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Proceedings Paper

Constraining the models' response of tropical clouds to SST forcings using CALIPSO observations
Author(s): Gregory Cesana; Anthony D. Del Genio; Andrew Ackerman
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Paper Abstract

Here we present preliminary results from the analysis of the low cloud cover (LCC) and cloud radiative effect (CRE) interannual changes in response to sea surface temperature (SST) forcings in two GISS climate models, and 12 other climate models. We further classify them as a function of their ability to reproduce the vertical structure of the cloud response to SST change against 10 years of CALIPSO observations: “the constrained models, which match the observation constraint, and the unconstrained models”. The constrained models replicate the observed interannual LCC change particularly well (ΔLCCcon=-3.49 ±1.01 %/K vs. ΔLCCobs=-3.59 ±0.28 %/K) as opposed to the unconstrained models, which largely underestimate it (ΔLCCunc = -1.32 ± 1.28 %/K). As a result, the amount of short-wave warming simulated by the constrained models (ΔCREcon=2.60 ±1.13 W/m2 /K) is in better agreement with the observations (ΔCREobs=3.05 ± 0.28 W/m2 /K) than the unconstrained models (ΔCREcon=0.87 ±2.63 W/m2 /K). Depending on the type of low cloud, the observed relationship between cloud/radiation and surface temperature varies. Over the stratocumulus regions, increasing SSTs generate higher cloud top height along with a large decrease of the cloud fraction below as opposed to a slight decrease of the cloud fraction at each level over the trade cumulus regions. Our results suggest that the models must generate sustainable stratocumulus decks and moist processes in the planetary boundary layer to reproduce these observed features. Future work will focus on defining a method to objectively discriminate these cloud types that can be applied consistently in both the observations and the models.

Paper Details

Date Published: 23 October 2018
PDF: 13 pages
Proc. SPIE 10782, Remote Sensing and Modeling of the Atmosphere, Oceans, and Interactions VII, 107820A (23 October 2018); doi: 10.1117/12.2324800
Show Author Affiliations
Gregory Cesana, Columbia Univ. (United States)
NASA Goddards Institute for Space Studies (United States)
Anthony D. Del Genio, NASA Goddard Institute for Space Studies (United States)
Andrew Ackerman, NASA Goddard Institute for Space Studies (United States)

Published in SPIE Proceedings Vol. 10782:
Remote Sensing and Modeling of the Atmosphere, Oceans, and Interactions VII
Guosheng Liu; Ziad S. Haddad, Editor(s)

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