An atmospheric radiative-convective model with interactive water vapor transport and cloud development

Abstract

In the present generation of radiative-convective models, clouds are assigned specific levels or temperatures that do not change during the course of the calculations. In addition, a single water vapor distribution is used for the “mean atmosphere” instead of separate distributions for the clear sky and cloudy sky atmospheres. We present results from a one-dimensional radiative-convective model that includes interactive water vapor transport and predicts cloud altitudes and thicknesses.The fully interactive model and one with a single, fixed cloud with a single water vapor profile can both reproduce a mean global temperature profile, their surface temperatures agreeing within a few tenths of a degree of the observed surface temperature. However, for surface temperature sensitivity studies, major differences between the two models can exist.The differences result from the use of separate clear and cloudy sky water vapor profiles and from the coupling of cloud numbers, locations, and thicknesses to temperature. The interactive model’s sensitivities to changes in the maximum altitude of convective extent, carbon dioxide, and surface relative humidity are presented. It is demonstrated that for global average conditions, the assumption of a constant distribution of relative humidity underestimates the water vapor amount and thermal contributions in radiative-convective models.