A Discrete Ordinate, Multiple Scattering, Radiative Transfer Model of the Venus Atmosphere from 0.1 to 260 micron

Abstract

We describe a new radiative transfer model of the Venus atmosphere. We have implemented a moderate resolution radiative transfer model (RTM) that includes optical properties from nine gases and four cloud modes between 0.1 microns and 260 microns. We use a multiple stream discrete ordinate flux solver to calculate Solar and atmospheric IR fluxes with a prescribed temperature profiles, and calculate radiative/convective equilibrium temperatures using the model. We validate components of the RTM using observations from Pioneer Venus and Venus Express. We calculate a visible bond albedo of 0.74 and sub-solar surface visible flux of 50 W/m2 (4.0 percent of the Top-Of-Atmosphere insolation) for a suitable temperature and composition profile derived from the Venus International Reference Atmosphere. Solar fluxes are simulated over a range of latitudes and we find good agreement with results from the Pioneer Venus probes and Venera landers. Top-Of-Atmosphere infra-red fluxes are compared with Venus Express observations and found to compare well at all observed wavelengths. We have used the RTM to calculate radiative heating rates and compare these calculated heating rates with those prescribed in a modern Venus GCM. We identify a number of errors in the prescribed profile and suggest modifications to the prescribed forcing. We calculate radiative equilibrium temperatures and radiative/convective equilibrium temperatures using the RTM. Using a small family of numerical and physical configurations we find little sensitivity to changes in the vertical resolution used in the model. For suitable global mean solar forcing we calculate a surface temperature of 750K at radiative/convective equilibrium, in good agreement with observations and other recent modeling efforts.

Publication
Journal of Atmospheric Sciences
Date