Journal Article

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

Harrop, Bryce E., Hartmann, Dennis L.

2012

Overview

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.

• Publisher: American Meteorological Society
• Subject: 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