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Interpretation of the positive low-cloud feedback predicted by a climate model under global warming.
- Source :
-
Climate Dynamics . May2013, Vol. 40 Issue 9/10, p2415-2431. 17p. 3 Charts, 13 Graphs, 1 Map. - Publication Year :
- 2013
-
Abstract
- The response of low-level clouds to climate change has been identified as a major contributor to the uncertainty in climate sensitivity estimates among climate models. By analyzing the behaviour of low-level clouds in a hierarchy of models (coupled ocean-atmosphere model, atmospheric general circulation model, aqua-planet model, single-column model) using the same physical parameterizations, this study proposes an interpretation of the strong positive low-cloud feedback predicted by the IPSL-CM5A climate model under climate change. In a warmer climate, the model predicts an enhanced clear-sky radiative cooling, stronger surface turbulent fluxes, a deepening and a drying of the planetary boundary layer, and a decrease of tropical low-clouds in regimes of weak subsidence. We show that the decrease of low-level clouds critically depends on the change in the vertical advection of moist static energy from the free troposphere to the boundary-layer. This change is dominated by variations in the vertical gradient of moist static energy between the surface and the free troposphere just above the boundary-layer. In a warmer climate, the thermodynamical relationship of Clausius-Clapeyron increases this vertical gradient, and then the import by large-scale subsidence of low moist static energy and dry air into the boundary layer. This results in a decrease of the low-level cloudiness and in a weakening of the radiative cooling of the boundary layer by low-level clouds. The energetic framework proposed in this study might help to interpret inter-model differences in low-cloud feedbacks under climate change. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 09307575
- Volume :
- 40
- Issue :
- 9/10
- Database :
- Academic Search Index
- Journal :
- Climate Dynamics
- Publication Type :
- Academic Journal
- Accession number :
- 87303856
- Full Text :
- https://doi.org/10.1007/s00382-011-1279-7