Climate feedbacks in a general circulation model incorporating prognostic clouds
Climate feedbacks in a general circulation model incorporating prognostic clouds
复制标题
包含预测云的大气环流模型中的气候反馈
DOI：
10.1007/s003820100162
复制
发表时间：
2001
期刊：
影响因子：
4.6
通讯作者：
L. Rotstayn
中科院分区：
文献类型：
--
作者：
R. Colman;J. Fraser;L. Rotstayn
摘要本研究对气象局研究中心环流模式进行了全面的反馈分析，量化了在大气CO2增加下运行的所有重要反馈。利用离线辐射摄动方法，对个别反馈进行了详细分析，包括长波和短波分量、纬度分布、云影响、2 × co2和4 × co2增温下的非线性以及年际变率。根据水汽高度和水汽量的变化，将水汽反馈分为若干项。净云反馈根据云量、高度、含水量、水相、物理厚度和对流云分数进行分段。在全球范围内，发现最重要的反馈是由水蒸气、云、地表反照率、递减率和地表温度引起的反馈（从最强的正反馈到最强的负反馈）。对于长波（LW）响应，云的“光学性质”反馈中最重要的一项是由于含水量。在短波（SW）中，水的含量和水的相位变化都很重要。云量和高度对LW和SW也很重要。由物理云厚度和对流云分数引起的反馈相对较小。所有云组件反馈（除了高度）在模型中产生相互冲突的LW/SW反馈。此外，光学性质和云分数反馈也是相反的符号。结果是，净云反馈是相互冲突的物理过程的（相对较小的）产物。除了地表反照率响应和一些云分量的贡献外，所有反馈的非线性都相对较小。云对非云反馈的影响也进行了讨论：对地表反照率的影响最大，但对水蒸气反馈的影响也很显著。这里的分析方法被证明是一个强大的工具，可以详细说明不同模式过程（尤其是云的过程）对最终气候模式敏感性的贡献。
Abstract This study performs a comprehensive feedback analysis on the Bureau of Meteorology Research Centre General Circulation Model, quantifying all important feedbacks operating under an increase in atmospheric CO2. The individual feedbacks are analysed in detail, using an offline radiation perturbation method, looking at long- and shortwave components, latitudinal distributions, cloud impacts, non-linearities under 2xCO2 and 4xCO2 warmings and at interannual variability. The water vapour feedback is divided into terms due to moisture height and amount changes. The net cloud feedback is separated into terms due to cloud amount, height, water content, water phase, physical thickness and convective cloud fraction. Globally the most important feedbacks were found to be (from strongest positive to strongest negative) those due to water vapour, clouds, surface albedo, lapse rate and surface temperature. For the longwave (LW) response the most important term of the cloud ‘optical property’ feedbacks is due to the water content. In the shortwave (SW), both water content and water phase changes are important. Cloud amount and height terms are also important for both LW and SW. Feedbacks due to physical cloud thickness and convective cloud fraction are found to be relatively small. All cloud component feedbacks (other than height) produce conflicting LW/SW feedbacks in the model. Furthermore, the optical property and cloud fraction feedbacks are also of opposite sign. The result is that the net cloud feedback is the (relatively small) product of conflicting physical processes. Non-linearities in the feedbacks are found to be relatively small for all but the surface albedo response and some cloud component contributions. The cloud impact on non-cloud feedbacks is also discussed: greatest impact is on the surface albedo, but impact on water vapour feedback is also significant. The analysis method here proves to be a␣powerful tool for detailing the contributions from different model processes (and particularly those of the clouds) to the final climate model sensitivity.