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

Abstract

he authors describe a new radiative transfer model of the Venus atmosphere (RTM) that includes optical properties from nine gases and four cloud modes between 0.1 and 260 ?m. A multiple-stream discrete ordinate flux solver is used to calculate solar and atmospheric infrared fluxes with a prescribed temperature profiles and calculate radiative?convective equilibrium temperatures using the model.Components of the RTM are validated using observations from Pioneer Venus and Venus Express. A visible bond albedo of 0.74 and subsolar surface visible flux of 50 W m?2 [4.0% of the top-of-atmosphere (TOA) insolation] are calculated for a suitable temperature and composition profile derived from the Venus International Reference Atmosphere. Solar fluxes are simulated over a range of latitudes and good agreement is found with results from the Pioneer Venus probes and Venera landers. TOA infrared fluxes are compared with Venus Express observations and found to compare well at all observed wavelengths.The RTM is used to calculate radiative heating rates and these calculated heating rates are compared with those prescribed in a modern Venus GCM. Modifications are suggested to improve the prescribed thermal forcing used in recent GCMs. Using a small family of numerical and physical configurations, little sensitivity to vertical resolution is found in the model. For suitable global mean solar forcing a surface temperature of 750 K at radiative?convective equilibrium is calculated, in good agreement with observations and other recent modeling efforts.