Aerosol Radiative Forcing and Climate Response: A Regional Focus

从区域上看，人为气溶胶可导致地表太阳辐照度大幅降低，大气太阳加热相应增加，低空逆温增强，由于直接微物理效应抑制降雨，以及污染物去除效率降低。这些气溶胶效应除了改变温度分布外，还可能导致水文循环减弱，这是21世纪的一个主要环境问题。本项目的总体目标是了解上述气溶胶效应。具体目标有两个：1)通过将现场、地面和卫星观测与综合蒙特卡洛气溶胶-云辐射（MACR）模式相结合，量化区域尺度上的直接和间接气溶胶辐射强迫，该模式考虑了无机、有机和黑碳种的混合混合。MACR还将准确地解释多云天空中的气溶胶强迫（直接和首先是间接）。这些估计也将用于改进NCAR社区气候模式（CCM）中气溶胶辐射效应和气溶胶-云相互作用的处理。会议的重点将放在对全球平均人为气溶胶负荷贡献最大的区域气溶胶热点，包括亚洲、非洲和北美地区。所选地区与有实地观测资料的地区相吻合。2)利用区域气溶胶强迫作为NCAR CCM/气候系统模式（CSM）的输入，估算强迫对气候和水文循环的影响。我们的重点将主要放在亚洲气溶胶上，它们贡献了全球人为气溶胶光学深度的30 ~ 50%。该气候模式将在规定表面海温模式（CCM）和全耦合模式（CSM）下运行。到目前为止，气溶胶被简单地描述为抵消温室气体引起的武装，其抵消程度一直是主要关注的问题。纳入吸收碳质气溶胶可能会从本质上挑战这一传统观点。利用吸收气溶胶的印度洋实验（INDOEX）进行的初步CCM实验表明，南亚雾霾区域性地冷却了地面，使热带辐合带向北移动，并远程抑制了赤道西太平洋的对流，这与厄尔尼诺-南方涛动周期有关。拟议的研究建立在NSF云化学与气候中心（C4）和INDOEX开发的基础设施基础上，包括：C4数据集成系统（CIDS）；宏观;基于化学数据的卫星气溶胶反演三维气溶胶同化模式；贝奥武夫集群计算机；以及通过INDOEX建立的合作网络。将使用一系列地面、空中和卫星观测。这项工作产生的气溶胶强迫和气候响应结果将直接有助于未来的国家和国际气候影响评估。这项工作产生的气溶胶强迫将作为独立于全球模式提供的估计。它还将导致对气溶胶强迫的GCM处理的显著改进。

Regionally, anthropogenic aerosols can lead to large reductions in the surface solar irradiance, a corresponding increase in atmospheric solar heating, stronger low-level inversions, suppression of rainfall due to the direct microphysical effect, and less efficient removal of pollutants. These aerosol effects, in addition to altering the temperature distribution, can also lead to a weaker hydrological cycle, a major environmental issue for the 21st century. The overall goal of this project is to understand the above-mentioned aerosol effects. The specific objectives are twofold:1) To quantify the direct and the indirect aerosol radiative forcings on regional scales by integrating in-situ, surface and satellite observations with a comprehensive Monte-Carlo Aerosol-Cloud Radiation (MACR) model that accounts for hybrid mixing of inorganic, organic and black carbon species. MACR will also account accurately for aerosol forcing (direct and first indirect) in cloudy skies. These estimates will also be used to improve the treatment of aerosol radiative effects and aerosol-cloud interactions in the NCAR Community Climate Model (CCM). The focus will be on regional Aerosol Hot Spots, which contribute the most to the global mean anthropogenic aerosol loading including the Asian, African and N. American regions. The selected regions coincide with regions where field observations are available.2) To use the regional aerosol forcing as input to the NCAR CCM/Climate System Model (CSM) and estimate impacts of the forcing on climate and the hydrological cycle. Our focus will be primarily on the Asian aerosols which contribute as much as 3O~5O% of the global anthropogenic aerosol optical depth. The climate model will be run both in prescribed-surface sea temperature mode (CCM) as well as in fully coupled mode (CSM). So far, aerosol has been portrayed simply as counteracting greenhouse gas induced arming, and its counteracting extent has been the primary concern. The inclusion of absorbing carbonaceous aerosols is likely to challenge this traditional view substantially. Preliminary CCM experiments with the Indian Ocean Experiment (INDOEX) absorbing aerosols reveal that the South Asian haze regionally cools the surface, shifts the inter-tropical convergence zone northwards and remotely suppresses the convection in the equatorial western Pacific with implications to El Nino-Southern Oscillation cycles.The proposed research builds on the infrastructure developed under NSF Center for Clouds Chemistry and Climate (C4) and INDOEX, including: C4 Data Integration system (CIDS); MACR; Satellite aerosol retrieval based on chemical data; three dimensional aerosol assimilation model; Beowulf cluster computers; and the network of collaborators developed through INDOEX. An array of ground based, airborne and satellite observations will be used.The aerosol forcing and climate response results generated by this work should contribute directly to future national and international climate impact assessments. The aerosol forcing from this work will serve as an independent estimate from that provided by global models. It also should lead to significant improvements in GCM treatment of aerosol forcing.