夏季赤道东太平洋海温异常对全球及东亚短期气候变化影响的数值试验

本文应用中国科学院大气物理研究所设计的两层大气环流模式（IAP-AGCM）研究了夏季赤道东太平洋地区负的海温异常对全球大气及赤道太平洋地区和东亚局地短期气候变化的影响，着重分析了海温异常（SSTA）所造成的降水、高度场、风场以及赤道太平洋地区海表感热和潜热输送等一些物理场的异常，并对赤道东太平洋海温异常影响全球及赤道太平洋和东亚局地短期气候变化的物理机制进行了探讨，得到了一些有意义的结果。     

夏季青藏高原与热带西太平洋下垫面热源异常对中国短期气候的影响

本文利用一个两层全球大气环流格点模式进行了控制试验、青藏高原地表反照率增加及热带西太平洋海温升高等三个数值试验,以研究夏季这两个地区下垫面热源异常对短期气候变化的影响。结果表明,高原地面热源减弱将造成海平面气压场上亚洲大陆低压减弱;高原及其以西地区500 hPa高度下降,黄河以北地区高度升高;同时高原地区、江淮流域以及黑龙江流域降水减少,但从北疆、内蒙到辽河流域以及我国西南局部和东南沿海地区降水增加。热带西太平洋海温异常带来的变化与此不同.文中还就下垫面热源异常在短期气候预测方面的可能应用等问题进行了讨论。     

中国短期气候变化的一个重要原因

通过数值试验对高原地表反射率变化的气候效应进行了敏感性研究，同时与观测的近４０年中国区域气候变化趋势作了对比分析。结果表明，高原主体地表反射率增加是我国短期气候变化的重要控制因子之一，它能造成东亚夏季风和高原夏季风的显著减弱，使夏季我国东部季风区北方变暖，南方变冷，季风降水普遍减少     

青藏高原地面热力异常对夏季江淮流域持续暴雨形成作用的数值试验

本文采用OSU-AGCM大气环流模式，对青藏高原下垫面热力异常与夏季江淮流域暴雨形成的关系进行了数值试验。模拟结果表明，青藏高原下垫面热力状况的异常对东亚环流形势及云量分布异常的影响是形成1991年夏季江淮流域持续性降水的重要原因之一。青藏高原异常热力强迫还可以引起大范围云量的异常分布和云量异常区类似于二维Rossby波列没大圆路径传播的特征。     

Regional warming induced by urban surface expansion in Shanghai

如何量化城市下垫面扩张对增暖的贡献,减小气候变化评估和预估的不确定性,是城市化影响研究中的一个难点。本文基于卫星遥感得到的反映过去三十多年城市下垫面扩张的土地利用数据,开展高分辨率的嵌套数值试验,量化了城市下垫面扩张在上海不同空间尺度上对增暖的贡献。城市下垫面扩张对整个区域增暖的贡献在19%左右,而城市下垫面扩张区(N2U)的贡献比一直是城市下垫面区域(U2U)要高得多,分别在42%和17%左右。同时城市下垫面扩张对最低温度的增加强于最高温度的变化,日较差减小,尤其在城市下垫面扩张区更加显著。     

气候变化中下垫面作用的数值模拟

本文利用一个三维数值模式,对下垫面在气候变化中的作用进行了数值模拟.共做了两个均一土壤下垫面试验和一个非均一土壤下垫面试验.结果表明,东半球夏季季风气候区的基本气候特征,主要是由海陆分布和大地形的影响所产生.但是,细致的气候特征却受下垫面土壤物理性质和初始湿度的很大影响.而且,通过环流系统的相互作用,除对本地区天气气候产生影响外,还会影响周围地区.非洲撒哈拉大沙漠的形成很可能是长期受到海陆分布及高原地形所造成的基本气候场作用的结果.     

2000年《气象》选题计划要点

1综合评述 本专题主要刊登气象学及相关学科国内外研究动态的综合评述: 1.1气候变化与变异模拟的研究进展,气候变化对人类社会、环境与经济的影响。 １．２天气预报技术及预报业务系统的发展现状及趋势． １．３数值天气预报模式及产品释用技术的发展． １．４气象通信网络系统的应用及发展趋势． １．５气象灾害的监测、预测及减灾对策的研究进展。 ２　气候变化及预测 ２．１关于气候变化的诊断和监测; ２．２气候变化的数值模拟,和短期气候变化的数值预测模式研究进展; ２．３洪涝、干旱等气候异常的诊…     

植被覆盖变化对区域气候影响的研究进展

陆面植被覆盖变化作为全球及区域气候变化的重要影响因素之一，在近几十年来逐渐受到科学家们的关注，特别是通过大量的数值模拟研究了不同陆面覆盖状况对大气和气候变化的影响，取得了重要进展。研究结果普遍认为，植被覆盖变化通过改变地表反照率、粗糙度和土壤湿度等地表属性，从而影响辐射平衡、水分平衡等过程，最终可以导致区域降水、环流形势及大气温度、湿度等气候变化。总结了近十年国内外的相关研究及初步成果，尤其是植被变化对中国区域气候的影响，大部分研究认为，大范围植被退化使我国地表温度升高，东亚夏季风环流减弱，降水减少，使华北干旱加剧。同时指出了研究中存在问题及今后的工作重点。     

短期气候预测因子的选取及利用

短期气候预测是近年来气象科学研究的热点问题，文章就短期气候预测研究中因子选取、因子分析及因子利用等问题进行了初步探讨。文中认为，普查影响短期气候变化的所有因子组成备选因子集是进行短期气候预测的最基础的工作，对备选因子进行合理性、稳定性及代表性分析是预报是否取得成功的最关键问题，而使用先进的统计预报方法则是提高预报准确率的前提条件。另外，还要充分考虑到一些非线性因子的选取及利用，同时还要尽可能地利用数值预报产品作为预报因子。     

中国短期气候变化的一个重要原因——青藏高原地表反射率的变化

通过数值试验对高原地表反射率变化的气候效应进行了敏感性研究,同时对观测的近４０年中国区域气候变化趋势作了对比分析。结果表明,高原主体地表反射率增加是我国短期气候变化的重要控制因子之一,它能造成东亚夏季风和高原夏季风的显著减弱,使夏季我国东部季风区北方变暖,南方变冷,季风降水普遍减少。     

森林下垫面陆面物理过程及局地气候效应的数值模拟试验

文中基于大气边界层和植被冠层微气象学基本原理 ,建立了一个森林植被效应的陆面物理过程和二维大气边界层数值模式。并应用该模式进行了植被和土壤含水量等生物和生理过程在陆面过程和局地气候效应方面的数值模拟试验。所得数值模拟试验结果与实际情况相吻合。结果表明 ,应用该模式可获得植被温度、植被冠层内空气温度、地表温度日变化特征 ;森林下垫面大气边界层风速、位温、比湿、湍流交换系数的时空分布和日变化特征。该模式还可应用于不同下垫面 ,模拟陆面物理过程与大气边界层相互作用机制及其局地气候效应的研究 ,这将为气候模式与生物圈的耦合研究奠定一个良好的基础。     

区域气候模拟研究

区域气候模拟是近几年发展起来的研究有限区域气候及气候变化的方法。由于区域气候模式较好地表示了地形和地表状况,同时包含较详细的陆地过程方案,因而能捕获许多大气环流模式难以分辨的区域尺度温度、降水分布和土壤水分变化特征。此外,区域气候模拟对于了解温室气体强迫可能导致的全球增暖在区域尺度上的特征及生态、环境效应也具有重要的意义。该文总结区域气候模式和模拟试验结果,并指出存在问题及今后研究的重点。     

动力数值模式侧边界强迫的改进试验

通过修正嵌套模式侧边界缓冲区温度强迫项的计算方法,使区域气候模式所刻画的温度日变化信息与不同下垫面区域的天气变化规律相符合.进而利用数值模式ASRegCM研究了侧边界缓冲区温度强迫的改进处理对嵌套模式模拟效果的影响,并讨论了其对模拟结果改进的可能机制.数值试验结果表明,该侧边界缓冲区强迫的改进对地面气温和降水距平分布的...     

INFLUENCE OF SOIL MOISTURE AND VEGETATION ON CLIMATE CHANGES INDUCED BY THERMAL FORCING*

A land-process scheme has been incorporated in a vertical one-dimensional time-dependent atmospheric model and numerical experiments have been performed with the coupled model to examine influences of soil wetness and vegetation on climate changes associated to thermal forcing.It is showed that response of land-surface temperature to the thermal forcing becomes small with increase of soil water content and vegetation cover.Furthermore,the response is more obvious in arid climate region than in humid one.The result also shows that there exist two patterns of corresponding relation between variations in air temperature and humidity on the land surface in response to hydrologic and thermal focing.     

A NUMERICAL SIMULATION OF THE EFFECT ON CHINESE REGIONAL CLIMATE DUE TO SEASONAL VARIATION OF LAND SURFACE PARAMETERS(PART I)

Sensitivity experiment is an important method to study the effect on regional climate due toseasonal variation of land surface parameters.Using China Regional Climate Model(CRCM)nested in CCM1.we first simulate Chinese regional climate,then two numerical sensitivityexperiments on the effect of vegetation and roughness length are made.The results show that:(1)If the vegetation is replaced with the monthly data of 1997.precipitation and land-surfacetemperature are both changed clearly,precipitation decreases and land surface temperatureincreases,but there is no regional correspondence between these changes.And the results aremuch better than the results when climate average vegetation was used in the CRCM.(2)If theroughness length is replaced with the monthly data of 1997,there is significant change on landsurface temperature,and there is very good regional correspondence between these changes.Butthe effect on precipitation is very small.     

INFLUENCE OF SOIL MOISTURE AND VEGETATION ON CLIMATE CHANGES INDUCED BY THERMAL FORCING

A land-process scheme has been incorporated in a vertical one-dimensional time-dependent atmospheric modeland numerical experiments have been performed with the coupled model to examine influences of soil wetness and vege-tation on climate changes associated to thermal forcing.It is showed that response of land-surface temperature to thethermal forcing becomes small with increase of soil water content and vegetation cover.Furthermore,the response ismore obvious in arid climate region than in humid one.The result also shows that there exist two patterns of corre-sponding relation between variations in air temperature and humidity on the land surface in response to hydrologic andthermal focing.     

土壤类型变化对区域气候影响的数值试验

利用地气耦合区域气候模式研究了我国华北和西北部分地区土壤类型变化的区域气候效应，着重分析了土壤类型变化对海平面气压场、近地层气温和湿度、土壤温度、边界层风速、垂直运动以及地面能量平衡和转换关系的影响，所得结果可为我国北方干旱半干旱地区土地资源的合理开发和利用提供一定的气候依据。     

Direct Radiative Forcing and Climatic Effects of Aerosols over East Asia by RegCM3

The authors used a high-resolution regional climate model(RegCM3) coupled with a chemistry/aerosol module to simulate East Asian climate in 2006 and to test the climatic impacts of aerosols on regionalscale climate.The direct radiative forcing and climatic effects of aerosols(dust,sulfate,black carbon,and organic carbon) were discussed.The results indicated that aerosols generally produced negative radiative forcing at the top-of-the-atmosphere(TOA) over most areas of East Asia.The radiative forcing induced by aerosols exhibited significant seasonal and regional variations,with the strongest forcing occurring in summer.The aerosol feedbacks on surface air temperature and precipitation were clear.Surface cooling dominated features over the East Asian continental areas,which varied in the approximate range of-0.5 to-2°C with the maximum up to-3-C in summer over the deserts of West China.The aerosols induced complicated variations of precipitation.Except in summer,the rainfall generally varied in the range of-1 to 1 mm d-1 over most areas of China.     

Numerical Simulation Experiment of Land Surface Physical Processes and Local Climate Effect in Forest Underlying Surface

Based on the basic principles of atmospheric boundary layer and plant canopy micrometeorology, a forest underlying surface land surface physical process model and a two-dimensional atmospheric boundary layer numerical model are developed and numerical simulation experiments of biosphere and physiological processes of vegetation and soil volumetric water content have been done on land surface processes with local climate effect. The numerical simulation results are in good agreement with realistic observations, which can be used to obtain reasonable simulations for diurnal variations of canopy temperature, air temperature in canopy, ground surface temperature, and temporal and spatial distributions of potential temperature and vertical wind velocity as well as relative humidity and turbulence exchange coefficient over non-homogeneous underlying surfaces. It indicates that the model developed can be used to study the interaction between land surface process and atmospheric boundary layer over various underlying surfaces and can be extended to local climate studies. This work will settle a solid foundation for coupling climate models with the biosphere.     

Influence of modern land cover on the climate of the United States

I have used a high-resolution nested climate modeling system to test the sensitivity of regional and local climate to the modern non-urban land cover distribution of the continental United States. The dominant climate response is cooling of surface air temperatures, particularly during the warm-season. Areas of statistically significant cooling include areas of the Great Plains where crop/mixed farming has replaced short grass, areas of the Midwest and southern Texas where crop/mixed farming has replaced interrupted forest, and areas of the western United States containing irrigated crops. This statistically significant warm-season cooling is driven by changes in both surface moisture balance and surface albedo, with changes in surface moisture balance dominating in the Great Plains and western United States, changes in surface albedo dominating in the Midwest, and both effects contributing to warm-season cooling over southern Texas. The simulated changes in surface moisture and energy fluxes also influence the warm-season atmospheric dynamics, creating greater moisture availability in the lower atmosphere and enhanced uplift aloft, consistent with the enhanced warm-season precipitation seen in the simulation with modern land cover. The local and regional climate response is of a similar magnitude to that projected for future greenhouse gas concentrations, suggesting that the climatic effects of land cover change should be carefully considered when crafting policies for regulating land use and for managing anthropogenic forcing of the climate system.