Response of Upper Clouds in Global Warming Experiments Obtained Using a Global Nonhydrostatic Model with Explicit Cloud Processes

Using a global nonhydrostatic model with explicit cloud processes, upper-cloud changes are investigated by comparing the present climate condition under the perpetual July setting and the global warming condition, in which the sea surface temperature (SST) is raised by 2°. The sensitivity of the upp...

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Bibliographic Details
Published in:Journal of climate 2012-03, Vol.25 (6), p.2178-2191
Main Authors: Satoh, Masaki, Iga, Shin-Ichi, Tomita, Hirofumi, Tsushima, Yoko, Noda, Akira T.
Format: Article
Language:English
Subjects:
Climate change
Climate models
Climatic conditions
Cloud cover
Clouds
Convection
Convection clouds
Earth, ocean, space
Exact sciences and technology
Experiments
External geophysics
Fluctuations
General circulation models
Global climate models
Global warming
Humidity
Hydrometers
Marine
Meteorology
Microphysics
Relative humidity
Remote sensing
Science
Sea surface temperature
Studies
Subsidence
Tropical climates
Tropical environments
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Summary:Using a global nonhydrostatic model with explicit cloud processes, upper-cloud changes are investigated by comparing the present climate condition under the perpetual July setting and the global warming condition, in which the sea surface temperature (SST) is raised by 2°. The sensitivity of the upper-cloud cover and the ice water path (IWP) are investigated through a set of experiments. The responses of convective mass flux and convective areas are also examined, together with those of the large-scale subsidence and relative humidity in the subtropics. The responses of the IWP and the upper-cloud cover are found to be opposite; that is, as the SST increases, the IWP averaged over the tropics decreases, whereas the upper-cloud cover in the tropics increases. To clarify the IWP response, a simple conceptual model is constructed. The model consists of three columns of deep convective core, anvil, and environmental subsidence regions. The vertical profiles of hydrometers are predicted with cloud microphysics processes and kinematically prescribed circulation. The reduction in convective mass flux is found to be a primary factor in the decrease of the IWP under the global warming condition. Even when a different and more comprehensive cloud microphysics scheme is used, the reduction in the IWP due to the mass flux change is also confirmed.
ISSN:0894-8755
1520-0442
DOI:10.1175/JCLI-D-11-00152.1