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.     

RESPONSE OF THE ATMOSPHERIC GENERAL CIRCULATION TO WINTER SNOW COVER ANOMALY

In this paper,the response of the atmospheric general circulation to winter anomalous snowcover was investigated through observations studies and model simulation.Results from the observations show that:(1)the anomalous winter snow cover in theextratropics of Eurasian Continent bears an intimate relation to the contemporary atmosphericgeneral circulation.The positive anomaly of winter snow cover is usually accompanied by positiveatmospheric EUP teleconnection pattern and stronger East Asian winter monsoon:or vice versa.(2)The linkage between them suggests that the abnormal winter snow cover has an importantimpact on winter atmospheric general circulation.The anomalous snow cover pattern can lead tothe anomaly of winter atmospheric EUP teleconnection pattern and thus influence East AsianWinter monsoon.With NCAR CCM2 including BATS land surface scheme,three groups of experiments wereperformed to examine the atmospheric response to the anomalous snow cover pattern and explorethe relevant mechanism.Simulated results agree well with the observations,which testify thesignificant response of the atmosphere to snow cover anomaly.It is found that the radiative coolinginduced by anomalous snow cover plays an important role in above processes,and the feedback oflong-wave radiation can not be neglected.     

东亚夏季风环流与ENSO循环的关系

采用NCEP/NCAR再分析资料和NCAR海温资料 ,对ENSO循环不同阶段东亚夏季风环流的变化进行了分析。计算了各年夏季风环流的强度系数及其与多年平均夏季风环流的相似系数和差异系数 ,分析它们与海温变化的关系。结果表明 :东亚夏季风环流强度有明显的年际变化和年代际变化 ,且与赤道东太平洋SST有较好的负相关关系 ,其中又以与三个月前的海温变化关系最好。在春季 (3～4月 )Nino 1+2区为冷、暖水时 ,当年夏季 (6～ 7月 )东亚季风区中 85 0hPa等压面上 >2m·s-1的经向风北伸纬度和东亚季风区的垂直经圈环流都有明显差异 ,在冷水期 >2m·s-1的经向风北伸纬度比暖水期高 ,季风环流圈的上升支北移 ,东亚夏季风环流较暖水期强。     

Relationship between land cover and monsoon interannual variations in east Asia

Asian monsoon have multiple forms of variations such as seasonal variation, intra-seasonal variation, interannual variation, etc. The interannual variations have not only yearly variations but also variations among several years. In general, the yearly variations are described with winter temperature and summer precipitation, and the variations among several years are reflected by circulation of ENSO events. In this study, at first, we analyze the relationship between land cover and interannual monsoon variations represented by precipitation changes using Singular Value Decomposition method based on the time series precipitation data and 8km NOAA AVHRR NDVI data covering 1982 to 1993 in east Asia. Furthermore, after confirmation and reclassification of ENSO events which are recognized as the strong signal of several year monsoon variation, using the same time series NDVI data during 1982 to 1993 in east Asia, we make a Principle Component Analysis and analyzed the correlation of the 7th component eigenvectors and Southern Oscillation Index (SOI) that indicates the characteristic of ENSO events, and summed up the temporal-spatial distribution features of east Asian land cover’s inter-annual variations that are being driven by changes of ENSO events.     

东亚土地覆盖动态与季风气侯年际变化的关系

以东亚地区 １９８２～１９８９年时间序列降水资料及 ＡＶＨＲＲ ８ ｋｍ ＮＤＶＩ数据为基本数据源，应用地理信息系统技术，分别研究了东亚地区夏季（５－９月）降水及土地覆盖的年际变化，并揭示了研究时间段内各自的变化规律。进一步用奇异值分解（ＳＶＤ）模型方法分析了以降水变化为表征的东亚地区气候年际变化与土地覆盖年际变化之间的关系。     

Rescaling the Region: The integration of Hawkes Bay food and forestry industries into East Asia

This paper explores the changing relationship of a region (Hawkes Bay, New Zealand), its industries and enterprises to Asia-Pacific industrial complexes. Land-based industries in Hawkes Bay provide examples of new connections and local adaptations of production to emerging agro-food and forestry complexes, centred upon East Asia. Integration into these complexes, which has only been possible in the context of the gradual relaxation of regulatory regimes that has occurred over the past two decades, has facilitated access to new markets. In some cases, integration is an outcome of East Asian ownership of New Zealand-based nodes along the commodity chain. In others, it is an outcome of New Zealand actors producing to meet 'site of consumption' demand. The paper concludes that new dynamics in the spheres of trade, production and investment are instituted by and feed into new geographic links and interactions, referred to in the paper as a rescaling of the region.     

中国海军崛起及其对东亚安全秩序的影响

近年来,中国海军的发展开始进入快车道。武器装备规模的扩大、武器装备性能的提升以及武器装备体系的完善是中国海军崛起的主要表现。中国海军的崛起是需求侧和供给侧合力作用的结果。需求侧指的是应对日益严峻的外部压力、保护海外利益和海上交通线、维护国家主权和领土完整以及汲取历史教训的需要;供给侧指的是中国综合国力的提高、中国对海洋和海权重视度的提升以及中俄关系的稳定提供了中国发展海军的良好内外部环境,使得中国可以发展出强大海军。中国海军的崛起将会给东亚安全秩序带来深远的影响,这些影响主要集中在改变东亚地缘结构、冲击美国同盟体系、安全公共物品供给这三方面。     

南海北部陆坡沉积记录的全新世早期夏季风极强事件

在AMS14C精确定年的基础上,通过南海北部MD05-2905站高分辨率的氧同位素、粒度、元素分析,其结果显示所有指标均在11.2～8.5kaB.P.期间发生异常,根据夏季风指标认为这是夏季风极强事件。将本站位相同纬度（20°N）的夏季平均日辐射量与季风指标进行对比,发现全新世早期（11.2～8.5kaB.P.）东亚夏季风极强事件对应着夏季太阳辐射量最大值和热带辐合带（ITCZ）的位置向北移动,说明全新世早期夏季风突然增强可能是在岁差周期控制下,较高的太阳辐射量驱动了热带辐合带（ITCZ）及其有关的雨场向北移动,在南海北部产生了大量的降水,导致氧同位素偏负、碳酸盐的含量较低以及线性沉积速率较高。这与前人对相邻地区湖光岩玛珥湖的孢粉研究、江西南岭地区泥炭的记录以及中国南方石笋记录的研究结果相吻合。该季风最强事件与阿拉伯海发现的早全新世季风最强事件以及根据格陵兰冰芯记录的早全新世甲烷最大值推测低纬地区湿地扩张相一致,这反映了南海北部全新世早期与全球低纬地区早全新世气候变化格局一致。     

长江中下游夏季降水变化与亚洲夏季风系统的关系

以长江中下游流域实测降水数据和亚洲季风指数为基础,采用Mann-Kendall检验、线性相关和偏相关分析、小波分析等方法,揭示长江中下游夏季降水的时空变化特征及其与亚洲季风系统之间的相互关系和影响差异。结果表明,近50 a来长江中下游夏季降水量呈显著的增加趋势,其与亚洲主要夏季风指数之间均呈负的线性相关关系,且显著性影响范围东亚夏季风大于南海夏季风大于南亚夏季风。不同亚洲夏季风子系统间存在复杂的相互作用关系,尤其是东亚夏季风和南海夏季风之间的相互作用对长江中下游夏季降水产生了重要影响。长江中下游夏季降水量与亚洲主要夏季风指数存在2~4 a时间尺度上的显著相关性,且以反位相关系为主。此外,长江中下游夏季降水量与东亚夏季风的相干性最为突出,在小于8 a的时间尺度上,两者之间的相关性在近50 a来呈现减弱的趋势,特别是自20世纪80年代中后期以来。     

2003年秋季华北地区一次区域性大暴雨分析

通过对2003年10月10～12日发生在华北地区的一场罕见大范围暴雨、区域性大暴雨天气的分析发现,生成于孟加拉湾的季风云团及其向东北方向扩展的西南季风云系与高空急流云系的结合为区域性大暴雨的形成打下了基础;高、低空急流的耦合及中、低空系统的上下叠加为大暴雨的形成创造了良好的动力场;多支低空急流的形成为大暴雨提供了有利的水汽条件。