Radiative damping of annual variation in global mean surface temperature: comparison between observed and simulated feedback
Radiative damping of annual variation in global mean surface temperature: comparison between observed and simulated feedback
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全球平均地表温度年变化的辐射阻尼：观测反馈与模拟反馈之间的比较
DOI：
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
S. Manabe
中科院分区：
文献类型：
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作者：
Y. Tsushima;A. Abe‐Ouchi;S. Manabe
全球气候的敏感性实质上是由大气顶部向外辐射对全球平均地表温度异常的辐射衰减决定的。利用从地球辐射收支实验（埃尔贝）获得的地面和反射太阳辐射的TOA通量，本研究估计的整体反馈的大小，它修改了全球平均表面温度的年变化的辐射阻尼，并将其与模式模拟进行比较。虽然每年变化的异常的模式是完全不同的全球变暖，这里进行的分析可用于评估的反馈，对CO2引起的地表温度变暖的系统偏差。在没有反馈效应的情况下，在TOA处的出射地球辐射近似遵循行星辐射温度的Stefan-Boltzmann四次方。然而，它偏离显着的黑体辐射，由于各种反馈涉及水蒸气和云量。此外，反射的太阳辐射被海冰、雪和云的反馈所改变，从而影响表面温度的辐射阻尼。对埃尔贝的分析表明，由于反馈的整体效应，辐射阻尼被削弱了多达70%，并且仅为具有行星发射温度的黑体所期望的辐射阻尼的30%。本文还对三个大气环流模式进行了相似反馈分析，这三个模式在前面的研究中曾用于云反馈的研究。三个模型中的总体反馈的符号和幅度与观察到的相似。然而，当它被细分为太阳和地球的组成部分，他们是相当不同的观测主要是由于失败的模式，以模拟单独的太阳和地球组成部分的云反馈。因此，不仅需要对总体反馈进行类似的比较，而且还需要对其各个组成部分进行类似的比较，例如云反馈和云反馈。虽然年变距平的模式与全球变暖的模式有很大的不同，但这里提出的比较分析方法可用于识别模式中总体反馈的系统偏差。提出了一个利用政府间气候变化专门委员会提交的许多气候模式的输出来估计气候敏感性的最佳猜测值的建议。
The sensitivity of the global climate is essentially determined by the radiative damping of the global mean surface temperature anomaly through the outgoing radiation from the top of the atmosphere (TOA). Using the TOA fluxes of terrestrial and reflected solar radiation obtained from the Earth radiation budget experiment (ERBE), this study estimates the magnitude of the overall feedback, which modifies the radiative damping of the annual variation of the global mean surface temperature, and compare it with model simulations. Although the pattern of the annually varying anomaly is quite different from that of the global warming, the analysis conducted here may be used for assessing the systematic bias of the feedback that operates on the CO2-induced warming of the surface temperature. In the absence of feedback effect, the outgoing terrestrial radiation at the TOA is approximately follows the Stefan-Boltzmann’s fourth power of the planetary emission temperature. However, it deviates significantly from the blackbody radiation due to various feedbacks involving water vapor and cloud cover. In addition, the reflected solar radiation is altered by the feedbacks involving sea ice, snow and cloud, thereby affecting the radiative damping of surface temperature. The analysis of ERBE reveals that the radiative damping is weakened by as much as 70% due to the overall effect of feedbacks, and is only 30% of what is expected for the blackbody with the planetary emission temperature. Similar feedback analysis is conducted for three general circulation models of the atmosphere, which was used for the study of cloud feedback in the preceding study. The sign and magnitude of the overall feedback in the three models are similar to those of the observed. However, when it is subdivided into solar and terrestrial components, they are quite different from the observation mainly due to the failure of the models to simulate individually the solar and terrestrial components of the cloud feedback. It is therefore desirable to make the similar comparison not only for the overall feedback but also for its individual components such as albedo- and cloud-feedbacks. Although the pattern of the annually-varying anomaly is quite different from that of global warming, the methodology of the comparative analysis presented here may be used for the identification of the systematic bias of the overall feedback in a model. A proposal is made for the estimation of the best guess value of climate sensitivity using the outputs from many climate models submitted to the Intergovernmental panel on Climate Change.