Positive Tropical Marine Low-Cloud Cover Feedback Inferred from Cloud-Controlling Factors

TitlePositive Tropical Marine Low-Cloud Cover Feedback Inferred from Cloud-Controlling Factors
Publication TypeJournal Article
Year of Publication2015
AuthorsQu, Xin, Hall Alex, Klein Stephen A., and DeAngelis Anthony M.
JournalGeophysical Research Letters
Volume42
Date Published09/2015
Abstract / Summary

Differences in simulations of tropical marine low-cloud cover (LCC) feedback are sources of significant spread in temperature responses of climate models to anthropogenic forcing. Here we show that in models the feedback is mainly driven by three large-scale changes—a strengthening tropical inversion, increasing surface latent heat flux, and an increasing vertical moisture gradient. Variations in the LCC response to these changes alone account for most of the spread in model-projected 21st century LCC changes. A methodology is devised to constrain the LCC response observationally using sea surface temperature (SST) as a surrogate for the latent heat flux and moisture gradient. In models where the
current climate’s LCC sensitivities to inversion strength and SST variations are consistent with observed, LCC decreases systematically, which would increase absorption of solar radiation. These results support a positive LCC feedback. Correcting biases in the sensitivities will be an important step toward more credible simulation of cloud feedbacks.

DOI10.1002/2015GL065627
Journal: Geophysical Research Letters
Year of Publication: 2015
Volume: 42
Date Published: 09/2015

Differences in simulations of tropical marine low-cloud cover (LCC) feedback are sources of significant spread in temperature responses of climate models to anthropogenic forcing. Here we show that in models the feedback is mainly driven by three large-scale changes—a strengthening tropical inversion, increasing surface latent heat flux, and an increasing vertical moisture gradient. Variations in the LCC response to these changes alone account for most of the spread in model-projected 21st century LCC changes. A methodology is devised to constrain the LCC response observationally using sea surface temperature (SST) as a surrogate for the latent heat flux and moisture gradient. In models where the
current climate’s LCC sensitivities to inversion strength and SST variations are consistent with observed, LCC decreases systematically, which would increase absorption of solar radiation. These results support a positive LCC feedback. Correcting biases in the sensitivities will be an important step toward more credible simulation of cloud feedbacks.

DOI: 10.1002/2015GL065627
Citation:
Qu, X, A Hall, SA Klein, and AM DeAngelis.  2015.  "Positive Tropical Marine Low-Cloud Cover Feedback Inferred from Cloud-Controlling Factors."  Geophysical Research Letters 42.  https://doi.org/10.1002/2015GL065627.