城市气候效应研究进展

城市是人类社会发展的必然产物.随着城市的快速发展,城市气候效应凸显,并对社会经济可持续发展和人体健康等造成影响.基于国内外已有的研究成果,综述了城市气候效应,包括城市热岛效应、雨岛效应、混浊岛效应、于岛效应和雷暴岛效应的研究历史、现状及其与城市化、天气气候变化的相互关系,并对未来城市气候效应的研究方向及技术方法进行了展望.     

低空越赤道气流的研究进展

越赤道气流是南、北半球物质、能量交换的主要通道,其强弱对夏季风爆发、台风的发生及中国降水等有重要影响。简要回顾了低空越赤道气流强弱突变对亚洲夏季风爆发早晚、西太平洋副热带高压脊线北抬位置、西北太平洋地区台风生成多寡及中国夏季降水影响的研究进展,并简要讨论了越赤道气流研究中存在的问题及未来的研究前景。     

THE POSITION VARIATION OF THE WEST PACIFIC SUBTROPICAL HIGH AND ITS POSSIBLE MECHANISM

Using NCEP/NCAR daily reanalysis data and SCSMEX data, an investigation is carried out of the relationship between the position variation of the west Pacific subtropical high (WPSH) and the apparent heating in June 1998 based on the complete vertical vorticity equation. It is found that the non-adiabatic heating plays an important role in the position variation of WPSH. In comparison with climatic mean status, the vertical change of non-adiabatic heating is stronger in the north side of WPSH in June 1998, but weaker in the south side of WPSH. The anomalous non-uniform heating induces anomalous cyclonic vorticity in South China, areas to the south of the Yangtze and its mid-lower valleys, but anomalous anticyclonic vorticity in the Indo-China Peninsula and South China Sea areas lead to the more southward position of WPSH than the mean.     

太平洋区域海温跃变及其与东亚夏季风的关系

本文利用英国气象局提供的全球SST月平均资料和NCAR／NCEP提供的500百帕高度场资料，分析了全球SSTA的年际和年代际变化，发现夏季全球SST在70年代发生了一次跃变，尤其北太平洋区域SST在1976年前后，由正距平变为负跨燕，并且跃变前后东亚夏季风也发了显著变化，我国汛期降水异常形势成相反分布，海温对东亚夏季风的影响途径和机制也发生了改变，1976年以前北太平洋区域海温起主要作用，跃变后，北太平洋区域海温异常与东亚夏季风关系变得不明显，而赤道中东太平洋海温的作用变得异常重要。     

AN EAST ASIAN SUBTROPICAL SUMMER MONSOON INDEX DEFINED BY MOISTURE TRANSPORT

Using daily NCEP/NCAR reanalysis dataset and observation rainfall data in China for the 1971- 2000 period, a subtropical summer monsoon index has been defined by meridional moisture transport of the total atmosphere column. Results show that the subtropical summer monsoon index defined by the difference of meridional moisture transport between South China and North China can be used to describe the intensity of the subtropical summer monsoon. High (low) index is corresponding to strong (weak) subtropical summer monsoon. And the new index is well related to the summer rainfall over the middle and lower reaches of Yangtze River. In addition, the convergence of moisture transport from the west Pacific via the South China Sea and that from the North China may be responsible for the anomalously excessive summer rainfall over the middle and lower reaches of Yangtze River.     

GISS海气耦合模式的基本气候态评估

该文简单介绍了GISS海气耦合模式, 并且利用该模式进行数值模拟, 以此来判断其模拟能力, 尤其是对亚洲地区的模拟。结果表明:该模式模拟的亚洲地区大气和海洋的气候状况比较接近实况, 具有一定的气候模拟能力。同时, 由于其较粗的分辨率, 对计算机要求不高, 容易利用目前国内中小型计算机进行长期运转, 是一个简易的数值模拟工具。文章也讨论了该模式模拟的不足之处, 如亚洲地区模拟的地面气温偏低, 海温略偏高, 青藏高原南部夏季降水过大, 中国华北夏季降水偏少等。     

SST年循环对El Niño事件局地海气过程的影响

利用Hadley中心逐月海表温度、欧洲中心ERA-40的10 m风场及CMAP降水资料探讨了年循环对热带太平洋El Niño海气相互作用过程的影响。尽管El Niño对应的海表温度异常主要出现在赤道东太平洋,经向上呈南北对称分布,然而其对应的大气响应在El Niño年衰减阶段却有着强的向南移动特征。在El Niño发展年的11月之前,强的西风和降水异常主要出现在赤道中太平洋;在12月份之后,赤道上的西风和降水异常迅速南移至5°S,随后西风一直维持在该位置直至衰亡。同时,西太平洋负降水和反气旋异常向北移动。这种SST异常与其大气响应的经向移动不一致,主要是由热带中太平洋气候态SST的季节性南移导致的。由于对流与海温之间存在非线性关系,即当总SST超过一定的阈值,对流降水才会迅速增强;因此相应的对流响应也随着总海温的南移而南移,风场响应也同时南移。此外,南半球增强的对流会通过经向环流进一步抑制北半球的降水,从而使西太平洋负降水和反气旋异常增强并北移。通过分析有/无年循环的两组数值试验结果验证了上述结论,即有年循环的试验较真实地模拟出了观测中异常西风南移和西北太平洋反气旋异常的出现;无年循环试验尽管能模拟出El Niño年赤道中太平洋的西风异常,但其却没有南北向的移动,西北太平洋的反气旋也没有出现。因此,热带中太平洋气候态暖海温的季节循环对El Niño事件大气响应有着至关重要的作用。     

华南持续性暴雨的大尺度降水条件分析

利用1958-2004年NCEP/NCAR全球逐日再分析格点资料和同期我国华南地区45站的逐日降水资料,从水汽条件、不稳定能量及抬升条件对发生在华南地区的157个连续性暴雨进行分析,并结合各自的爆发时间,对暴雨进行分类,讨论了不同类型华南持续性暴雨的形成原因.     

CH4和N2O的辐射强迫与全球增温潜能

CH₄和N₂O作为主要温室气体,自工业革命以来排放量急剧增加,已经被列入《京都议定书》要求控制它们的排放。本文利用高光谱分辨率的辐射传输模式,计算了CH₄、N₂O在晴空大气和有云大气条件下的瞬时辐射效率和平流层调整的辐射效率,以及它们的全球增温潜能(GWP)和全球温变潜能(GTP),并根据模式结果拟合了CH₄和N₂O的辐射强迫的简单计算公式。本文的研究表明:CH₄和N₂O在有云大气下的平流层调整的辐射效率分别为4.142×10-4 W m-2 ppb-1和3.125×10-3 W m-2 ppb-1 (1ppb=10-9),经大气寿命调整后的辐射效率分别为3.732×10-4 W m-2 ppb-1和2.987×10-3 W m-2 ppb-1,与IPCC(2007)的相应结果高度一致。CH₄和N₂O 100年的全球增温潜能GWP分别为16和266;100年的脉冲排放的全球温变潜能GTPP分别为0.24和233;持续排放的全球温变潜能GTPS分别为18和268。它们在未来全球变暖和气候变化中,影响仅次于CO₂,仍然起着非常关键的作用。     

ANALYSIS OF THE WESTWARD EXTENSION OFWESTERN PACIFIC SUBTROPICAL HIGH DURING A HEAVY RAIN PERIOD OVERSOUTHERN CHINA IN JUNE 2005

The NCEP/NCAR II daily mean reanalysis data and observed precipitation data are employed to investigate the westward extension of the western Pacific subtropical high (WPSH) during the heavy rain period over the southern China in June 2005. Results show that there may exist a relationship between the east-west shift of the WPSH and the process of a southern China heavy rain. The analysis indicates that the vertical motion in the WPSH area is mainly caused by the latent heat release of monsoon rain belts on its northern and southern sides. The vertical motion could cause the accumulation of air mass in the center and west of the WPSH, which leads to its strengthening. The appearance of the northern and southern monsoon rain belts could not only enhance the WPSH by strengthening the descending draft, but also excite the development of positive vorticity and restrict the WPSH’s movement in the north–south direction. Moreover, the Indian monsoon rainfall to the west of the WPSH may excite the development of anticyclonic vorticity on its eastern side, which leads to the westward extension of the WPSH.