Testing the Role of Radiation in Determining Tropical Cloud-Top Temperature

A cloud-resolving model is used to test the hypothesis that radiative cooling by water vapor emission is the primary control on the temperature of tropical anvil clouds. The temperature of ice clouds in the simulation can be increased or decreased by changing only the emissivity of water vapor in th...

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Bibliographic Details
Published in:Journal of climate 2012-09, Vol.25 (17), p.5731-5747
Main Authors: Harrop, Bryce E., Hartmann, Dennis L.
Format: Article
Language:English
Subjects:
Anvil clouds
Anvils
Atmosphere
Climate change
Clouds
Cold
Convection
Convection clouds
Cooling
Domains
Earth, ocean, space
El Nino
Emission analysis
Emissions control
Emissivity
Exact sciences and technology
External geophysics
Heat of fusion
High altitude
Humidity
Hypotheses
Ice clouds
Latent heat
Meteorology
Modelling
Observational studies
Ozone
Pressure dependence
Radiation
Radiative cooling
Satellites
Sea surface
Sea surface temperature
Stratospheric water vapor
Surface temperature
Temperature
Tropical clouds
Troposphere
Upper troposphere
Vapor emission
Water temperature
Water vapor
Water vapour
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Summary:A cloud-resolving model is used to test the hypothesis that radiative cooling by water vapor emission is the primary control on the temperature of tropical anvil clouds. The temperature of ice clouds in the simulation can be increased or decreased by changing only the emissivity of water vapor in the upper troposphere. The effect of the model’s fixed ozone profile on stability creates a pressure-dependent inhibition of convection, leading to a small warming in cloud-top temperature as SST is increased. Increasing stratospheric water vapor also warms the cloud-top temperature slightly. Changing the latent heat of fusion reduces the cloud fraction at high altitudes, but does not significantly change temperature at which cloud fraction peaks in the upper troposphere. The relationship between radiatively driven horizontal mass convergence and cloud fraction that causes cloud temperature to be insensitive to surface temperature is preserved when a large model domain is used so that convection aggregates in a small part of the model domain.
ISSN:0894-8755
1520-0442
DOI:10.1175/jcli-d-11-00445.1