Plateau Meteorology

Current Issue

28 February 2015, Volume 34 Issue 1   
  • Impact of Bay of Bengal Storms on Precipitation over Plateau Area
  • DUAN Xu;DUAN Wei
  • 2015 Vol. 34 (1): 1-10.  DOI:10.7522/j.issn.1000-0534.2014.00001
  • Abstract ( ) PDF (14610KB) ( )
  • By using TBB data, NCEP/NCAR reanalysis data and precipitation assimilation data from TRMM(3B42) and rain gauge data, the influence of landing path, impact strength, cold air intrusion and atmospheric seasonal changes of 25 processes of Bay of Bengal storms from 1998 to 2010 on precipitation over the plateau region were classified statistical analyzed. The results show that: (1) The Bay of Bengal Storm is the important weather system affected rainfall over the plateau area. Its most active period focused on the annual May and October to November. (2) The landing path of Bay of Bengal storm can be divided into three categories, NE (northeast), NW (northwest) and W (west) paths. Storms from NE path landing with maximal impact rainfall over Yunnan-Guizhou Plateau and the southeast of the Qinghai-Xizang Plateau. Storms from NW path landing mainly affected the south of the Qinghai-Xizang Plateau. Storms from W path landing with minimal impact on the Qinghai-Xizang Plateau. (3) Storm from NE path landing with TS (tropical storm) intensity can bring more precipitation for plateau than the H (hurricane) intensity, and to NW path, the H intensity can bring more precipitation for plateau that the TS. (4) For storms from NE path landing, when mated with cold air over Yunnan-Guizhou Plateau, the precipitation can reach more than 15 mm, even 50 mm or more in some areas. But, when no cold air, the precipitation does not exceed 15 mm. (5) Seasonal atmospheric circulation (steering flow) and water vapor transport (strength) and tropical cyclone formation conditions are different between two storms activities peak periods in May and October to November. The differences lead to different scale precipitation on the plateau.
  • New Variation Characteristics of Winter Monsoon over Qinghai-Xizang Plateau and Its Influences on Temperature over Southwest China
  • WANG Ying;LI Dongliang;WANG Hui;ZHENG Ran
  • 2015 Vol. 34 (1): 11-20.  DOI:10.7522/j.issn.1000-0534.2013.00196
  • Abstract ( ) PDF (5366KB) ( )
  • Based on the NCEP/NCAR reanalysis monthly data from 1951 to 2011 and monthly temperature data at 77 stations in southwest China from 1960 to 2011, the spacial-temporal variability of winter monsoon over Qinghai-Xizang Plateau(WMQXP) and southwestern temperature in January has been analyzed by EOF method. Meanwhile, intensity and location indices of WMQXP are defined. For recent 60 years, WMQXP has significant annual and inter-annual variability. There is an abrupt change of WMQXP in late 1970s from week to strong and mid 1980s from north to south. Under the global warming, the oscillation frequency of the intensity and location both accelerates that the period varies from 7 a to 4 a and from 10 a to 4 a, respectively. According to correlation and synthesis analysis, there exists a close contact between WMQXP and southwestern temperature. When the plateau high strengthens, the intersection between the northern cold air and southwest warm air becomes less than normal, which causes less cloud. Otherwise, abnormal downdraft center appears in the east of southwest China. The whole southwestern region is consistent with higher temperature and eastern part is more obvious. Vice versa. When plateau high is located north, more warm-wet air from the south and cold-dry air from the north join together at the eastern Qinghai-Xizang Plateau. Simultaneously, abnormal northeasterly winds dominate the eastern part of southwest China, and the western part exist abnormal updraft and increases cloud cover. The whole southwestern region is consistent with lower temperature and western part is more obvious. Vice versa. The relationship between the intensity and location of WMQXP and southwestern temperature has great significance to analyze the climate change of the latter.
  • Anomaly Temporal-Spatial Distribution of Spring Drought on Loess Plateau in China
  • YAO Yubi;WANG Jingsong;WANG Ying;YANG Jinhu;LI Jianfeng;LEI Jun
  • 2015 Vol. 34 (1): 30-38.  DOI:10.7522/j.issn.1000-0534.2013.00179
  • Abstract ( ) PDF (3632KB) ( )
  • Drought index analytical method which was based on relative moisture index was used to study the temporal and spatial variation, abnormal distribution and sub-regional evolution characteristic of spring drought on Loess Plateau, according to meteorological data between 1961 and 2010. The results showed that, the intensity variation of spring drought on Loess Plateau from 1960 to 2010 had an obvious distribution characteristic that intensity is higher in central area and lower in surrounding area. Among which the increase of drought intensity in hinterland of central area has the highest rate of tendency, and then in rest places of central area. West and northeast region of the plateau have an attenuate tendency. The main spatial distribution mode of drought variation is the phase variation for spring drought, central abnormal areas located in north Shaanxi, east Gansu and southwest Ningxia. Secondly, opposed phase distribution model in east and west areas provide a reflection of characteristics of differences between east and west region of Loess Plateau, which was caused by the influence of atmosphere system. According to spatial abnormal distribution of different loading vectors and modes, spring drought can be divided into three sub-regional abnormal distributions, e.g. northwest kind, northeast kind and south kind. The intensity of spring drought in south sub-region has a significant increasing tendency, the mutation point of which from weak to strong appeared in 1977, drought intensity in northwest and northeast regions also showed a fluctuated increasing tendency, but no mutation was emerged since the fluctuation failed to pass the significance test. The index of spring drought in northwest and south regions has an obvious high frequency fluctuating period of 3~4 years, while northeast part has an obvious high frequency fluctuating period of 5~6 years.
  • Climate Regionalization and Characteristics of Surface Winds over China in Recent 30 Years
  • XIONG Minquan
  • 2015 Vol. 34 (1): 39-49.  DOI:10.7522/j.issn.1000-0534.2013.00159
  • Abstract ( ) PDF (7271KB) ( )
  • Climate regionalization of surface winds imply associated to wind speed distribution in China. According to the daily mean wind speed data of 608 stations in China from 1980 to 2009, the distribution of predominant patters is analyzed by the Rotated Empirical Orthogonal Function (REOF) method. The results show that there are ten regions which is related to the topography of China. There is higher wind speed in the north and smaller in the middle of China. It is also analyzed between the frequency of effective wind speed and distribution of wind energy. Based on the harmonic analysis, the results show that there are two kind variation including a single peak-valley pattern and double peak-valley pattern. According to the different atmospheric circulation features, it is analyzed that the higher wind speed happed in spring. A significant declining trend of wind speed existed in a large part of China by using the methods of linear regression. The mean declining rate in first, fourth and fifth region is within range of -0.028~-0.023 m·s-1·a-1. Therefore, it is inverse trend in the middle part of China (the second, sixth and tenth region). The results showed that the abrupt change points appeared in 2000 for the second, third and fifth regions and in earlier year of 1990 for the first, fifth and sixth region by using Mann-Kendall test. The contemporaneous correlation between characteristic quantities of atmospheric circulation and wind speed in China is studied. The result show that northern polar vortex and subtropical anticyclone play a great role in the variation of wind speed.
  • Assessing Quality of Grid Daily Precipitation Datasets in China in Recent 50 Years
  • ZHAO Yufei;ZHU Jiang
  • 2015 Vol. 34 (1): 50-58.  DOI:10.7522/j.issn.1000-0534.2013.00141
  • Abstract ( ) PDF (7373KB) ( )
  • Precipitation is an important meteorological factor, ecological and water balance process in ecosystem. By using the quality controlled observational daily precipitation data series over China Mainland observed by 2472 gauges, through the ANUSPLIN software developed by the Australian National University based on the thin plate smooth spline method, the datasets of daily grid-based precipitation are established over China in recent 50 years from 1961 to 2010. The research results show the mean bias error of large part gauge is between -10 mm·mon-1 and 10 mm·mon-1. There are 96.7%, 91.8%, 63.2% and 94.0% gauge that the bias error is between -1 mm·d-1 and 1 mm ·d-1. This developed datasets are helpful to explore the spatial and temporal distributions of the precipitation. Based on results of typhoon Bilis and 7 interpolation experiments, RBEa falls off to the bottom when M equal to 9 and mounts up to the peak when M equal to 1. The APHRO grid value can represent the pattern of South China precipitation which reflect in gauge data. The CP grid data is more exact in describing the precipitation characteristic of Qinghai-Xizang Plateau, the Tianshan Mountains and Tarim Basin. Moreover, both CP data and APHRO data are able to depict the daily variation of Jiang-Huai Meiyu mainly. The two kinds of grid data reduce the rain intensity in the same way when heavy rain or moderate rain comes. Over the light rain, CP data has more veracity.
  • Case Analysis of Extreme Rainstorm in Arid Zone of the Midwestern Gansu Corridor
  • KONG Xiangwei;TAO Jianhong;LIU Zhiguo;FU Zhao;JI Huimin
  • 2015 Vol. 34 (1): 70-81.  DOI:10.7522/j.issn.1000-0534.2013.00138
  • Abstract ( ) PDF (8078KB) ( )
  • An extreme rainstorm has occurred in the midwestern of Gansu Corridor arid zone on 45 June 2012. Using the data of conventional and automatic weather stations, FY-2D satellite cloud image as well as NCEP 1°×1° reanalysis data, the impacts of influence system configuration, meso-scale characteristics, water vapor transport and unstable energy have been analyzed. The main results are as follows. After the ground cold front had passed, rainstorm happened, cooling condensation effect was significant. No convergence system formed on ground, while strong suction existed in upper troposphere; plateau low vortex which was blocked by its downstream weak ridge stayed longer over the rainstorm area in middle troposphere; a shear line could be found in low troposphere, the configuration of the upper and low influence systems provided meso-scale convection conditions. Water vapor came from east and west in the low troposphere and south in the upper troposphere, the west vapor transport was strongest, and east vapor transport was affected significantly by high pressure. The whole precipitation water was twice more than the climate. Cooling and humidifying in the boundary layer forced the convective energy to be unstable, and free convection altitudes was low, without the need of strong uplift triggering mechanism. The six meso-β-scale convection cells had been activated at the cold air intrusion of low vortex cloud, and Yumen station which was affected by four convection cells was divided into two periods to produce short-time severe precipitation.
  • PV Inversion Analysis of a Mid-level Vortex Induced a Tropical Depression Formation in South China Sea
  • YUAN Jinnan;GU Dejun;LIAO Fei
  • 2015 Vol. 34 (1): 93-102.  DOI:10.7522/j.issn.1000-0534.2013.00145
  • Abstract ( ) PDF (5500KB) ( )
  • Using NCEP 1°×1° Final Analysis (FNL) data and potential vorticity (PV) inversion technique, the process of a mid-level vortex induced tropical depression formation in the South China Sea (SCS) in late August 2006 was analyzed. The results show that: The upper warm-core structure experienced a process of gradual development from up to down and the mid-level cyclonic circulation experienced a process of fast development from up to down during the mid-level vortex induced tropical depression formation in the SCS. The downward development of upper warm-core structure is mainly associated with the action of condensation latent heating in middle and low level and dry air intrusion from high level to middle level. The influence of high level fluctuations is not obvious. However, the warm-core developing downward to near sea surface need the common actions of bottom thermodynamic anomaly together with condensation latent heating in middle and low level. The downward development of mid-level cyclonic circulation is also mainly associated with the action of condensation latent heating in middle and low level. The influence of high level fluctuations on the vorticity in middle and low level is not obvious. And the bottom thermodynamic anomaly mainly causes negative vorticity below 900 hPa. The comprehensive analysis shows that the condensation latent heating in middle and low level plays a key role in the tropical depression formation and development in the SCS.
  • Numerical Simulation of ‘7·31' Severe Convection Event in Shanghai Using Rapid Refresh Technique
  • WANG Xiaofeng;WANG Ping;ZHANG Lei;XU Xiaolin;LI Jia
  • 2015 Vol. 34 (1): 124-136.  DOI:10.7522/j.issn.1000-0534.2013.00202
  • Abstract ( ) PDF (17877KB) ( )
  • Using multi-source observations, such as Doppler radar, AWS, AMDAR and radiosonde measurements, and the high-resolution numerical model WRF as well as the advanced data assimilation system ADAS, a numerical simulation of the server convection event, which occurred in Shanghai on 31 July 2011, was conducted using rapid refresh technique. The results showed that the model correctly predicted this server convective weather process, the timing and location, as well as the variation of the precipitation along with the time were well consistent with the observations. It was also found that due to the thermal difference between land and sea, two sea breeze from different north and south directions met in shanghai area and low level convergence line formed, as a results, weak updraft in boundary layer appeared, combined with the local urban heat island effect, created favorable conditions for triggering the server convections; and the high gradient of moisture between low level and middle level and its unstable vertical structure provided favorable conditions for moisture vertical transportation. The numerical simulation using rapid refresh technique issued early warning of this server convection occurrence 10 hours in advance, and this provided a new way for the megacity operational convection forecasts.
  • Numerical Simulation Study of the Factors Influencing High Temperature over Hangzhou
  • FAN Gaofeng;ZHU Rong;ZHANG Xiaowei;MA Hao
  • 2015 Vol. 34 (1): 137-144.  DOI:10.7522/j.issn.1000-0534.2013.00109
  • Abstract ( ) PDF (5169KB) ( )
  • With global warming and the accelerated urbanization-process, the impact of urban high temperature-induced disaster becomes more and more distinct. By using the WRF/UCM model, the influence of two factors of existence of the West Lake and urbanization-process on high temperature over Hangzhou is investigated. Three experiments were designed: Experiment 1 is set-up as the control run with the land-use data in 2010 is adopted. In experiment 2, the West Lake is replaced by paddy field and other parameters are the same as that in the first run; In experiment 3, the land-use data in 2000 is adopted and other parameters are the same as that in the first run. While comparing the result of experiment 1 run with that of experiment 2, it can be concluded that the West Lake is able to reduce high temperature in daytime and prompt high temperature at night, respectively. Generally, the West Lake contributes to enhance high temperature over Hangzhou. While comparing the result of experiment 1 with that of experiment 3, it can be found that urban heat island effect (UHIE) induced by the urbanization-process helps to intensify high temperature over Hangzhou and enlarge the high temperature area. UHIE prompts high temperature both in daytime and at nighttime, and exerts more important influence in daytime.
  • Climate Characteristics of Rain Days and the Relationship between Rain Days and Total Amount of Precipitation in Guizhou
  • WANG Fen;CAO Jie;LI Fuguang;SUN Xudong;GU Xiaoping;XIONG Wei;DUAN Rong
  • 2015 Vol. 34 (1): 145-154.  DOI:10.7522/j.issn.1000-0534.2013.00144
  • Abstract ( ) PDF (6245KB) ( )
  • Using the daily precipitation data from 81 station in Guizhou Province from 1963 to 2011, climate characteristics of the rainy day and the impact to the total precipitation over Guizhou were analyzed. The results are as follows: With increasing precipitation levels, the rainy days reduce rapidly; total rainy days and light rainy days in western are more than those in eastern. While moderate rainy days, heavy rainy days and storm rainy days in southern are more than those in northern. In recent 49 years in Guizhou the total rainy days, light rainy days, moderate rainy days and heavy rainy days have all decreased, but storm rainy days have increased slightly. The light rainy days and the total rainy days reduced gradually in the early nineteen eighties, early in twenty-first Century after the drop is more obvious, and moderate rainy days in 1960's—1980's have many fluctuations, decreased rapidly at the beginning of the twenty-first century, the heavy rainy days and storm rainy days both have undergone two obvious fluctuation. With the rising level of precipitation the correlation coefficient increases rapidly, light rainy days and rainfall relate the worst, storm rainy days and rainfall relate the best. In positive yeas, the number of rainy days is obviously more, the light rainy days, moderate rainy days and heavy rainy days change significantly, in negative year, the number of rainy days is obviously less, the moderate rainy days changed significantly, then is heavy rainy days and storm rainy days. Therefore, the totod precipitation increase is mainly caused by the iuerease of the days about light rain, moderate rain and heavyrain, but precipitation decrease is moinly due to the decreesecd the days about moderate rain, heavy rain and storm rain. Comparison the levels of precipitation days, both in positive years or negative years, the days of moderate rain and heavy rain changes are signiticont.
  • Atmospheric Circulation and Water Vapor Characteristics of Snowstorm Anomalies in Northern Xinjiang in 2010
  • LI Ruqi;TANG Ye;ROUZI Aji
  • 2015 Vol. 34 (1): 155-162.  DOI:10.7522/j.issn.1000-0534.2013.00163
  • Abstract ( ) PDF (6603KB) ( )
  • The snowstorm in northern Xinjiang was extremely excessive in 2010, the snowfall and snow depth were exceed historical maximum and huge economic losses were made. The snowstorms in northern Xinjiang are divided into cold front snowstorm and warm sector snowstorm. Based on analysis of time and space distribution of the snowstorm in northern Xinjiang, using the NCEP/NCAR 2.5°×2.5° reanalysis data, the circulation and water vapor transfer features in snowstorm were analyzed. The results show that: The snowstorm in northern Xinjiang often occur in mountain area and windward slope, and geomorphic effect can't be ignored. The snowstorm in northern Xinjiang is closely related to the location and intensity of polar front jet and subtropical jet, and the overlying and confluence of two rapid zone is major large-scale circulation background of cold front snowstorm, and polar front jet is dominant during warm sector snowstorm. The cause of cold front snowstorm is confluence of the north cold air and the southwest warm moist air flow, and if warm sector snowstorm occur, the colder north cold air southward is the cause. The cold front snowstorm occurs in strong cold frontal zone, and the ground cold high pressure exhibits northeast southwest. When the ground cold high pressure exhibits northwest southeast, the warm front ahead of cold front trigger warm sector snowstorm. The water vapor of the snowstorm in northern Xinjiang is transfer in a relay, and the location and intensity of the Iran subtropical high is crucial for water vapor transfer of snowstorm.
  • Procession and Causes of the Extreme Rainstorm Event in Inner Mongolia in July 2012
  • SONG Guiying;LI Xiaoze;JIANG Jing;XUN Xueyi;CHEN Lei;MA Suyan
  • 2015 Vol. 34 (1): 163-172.  DOI:10.7522/j.issn.1000-0534.2013.00148
  • Abstract ( ) PDF (8042KB) ( )
  • An extreme rainstorm named as ‘7·27' occurred in the middle of Inner Mongolia in China during late July 2012. Using data from NCEP reanalysis, conventional observations, and monitoring, the causes of the ‘7·27' extreme heavy rain were analyzed and discussed. The results showing: (1) Bell-Lake vortex happened in ‘7·27' rainstorm was quite different from that in perennial years. The area from Balkhash Lake to the Ochotsk Sea was controlled by blocking high, the bottom of the blocking high was occupied by Bell-Lake vortex.(2)‘7·27' rainstorm has strongly the characteristics of the meso-scale. Many meso-scale rain belts were generated by surface shear lines formed constantly and swung north and south. The β meso-scale convective clouds were produced constantly and enhanced by amalgamation and further formed the convective complexes (MCS or MCC). The rainstorms in the northwestern and southern Hetao area, and the western Xilin Gol League were all resulted from the meso-scale convective complex (MCC) or MCS and ground shear lines, (3) The distribution characteristics of the water-vapor were: the atmospheric specific humidity in vertical was up to 10~22 g·kg-1 from ground to 700 hPa. The water vapor transported strongest in the scope from 850 hPa to 700hPa. Horizontally, the south winds reached 45°N, which made the "moisture sink" of Southern Hetao. (4) Atmospheric vortex in Troposphere was the direct cause of the event. The atmosphere vortex spread from 200 hPa down to 700 hPa. Heavy rains were hence produced by the upper atmosphere divergence and the lower compensate convergence. (5) The thermodynamical mechanics of ‘7·27' rainstorm is: The instable energy of atmosphere was rebuilt constantly with the mid-level dry intrusion and the low-level humid transport. (6) With global warming, the Asian summer monsoon intensifying, from the bay of Bengal and the South China Sea to the East Asian subtropical region water vapor transport strengthening, water vapor transport further northward expansion into North China's inland areas, is an important reason for ‘7·27' rainstorm process.
  • Characteristics and Causes of High-Impact Weathers in the Yangtze River Delta
  • SHI Jun;CHEN Bomin;MU Haizhen;LIANG Ping
  • 2015 Vol. 34 (1): 173-182.  DOI:10.7522/j.issn.1000-0534.2013.00157
  • Abstract ( ) PDF (5161KB) ( )
  • Based on the observed data from 32 meteorological stations, atmospheric circulation data and regional land use data, the evolution characteristics of high-impact weathers and the impacts of atmospheric circulation and regional urbanization and land use on them were analyzed. The results indicate that from 1959 to 2010, the decrease of low temperature, thunderstorm, strong wind, fog, snowfall and tornado days are all statistically significant, and the increase of high temperature and rainstorm days are statistically insignificant in the Yangtze River Delta. Meanwhile, the snowfall, fog, thunderstorm and low temperature had one decreased climatic jump change, but the high temperature and rainstorm days had one increased climatic jump change. Spatially, thunderstorm and strong wind days have decreased significantly in the whole Yangtze River Delta. Low temperature days have decreased significantly in the northern and middle parts, and snowfall days have decreased significantly in the eastern and southern parts of the Yangtze River Delta. High temperature days have increased significantly only in Nantong, Shanghai, Hangzhou Bay area and the eastern parts of Zhejiang. The spatial trend of rainstorm and tornado days is insignificant in the whole region, and the trend of fog days is more local. In the past 52 years, western Pacific subtropical high and northern hemisphere annular mode or arctic oscillation has increased, and polar vortex in northern hemisphere and Eurasian meridional circulation has decreased. The combined action from these atmospheric circulation systems has result in the decrease of strong wind, low temperature and snowfall days and the increase of high temperature days in the Yangtze River Delta. Urbanization and land use change have also resulted in the increase of high temperature days and the decrease of fog and strong wind days to some extent in the Yangtze River Delta.
  • Ts-NDVI Space Structure and Relationship between Structure and Climate Feature
  • YU Min;ZHANG Hongling;ZHANG Guihua
  • 2015 Vol. 34 (1): 183-189.  DOI:10.7522/j.issn.1000-0534.2013.00132
  • Abstract ( ) PDF (2458KB) ( )
  • Ts-NDVI space is a method used extensively to monitor drought, which combines spectral reflectivity and thermal infrared information. The temporary and spatial dependence and instability exist in Ts-NDVI space. Studying the features of Ts-NDVI space's structure and the relationship between the structure and climate feature is necessary to evaluate the Ts-NDVI space's temporary and spatial dependence and instability and to prove the drought monitoring and drought forecast. With the modis data and precipitation of Heilongjiang Province from 2000 to 2008, the study about interannual and seasonal variation of Ts-NDVI space and the relationship between the structural variation and climate characteristics are conducted. The single Ts-NDVI space based on primary satellite data and the composed general Ts-NDVI space based on multi-year satellite data are used in the study. The results show that: Some features are the variation of Ts-NDVI space's intercept and slope of dry and wet edge. The interannual variation ranges of the intercept and slope of dry and wet edge of Ts-NDVI space are all large, while the variation of slope is in the inverse way of the variation of intercept. The slope is to decrease if the intercept increases and vice versa, which is more obvious in wet. The seasonal variation of Ts-NDVI space is very evident and the variations of dry and wet edge are in the same way. The dry and wet edge's intercepts increase from spring to summer and decrease from summer to autumn. The max intercepts of both dry edge and wet edge are all in summer. The variation range of intercept is larger than that of slope. The wet edge is more sensitive to the environment, especially from spring to summer. The precipitation gives more impact on Ts-NDVI space, especially on wet edge. The composed general Ts-NDVI space by multi-year satellite data can reflect the climate feature within the same temporary and spatial scale. The intercept of dry edge can denote the min precipitation, and the intercept of wet edge can denote the max precipitation during the years. The correlation between the wet edge and the max precipitation is more evident.
  • Analysis of a Meiyu-Front Rainstorm Caused by ‘Train Effect'
  • SUN Suqin;ZHEN Jin;ZHI Shulin;XU Aihua;CHEN Yunhui;SHEN Zhijun;YU Aibin
  • 2015 Vol. 34 (1): 190-201.  DOI:10.7522/j.issn.1000-0534.2013.00146
  • Abstract ( ) PDF (17895KB) ( )
  • Using Micaps, Doppler radar data and NCEP reanalysis data, the rainstorm occurred in the north of Jiangxi with the rainfall exceeding the history extreme value on 14 June 2011 was analyzed. Synoptic scale systems、mesoscale systems、microscale systems and their relationship of the rainstorm were also analyzed. It is shown that: The main impact system of this extreme precipitation are the south trough, Mid-level dry air intrusion, the strong low level jet(LLJ), the coupling of high and low level jet stream and the maintenance of the surface convergence line. Due to the low mass center structure、strong vertical development and high efficiency of precipitation strong echo through the same area continuously, the ‘train effect' was occurred in the short-duration rainstorm. Meanwhile, the radar echo which was similar to tropical heavy synoptic scale systems had the characteristic of the backward propagation. There was the characteristic of frontal passage in the speed image, and the speed image with a ‘bull eye' structure shows that there was a low level southwest jet. When the direction of the warm and humid Jet was paralleling to the trend of the ground convergence lines, the ever fount vapor from the Bengal reached the convergence lines along the southwest airflow of the trough, and the convergence lines were stable, maintained and developed. Dry cold air invasion prompted the occurrence of the microscale and mesoscale system in the heavy precipitation. The development of the large wind velocity zone and the convergent region were favorable to the maintenance and development of the microscale and mesoscale convective cells and their sub-vertical circulation, thus the ‘train effect' can be maintained. The activity of organized multi-cell storm, the ground quasi-stationary front and the mesoscale lines which maintained for a long time are the main causes for the formation of ‘train effect'. The precipitation echoes move along with the CAPE center, and the special terrain is also one reason of the ‘train effect'.
  • Research and Analysis of Dry Intrusion during Beijing ‘7·21' Extreme Torrential Rain
  • TANG Pengyu;HE Hongrang;YANG Xiangrong;YAN Yuxiang;WANG Yahua;MIAO Ziqing
  • 2015 Vol. 34 (1): 210-219.  DOI:10.7522/j.issn.1000-0534.2013.00128
  • Abstract ( ) PDF (6107KB) ( )
  • The weather situation and mesoscale systems characteristics of the extreme torrential rain occurred in Beijing on 21 July 2012 was analyzed. With the mesoscale numerical mode WRFV3.2 the extreme heavy precipitation is simulated. And based on the dry intrusion theory, the process of dry cold air activities during the heavy rain and its impact of the torrential rain are analyzed. The results show that: The torrential rain occurred in weather situation of the violent intersection of the southward cold air guided by upper trough and strong southwest warm wet air in North China area. WPSA prevented the upper-level trough from moving eastward and thus the precipitation process in Beijing kept a long time. The convective development process is along with the obvious mesoscale convective complex (MCC) activities, and MCC's ongoing activities and the rainfall centers are temporal and spatial consistent. The WRF model could accurately simulate this torrential rain process. Within 24 h before the precipitation occurs there is constant high potential vorticity and low humidity dry cold air from 35°N near the tropopause being transported along northward and downward path to 39°N near 700 hPa at the lower-level atmosphere in Beijing area. Dry intrusion changed little from 24 h to 10 h before the start of the precipitation, soon afterwards had a slight weakening and weakened rapidly after the precipitation started. The dry intrusion changed atmospheric thermal and dynamic environment of the Beijing area to impact the torrential rain before the precipitation started. Dry intrusion could increase the atmospheric potential instability in rainfall area and reserve CAPE abundant for the development of convection, providing the environment conducive for the occurrence and development of MCC. At the meantime, it increased the low-level cyclonic vorticity which is conducive to low-level air convergence and upward motion and this may be the trigger mechanism of severe convective weather, such as the MCC and its accompanying torrential rain in Beijing area.
  • Decadal Variations of Summer Precipitation in Northeast China and the Associated Circulation
  • DING Ting;CHEN Lijuan;CUI Dahai
  • 2015 Vol. 34 (1): 220-229.  DOI:10.7522/j.issn.1000-0534.2013.00155
  • Abstract ( ) PDF (6522KB) ( )
  • Based on 91 stations monthly data, NCEP/NCAR reanalysis data and sea surface temperature data, the distribution characteristics, decadal variation of precipitation and circulation pattern were analyzed by empirical orthogonal function (EOF) and significant test, and the annual variations in different decades are discussed. It is found that precipitation in Northeast China in summer has large decadal variability. Less precipitation in Northeast China in summer was observed in 1961—1983 (P1), more in 1984—1998(P2), and less in 1999—2012(P3). Compared with P1, cyclone anomaly in Northeast China, anticyclone anomaly in Mongolia, and cyclone anomaly in subtropical northwest Pacific were intensified in P2, and the contribution of easterly water vapor transport from Northwest Pacific was obvious. Compared with P2, Northeast cold vortex was weaker, and anomalous northerly wind on 850 hPa was over the east of Northeast China in P3. Furthermore, the southerly water vapor transport became weaker obviously. Pacific decadal oscillation (PDO) has a modulation effect on the decadal variation of precipitation in Northeast China and the associated circulation. Less precipitation is observed in P1 and P3. In these two periods, PDO are in negative phase, and anticyclone circulations in Northeast China are strong. For wet years in P1, the water vapor transport is mainly from the strong summer southerly wind, while in P3 may from the Northwest Pacific.
  • Prediction of Air Quality in Lanzhou Using Time Series Model and Residual Control Chart
  • WANG Li;ZHAO Yuan;YANG Xianming;MA Jianmin;HUANG Tao;GAO Hong
  • 2015 Vol. 34 (1): 230-236.  DOI:10.7522/j.issn.1000-0534.2013.00150
  • Abstract ( ) PDF (1940KB) ( )
  • The mean monthly air pollution index (API) in Lanzhou from 2003 to 2012 was fitted by time series model SARIMA, and seasonal variation and trend of the API was analyzed. Using combined SARIMA model and residual control chart method, a model has been established to forecast daily API in Lanzhou. This model firstly need to select an appropriate stage as a control state from the fitted API data series from 2003 to 2012 using the time series model ARIMA. In the present study, we selected the months from June 2012 to February 2013 as the control state to establish control limits based on the ARIMA (1, 1, 1) fitting for 2003—2012 API data. The model then employed a residual control chart method to forecast and monitor the average daily API in Lanzhou in March 2013. Results indicate that SARIMA (0, 1, 1)×(0, 1, 1)12 model yielded a better-fit to API in Lanzhou City, showing higher air pollution in winter and spring and relatively mild pollution during summer and autumn. Overall both modeled and monitored data revealed the improvement of air quality in Lanzhou for the last decade. Residual control charts model for March 2013 API established in this study predicted that API on 6, 9, 10, 11, 12, 13 exceeded the control limits, and issued a warning on API in 6 and 9 March, respectively. The model forecasting results are consistent with the monitored results, confirming the usefulness and reliability of the model using combined time series model and residual control chart.
  • Forecast Model Establishment of Air Negative Oxygenion in Yuxi
  • WANG Bao;XIE Fuyan;ZHANG Zixiang;LIU Chunxue
  • 2015 Vol. 34 (1): 251-257.  DOI:10.7522/j.issn.1000-0534.2014.00131
  • Abstract ( ) PDF (2003KB) ( )
  • First, the main meteorological factors imfluencing air negative oxygen ion concentration and the relationship between impact factors and air negative oxygenion concentration was analysed using in-site negative oxygenions concentration observations from 14 automatic measuring system and synchronous meteorological elements observations, and using correlation analysis, regression analysis method. Then oxygen ions concentration forecasting model is established. The results show that: There was no significant correlation between air negative oxygenion concentration changes and seasonal changes of meteorological factors in Yuxi, the main meteorological factors influencing diurnal variations of air negative oxygenion Yuxi are relative humidity and air temperature. When the air temperature is less than 20.4℃, the negative oxygenion concentration diurnal variation with air temperature was negatively correlated. However, when the air humidity is greater than 45.6%, negative oxygenion concentration with air humidity was positively correlated. Based on the research results, the negative oxygenion concentration prediction model was established. The forecast effect is better and through statistics test and it could be useful for the operational service.
  • Monitoring Application of Hailstorm Event with the Observation of Wind Profile Radar and Ground-Based Microwave Radiometer
  • HUANG Zhiyong;ZHOU Zhimin;XU Guirong;ZHANG Wengang;WANG Yu
  • 2015 Vol. 34 (1): 269-278.  DOI:10.7522/j.issn.1000-0534.2013.00130
  • Abstract ( ) PDF (7046KB) ( )
  • The evolution characteristics of hail potential conditions, such as mesoscale weather system, wind shear, water vapor, vertical velocity and unstable stratification at Xianning City in Hubei Province on 12 April 2010 were analyzed with wind profiler radar data and ground-based microwave radiometer that were applied to monitoring of hail fall process. Results show that: (1) The hail-fall process initiated during the process of low trough moving eastwardly and cold air moving southwardly. The mesoscale weather system such as southwest jet at middle and low levels, the shear line on 850 hPa, moist tongue and cold front at the ground afforded dynamic, thermal and water vapor conditions. The deep vertical wind shear from 0 to 6 km and the zero elevation at 3.5 km afforded circumstance condition for hail fall.(2)The passage of the low trough between 850 hPa and 700 hPa is about 0.5 hour earlier than hail-fall process. And the influence of the cold front near the ground was 2 hours earlier than low trough on 850 hPa. And the temperature advection between 1400 m to 5000 m changed from positive to zero, then to negative. The warm and wet flow followed air of higher temperature and greater humidity. Cold advection at middle level was beneficial to the development of convectively un-stability. (3) The fluctuation of vertical velocity increased with the height from 0 to 4 km 0.5 hour earlier of hail fall process. The maximum vertical velocity difference could reach 11 m·s-1. It shows that the thermal and dynamical structure in the atmosphere were very different at different level at the convective storm. (4) There existed deep wind shear at the vertical direction all the time from 0 km to 6 km before hail fall. And it was positive and stable calculated every 200 m. At the same time, the maximum appeared about 1.5 hour earlier which was significant to the monitoring and prediction of hail-fall. (5) The relative humidity was less and drier between 5 km to 10 km while it was greater and wetter between 0 km to 5 km before the hail-fall process. It showed three-layer distribution of "wet at high and low levels, dry at middle level". ILW and IWV increased rapidly from 4 mm to about 15 mm and from 40 mm to more than 60 mm respectively. When ILW and IWV reached maximum, the hail-fall initiated. (6) The K index exceeded 35℃ about 6 hours earlier than hail-fall process. The averaged value of CAPE was about 627 J·kg-1 before hail-fall process. Heights of 0℃, -10℃ and -20℃ were at 5 km, 6 km, 7.5 km respectively. The indexes evolution could show the unstability of atmospheric stratification to some extent.
  • Intercomparison of Vertical Wind Profiles Retrieved Using Two Techniques from Doppler Weather Radar
  • XIAO Yanjiao;WAN Yufa;WU Tao;WANG Jue
  • 2015 Vol. 34 (1): 288-297.  DOI:10.7522/j.issn.1000-0534.2013.00136
  • Abstract ( ) PDF (4346KB) ( )
  • The vertical wind profile product from Doppler weather radar has important role for the weather analysis. This paper retrieved vertical wind profiles using three different layered VVP algorithms with an increasing level of complexity (VVP1, VVP2 and VVP3). Radiosonde data, radar volume scan data and vertical wind profile product data retrieved using PUP-VAD algorithmfrom CINRAD-SA were collected, which were measured during Yangjiang 8th international radiosondeintercomparisontest sponsored by WMO from 12 July to 1 August 2010. Take soundingwind as reference, the mean-square deviation and correlation coefficient of wind directions/speeds between sounding wind and retrieved wind were calculated. Take the mean-square deviation and correlation coefficient as evaluation factors, the vertical wind profiles retrieved using layered VVP and PUP-VAD algorithms were intercomparedin two different conditions of relatively uniform and uneven precipitation echo distribution around radar. Results show that, in the two cases, the layered VVP retrieval algorithm provides vertical wind profiles with a higher availability and a better quality than the PUP-VAD algorithm, especially in the case of uneven precipitation echo distribution around radar. Compared to analyze the causes, at a certain height layer, in contrast to a PUP-VAD retrieval, where only those data from a range circle is used, all available scan data in the height layer within 10~100 km range is processed using a multi-dimensional linear regression. The impact of the data coverage ratio on layered VVP retrieval is less than that on PUP-VAD retrieval.

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