环渤海地区1961-2007年极端强降水时空变化特征

20世纪90年代以来,环渤海地区降水总量持续偏少,极端强降水和干旱缺水问题十分突出。利用环渤海地区60个台站1961—2007年逐日降水资料,应用百分位方法确定极端强降水阈值,分析了极端强降水量、降水强度和频率的空间分布及时间变化趋势。结果表明:环渤海地区极端降水强度大、频率高的地区与年降水量高值区相一致,说明极端降水量的多少影响年降水量;极端降水日数呈减少趋势,特别是京津冀中部地区减少显著;极端降水多发生在7月中旬到8月中旬,最高频次在7月下旬,近10年极端降水季节分配比较分散,很少出现每候25站次以上的极端强降水;间隔30d以上的极端强降水近年来增加明显。     

黑河实验区地表净辐射区域分布及季节变化

利用卫星遥感信息和地面观测资料，分析研究黑河实验区地表净辐射的区域分布及季节变化特征。结果表明，卫星遥感结合地面观测，首先可以得到较为精确的地表反射率和地表温度分布，进而得到较为合理的地表净辐射的区域分布和季节变化特征。     

The relationships between tropical Atlantic sea level variability and major climate indices

Relationships were examined between variability in tropical Atlantic sea level and major climate indices with the use of TOPEX/POSEIDON altimeter and island tide gauge data with the aim of learning more about the external influences on the variability of the tropical Atlantic ocean. Possible important connections were found between indices related to the El Niño–Southern Oscillation (ENSO) and the sea levels in all three tropical regions (north, equatorial, and south), although the existence of only one major ENSO event within the decade of available altimetry means that a more complete investigation of the ENSO-dependence of Atlantic sea level changes has to await for the compilation of longer data sets. An additional link was found with the Indian Ocean Dipole (IOD) in the equatorial region, this perhaps surprising observation is probably an artifact of the similarity between IOD and ENSO time series in the 1990s. No evidence was obtained for significant correlations between tropical Atlantic sea level and North Atlantic Oscillation or Antarctic Oscillation Index. The most intriguing relationship observed was between the Quasi-Biennial Oscillation and sea level in a band centered approximately on 10°S. A plausible explanation for the relationship is lacking, but possibilities for further research are suggested.     

基于面向对象分类技术的沈阳市土地利用动态变化研究

基于RS和GIS技术,采用面向对象分类技术,根据沈阳市的实际情况,建立土地利用类型解译标志,利用多尺度分割方法进行影像分割,然后利用决策树法和最近邻的分类方法,建立分类规则,提取区域土地利用信息,得到该区域的两期土地利用/土地覆被数据,并对研究区的土地利用动态变化及引起这种变化的驱动力进行分析.研究中所采用的面向对象的分类方法在地表景观信息提取中充分利用了地物的光谱信息、纹理特征等特征,最大程度上克服由于不同地物光谱信息相似、相同地物光谱信息不同而造成的混分现象.     

河流入海物质通量对海、陆环境变化的响应

入海河流物质通量研究是陆—海相互作用和全球海洋通量联合研究计划的重要命题。我国是最早开展物质通量研究的国家之一。自20世纪90年代以来,国家自然科学基金项目和国家重大基础研究计划项目都开展了有关河流和边缘海物质通量的研究,即将开始的全国海岸带环境调查专项也把主要河流物质入海通量及其海洋环境效应研究作为主要内容之一。根据当前国内外河流物质通量研究的最新进展,较系统地阐述了河流入海物质通量的概念和对邻近大陆和海洋环境变化的响应。并在此基础上强调指出,河流入海物质通量是研究陆—海相互作用及其全球变化效应的重要参量。归纳了河流入海物质通量研究中需要解决的关键问题。     

华南三水盆地白垩纪—早第三纪古纬度漂移与南海演化

本文主要依据三水盆地古地磁数据所反映的华南地块的古纬度漂移讨论南海的演化模式。结果认为,华南在南海的形成演化中居主导地位,南海基本上是晚白垩世至中新世期间通过华南的南漂及其后的北向回漂过程中,华南大陆南部的拉张、断裂、解体并自东向西扩展的方式形成的,而南海中散布的微大陆碎块则是在华南回漂时被滞留下来的。演化过程中,其周缘菲律宾岛弧自南向北漂,直到上新世后才构成南海的东界;印支地块则仅起转换边界作用;加里曼丹则基本土没有明显的漂移。     

中蒙地块的水平运动及应变特征

GPS观测结果显示中蒙块体的位移速率较小,块体各部分的位移方向存在差别,说明块体有差异活动但不显著。连续应变场的应变率参量值在10-8/a以下;主压应力轴方向为NE74.6°,与该区内的浅源强震震源机制解的P轴方向基本一致。由应变产生的贝加尔湖裂谷的裂开速率为4.71mm/a,最大主应变率为34.34×10-9/a,张应变主轴方向NW310.49°,垂直于裂谷走向;嫩江断裂带和萝北-营口断裂带为走滑兼挤压或拉张活动断裂,位移速率和应变率都较小,活动性不显著。2003年8月16日巴林左旗5.9级地震和2004年3月24日东乌珠沁旗6.4级地震均发生在由1999~2003年GPS资料得出的多种应变速率参量的相对高值带和应变率高梯度带上。     

陆面模式中土壤呼吸的研究概况

土壤呼吸是陆地植被吸收的CO2返回大气的基本途径,土壤呼吸速度轻微变化也会引起大气中CO2浓度的明显改变,进而影响气候变化。陆面过程模式中更好地描述土壤呼吸过程对于预测未来气候变化是至关重要的。对于土壤呼吸的模拟研究,介绍了经验模型和以过程为基础的机理模型,以及国内外陆面过程模式中土壤呼吸的研究情况,并讨论了土壤呼吸模式中需要改进的问题。       

Relationship Between the Number of Summer Typhoons Engendered over the Northwest Pacific and South China Sea and Main Climatic Conditions in the Preceding Winter and Spring

Based on the monthly NCEP/NCAR reanalysis data, OLR (outgoing longwave radiation) data, and tropical cyclone data from the Typhoon Annual and Tropical Cyclone Annual edited by China Meteorological Administration, the relationship between the number of tropical cyclones (with the strongest wind ≥17 m s-1, including tropical storm, strong tropical storm, and typhoon, simply called typhoon in this paper)engendered over the Northwest Pacific and South China Sea in summer and the associated climate conditions is studied. First, the characteristics and di?erences of the climatic conditions between the years with more typhoons and those with fewer typhoons are compared. The results show that the summer typhoon has a close relationship with SST (sea surface temperature) and ITCZ (intertropical convergence zone) anomalies in the preceding winter and spring. With a La Niena like SST anomaly (SSTA) pattern in the preceding winter and spring, the ITCZ will move northwestward and be enhanced around 160°E in the equatorial central Pacific from the preceding winter to spring.The activity of the Pacific ITCZ is in general stronger and its location is more northward than usual, especially in the typhoon genesis region in West Pacific. This background is propitious to have more typhoons in summer. On the other hand, an El Nieno like SSTA pattern in the preceding winter will be companied with weaker ITCZ activities, and its location is more southward over the equatorial western Pacific from the preceding winter to spring; this background is propitious to have fewer typhoons in summer. In the year with more typhoons, the warm SST over West Pacific in the preceding winter provides a favorable condition for typhoon fromation in the following summer. It enhances the convergence in the troposphere and increases the water vapor supply to the warm SST region. In the following spring, the perturbation of the tropical ITCZ plays a more important role.When the ITCZ moves northward in spring, anomalous convergence will appear over the warm SST region and inspire the positive feedback between the large-scale moisture flux at low levels and the latent heat release in the atmosphere, which benefits the typhoon genesis in summer. Otherwise, if cold SST maintains over the northwestern Pacific during the preceding winter and spring, the convergence in the troposphere is disfavored and the water vapor supply to the cold SST region is reduced, which will bring about weaker ITCZ activities and the perturbation is lacking in the following spring. It then results in fewer summer typhoons.