Observational evidence for a negative shortwave cloud feedback in middle to high latitudes
Observational evidence for a negative shortwave cloud feedback in middle to high latitudes
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DOI：
10.1002/2015gl067499
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发表时间：
2016-02-16
影响因子：
5.2
通讯作者：
Hartmann, Dennis L.
中科院分区：
文献类型：
--
作者：
Ceppi, Paulo;McCoy, Daniel T.;Hartmann, Dennis L.
利用观测到的温带云中温度和光学深度之间的稳健关系，我们通过将观测到和建模的云特性直方图回归到南半球中高纬度地区的局部温度来计算历史数据中的短波云反馈。在该区域，所有 CMIP5 模型和观测数据集都预测负云反馈，主要由光学增厚驱动。在南纬 45 度到 60 度之间，观测到的平均短波反馈（-0.91 0.82Wm(-2)K(-1)，相对于局部而非全球平均变暖）非常接近 RCP8.5 中的多模式平均反馈（-0.98Wm(-2)K(-1)），尽管经向结构存在差异。在模型中，历史温度-云属性关系可以可靠地预测强制 RCP8.5 响应。因为简单的理论预测这种光学增厚会随着变暖而增加，而且云量变化相对较小，所以我们得出结论，在中高纬度地区的现实世界中，短波云反馈很可能是负的。
Exploiting the observed robust relationships between temperature and optical depth in extratropical clouds, we calculate the shortwave cloud feedback from historical data, by regressing observed and modeled cloud property histograms onto local temperature in middle to high southern latitudes. In this region, all CMIP5 models and observational data sets predict a negative cloud feedback, mainly driven by optical thickening. Between 45 degrees and 60 degrees S, the mean observed shortwave feedback (-0.91 0.82Wm(-2)K(-1), relative to local rather than global mean warming) is very close to the multimodel mean feedback in RCP8.5 (-0.98Wm(-2)K(-1)), despite differences in the meridional structure. In models, historical temperature-cloud property relationships reliably predict the forced RCP8.5 response. Because simple theory predicts this optical thickening with warming, and cloud amount changes are relatively small, we conclude that the shortwave cloud feedback is very likely negative in the real world at middle to high latitudes.