DCT ANALYSIS DISTRIBUTION FEATURES OF NEAR-SURFACE WIND FIELDS DURING THE LANDFALL OF VONGFONG

1 INTRODUCTION The typhoon is a destructive weather phenomenon that stands at the top of ten major natural disasters[1]. Typhoon-related damages are the immediate consequences of weather it brings forth, which include heavy rain, strong winds and storm surges (water gain). They cause flash floods, bring down houses and break through dams[1]. Of the research on typhoons for the recent 10 years[2], new advances have been reported on abrupt changes in the motion, structure and intensity of…     

西太平洋副热带高压强度和位置的气候特征

利用45年西太平洋副热带高压5个特征指数的月平均资料,对副高强度和位置变化的气候特征进行了诊断研究.结果表明,副高的强度在一年中出现两次峰值,第一次出现在6月,第二次在9月.在45年里,副高强度有明显加强,副高位置有南落西移的趋势.副高强度存在3～4 年、10～13 年的振荡周期,10～13年的周期振荡在1950、1960、1970年代占主要地位,3～4年的周期振荡在1980、1990年代占主要地位.副高在1978年附近发生气候突变,副高强度由负距平为主转为正距平为主,而脊线位置正好相反.     

热带气旋影响下高臭氧污染的调控机理

利用美国环保局开发的第3代空气质量模式Models-3,对珠三角地区一次热带低压影响下的高臭氧空气污染事件进行了数值模拟,并通过一系列的一次污染物排放量的增减试验,探讨了不同的一次污染物排放情景,即采取不同的空气污染物的调控情况下,对珠三角地区低层臭氧生成的影响。研究结果表明,在热带低压影响下,要降低珠三角地区的日臭氧峰值,需采取的主要调控措施是控制氮氧化物的排放;或者随着氮氧化物的增长,相应增加生物源VOC(volatile organic compounds,易挥发有机化合物)的排放,以维持较高的VOC与NOx(氮氧化物)的比率。     

THE THREE-LEVEL GLOBAL ATMOSPHERIC GENERAL CIRCULATION MODEL:FORMULATION AND RESULTS

The“climate draft”often occurs in the coupling process of the atmospheric general circulation model (AGCM) andoceanic general circulation model (OGCM).One of the main methods to overcome the“climate draft”is to simulate theflow and temperature fields in the low-layer correctly.Therefore we designed a three-level AGCM including a planeta-ry boundary layer (PBL) and have run it seven model years to do climate simulation.The results show that the simulatedlower level air flow,surface air temperature and sea-level pressure in January and July,approximate to the climate av-erage fields,especially in Asian monsoon area.The simulated upper level flow and geopotential height are also in betteragreement with the observed fields.Moreover,the two westerly jets over the northern and southern sides of theQinghai-Xizang Plateau in winter,the disappearance of its southern subtropical jet during the seasonal transition fromspring to summer,the establishment of the two easterly jets near the equator and over the subtropical region during theseasonal transition,are also simulated well.In the mainland of China,the seasonal abrupt shift of the rainfall belt,suchas the Meiyu belt in South China during April to May,which jumps to the Changjiang River region in June,again jumpsback to the north China in July,and rapidly withdraws to the south in August,are simulated very well.Now we arecoupling this model to a global six-level OGCM and nesting a fine mesh (1°×1.25°)regional climate model over Chinaarea with it.     

ANALYSIS OF THE IMPACT OF URBAN GROWTH ON THE TEMPERATURE FIELD IN GUANGZHOU

Based on the 1973 – 2003 temperature data of Guangzhou meteorological station and 1980 – 2000 temperature data of Foshan airport, the variations of urbanization effect on temperature of Pearl River Delta (PRD) and Guangzhou city were analyzed. It was found that the temperature has increased significantly due to the PRD’s urbanization. During the last 20 years, Foshan airport’s temperature has increased by 0.7°C, and the Guangzhou city’s temperature increased by about 1.1°C during last 30 years. The heat island of Guangzhou city is obvious but has some differences from other big Chinese cities.     

夏季青藏高原对它附近流场影响的数值试验

本文利用简单的两层模式和椭园体地形,以纬向气流及常定热源为初始场,进行了青藏高原对它附近环流系统的热力和动力影响的各种数值试验,得到以下一些初步的定性结论: 1.夏季高原上500mb切变线的形成发展主要决定于它的动力影响,但它的热力影响也起到了加强作用。西南低涡的生成在一定条件下完全决定于高原的动力影响,而高原的热力影响是不利于它生成的。孟加拉湾低压的存在也可能与高原的动力作用有关。 2.在青藏高原上空的西风风速较弱时,高原的加热作用对100mb青藏高压的形成与维持影响很大,此时高原南边的热源即使比高原的强很多倍,对这个高压形成的影响也不大。高原的动力作用对100mb青藏高压的生成维持是不利的。     

CLIMATIC CHARACTERISTICS OF THE ONSET OF SOUTH CHINA SEASUMMER MONSOONⅡ.INTER—DECADAL VARIATION

By using the 40-year NCEP(1958-1997) grid point reanalysis meteorological data.we analyzed the inter-decadal variation on the climatic characteristics of the onset of South China Sea summer monsoon.The results are as follows.(1) There was great difference on the onset date of the SCS summer monsoon between the first two decades and the last two decades,It was late on the 6^th pentad of May for the first two decades and was on the 4^th and 5^th pentad of May for the next two decades.(2)Except for the third decade(1978-1987),the establishment of the monsoon rainfall was one to two pentads earlier than the onset of the summer monsoon in all other three decades.(3) The onset of the SCS monsoon is the result of the abrupt development and eastward advancement of the southwesterly monsoon over the Bay of Bengal.The four-decade analysis shows that there were abrupt development of the southwesterly monsoon over the Bay of Bengal between the 3rd and 4th pentad of May,but there was great difference between its ewastward ovement and its onset intensity.These may have important effect to the earlier or later onset of the SCS summer monsoon.(4) During the onset of the SCS summer monsoon.there were great difference in the upper and lower circulation feature between the first two and the next two decades.At the lower troposphere of the first two decades.The Indian-Burma trough was stronger and the center of the subtropical high was located more eastward.At the upper troposphere.the northward movement of the center of subtropical high was large and located more northward after it landed on the lndo-China Peninsula.After comparison.we can see that the circulation feature of the last two decades was favorable to the establishment and development of the SCS summer monsoon.     

THE CLIMATIC CHARACTERISTICS OF SUMMER MONSOON ONSET OVER THE SOUTH CHINA SEA I.40-YEAR AVERAGE

By using 40-year NCEP reanalysis daily data (1958-1997), we have analyzed the climatic characteristics of summer monsoon onset in the South China Sea (105°E ~ 120°E, 5°N ~ 20°N, to be simplified as SCS in the text followed) pentad by pentad (5 days). According to our new definition, in the monsoon area of the SCS two of the following conditions should be satisfied: 1) At 850hPa, the southwest winds should be greater than 2m/s. 2) At 850 hPa, θ_se should be greater than 335°K. The new definition means that the summer monsoon is the southwest winds with high temperature and high moisture. The onset of the SCS summer monsoon is defined to start when one half of the SCS area (105°E ~ 120°E,5°N ~ 20°N) is controlled by the summer monsoon. The analyzed results revealed the following: 1) The summer monsoon in the SCS starts to build up abruptly in the 4th pentad in May. 2) The summer monsoon onset in the SCS is resulted from the development and intensification of southwesterly monsoon in the Bay of Bengal. 3) The onset of the summer monsoon and establishment of the summer monsoon rainfall season in the SCS occur simultaneously. 4) During the summer monsoon onset in the SCS, troughs deepen and widen quickly in the lower troposphere of the India; the subtropical high in the Western Pacific moves eastward off the SCS in the middle troposphere; the easterly advances northward over the SCS in the upper troposphere.     

南海夏季风维持期的气候特征Ⅱ--年代际变化

利用NCEP1958～1997年逐日格点气象资料对我国南海地区(105～120°E,5～20°N)夏季风维持期的年代际变化进行了仔细分析,分析结果发现对南海地区夏季风影响最大的是1970年代末期大气环流的突变.突变以1978年为界,分析工作主要是将前20年情况与后20年进行对比.前20年夏季风建立晚、结束早、降水较少、对流活动较弱、季风较弱;后20年则与此相反,季风建立早、结束晚、降水较多、对流活动较强、季风较强.分析对比前20年与后20年夏季风维持期高低空环流形势后发现,后20年南海地区上空对流下层辐合较强而对流层上层辐散较强,显然这种形势对后20年南海夏季风和对流降水的发展是十分有利的.需指出的是南海地区中心部分夏季风维持期的降水和OLR值的年代际变化趋势正好与南海其它地区相反,也就是说后20年南海地区中心部分降水较少,OLR值较高,而前20年正好相反.后20年和前20年的ENSO指数和南海地区海温的差别也十分明显,前20年ENSO指数和海温较低,而后20年都较高.     

广州大气环境因素与SARS疫情短期变化关系的研究

根据SARS疫情和同期大气环境要素资料,利用时间尺度分离技术、谱分析和相关分析方法,研究大气环境因素对SARS疫情的影响,结果发现大气环境因素与SARS发病有密切关系：广州SARS每日新增病例数和大气要素存在几乎一致的3—5天变化周期,且疫情涨落和大气要素变化间有显著的相关性。由此推论天气变化对SARS疫情起伏有影响。此外,统计结果表明冷空气活动使SARS疫情加重。