Location
East-West Center, University of Hawai'i at Manoa (Honolulu, Hawai'i)
Start Date
16-10-2012 5:30 PM
End Date
16-10-2012 7:30 PM
Document Type
Poster
Description
Tropical anvil clouds that detrain near the mixing barrier near 13km in the tropics have a strong effect on the longwave and shortwave energy budgets of Earth. A cloud-resolving model is used to test the Fixed Anvil Temperature (FAT) Hypothesis proposed by Hartmann and Larson (2002). Results show that the radiative cooling, primarily due to water vapor, is the strongest control of the anvil cloud detrainment temperature. Water vapor concentrations are largely controlled by temperature, so, following the FAT hypothesis, the cloud detrainment should follow a fixed temperature. The results also show, however, that ozone contributes a significant heating rate in the upper tropical troposphere. If ozone is fixed as a function of pressure as the SST is warmed, anvil clouds warm and their fractional coverage decreases. The presence of a fixed ozone profile in our model can be thought of as a pressure dependent contribution to stability that inhibits convection from rising to the level of diminished water vapor cooling. This suggests that to model the response of tropical anvil clouds to climate change, one must also predict ozone in the upper tropical troposphere and TTL region, where ozone concentrations are also influenced by convection, forming a strong interaction between ozone and cold clouds in the tropics. Broader implications of the influence of the TTL on the detrainment temperature of tropical anvils include the modification of the longwave cloud radiative effect and the net radiative energy budget effect of tropical deep convective systems.
Testing the role of radiation in determining tropical cloud top temperature
East-West Center, University of Hawai'i at Manoa (Honolulu, Hawai'i)
Tropical anvil clouds that detrain near the mixing barrier near 13km in the tropics have a strong effect on the longwave and shortwave energy budgets of Earth. A cloud-resolving model is used to test the Fixed Anvil Temperature (FAT) Hypothesis proposed by Hartmann and Larson (2002). Results show that the radiative cooling, primarily due to water vapor, is the strongest control of the anvil cloud detrainment temperature. Water vapor concentrations are largely controlled by temperature, so, following the FAT hypothesis, the cloud detrainment should follow a fixed temperature. The results also show, however, that ozone contributes a significant heating rate in the upper tropical troposphere. If ozone is fixed as a function of pressure as the SST is warmed, anvil clouds warm and their fractional coverage decreases. The presence of a fixed ozone profile in our model can be thought of as a pressure dependent contribution to stability that inhibits convection from rising to the level of diminished water vapor cooling. This suggests that to model the response of tropical anvil clouds to climate change, one must also predict ozone in the upper tropical troposphere and TTL region, where ozone concentrations are also influenced by convection, forming a strong interaction between ozone and cold clouds in the tropics. Broader implications of the influence of the TTL on the detrainment temperature of tropical anvils include the modification of the longwave cloud radiative effect and the net radiative energy budget effect of tropical deep convective systems.
