Analysis of the radiative budget of the Venusian atmosphere based on infrared Net Exchange Rate formalism

Abstract

AbstractA detailed one‐dimensional analysis of the energy balance in Venus atmosphere is proposed in this work, based on the Net Exchange Rate formalism that allows the identification in each altitude region of the dominant energy exchanges controlling the temperature. Well‐known parameters that control the temperature profile are the solar flux deposition and the cloud particle distribution. Balance between solar heating and infrared energy exchanges is analyzed for each region: upper atmosphere (from cloud top to 100 km), upper cloud, middle cloud, cloud base, and deep atmosphere (cloud base to surface). The energy accumulated below the clouds is transferred to the cloud base through infrared windows, mostly at 3–4 μm and 5–7 μm. The continuum opacity in these spectral regions is not well known for the hot temperatures and large pressures of Venus's deep atmosphere but strongly affects the temperature profile from cloud base to surface. From cloud base, upward transport of energy goes through convection and short‐range radiative exchanges up to the middle cloud where the atmosphere is thin enough in the 20–30 μm window to cool directly to space. Total opacity in this spectral window between the 15 μm CO2 band and the CO2 collision‐induced absorption has a strong impact on the temperature in the cloud convective layer. Improving our knowledge of the gas opacities in these different windows through new laboratory measurements or ab initio computations, as well as improving the constraints on cloud opacities would help to separate gas and cloud contributions and secure a better understanding of Venus's atmosphere energy balance.