Tropical free‐tropospheric humidity differences and their effect on the clear‐sky radiation budget in global storm‐resolving models

Theresa Lang, Ann Kristin Naumann, Bjorn Stevens, Stefan A. Buehler
2021 Journal of Advances in Modeling Earth Systems  
Free-tropospheric water vapor strongly impacts the Earth's outgoing longwave radiation (OLR) and therefore plays a key role in controlling the clear-sky response of the climate system to an increase in greenhouse gases. It is now widely accepted that this response is described by a warming and moistening of the atmosphere that is implied if the relative humidity (RH) and lapse rate were to depend on temperature alone, which corresponds to a warming at approximately constant RH (e.g., Held &
more » ... n, 2000; Po-Chedley et al., 2019; Romps, 2014) . This reduces the radiative response compared to a warming at constant absolute humidity, and can be described as a positive water-vapor-lapse-rate feedback. While general circulation models (GCMs) agree on this basic response (e.g., Bony et al., 2006; Soden & Held, 2006) , there is still an appreciable inter-model spread in the magnitude of the water-vapor-lapse-rate feedback. This spread, which primarily originates from the tropics, contributes a non-negligible (about 30%) uncertainty to the climate sensitivity (Vial et al., 2013) .
doi:10.1029/2021ms002514 fatcat:fzu2zp4xozan3daj7vkyhnit34