Plateau Meteorology

Current Issue

28 June 2012, Volume 31 Issue 3   

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  • Numerical Simulation of Land Surface Process at Different Underlying Surfaces in Tibetan Plateau
  • LI Yan;LIU Xin;LI Wei-Ping
  • 2012 Vol. 31 (3): 581-591. 
  • Abstract ( ) PDF (1440KB) ( )
  • The simulations of  typical land surface processes at three stations in the Tibetan Plateau are evaluated using Common Land Model (CoLM). The three observation stations are affiliated to the Institute of Tibetan Plateau Research, Chinese Academy of Sciences: Southeast Tibet station, Namco station and Qomolangma station. The offline validation experiments were conducted with the observation data from 2007 to 2008. Default soil porosity and hydraulic conductivity of saturated soil in CoLM are adjusted according to the analyzed  soil samples from Southeast Tibet station and Namco station. Vertical soil layering scheme in CoLM is also adjusted to a shallower height according to the soil samples. The results indicate that after the adjustment of soil layer scheme in CoLM, the model can simulate the soil moisture distribution at three stations more reasonably. The average deviation of the simulated soil moisture decrease 0\^014 or even more. However, there are still biases comparing with the observation: The simulated soil moisture is less than the observed at Southeast Tibet station, but more at Namco  and Qomolangma stations. As to simulations of soil temperature, net surface radiation, surface sensible and latent heat flux, the bias is reduced after the adjustment of soil layer scheme, especially the simulation of surface latent heat flux.
  • Statistical Analysis on Influence of Qinghai-Xizang Plateau Vortex Activity on Precipitation in China
  • YU Shu-Hua;GAO Wen-Liang;PENG Jun
  • 2012 Vol. 31 (3): 592-604. 
  • Abstract ( ) PDF (999KB) ( )
  • Based on the daily synoptic maps at 08:00 and 20:00 on 500 hPa from 1998 to 2004,  the yearbook Qinghai-Xizang Plateau vortex, the activities of the plateau vortex in the winter half-year and the summer half-year, and the different life time of the plateau vortex influences on the rainfall in China and Sichuan basin are analyzed with the statistical-synoptic method. The results show that the eastern vortices appear in the most time during the summer half-year and the winter half-year. From June to October, one third of the vortices can move out of the plateau. The number of the plateau vortiex reduces in the winter half-year (about 1/5 of the whole year vertices). However, those vortices in the winter half-year can cause the rain and snow weathers in Qinghai-Xizang Plateau and its neighboring regions. Especially, about half of the plateau vortices, which last for more than 36 h, move out of the Plateau and cause the snowstorm in the Qinghai-Xizang Plateau, the moderate rainfall in Sichuan Basin and  snowstorm or heavy rain in Yunnan Province at the same time. Longer life time the Plateau vortices have in summer half-year, larger scope and intensity of precipitation in the Plateau and neighboring regions happen. The plateau vortices, which last for more than 60 h, can cause the heavy rain   in the Qinghai-Xizang Plateau, the moderate rainfall in Gansu Province, the heavy rain or rain storm in Sichuan Province, and the half of heavy rainfall in Yunnan Province. Such vortices can even cause from moderate to heavy  rain in the central and eastern China, one to five times per year. The plateau vortices, which move to the east of 100°E, can cause the moderate rain in Sichuan Basin. These vortices moving tracks influence to the rainfalls in Sichuan Basin are mostly the eastern direction. However, those in the southeast direction normally have much influence on the rainfall in Sichuan Basin.
  • Distribution and Change Feature of Intense Precipitation in the West Part of Northwestern China during Summer Half Years
  • LUAN Chen;SONG Min-Hong;CAI Ying;QIAN Zheng-An
  • 2012 Vol. 31 (3): 629-637. 
  • Abstract ( ) PDF (1115KB) ( )
  • Utilizing the daily precipitation data of 104 stations in the west part of Northwestern China(W-NWC) from May to October during 1961 to 2007,  the temporal and spatial distribution and change tendency of intense rainfall during summer half year of nearly 47 years are analyzed. The results show that: (1) Intense rainfall frequency is more in the east of W-NWC than that in the west. The most intense rainfall days occurs in the east of Qinghai plateau which belongs to sub-humid areas, and the second one occurs in Tianshan Mountains and Qilian Mountains which belongs to semiarid region, and it rarely occurs and even has never occurred in the arid and extreme arid regions including the edge of South and North Xinjiang Basin and the west of Qaidam Basin. （2） It seems to be easier for maximum precipitation to appear in the west of W-NWC where is more arid than Qinghai Plateau, especially in Balguntay, Urumqi, Akqi, Charkhlik and Alxa Left Banner. (3) The earliest date  occurred intense rainfall day  presents that it is earlier in the east of W-NWC and the west and later in the middle, while the latest one is opposite. (4) Intense rainfall frequency in this region (especially Tianshan Mountains) has a growing trend, but increasing intensity is not obvious.
  • Study on Division of Precipitation in Northern China
  • LIU Yang;WEI Zhi-Gang;LI Zhen-Chao;LIU Hui
  • 2012 Vol. 31 (3): 638-645. 
  • Abstract ( ) PDF (881KB) ( )
  • The study of division, according to the annual and interannual variations, is separately carried out by using the cluster analysis and REOF analysis methods based on the monthly precipitation data at243 stations in  Northern China during 1958-2009. According to the correspondence of changes of monthly precipitation, Northern China can be divided into seven regions.The study result shows that except for a few stations where there are two peaks of precipitation within one year, the characteristics of annual precipitation around the most areasof  Northern China are similar, which precipitation in summer is much more than that in other seasons. With the same methods, the four-level divisionsof annual precipitation are obtained: 2, 4, 9 and 12 regions. In recent 52 years, the precipitation trend appeared downward in the eastern and central part of  Northern China, while it increased in the westone. The division pattern of annual precipitation experienced a change in the 1980′s. From 1960′s to 1970′s, there are three regions. The east region and the west are more likely, distinguished from the central region. However, there weretwo regions since 1980′s, which represented the remarkable differences between the east region and the west.
  • Simulation Study on the Spatial and Temporal Distributions and Emission Flux of Dust Aerosol over East Asia in the Latest Decade
  • SU Xing-Tao;WANG Han-Jie
  • 2012 Vol. 31 (3): 676-687. 
  • Abstract ( ) PDF (1490KB) ( )
  • A regional climate model RegCM3 coupled with an on-line sandy dust module is used to simulate the dust aerosol (smaller than 20 μm in diameter) over East Asia in the latest decade from 2000 to 2009. The model is driven by NCEP re-analysis data. Based on the simulation results, the spatial and temporal distributions of sandy dust aerosol over East Asia are discussed, and the dust emission flux is also calculated. The model capability to simulate sandy dust aerosol is firstly validated. The simulation results show that the model can capture the characteristicsof spatial and temporal distributions of dust aerosol very well over East Asia. There always exist two extremes of dust aerosol optical depth and column burden, one is in the Taklimakan Desert of Xinjiang UygurAutonomous Region, China, and the other is in the Badain Juran Desert of Inner Mongolian Autonomous Region, China. The seasonal variation characteristic is evident, with the maximum value appears in spring, the secondary maximum in winterand the minimum in autumn.To the east of 110°E, the dust is transported eastward from a maximum center at a height of 700 hPa over East Asia. The dust emission sources are mainly located in the Taklimakan Desert, Badain Juran Desert, North Qinghai-Xizang Plateau and Southwest Mongolia. There is also an evident seasonal variation of dust emission flux. The annual mean dust emission flux is 1015.34 mg·m-2·d-1, of which 62.4% and 2.3% are re-deposited onto continentof East Asia through dry and wet deposition process, respectively, and the remaining 35.3% is injected into the atmosphere or subject to long-range transport.
  • Characteristic Analysis of the Severe Dust Event Occurred in Hexi Corridor on April 24, 2010
  • ZHAO Qing-Yun;ZHANG Wu;吕Ping;BI Jian-Rong;DI Xiao-Hong;HUANG Jian-Ping
  • 2012 Vol. 31 (3): 688-696. 
  • Abstract ( ) PDF (1095KB) ( )
  • The features of dust event occurred in the Hexi corridor of Gansu province on April 24, 2010 were analyzed, using the data measured by Total Sky Imager (TSI), routine surface and upper air measurements, numerical weather forecastproducts and NCEP/NCAR reanalysis data. The results show that it only took 2.5 minutes from the bright sky to totally be covered by dust. The northern wind from middle Siberia to north Xinjing with strong polar cool air caused the severe dust storm. Further analyses show that there was a center of westerly between 200 and 250 hPa over this region. The wind speed of the westerly center reached to 40 m·s-1when the duststorm burst up, then the height of the center dropped down and extended. When the gale area extended from the upper level to near surface, the momentum of west wind would be transmitted downward. There were major changes of  north and south wind below 250 hPa, the center of maximum wind speed was on 400 hPa. The duststorm broke when the   frontier of north wind reached to the low level of south wind area. The outbreak of cold air led to the extreme air temperature decrease successivelyfrom near surface to 700 hPa and 500 hPa. The intense development of surface hot low-pressure system resulted in not only the increase of barometricgradient, but also the convective instability in boundary layer. The intensity of duststorm was enhanced by both of these consequences.
  • Model-Experimental Analysis of Variational Assimilation of Dust Concentration with GRAPES Sand-Dust Numerical Forecasting System in a Sand-Dust Storm
  • ZHAO Jian-Hua;LI Yao-Hui;PU Chao-Xia;LIU Shi-Xiang;ZHANG Liang;DUAN Hai-Xia
  • 2012 Vol. 31 (3): 697-705. 
  • Abstract ( ) PDF (1139KB) ( )
  • In order to improve the accuracy rate of dust model, a dust assimilation system named GRAPES_3DVAR_DUST was developed through adding a new control variable (namely, dust concentration) in the three-dimensional variational data assimilation system of regional GRAPES (Global/Regional Assimilation and Prediction System) model which is developed by Chinese scientists by themselves . Three schemes of control experiment, one-time assimilation experiment and intermittent assimilation experiment with observed dust PM10 concentration from 8 sand-dust-monitored stations in North China and background fields provided by a sand-dust model (GRAPES_CUACE/Dust system) are performed to test the assimilation influence on dust-concentration forecast through modeling a sand-dust storm occurring from February 29 to March 1,  2008. The sensitivity test results show: (1) comparing with the satellite-monitoring image, the modeled spatial distributions of surface dust concentration of one-time assimilation experiment and intermittent assimilation experiment are more precise than those from control experiment which has no data assimilation, while the result of intermittent assimilation experiment is the most precise; (2) one-time assimilation experiment fails to grasp the continual evolutions of PM10 concentration of the majority of single station as well as control experiment; (3) the results of intermittent assimilation experiment capture the main features of continual evolutions of  PM10 concentration at the single station; (4) to some degree, the effect of intermittent assimilation experiment is better than that of one-time assimilation experiment. In a total, GRAPES_3DVAR_DUST system is able to improve the dust prediction of dust model.
  • Relationship between Eurasian Snow Cover and Late-Spring and Early-Summer Rainfall in China in 2010
  • XU Li-Yan;WU Bing-Yi
  • 2012 Vol. 31 (3): 706-714. 
  • Abstract ( ) PDF (1483KB) ( )
  • The relationship between Eurasiansnow cover anomalies from Februaryto Apriland rainfall from May to June of 2010 in China has been investigated  using SVD analysis and numerical experiment, based on the datasets of snow cover days from NOAA, precipitation data at 160 stations and atmospheric circulation variation from the NCEP/NCAR reanalysis data in the period of 1973-2010. The secondSVD mode properly represents the time and space characteristics of snow cover and rainfall in 2010：  Excessivesnow cover in Europe, eastern TibetanPlateau and East Asia tend to be associated with increased precipitation in South China and decreased precipitation in Central China. Snow cover in western and eastern Eurasiais positively correlated with succeeding precipitation in South China. Based on the statistical linkage, the impact of anomalous snow pattern on rainfall in South China is simulated  using CAM3.1 model. Theresult consists with the statistical fact. The physical mechanism between snow cover and rainfall is due to the albedo and hydrology action of snow cover, changing the thermal condition, which can modify the atmosphericgeneral circulation and result in the abnormal rainfall of South China. Eurasiansnow cover anomaly may be a major factor which forces late-spring and early-summer rainstorm in South China in 2010.
  • Percentile Statistical Downscaling Method and Its Application in the Correction of GCMs Daily Precipitation in China
  • LIU Lu-Liu;REN Guo-Yu
  • 2012 Vol. 31 (3): 715-722. 
  • Abstract ( ) PDF (1010KB) ( )
  • The bias of simulated rainfall by GCMs is corrected using daily percentile scaling method. This method relates each percentile of GCMs daily rainfall to the observed ‘natural’ rainfall of the same percentile. Using this relationship, the projected daily rainfall by GCMs for future climate periods is converted to the ‘natural’ rainfall in the same periods. It is shown that twelve percentiles is optimal in the terms of bias magnitude and time consuming compared with other four schemes. By analyzing multi-year averaged annual, monthly rainfall and their temporal tendency, and the probability distribution of daily rainfall for observational, simulated and corrected data, the following conclusions are drawn: (1) The bias of simulated rainfall by GCMs can be reduced in some degree over China, especially over the south of the Yangtze River, central China and parts of Northeast China. The most significant reduction of the biases among the three GCMs analyzed is for MPI-EHCAM5. (2) The difference of seasonal cycle pattern between observational and corrected data is smaller than that between observational and simulated data, and this is the case for MPI-ECHAM5 in all of the basins. (3) More corrected data series than the simulated data series have the same trends with observations in some basins. (4) The biases are reduced significantly in most basins when daily rainfall is less than 30 mm. However, the biases become positive from negative in some basins when daily rainfall is greater than 30 mm. If more accurate projections of precipitation change and its impact on water resources are expected, as many models as possible should be used due to the uncertainties and limitations of GCMs simulations and downscaling.
  • Analysis on Climatic Disaster in Winter in Middle and High Latitude Regions of Northern Hemisphere
  • FANG Hai-Yi;YANG Shu-Yun
  • 2012 Vol. 31 (3): 723-730. 
  • Abstract ( ) PDF (1368KB) ( )
  • The large-scale disastrous frozen weather caused by heavy rain and snow in the winter from 2007 to 2008 was diagnosed and analyzed. The relationship between the blocking high and the disastrous weather was mainly discussed. According to the influence of the transmission and development of Rossby wave on the blocking high,  the appearing reason of the blocking high and its function in the weather process were analyzed. The results indicate that a little current of cold air go down south common action of Ural  and Okhotsk Sea blocking highs,  and cause a widespread drop of temperature and lasting snow when the southern cold air meet with  warm airflow  from Subtropical High in the Western Pacific. Blocking high collapseswith the transportation of cold air stream,  a new blocking high locatesto the west of blocking high with the transportation of warm advection. Moreover,  the blocking high in North America leads to the snowstorm in most region of America and eastern part of Canada in the end of 2007 as well. The propagation and evolution of Rossby wave promote the formation of blocking high, and polar vortex also causessnow and blizzard in these areas. The restructure of the blocking high (collapses and reconstruct) leads to the onset of  strong cold air.
  • Comparative Analysis on MCC and Cloud Clusters of General Rainstorm during ‘0811’ Rainstorm Process
  • MIAO Ai-Mei;DONG Chun-Qing;ZHANG Hong-Yu;SHEN Li-Wen;LI Miao
  • 2012 Vol. 31 (3): 731-744. 
  • Abstract ( ) PDF (2222KB) ( )
  • The mesoscale convective complex(MCC) in the south of Shanxi and the rainstorm cloud clusters in the north of Shanxi on August 11, 2010 are comparatively analyzed by using T639 1°×1° reanalysis data, FY-2 infrared satellite image and infrared black body temperature (TBB) data, lightning data and total column water vapor data. Itdemonstrate that rainstorm area in the north of Shanxi was causedby the generation, development, merger of 6 meso-β-scale convective cloud clusters, and the south regional rainstorm happened with the generation, development and eastward movement of the mesoscale convective complex (MCC). The analyzed results indicate that: (1) The northern rainstromcloud cluster developedin the south of warm shear line on 850 hPa, and mergednear by shear lineon surface. At the same time, the southern MCC was merged by 3 meso-β-scale convective cloud clusters, which developed on the weather-scale shear lineon 700 hPa. In the process of MCC development and maturity stage, meso-α-scale convective cloud clusters moved east along the warm shear lineon 925 hPa, and intheprocess of MCC weakening, meso-α-scale convective cloud clusters moved south with the southward movementof subtropical high belt. (2) With the northwestward advance of the subtropical high during thesame rainstorm, MCC developed in the weak baroclinic environment of the 5 880 gpm region, and in the anticyclone north of high onupper levels; rainstorm cloud clusters tended to develop in the strong baroclinic environment of  5 840 gpm region, and in the the right of the upper jet stream entrance area. (3) As a large scale mesoscale convective system, MCC required more energy of high temperature and high humidity than general rainstorm cloud clustersinlower levers, and deeper vertical structure of high humidity, high energy tongue and high temperature. (4) The negative cloud-to-ground lightning appeared in the area which was influenced by the southern MCC and near the 5 880 gpm region; the positive cloud-to-ground lightning appeared in the area which was influenced by the northern rainstromcloud clusters and near the 5 840 gpm region. The time of the begin of lightning and the appearanceof the lightning peak was more earlierthan the time of rainfall and the appearance of the rain intensity peak in the backgroud of general rainstorm cloud clusters, comparing with the banckground of MCC. (5) The northern rainstorm cloud clusters developed in the area of high gradient of vertically integrated water content and on the front of water vapor; the southern MCC developed in the area of high value of total column water vapor, thesouth of the water vapor front. There is  ahead 36 h  to exactly forecast  the total column water vapor data of the rainstorm process on August 11, which showsa significant indication to rainstorm area.
  • Analysis on Variation of Precipitation in May in Ningxia and Its Response to Prior SST
  • CHEN Hai-Bo;YANG Jian-Ling;YAN Hua-Sheng;DAN Xin-Lan;XIA Yong-Sheng
  • 2012 Vol. 31 (3): 752-759. 
  • Abstract ( ) PDF (1097KB) ( )
  • Based on the global monthly mean sea surface temperature(SST) and wind field from NCEP/NCAR reanalysis data and  precipitationdata in May at 19 meteorological stations  in   Ningxia, the relations of prior SST with precipitation in May and key affecting area of prior SST on precipitation were studied using the Empirical Orthogonal Function（EOF）, related survey and departure syntheticmethod. The results indicated that the variance contribution of EOF1 of precipitation in May was close to 75%, while the variation trend of time coefficient appeared convex type. There was significant correlationbetween prior monthlymean SST with precipitation in May in Ningxia. There were some significant positive correlation regions in the equatorialEast Pacific Ocean, the equatorial Indian Ocean and the mid-Atlantic. The area of significant negative correlation was small. The amount of grid points passed the confident level of 90% was maximum in February, but minimum in April. The SST anomaly synthesis was contrary in  more and less precipitation  years in May. The  positive and negativedeparture centres were no  differencewhich was similar to the related area. The positive correlation was corresponding to the  positive departure centre in more precipitation year and the negative correlation was corresponding to the negative departure centre; and on the contrary in less precipitation year, there is well inconsistent.
  • Analyses on Spatial-Temporal Differentiations of Air Temperature in Gansu Province during 1979-2008
  • MA Zhong-Hua;ZHANG Bo;ZHANG Jian-Xiang;WANG Xing-Mei
  • 2012 Vol. 31 (3): 760-767. 
  • Abstract ( ) PDF (944KB) ( )
  • Based on the ArcGIS Analyst platform, the ten-day mean air temperature in Gansu Province during 1979-2008 is analyzed by the CoKriging method with spatial interpolation, and 1 km×1 km surface data of  ten-day mean air temperature are obtained. The results show that the averages of mean error, root mean square error, mean standard deviation, standardized mean error and root mean square standard deviation are -0.00046, 1.998, 1.809, 0.0035 and 1.087 ℃, respectively. According to the characteristic of spatial-temporal differentiations of ten-day, monthly and annual mean air temperatures, it is found that there is lesser differentiation in the Southeast, and larger in other region in space. The trend of ten-day mean air temperature has been steadily dropping in the periods of the 23th-24th, the  24th-26th,  the 25th-27th, the  33th-35th and the  34th-36th, in contrast, it has a steadily decreasing trend in the periods of  the 4th-6th, the  5th-7th, the  6th-8th, the  7th-9th and the  8th-10th. Moreover, the monthly mean air temperature appears slight descendent trend in July and slight ascendent trends in March, May and October. The annual mean air temperature in Gansu Province in 1979-2008 is 8.05 ℃. The minimun temperature of 3-year running mean in 1983-1985 is  7\^13 ℃ and the maximum temperature, 8.82 ℃,  which has obviously ascendent trend.
  • Multi-Scale Physical Statistic Prediction Model for Rain Season Onset Date in Guangdong Province
  • GU De-Jun;GAO Xiao-Rong;JI Zhong-Ping;LI Qiong
  • 2012 Vol. 31 (3): 768-776. 
  • Abstract ( ) PDF (1139KB) ( )
  • In order to do better short-term climate prediction for the rain season onset date (RSOD) in Guangdong Province in each year, the multi-scale optimal subset regression prediction model for RSOD have already developed and tested through its multi-scale variation characteristics and relationship with the antecedent SST and 500 hPa height in different time scales  using the wavelet transform, Lanczos filter, correlation analysis, optimal subset regression and cross-validation. The results show that the RSOD in Guangdong Provincehas significant early trend, and exhibits interdecadal variation with 17.1-year period and interannual variation with 6.2-year period (after detrending). There are twenty regions with significant correlation between RSOD and SST and 500 hPa heightfield in interannual and interdecadal time scales. The prediction models for interannual and interdecadal time scales are respectively constructed by optimal subset regression of RSOD in corresponding time scale with predictors defined by the mean of significant correlation region. The addition of interannual predictive value and interdecadal one is RSOD prediction. The model produces good regression effect. The percentage of hits of difference less than 5 days between regression and observation is 41.5%, and that less than 10 days  is 60.4%. The result of cross-validation analysis shows that the correlation coefficient between prediction and observation of RSOD is 0\^33, which has passed the confident level of 99%. The percentage of hits of predictive error less than 5 days is 26.7%, and that less than 10 days is 45%. So the predictive model of multi-scales optimal subset regression has good predictive ability for RSOD in Guangdong Province.
  • Characteristics of Upper Energy Transport and Coupling of Meteorology Elements on Upper and Lower Levels during Rainstorm Process in Meiyu Season of Jiangsu
  • LIU Mei;ZHANG Bei;YU Jian-Wei;HU Luo-Lin;GAO 苹
  • 2012 Vol. 31 (3): 777-787. 
  • Abstract ( ) PDF (1738KB) ( )
  • Focusing on fifteen regional rainstorm events during the flood seasons of 2003-2005 in Jiangsu in which South Asia High moved northward and extended eastward, the transportation spectrum of angular momentum in 30°-40°N was calculated the relation between upper-level energy changes and rainstorm in Jiangsu Province and  was macroscopically analyzed. The upper- and lower-level structure and physical quantity quantitative  forecast points in Jiangsu were diagnosed and analyzed, through calculating mean field, flow fields of rainstorm  in different regions and different physical quantities by closely studying 17 rainstorm and non-rainstorm processes in Jiangsu during June and July of 2006-2009. The results show that the angular momentum transport has the close relation with  rainstorm  in Jiangsu, and the upper-level  jets, the  position of South Asia High and lower-level southwest jet to the rainstorm  and non-rainstorm  occurring and its rainfull area have obvious forecast effect, which helps to establish conceptual models of rainstorms in different regions, and  the physical quantity coupling  between rainstorms and non-rainstorm  has obvious differences. When the upper divergence value is above (1~2)×10-5s-1, and lower vorticity is above 3×10-5s-1 and ascending velocity is above (3~4)×10-3hPa·s-1, the probability of occurring rainstorm is the characteristics of high  energy transportation, conceptual model and physical quantity  provide the new forecast points and quantitative reference for the accurate forecast of rainstorm  in Meiyu  season of Jiangsu.
  • Dynamic and Thermal Analyses on an Rapidly Developing Extratropical Cyclone after Entering Sea
  • ZHU Ying-Li;ZHOU Shu-Ling;LIN Qu-Feng;WU Zeng-Mao
  • 2012 Vol. 31 (3): 788-797. 
  • Abstract ( ) PDF (1413KB) ( )
  • An extratropical cyclone which rapidly developed in the Yellow Sea and Bohai Sea on 3-5 March 2007 is diagnostically analyzed by the extended Zwack-Okossi equation. Results show that latent heat release and horizontalwarm-air advection are main forcing terms at the early developing stage, and latent heat release is mostly responsiblefor thealmost explosive development of thecyclone, while horizontalabsolute vorticity advection become the main forcing term at the late developing stage. Cold-air advection which is the dominant weakening term during the weakening stage of the cyclone and adiabatic cooling act as weakening the cyclone during the whole period. The surface sensible and latent heat fluxes contributed little to the development of the cyclone, with the negative contribution in Yellow Sea and Bohai Sea and the positive contribution in Japan Sea. The  surface moist flux played more important role than the surface sensible and latent heat fluxes do in the development of cyclone. Changbai Mountain and Korean Mountain also are favorable for the development of cyclone by intensifying the precipitation and the latent heat. The cyclone resulted in a storm surge in Bohai Sea, so  the gale in Bohai Sea by kinetic energy equation is   analyzed. The results show that the increase of kinetic energy in Bohai Sea resulted from horizontal kinetic energy advection before 20:00 on 4 March 2007, with smaller contributions from available potential energy exchange and downward momentum transport. After 20:00,  the kinetic energy in Bohai Sea was supplied by available potential energy exchange and downward momentum transport. The contribution of downward momentum transportwas equal to that of available potential energy exchange, and sometimeslarger than that of available potential energy exchange.
  • Monthly Mean Temperature from February to March in Aksu River Basin on Southern Slope of Tianshan Mountain Recorded by Tree Ring
  • ZHANG Rui-Bo;YUAN Yu-Jiang;WEI Wen-Shou;YU Shu-Long;ZHANG Tong-Wen
  • 2012 Vol. 31 (3): 804-809. 
  • Abstract ( ) PDF (627KB) ( )
  • The tree ring samples of Schrenk Spruce(Picea Schrenkiana Fisch.et Mey) collected from six sites in Aksu River Basin and standard dendrochronological method on southern slope of Tianshan Mountain in 2005 are used to study six tree ring width chronologies. The mean temperatureseries  from February to March in recent  378 years can be reconstructed by using the tree-ring standardized chronologies. The reconstructed period is of obvious tree physiology, and the obtained result is reliable through the verification in many ways. The reconstructed temperature series showed the quasi-periods of  3.6, 42 and 50.4 years and theabrupt change in 1719 and 1827. The reconstructed temperature series have nine warm and nine cold stages,  the coldest stage is in 1911-1922, which is lower than average 1 ℃ or more, and the warmest stage is in 1640-1651, which is higher than the average 1 ℃. The temperature continuously decrease from the early 20thcentury to 1915, the mean temperaturemaintain at the lowest level in 1915-1921, the temperature value is -3 ℃ in 1916, it is the lowest year over the past 378 years. After 1921 years, the temperature slowly rise until the late 1930s, it drop slowly again from 1940s to 1970s. The mean temperature from February to March rapidly increase  in Aksu River Basin,southern slope of Tianshan Mountain from middle-late 1970s to now.
  • Numerical Simulation of Difference of Electric Structure and Discharge of Cloud Flash for Two Severe Thunderstorm Cases
  • ZHOU Zhi-Min;GUO Xue-Liang;CUI Chun-Guang;LI Xing-Yu;FU Dan-Hong;ZHAO Yu-Chun
  • 2012 Vol. 31 (3): 810-824. 
  • Abstract ( ) PDF (1800KB) ( )
  • The electric structure and discharge of cloud flash between two severe thunderstorm cases (one is with hail shooting process and the other is without hail shooting process, expressed by H case and NH case, respectively) in Changchun city, Jilin Provence was simulated and comparatively analyzedby a three-dimensional hail-category cloud model coupled with electrification process. Results show that the electric structures of the two cases caused by the weak updraft at the initial stage of severe thunderstorm are similar and both have  a weak positive-pole distribution. With the development of thunderstorm, the difference of the electric structure occurs.Stronger updraft and wind shear in H case make super-cooled water and ice phase particle be carried to higher level in different regions in where the ice phase particle grow, which produces several content center of ice phase particle so that the non-inductive processes at different regions with different environmentparameters and sign of charge in ice phase particles occur and several charge centers develop. And the charge is apt to show a multi-layered distribution.  The different distributions of charge at differentstages  could be initiated at both updraft zones and  divergence zone.With relatively weaker updraft and wind shear, the distribution of the ice phase particle in NH case is more regular, so is the non-inductive process. And the distribution of charge is well-distributed and more regular at different stages. Therefore, the position where lightning flashe might  is similar to some extent.
  • Numerical Simulation Study on Hail Formation Mechanism and Structure of a Strong Supercell Convective Storm
  • CHENG Xiang-Kun;YANG Hui-Ling;LI Hong-Bin;XIAO Hui;CAI Dong-Mei
  • 2012 Vol. 31 (3): 836-846. 
  • Abstract ( ) PDF (1888KB) ( )

  • Abstract: The circulation situation and vertical air flow structure of a strong convective storm  in Dalian on 15 June， 2010 was analyzed using the sounding data from GTS1 digital radiosonde, conventional observation data, and NCEP/NCAR 1°×1° reanalysis data. And the strong convective storm is simulated by the fully elastic three-dimensional convective storm model (IAP-CSM3D) that developed by the Institute of Atmospheric Physics (IAP), the Chinese Academy of Sciences. The initial field of the model is the observational data, combining the observational data by the Doppler weather radar, the distribution and evolution of macro-physical as well as micro-physical variations such as wind field structure, radar echo structure, overhang echo, bound weak echo region, strong echo wall and water content, et al. in the hailstone are analyzed. Some typical features of supercell structure are revealed on the basis of the analysis. The formation mechanism of hailstone in the storm was analyzed too. The results show that the auto-conversion of frozen drops is the main source of the hailstone in the strong convective storm process. Hailstones mainly depend on the processes of collecting supercooled water (CLch, CLrh) to grow. The process of hail particles collecting with graupel and snowflake is relatively stronger, while the growth process of hail particles collected with ice crystal is very small.

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