trends of soil water content at different depths are similar in the study area, the positive responses of soil water content to the local precipitation are the most at 5.0 cm soil layers. (2)There are two peaks (from March to May, July to November) for the annual variation of soil water content at 10.0 cm and 40.0 cm soil layers. (3)In the analyses of the relationship between soil water content and local precipitation, it is found that the soil water content at four soil depths is associated with the local antecedent effective precipitation. The correlation coefficient between soil water content at 20.0 cm soil layers and the antecedent effective precipitation reaches 0.84. This implies the response of soil water content at 20.0 cm soil layers to the effective precipitation is most significant. (4)During the experiment, the soil water content can lead to an obviously increase of the soil thermal conductivity. However, in a long term of observation, the soil thermal conductivity shows irrelevant change with the precipitation.
  • New Features of Polar Vortex and Its Impact on Winter Temperature of China
  • ZHANG Jingwen;LI Dongliang;LIU Yanju
  • 2014 Vol. 33 (3): 721-732.  DOI:10.7522/j.issn.1000-0534.2013.00044
  • Abstract ( ) PDF (5490KB) ( )
  • Using NCEP/NCAR reanalysis data, the variation of the area, intensity and location of the whole and four regions of Northern Hemisphere polar vortex on 500, 300, 200 and 100 hPa in winter is investigated. Meanwhile, the change of the percentage of polar vortex area in different layers and the variation characteristics of the main location of 500 hPa polar vortex are discussed. Finally the synchronous and later correlation between the area and intensity of each level polar vortex and their relation with winter average and extreme temperature are analyzed. The results are as followings: (1) The area size and intensity of Northern hemisphere polar vortex in winter at four levels increased at the beginning, which is followed by a decreasing trend, and the area mutated occurred in the middle 1980s as the beginning of the global warming and intensity mutated occurred in the middle of 1990s. Compared with the area, inter-decadal change of the intensity is weak. And the area and intensity of polar vortex at different layers have significant inter-decadal correlation. (2) The area of polar vortex on 100 hPa is the biggest, and the intensity is strong at the same level, both of which have the largest seasonal amplitude, especially in region Ⅰ and Ⅳ. As to the annual variation, the maximum polar vortex area appears later while the minimum area appears earlier than other layers. And winter polar vortex area index on 100 hPa has a certain influence on the ones on 500, 300 and 200 hPa in the next winter. (3) The polar vortex area of four layers all deviate from region Ⅳ (the Atlantic and Europe continental), and 500 hPa polar vortex deviate into region Ⅱ and Ⅲ (the Pacific Ocean and the continent of North America area), polar vortex on 300, 200 and 100 hPa deviate into region Ⅰand Ⅱ (the Asian mainland and the Pacific Ocean), the center of 500 hPa polar vortex almost located in region Ⅱ or Ⅲ. (4) In recent 50 years, under the background of global warming, the average temperature in winter and the occurrence of warm day (night) have a significant increasing trend, cold day (night) reduced significantly and the mutation occurred in the middle of 1980s. (5) The winter average temperature and extreme temperature index have a significant correlation with the 500 hPa polar vortex area. The correlation between the temperature and area of the region Ⅰ on 500 hPa is the most significant, the region Ⅰ on 300, 200 hPa and region Ⅳ on 100 hPa take the second place, which shows that the impact of polar vortex area on the winter temperatures is from the region Ⅳ on 100 hPa (Europe continent) in bottom of stratosphere to the region Ⅰ on 500 hPa (Asia continent) in the troposphere. (6) The expansion of polar vortex area of region Ⅰ on 500 hPa lead to increases (decreases) the occurrence of cold day/night (warm day/night) in most of China except the northeast, while the expansion of the polar vortex area of region Ⅲ, Ⅳ on 100 hPa and region Ⅳ on 500 hPa lead to increases (decreases) the occurrence of cold day/night (warm day/night) in northern China. And the correlation between polar vortex area and occurrence of cold (warm) night is better than cold (warm) day, while the correlation between polar vortex area and cold day (night) is better than warm day (night).
  • Comparison Tests of the Integration Effect of Surface Temperature by LAPS and STMAS
  • ZHANG Tao;MIAO Chunsheng;WANG Xin
  • 2014 Vol. 33 (3): 743-752.  DOI:10.7522/j.issn.1000-0534.2013.00046
  • Abstract ( ) PDF (13115KB) ( )
  • To test fusion effects of LAPS (Local Analysis and Prediction System) and STMAS (Space-Time Multiscale Analysis System) system at different spatial scales, different resolution conditions on the surface temperature, LAPS and STMAS fusion test were performedin Beijing, North China and the Country 3 different areas, using the regional automatic weather station observations and GFS (Global Forecast System) background information on 1, 5, 10 and 20 km four kinds of grid resolution, the differences of LAPS and STMAS fusion effect was analyzed from algorithm angle, and a year of hourly fusion analysis results by LAPS and STMAS was statistical analyzed using the national automatic station data. The results showed that: LAPS and STMAS both havegood performance in the observation-intensive areas, STMAS can resolve the small features in the observations, andthe fusion results by STMAS are more closer to the actual observation and that by LAPS relatively smooth obvious, and possibly losing observational information; the confusion of the longwave and shortwave information in data sparse areas can be avoided because of the multi-scale analysis of STMAS that the background field can be corrected more efficiently using observations; in addition, the irrational nature of the terrain height adjustment has affect the fusion effect of LAPS and STMAS in the mountains.
  • Numerical Simulations of the Extraordinary Rainstorm by Typhoon Nesat
  • YANG Renyong;MIN Jinzhong;ZHENG Yan
  • 2014 Vol. 33 (3): 753-761.  DOI:10.7522/j.issn.1000-0534.2013.00047
  • Abstract ( ) PDF (5390KB) ( )
  • Numerical simulation and terrain sensitivity experiments on the heavy rainfall caused by the typhoon Nesat during 29-30 September 2011 were studied using the weather and research forecast(WRF) model when Nesat made the landfall and went through the north Hainan Island. The results show that: The rainfall caused by the westing typhoon landfall on the north area distributed more in the north than the south. In the north, there is more rain in the west area than east area. 48 h and 3 h accumulative rainfall from the 12 km experiment are successfully modeled and the landing time and location is close to the observed. The typhoon track and intensity are good simulated as well. The terrain sensitivity experiment shows that 24 h precipitation from the experiments with terrain have increased generally by more than 50 mm in the west area in Hainan Island. Increase of more than 150 mm has been observed in the western mountainous regions, with 350 mm increase in the north part of the main peak. Heavy precipitation center is found responding to main mountain peak, It proves that, the terrain can result in general obvious rainfall increase in typhoon. However, there is a 50~150 mm rainfall reduction in the eastern coast of the island due to the block from the Wuzhishan Mountain. Analysing the comparison of low-level mesoscale flow field and the vertical velocity, significant difference can be found between control experiments and experiment with none terrain. The Wuzhishan terrain can enhance low-level disturbances, which can easily produce the vortex of mesoscale convection (MCS), then by increasing the typhoon rainfall. The special terrain of Wangxia plays an important role in increasing the typhoon rainfall.
  • Relationship between North Pacific Oscillation in May and Drought/Flood in Summer in North China
  • ZHENG Qiuyue;SHEN Baizhu;GONG Zhiqiang;ZHOU Jie;HU Jingguo
  • 2014 Vol. 33 (3): 775-785.  DOI:10.7522/j.issn.1000-0534.2012.00040
  • Abstract ( ) PDF (6202KB) ( )
  • The relationship between the North Pacific Oscillation (NPO) in May and the summer drought/flood in North China was analysed using the NCEP/NCAR month by month reanalysis data from 1948 to 2011 including sea level pressure, 500 hPa geopotential height, specific humidity(8 layers) and wind field(8 layers). The North Pacific Oscillation Index(NPOI) which reflects the changes of the sea level pressure in North Pacific was calculated firstly. Then the correlation coefficient between NPOI and Palmer Drought Severity Index(PDSI) which represents the situation of summer drought/flood in North China from 1960 to 2011 was also calculated. The results show that there is a positive correlation between NPO and summer drought/flood in North China. When in positive NPOI years, PDSI in summer is higher than normal, and North China has more summer floods; otherwise, in negative NPOI years, PDSI in summer is lower than normal, and North China has more summer droughts. In order to explain the positive correlation between NPO and summer drought/flood in North China, wind vector field on 850 hPa and geopotential height field on 500 hPa were composite analysed, respectively, and compare the different intensity, area and position of western boundary of Western Pacific Subtropical High(WPSH) when NPO is in different strength(weak and strong). The possible circulation mechanism is that when in positive(negative) NPOI years, on lower layer(850 hPa wind field), the common action of anti-cyclonic(cyclonic) in Ural Mountains, the cyclone(anti-cyclonic) of Lake Baikal, and the anti-cyclonic(cyclonic) anomaly circulation in West Pacific have strengthened(weakened) the convergence of south-west warm and humid air flows of low layer in North China region. And also, when in positive(negative) NPOI years, 500 hPa geopotential height anomaly shows‘+-+’(‘-+-’) wave train, and WPSH is stronger(weaker) shifting northwest(southeast) than normal years, cold and warm air activities make more(less) rainfall in North China. Vertically intergraded moisture fluxes was calculated, in order to show water transportation of summer drought/flood in North China and study the relationship between NPO in May and sea surface temperature in winter by using composition method. In the difference of vertically intergraded moisture fluxes field in summer, the moisture transport from the Arabian Sea and Bay of Bengal and the West Pacific make North China the positive anomaly of water vapor moisture, so there is more rainfall in North China; In divergence field, the water vapor divergence is negative in North China, so it is moisture sink and there is more rain. And also the Arabian Sea, Bay of Bengal, the south of Indo-China Peninsula to the South China Sea and the Western Pacific are the water vapor divergence centers, which are important vapor source for North China. The SST in winter in Pacific Ocean has forcing role on NPO in May, which influences summer drought/flood in North China.
  • The Multi-Scale Features of “0702” Heavy Rainstorm Process
  • MIAO Aimei;HAO Zhenrong;JIA Lidong;LI Miao
  • 2014 Vol. 33 (3): 786-800.  DOI:10.7522/j.issn.1000-0534.2013.00014
  • Abstract ( ) PDF (24071KB) ( )
  • With data of T639L19 1°×1° analysis field, FY-2 infrared cloud and infrared radiation brightness temperature(TBB), doppler radar, air vapor content, and so on, the multi-scale feature of the regional rainstorm occurred in Shanxi territory from 2 to 3 July 2011 was analysed. The results show that: (1) The subtropical high moves up northward, the southwest warm-wet air flow enhances, the cold air behind the northeast cold vortex moves down southward, the frontogenesis in the mid-north part of Shanxi are large-scale circulation features of the regional rainstorm. (2) The rainstorm in the middle of Shanxi was created by two β mesoscale convective cloud cluster, and triggered the convection developing nearby the two mesoscale shear line on the boundary layer, and formed two rainstorm centers; While, the rainstorm in the south of Shanxi was created by eight mesoscale convective cloud clusters, developed and combined, and triggered the convection developing nearby the α mesoscale herringbone shear line on the boundary layer. The four γ mesoscale cyclone on the α mesoscale herringbone shear cloud system were the direct reason of the occurrence of the local heavy rainstorm and super rainstorm; The black body brightness temperature area ≤-53℃ advanced the area where the doppler radar herringbone shear cloud system reflectivity gene ≥35 dBz. (3) During the early-middle period of precipitation, the convective cloud cluster combined led to the appearance of cloud-to-ground lightning frequency peak value and precipitation peak value. And the cloud-to-ground lightning frequency peak value appeared 12~18 minutes earlier than the precipitation peak value. (4) The rainstorm of middle part occurred in the area of air vapor content spatial distribution map, where the horizontal grads big value area overlapped with the boundary layer shear line. While, the rainstorm of south part occurred in the area of air vapor content spatial distribution map, where the high humidity area was at a distance of 0.5~1.0 latitude and longitude from south of the horizontal grads big value area, overlapped with the boundary layer herringbone shear; Both the forming time of the air vapor content spatial distribution map horizontal grads big value area and the forming time of the boundary layer shear line were 12 h earlier than the arising of rainstorm.
  • Relationship between Narrow Bipolar Events and Radar Echo in Southwest China
  • LIU Shasha;DONG Wansheng;WU Ting;LIU Hengyi
  • 2014 Vol. 33 (3): 801-810.  DOI:10.7522/j.issn.1000-0534.2013.00178
  • Abstract ( ) PDF (4437KB) ( )
  • A very low frequency and low frequency (VLF/LF) lightning location network has been established since 2010 in the southwestern Chinese city of Chongqing, which consists of 11 stations of fast electric field change meters. Using this system, the distinct class of intracloud lightning discharges named NBEs (Narrow Bipolar Events) are recorded. Six thunderstorm cases are used to analyze the relationship between NBEs and thunderstorm convective strength. Every storm produced NBEs of both polarities, and one of them produced more negative NBEs than positive ones, which is a very rare case. Our study statistically compare NBEs rates to the Doppler radar-inferred proxies of convective strength. It is concluded that although NBE rates show much weaker dependence on the volume of 40 dBZ radar reflectivity (V40) than ordinary lightning, they increase rapidly with the increased V40 and largely occur in high V40 area, especially for negative NBEs. The spatiotemporal relation of positive and negative NBEs to thunderstorm convection is also investigated. Compared with positive NBEs, the negative NBEs cluster more closely in time and space, they generally occur in the strongest development stage of the thunderstorm, largely clustering at the cloud top of the core of deepest convection. It seems that a very vigorous thunderstorm tends to produce more negative NBEs. Positive NBEs are scattered around the convective cores. These results indicate that negative NBEs are closely related to the deep convection, which is useful and meaningful to indicate thunderstorm convective strength.
  • Application of Diagnostic Analysis on Forecast of the Heavy Snow in Shanxi Province
  • ZHAO Guixiang
  • 2014 Vol. 33 (3): 838-847.  DOI:10.7522/j.issn.1000-0534.2012.00199
  • Abstract ( ) PDF (5388KB) ( )
  • A heavy snow occurred in Shanxi Province during 9-12 November 2009 were analyzed based on the observed data. The results show that: (1) There has the block circulation on 500 hPa. The vortex, shear line at low was remain steady. There are three strong air flows such as the southwest jet on 700 hPa, the southeast jet on 850 hPa and strong northeast on 850 hPa and 925 hPa. Reflow on surface and inverse trough in Hetao area develop strongly. (2) The analysis of total temperature advection shows that: There is warm and moisture air at low level transport to Shanxi constantly, and the intensity of center strengthen constantly before heavy snow. From its change of horizontal structure, this process can be divided into four stages, such occlusion snow, reflow snow, warmly inverse trough snow and cool down constantly, and there has different snow characteristic within different stage. (3) Above the heavy snow, there is a vertical thermal structure of cold at high and low level, and warm at middle. There is a center intensity of cold advection at low three times as that of ordinary snow. There is constant convection instability at troposphere low level, air divergence in instable area and warm and moisture advection to import constantly. So convective instability and its rain strengthen constantly. (4) In this process, the atmospheric precipitable water above Shanxi add up to 35~88 mm, and with strengthen and convergence of wind field at low level and near surface, there is an increasing of and strong snow will be amplitude constantly. (5) Diagnosis of vapor divergence flux shows that there is a positive value area under 300 hPa, its intensity reached the strongest on 500~600 hPa, while at high and low level, there is a weak divergence before and during heavy snow.
  • Analysis on the Observation and Simulation of Thunderstorms Triggered by Sea Breeze Front in Bohai Bay
  • WANG Yan;GAO Shouting;LIANG Zhaoming
  • 2014 Vol. 33 (3): 848-854.  DOI:10.7522/j.issn.1000-0534.2013.00030
  • Abstract ( ) PDF (5740KB) ( )
  • Using the Tianjin doppler radar data and the meso-scale numerical simulation method, the occurrence, developing and evolution characteristics of the thunderstorms triggered by the sea breeze front on 13 August 2007 was analysed. The results show that: The simulation not only reproduced the formation and dispersion times, morphological characteristics and locations of sea breeze front reasonably well, but also presented the physical characteristics of sea breeze front more clearly. Sea breeze front was the cross belt which converged northeaster and southeaster. Temperature decreasing and moisture increasing occurred under 850 hPa on the way of sea breeze front moving toward inland. Thermal inner boundary layer also formed behind the sea breeze front and its thickness increased as close to the sea breeze front. From the horizontal distributions of temperature and water vapor, the fore-end of the sea breeze front was the area with dense temperature and humidity gradients, while the behind was cold and moist air mass. In addition, the simulation reproduced the relatively cold and dry air and the sinking divergence motion at low level behind the gust front although the narrow radar echo line associated with gust front was not able to be simulated. Thunderstorms were more likely to form at the crossing point of the collision between gust front and sea breeze front, where convergence and upward motion were more favorable to maintain and rich CAPE and dynamic instability were provided.
  • Homogenization of Temperature Observation in Tianjin Since 1891
  • REN Yu;GUO Jun
  • 2014 Vol. 33 (3): 855-860.  DOI:10.7522/j.issn.1000-0534.2013.00041
  • Abstract ( ) PDF (1684KB) ( )
  • Regular observation of near surface air temperature in Tianjin began in October 1890. There is a temperature series over 110 years and the continuity of the temperature observations has been well conserved. However, there seems to be considerable inhomogeneity in the series before 1951 with less metadata can be collected. Unfortunately as well, there is no available reference series can be used to detect the possible inhomogeneity. In this paper, the inhomogeneity in daily minimum and maximum temperature observations in Tianjin from 1891 to 1950 was examined and adjusted using the RHtestV3 software package, without reliable reference series available. To verify the rationality of the adjustment, multiple temperature series from areas around Tianjin were collected from different sources and employed as consistency references. The examination indicated 6 breakpoints in the minimum temperature series mainly during 1897-1927 and 2 breakpoints in the maximum temperature series in February 1919 and January 1932. Annual mean temperatures are calculated as the mean of the adjusted minimum and maximum temperatures and the series is much better related with the consistency references and resulted in a trend of climate warming close to the average trend of North China, which verified the homogenization in the adjusted Tianjin temperature series.
  • The Earth-Atmosphere Science Forecast Method of Heavy Rainfall in Langfang Area in Hebei Province
  • GUO Liping;TANG Maocang;LIU Yanjie
  • 2014 Vol. 33 (3): 868-876.  DOI:10.7522/j.issn.1000-0534.2013.00008
  • Abstract ( ) PDF (1110KB) ( )
  • Using the seismic data of M≥4 which occurred in China and surrounding areas and the Langfang precipitation data from 1981 to 2011, the effect of‘beat vortexs’in Langfang area and the ‘seismic origin vortexs’in Hebei territory which caused by the earthquakes of M≥4 on precipitation of Langfang were analyzed and the relationship between the geothermal field distribution, change caused by geothermal vortex generation and activities and the occurrence and location distribution of heavy rainfall were further analyzed, finally, the precipitation and the cases of heavy rainfall in langfang area in 2011 were tested and analyzed. The results show that: the‘beat vortexs’ in Langfang area and the‘seismic origin vortexs’in Hebei territory which caused by the earthquakes of M≥4 can lead to the abnormal precipitation in Langfang; Several earthquakes a year frequent falls on the Langfang regions formed in the territory of more ‘beat vortexs’, and the ‘beat vortexs’ can cause Langfang area a few months precipitation abnormal more; From the viewpoint of earth-atmosphere science, the major earth-atmosphere systems of excessive rain and heavy rainfall are the earthquake ‘beat vortexs’ and the‘seismic origin vortexs’in Langfang area; Analyzing the precipitation and the cases of heavy rainfall in Langfang area in 2011, the results show that: if we master the underground earthquake activity information, calculate distribution of geothermal vortex strongest point (‘super energy value’) by analyzing the geothermal vortex formation caused by changes in the geothermal field, and combine the induction of the weather systems, we would found that they have very important reference value to the forecast of heavy rainfall and its location.

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