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Responses of regional high cloud cover to interannual variability and global warming: insights from a satellite simulator
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DOI:10.1007/s00382-026-08312-y.png)
Abstract
En 中文
A previous study has reported similarity in the variability of tropical high cloud cover in the present climate and in climate change (interannual and centennial scales) in the tropics, evaluated based on percentage cloud cover, which is a standard output of the Coupled Model Intercomparison Project (CMIP). However, physically interpreting intermodel comparisons of simulated clouds using the standard output of cloud cover is not necessarily straightforward. The present study uses data from the Atmospheric Model Intercomparison Project (AMIP), AMIP future4K and AMIP p4K to evaluate the feedback of high cloud cover (a change of high cloud cover per unit surface warming) based on the standard output of cloud cover and cloud cover evaluated using a satellite simulator under a common definition in general circulation models based mainly on modeled cloud radiative properties. We reveal that the feedback of high cloud cover at the interannual scale is consistently negative, as in the previous study. However, the feedback of high cloud cover at the centennial scale is nearly zero, different from that at the interannual scale. The reason lies in the previous study’s definition of high cloud cover by the standard output of cloud cover to be consistent with the result of cloud cover evaluated using a satellite simulator at the interannual scale. However, this definition does not necessarily hold in different climate states, such as future climates. The reduction of high cloud cover evaluated with the standard output of cloud cover in the future climate states tends to be more remarkable compared to the changes of high cloud cover based on cloud cover evaluated using a satellite simulator. Furthermore, the relationship between feedback of high cloud cover and the feedback of outgoing longwave radiation is stronger when using cloud cover evaluated using a satellite simulator than when using the standard output of cloud cover. This study also reveals large uncertainties in the projection of high cloud cover over the tropics in a perturbed climate (increase of sea surface temperature), even when using cloud cover evaluated using a satellite simulator, because of an almost equal number of models showing increased and decreased high cloud covers due to warming. This study demonstrates the need to include satellite simulator data as an endorsed output of major MIPs for the in-depth analysis of clouds, such as to determine the major causes of modeled uncertainties in future changes of high cloud cover, based on CMIP data.
Keywords:
Feedback of high-cloud cover
Importance of satellite simulator data
Global warming
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