ISSN 1000-0526
CN 11-2282/P

Volume 34,Issue 4,2008 Table of Contents

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  • 1  Largescale Features of the MeiYu Front Associated with Heavy Rainfall in 2007
    Tao Shiyan Wei Jie Zhang Xiaoling
    2008, 34(4):3-15. DOI: 10.7519/j.issn.1000-0526.2008.04.001
    [Abstract](721) [HTML](64) [PDF 7.05 M](954)
    The large scale features of the MeiYu front assoc iated with heavy rainfall along the Pearl River valley in South China, the Yangt ze River valley and the Huai River valley in 2007 are discussed. During the peri od 116 June, the MeiYu front extended along Pearl River valley with intense rainfall. In th e middle of June with the first westward extension of the subtropical anticyclone in the West Pacific, the MeiYu front jumped to the Yangtze River where it las ted for nine days. With the second westward extension of the subtropical anticycl one in the end of June, the MeiYu front jumped to the Huai River valley, where it lasted for two weeks and brought about severe floods with great damages. The dynamical and thermodynamic characteristics of the MeiYufront in the three valleys are compared. It is found that the dynamical and the rmodynamic structures are all the same and we suggest to use the same “MeiYu front” for the three valleys.  During middle of July there was a disastrous flood in the Huai river valley. The mechanism of the torrential rainf all that brings about the severe flood is discussed in the second part. It is fo und that with the intense develo pment of ridge and trough system along the subtropical jet stream in North China , there was an intense development of a deep trough along 110°E, which induced th e development cyclonegenesis and frontgenesis in the MeiYu frontal zone fr om 1000400hPa. With the development of the cyclonegenesis and frontgenesi s along the MeiYu front, there was rapid upward motion along the front zone ca using intense rainfall along the MeiYu front.
    2  Analysis about Extreme Weather Events and Their Endangerment of City in 2007
    Wang Weiguo Wang Xiurong
    2008, 34(4):16-21. DOI: 10.7519/j.issn.1000-0526.2008.04.002
    [Abstract](506) [HTML](1267) [PDF 418.97 K](1019)
    By analyzing the extreme weather events occurred in main cities of Chi na in 2007, and comparing with the developing process of city building, it is e xpatiated that the threaten of meteorological disasters to the safe running of c ity is more and more serious. Now some violent weather phenomena often occurred and capability of enduring disasters of big cities is weaker and weaker becaus e the extreme rainfall events are increasing day by day. The developing speed o f city and the population density in big cities are high, which leads to socal led “cityhot islanddomino effect" more obvious than before. The scientific q uestions to be solved in analyzing the factors and results of disasters are present ed, such as building layout of city and response management system for urgent w eather event. Meanwhile, the suggestion for makingdecision about how to preven t and reduce disasters in big city is brought forward.
    3  Synoptic Analysis and Numerical Simulation of  Area Snowstorms in Northeast China
    Bai Renhai Zhang Zhixiu Gao Yuzhong
    2008, 34(4):22-29. DOI: 10.7519/j.issn.1000-0526.2008.04.003
    [Abstract](659) [HTML](73) [PDF 3.67 M](912)
    The area snowstorm is a major severe weather in northeast China because it possi bly causes enormous losses. There are two area snowstorms in northeast China dur ing February 14-15 and March 4-6 of 2007. Their precipitation intensity and rang e are all greater than the historical records. By using basic data of precipitat ion, T213, surface and radiosonde observations, the synoptic situation of the tw o area snowstorms are analyzed. In addition, with the new generation numerical predi ction model GRAPES (Global/Regional Assimilation and Prediction Enhanced System) , the two area snowstorms are numerically simulated, and the results are compare d withthe observational data. The results of analysis and simulation show that t he snowstorm during February 1415 is caused by eastbound trough over Mongolia (Menggu c yclone) and the snowstorm during March 46 is caused by northeastward vortex ov er Southwest China (Jianghuai cyclone) owing to the difference in the strength a nd moving route of cold air mass. In a sense the second is resemblance to a weat her situation of storm rainfall in the summer. In these processes, the major syn optic system not only is simulated by GRAPES model successfully, such as formati on and movement of southwest vortex, but the mesoscale convergence zone or cente r is simulated more precisely than observational analysis. But the simulation va lues of the precipitation are greater than the observations. The numerical resul ts show that GRAPES model has a good ability to simulate area snowstorms in North east China, and is of good reference to the operational forecasting.
    4  Numerical Simulation Study of the Cause of Snowstorm Process in Northeast of China on March 35 of 2007
    Qin Huafeng Jin Ronghua
    2008, 34(4):30-38. DOI: 10.7519/j.issn.1000-0526.2008.04.004
    [Abstract](666) [HTML](94) [PDF 6.19 M](1069)
    Based on the routine observational data and the result of the Mesoscale Model (MM5V3.7) simulation, the cause of snowstorm process in northeast of china in Ma r.35, 2007 was analyzed. The results indicate that vertical shear of upper and lower air and strong ascending caused by upper air divergence and lower air con vergence, as well as the generation and maintenance of midlower air positive v orticity are the dynamical mechanism, and the cold and dry air invasion is the t rigger factor. Profuse water vapor from East Sea and South Sea with northward ai rflow from south at east of cyclone is the important reason of snowstorm.
    5  Mesoscale Characteristics Analysis of Severe Torrential Rain Caused by a Southwestern Low Vortex Process
    Gu Qingyuan Zhou Chunhua Qing Quan Zhang Ju
    2008, 34(4):39-47. DOI: 10.7519/j.issn.1000-0526.2008.04.005
    [Abstract](950) [HTML](71) [PDF 1.61 M](923)
    By using Barnes bandpass filter and mesoscale characteristic analysis method of unbalance dynamical forcing, the activity features of a Southwestern Vortex (SWV) producing severe torrential rain on 9 Sept. 2007 in Sichuan were discussed . The case study not only enables us to know that in SWV there might be a deep m idβ scale vortex with its axes westerly declining but also shows that S WV had a typical vertical structure of heavy rain, namely, it has strong converg ence in the lower level and divergence in the upper, and this kind of structure enhanced till to its top stage before wearing off. During this period, the rain area tended to approach to the center of SWV. In the point of air unbalance and at the early stage of this heavy rain process, the air had been in relatively unbalanced state. This unbalance in lower level became strong er and stronger as time goes, which was favorable for development of the mid β vortex. While heavy rain was at its largest stage, the air had changed from unbalanced state (U<0) into quasibalanced state, U≈0.
    6  Analysis of Hollow Phenomenon about Typhoon Sepat
    Zhang Changan Zheng Xiuzhuan Pan Yating
    2008, 34(4):48-52. DOI: 10.7519/j.issn.1000-0526.2008.04.006
    [Abstract](714) [HTML](72) [PDF 1.10 M](943)
    The hollow phenomenon about Sepat is analyzed in detail. It shows that the press ure after its landing was still much lower. Although theoretically speaking, the magnitude of this pressure is in typhoon level, the structure of typhoon eye w as destroyed, the wind power of central near by was low. The blank of cyclone ce nter in the radar echo chart is not typhoon eye. When Sepat was going to land, t here is no typhoon wall echo of intensively developing convective clouds, and th e structure of Sepat has been not integrated. Taiwan mountain destroys badly the lower structure of tropical cyclone over it, this also leads the appearance of dry tongue simultaneously. In a word, this hollow phenomenon is produced togethe r by the impact of the central mountain in Taiwan, the immixture of dry tongue a nd lower surface sea temperature.
    7  Causality Analysis of the Continuous Heavy Rain in  Eastern Guangdong in June 2007
    Huang Zhong Wu Naigeng Feng Yerong Cai Anan
    2008, 34(4):53-60. DOI: 10.7519/j.issn.1000-0526.2008.04.007
    [Abstract](716) [HTML](56) [PDF 4.73 M](789)
    Abnormal circulation characteristics and causes of the continuously heavy rain i n Eastern Guangdong in June 2007 are studied by using observational data, NCEP G lobal Data Assimilation System data and a linear diagnostic model. The results s how that this continuously heavy rain process is associated with the circulation pattern, i.e., two troughs respectively located over Urals Mts and East Asia an d a ridge located over northern China.The lower level shear line over north ern part of South China contributed to the moisture convergence and rainbe lt maintenance in eastern Guangdong.The lowlevel southwest flow from the Bay o f Bengal interacted with that from the South China Sea constituted the major moi sture channel. Lowlevel positive(negative) vetical helicity (divergence) and h ighlevel negative (positive) vetical helicity(divergence) over eastern Guangdong provided favorable dynamic conditions for development of the convective systems . The numerical diagnostic study results show that the contributions to the asce nding motion in eastern Guangdong are mainly from the forcing processes associat ed with the latent heating, which played the positive and simultaneous feedback role in heavy rain. Moreover, the horizontal transports of westerly momentum and horizontal temperature advection also made some positive contributions to this heavy rain process.
    8  Analysis of Rainstorm Event over Shandong Province During 18-19 July 2007
    Yang Xiaoxia Wang Jianguo Yang Xuebin Sun Jun Yang Chengfang Sheng Chunyan
    2008, 34(4):61-70. DOI: 10.7519/j.issn.1000-0526.2008.04.008
    [Abstract](972) [HTML](72) [PDF 3.09 M](968)
    By using routine observational data, mesoscale observatioal data, sate llite cloud image, radar echo,T213 model products and diagnosis analysis means, the ra instorm event over Shandong province during 18-19 July, 2007 is analyzed. The we ather system, vertical stability of atmosphere, convective available ene rgy, water vapor condition and dynamically triggering mechanism were discussed. The characteristic of convective clouds was worked out. The result shows that th e rainstorm was caused by the interaction of the cold vortex over northeast Chin a, westerly trough, the southwest warm and wet airflow on the edge of subtropica l high over the west Pacific and the cold air from the north. The strong southwe st airflow set up the water vapor channels where the water vapor can flow to Sha ndong province. The forwardtilling trough and increase in the temperature and humidity in the low level atmosphere caused the intensively convective instabilit y and symmetrical instability, which provide sufficient water vapor and energy f or the rainstorm. The strong northeast winds converged with strong southwest air flow on low level atmosphere, so that the vertical vorticity increased, the conv ergence and ascending motion augmented, which trigger the instability energy rel eased, produced mesoscale convective cloud mass and heavy precipitation. Meso scale low pressure formed before the ground cold front, so the convergence and as cending motion increased more and more, which resulted in MCC and rainstorm.
    9  Comparative Analysis Between Two Severe Lightning Disasters
    Xu Aihua Li Yuta Zheng Jing Ying Dongmei
    2008, 34(4):71-78. DOI: 10.7519/j.issn.1000-0526.2008.04.009
    [Abstract](727) [HTML](80) [PDF 3.10 M](896)
    Two severe lightning disasters, which happened on June 24 and July 25, 2007, were compared with lightning location information, circulation backg round, thermal and dynamic characters of ambient field, atmospheric instability and Doppler radar echo feature. Results show that the number of died people of t hunder stroke is relative to the lightning density. These two processes have sim ilar circulation background and synoptic system, but the former has lower sinkin g motion and ascending motion. Both of them are dry in upper air and wet in lowe r, as well as the negative temperature variation in middle atmosphere. Instability index such as CAPE, K index, SI index are all reach the threshold of lightning. The for mer has stronger cold air and higher humidity, as well as the temperat ure inversion in ground layer. The composite reflectivity, echo top heights, ver tical integrated liquid of June 2425 are extremely high for long time, but th e former is obviously larger than the latter. Lightning often happens in the are as of mesoscale convergence system.
    10  Causes Analysis of Abnormal Rainfall and Its Largescale Circulation During 2007 Meiyu Season
    Jin Ronghua Chen Tao Bao Yuanyuan Wang Xiuwen Zhang Fanghua
    2008, 34(4):79-85. DOI: 10.7519/j.issn.1000-0526.2008.04.010
    [Abstract](634) [HTML](68) [PDF 930.86 K](994)
    Using daily NCEP/NCAR reanalysis dataset and the historical Meiyu feature index etc., the causes of abnormal rainfall and its largescale circulation during 20 07 Meiyu season are analyzed in order to better understand the evolvement charac teristics of persistent rainfall and its atmospheric circulation on JiangHuai Meiyu, and to discuss technical approaches of midrange forecast. The results s how that the stability of the western Pacific subtropical high located in the so uth more persistently than normal in middlelate July during Meiyu season plays a crucial role in the temporal and spatial characteristics during 2007 Meiyu pe riod. The frequent appearance of blocking high and abnormal strong subtropical monsoon surge provide favored dyna mic, thermodynamic and moisture factors affecti ng maintenance and intensification of Meiyu front. The activity of “Iran type” south Asia High and upperlow level coupling dynamic action of subtropical jet in East Asia not only create favorable vertical circulation structure for pe rsistent heavy rainfall but also restrain northward movement of subtropical high . At last, the keys of midrange forecast are summarized on the basis of these results.
    11  Causality Analysis of Autumn Rainfall Anomalies in China in 2007
    Jia Xiaolong Zhang Peiqun Chen Lijuan Gao Hui Zhu Yanfeng Li Wei Han Rongqing
    2008, 34(4):86-94. DOI: 10.7519/j.issn.1000-0526.2008.04.011
    [Abstract](1645) [HTML](67) [PDF 3.53 M](892)
    The spatiotemporal characteristics of autumn rainfall anomalies in China in 20 07 and the related largescale atmosphere circulation are analyzed, and effects of the La Ni?a event started in August of 2007 are also studied. The a utumn rainfall distribution shows a typical feature of more than normal in North China and less than normal in South China, especially in September and Oc tober. In these two months, the deep IndianBurma trough and active southwest m onsoon over the east of the Tibetan Plateau strengthened the northward transport ation of wetwarm air from the Bay of Bengal and the South China Sea. Meanwhile , the geopotential height in wide ranges from Balkhash to Baikal is lower than nor mal, which leads to the cold air taken by the split short waves transporting sou thward. In addition, the west Pacific subtropical high is more northwardthan normal, which also supplies the humid southeast air. Under this circulation, the cold airs and warmwet air were combined constantly over the north China. The second EOF mode of autumn rainfall is similar to the rainfa ll anomalies in 2007, which explains variance of more 10% and closely related to the SSTA in the centraleastern Equatorial Pacific. Both autumn rainfall and r elated circulation anomalies in 2007 present the typical characteristics of La Ni?a event.
    12  Analysis of the Severe Cold Surge, Icesnow and Frozen Disasters in South Chi na During January 2008:I. Climatic Features and Its Impact
    Wang Ling Gao Ge Zhang Qiang Sun Jiamin Wang Zunya Zhang Yong Zhao Shanshan Chen Xianyan Chen Yu Wang Youmin Chen Lijuan Gao Hui
    2008, 34(4):95-100. DOI: 10.7519/j.issn.1000-0526.2008.04.012
    [Abstract](1183) [HTML](153) [PDF 1006.74 K](1626)
    During January 2008, a persistent process of severe weathers with cold surge, ic esnow and frozen rain attacked South China. These weatherrelated climate ext remes and accessed their impacts on South China are reviewed. The analysis sugge sts that the cold surge and heavy snowfalljointly caused frozen weather and affected 20 provinces in South China , where, Hunan, Hubei, Jiangxi, Anhui, and Guizhou witnessed persistent frozen w eathers of 10~20 days. It resulted in the most severe damage due to its powerfu l intensity and long time persistence in these areas, where the number of contin uous low temperature days and frozen days broke through the record in the winter of 1954/1955 in the lower reaches of the Yangtze River region and Guizhou Provi nce. These frozen weathers caused great damages through influencing transportation, agriculture, and people daily activities, particularly by stopping the power sup ply in South China.
    13  Analysis of the Severe Cold Surge, Icesnow and Frozen  Disasters in South China During January 2008:  Ⅱ. Possible Climatic Causes
    Gao Hui Chen Lijuan Jia Xiaolong Ke Zongjian Han Rongqing Zhang Peiqun Wang Qiyi Sun Chenhu Zhu Yanfeng Li Wei Sun Linhai Ren Fumin Wang Ling Gao Ge
    2008, 34(4):101-106. DOI: 10.7519/j.issn.1000-0526.2008.04.013
    [Abstract](1189) [HTML](123) [PDF 2.90 M](1319)
    Extreme low temperature, heavy snowstorm and frost disasters occurred in China i n January of 2008. The disasters are unprecedented owing to their nationalwide influences, their infrequent intensity, and the long lasting periods of the low temperature, snowstorm and frost days. They led to huge losses in the country. In the second part of this paper, the possible climatic causes are analyzed. Res ults show that the La Nina event began in August 2007 and developed very quickly . It led to the anomalous general circulations in the Northern Hemisphere, which was thought to be the most important causes of unprecedented disasters. In Janu ary, the geopotential height over the Ural was abnormally high while the count erpart over the Middle Asia, the Mongolia and the Far East regions of the Russia was low. This pattern is propitious to the cold air activity from the high lati tudes. In that month, the western Pacific subtropical high (WPSTH) located more northward, which favors the transportation of the warm and wet moisture to China along its west and north sides. The position of the WPSTH determined the disast er regions. In addition, the Indian and Burma trough (IBT) in the south side of the QinghaiXizang Plateau is quite active, which favors the moisture transport ation in another way to China, i.e., along the YunnanGuizhou Plateau from the Indian Ocean and the Bay of Bengal. Results also indicate that the inversion lay er in that month was the strongest in all Januaries since 1951 and its persisten ce was the main causes of the frozen rain in Hu'nan and Guizhou provinces.
    14  Sea Surface Temperature and the General Circulation in 2007 and Their Influences on the Climate of China
    Gao Hui Wang Yongguang
    2008, 34(4):107-112. DOI: 10.7519/j.issn.1000-0526.2008.04.014
    [Abstract](529) [HTML](66) [PDF 1020.08 K](789)
    2007 is the warmest year since 1951. In the spring of the year, the fr equency of the dust storm is less. And in the summer, extreme heavy rainfall eve nts occurred in many regions, especially along Huaihe river valley. But severe d rought occurred in South China in the autumn. During the whole year, the number of the tropical cyclones (TC) developed from the South China Sea and the western Pacific is less. Among them, eight landed on China. In 2007, the equatorial eastern Pacific experienced an El Nino event in January but La Nina event started s ince August. In the high latitudes of Northern Hemisphere, the geo-potential hei ght anomalies are positive and the zonal circulation prevails in most months. Th us the cold surges are not frequent. In the summer especially in July, the weste rn Pacific subtropical high was stronger and locates over South China stably. Th is is propitious to the transportation of warmer/wetter moisture from the Bay of Bengal to China. But on the other hand, during this period the South China expe rienced an extreme hightemperature and drought event due to the stability of h igh pressure. In 2007, the South China Sea summer monsoon onset at the 5th pentad of May and withdrew at the 3rd pentad of October, both are later. Owing to the weak monsoon in July, the warmer/wetter moisture can only be transported to the Huaihe river valley and formed a convergence over the area. Thus the flood event occurred in the area. 
    15  Global Significant Climate Events in 2007
    Liang Xiaoyun Guo Yanjun
    2008, 34(4):113-117. DOI: 10.7519/j.issn.1000-0526.2008.04.015
    [Abstract](549) [HTML](83) [PDF 342.60 K](871)
    Global climate was obviously warm in 2007, and is the seventh warmest year on record. A La Ni?a event came into being since August 2007. In th e beginning of 2007, strong cold waves and snowstorms raided Northeast China, Japan, USA and Canada, respectively. During boreal summer, heat wave swept East Asia, Sout h Asia, central-southern Europe and USA. In the year, severe drought occurred in southern China and southeastern USA; floods occurred in South Asia, and rainsto rm attacked many countries in Asia and South America frequently. In 2007, activi ty of typhoon was near normal in the northwestern Pacific, but stronger and more destructive than normal. Meanwhile, activity of hurricane was less than normal in the eastern Pacific and also near normal in the Atlantic Ocean.
    16  Overview of the Climate in China in 2007
    Zou Xukai Chen Yu Liu Qiufeng Sun Jiamin
    2008, 34(4):118-123. DOI: 10.7519/j.issn.1000-0526.2008.04.016
    [Abstract](855) [HTML](214) [PDF 750.71 K](985)
    The nationally averaged temperature in China for 2007 was 1.3℃ above the 1971 -2000 longterm mean, ranking this year as the warmest since 1951. The a veraged precipitation was close to normal, with considerable variability across the country and throughout the year. Huaihe River Valley was hit by severe flood in summer, and consecutive autumn rains occurred in northern China. Widespread droughts extended much of southern China in autumn. The number of landfalling tr opical cyclones was more than normal, mainly occurred in August, September and O ctober. The economic losses caused by tropical cyclones were near normal, while the number of dead was much less than normal. In early spring, Liaoning and Shan dong was slashed by heavy snowstorm. Thunderstorm occurred frequently in some re gions with many dead reports. The number of duststorm days was less than normal.

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