Low-Cloud Feedbacks from Cloud-Controlling Factors: A Review
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作者:
Klein, Stephen A.
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Lawrence Livermore Natl Lab, Cloud Proc Res Grp, 7000 East Ave,L-103, Livermore, CA 94551 USALawrence Livermore Natl Lab, Cloud Proc Res Grp, 7000 East Ave,L-103, Livermore, CA 94551 USA
Klein, Stephen A.
[1
]
Hall, Alex
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Univ Calif Los Angeles, Dept Atmospher & Ocean Sci, Los Angeles, CA 90095 USALawrence Livermore Natl Lab, Cloud Proc Res Grp, 7000 East Ave,L-103, Livermore, CA 94551 USA
Hall, Alex
[2
]
Norris, Joel R.
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Univ Calif San Diego, Scripps Inst Oceanog, La Jolla, CA 92093 USALawrence Livermore Natl Lab, Cloud Proc Res Grp, 7000 East Ave,L-103, Livermore, CA 94551 USA
Norris, Joel R.
[3
]
Pincus, Robert
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Univ Colorado, Cooperat Inst Res Environm Sci, Boulder, CO 80309 USA
NOAA, Div Phys Sci, Earth Syst Res Lab, Boulder, CO 80305 USALawrence Livermore Natl Lab, Cloud Proc Res Grp, 7000 East Ave,L-103, Livermore, CA 94551 USA
Pincus, Robert
[4
,5
]
机构:
[1] Lawrence Livermore Natl Lab, Cloud Proc Res Grp, 7000 East Ave,L-103, Livermore, CA 94551 USA
[2] Univ Calif Los Angeles, Dept Atmospher & Ocean Sci, Los Angeles, CA 90095 USA
[3] Univ Calif San Diego, Scripps Inst Oceanog, La Jolla, CA 92093 USA
[4] Univ Colorado, Cooperat Inst Res Environm Sci, Boulder, CO 80309 USA
[5] NOAA, Div Phys Sci, Earth Syst Res Lab, Boulder, CO 80305 USA
The response to warming of tropical low-level clouds including both marine stratocumulus and trade cumulus is a major source of uncertainty in projections of future climate. Climate model simulations of the response vary widely, reflecting the difficulty the models have in simulating these clouds. These inadequacies have led to alternative approaches to predict low-cloud feedbacks. Here, we review an observational approach that relies on the assumption that observed relationships between low clouds and the "cloud-controlling factors" of the large-scale environment are invariant across time-scales. With this assumption, and given predictions of how the cloud-controlling factors change with climate warming, one can predict low-cloud feedbacks without using any model simulation of low clouds. We discuss both fundamental and implementation issues with this approach and suggest steps that could reduce uncertainty in the predicted low-cloud feedback. Recent studies using this approach predict that the tropical low-cloud feedback is positive mainly due to the observation that reflection of solar radiation by low clouds decreases as temperature increases, holding all other cloud-controlling factors fixed. The positive feedback from temperature is partially offset by a negative feedback from the tendency for the inversion strength to increase in a warming world, with other cloud-controlling factors playing a smaller role. A consensus estimate from these studies for the contribution of tropical low clouds to the global mean cloud feedback is 0.25 +/- 0.18 W m(-2) K-1 (90% confidence interval), suggesting it is very unlikely that tropical low clouds reduce total global cloud feedback. Because the prediction of positive tropical low-cloud feedback with this approach is consistent with independent evidence from low-cloud feedback studies using high-resolution cloud models, progress is being made in reducing this key climate uncertainty.
机构:
Lawrence Livermore Natl Lab, Program Climate Model Diag & Intercomparison, Livermore, CA USALawrence Livermore Natl Lab, Program Climate Model Diag & Intercomparison, Livermore, CA USA
Gordon, Neil D.
Klein, Stephen A.
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机构:
Lawrence Livermore Natl Lab, Program Climate Model Diag & Intercomparison, Livermore, CA USALawrence Livermore Natl Lab, Program Climate Model Diag & Intercomparison, Livermore, CA USA
机构:
Lawrence Livermore Natl Lab, Program Climate Model Diag & Intercomparison, Livermore, CA USALawrence Livermore Natl Lab, Program Climate Model Diag & Intercomparison, Livermore, CA USA
Gordon, Neil D.
Klein, Stephen A.
论文数: 0引用数: 0
h-index: 0
机构:
Lawrence Livermore Natl Lab, Program Climate Model Diag & Intercomparison, Livermore, CA USALawrence Livermore Natl Lab, Program Climate Model Diag & Intercomparison, Livermore, CA USA