Validation of the IPSL Venus GCM Thermal Structure with Venus Express Data

Sebastien Lebonnois,Itziar Garate-Lopez,Silvia Tellmann,Davide Grassi,Alessandra Migliorini,Pietro Scarica,Giuseppe Piccioni

doi:10.3390/atmos10100584

Abstract

General circulation models (GCMs) are valuable instruments to understand the most peculiar features in the atmospheres of planets and the mechanisms behind their dynamics. Venus makes no exception and it has been extensively studied thanks to GCMs. Here we validate the current version of the Institut Pierre Simon Laplace (IPSL) Venus GCM, by means of a comparison between the modelled temperature field and that obtained from data by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) and the Venus Express Radio Science Experiment (VeRa) onboard Venus Express. The modelled thermal structure displays an overall good agreement with data, and the cold collar is successfully reproduced at latitudes higher than +/−55°, with an extent and a behavior close to the observed ones. Thermal tides developing in the model appear to be consistent in phase and amplitude with data: diurnal tide dominates at altitudes above 102 Pa pressure level and at high-latitudes, while semidiurnal tide dominates between 102 and 104 Pa, from low to mid-latitudes. The main difference revealed by our analysis is located poleward of 50°, where the model is affected by a second temperature inversion arising at 103 Pa. This second inversion, possibly related to the adopted aerosols distribution, is not observed in data.

Highlights

Remote-sensing measurements and probe data from space missions [1,2,3,4], have been used for decades to investigate the vertical temperature structure of the atmosphere of Venus
We focus on comparing the thermal structure reproduced by the general circulation models (GCMs) developed at the Laboratoire de Météorologie Dynamique of Paris, with the one retrieved by Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) and VeRa (Venus Express Radio Science Experiment), flown on board the ESA Venus Express mission
In order to validate the global thermal characterization of the Venus atmosphere obtained with the Institut Pierre Simon Laplace (IPSL) Venus GCM, we first analyze the zonally and temporally averaged temperature field and the main variations with respect to that mean, i.e., the thermal tides, by comparing them with the structures obtained from observations made by Venus Express

Summary

Introduction

Remote-sensing measurements and probe data from space missions [1,2,3,4], have been used for decades to investigate the vertical temperature structure of the atmosphere of Venus. Either relaxing the temperature towards a specified temperature profile or using a radiative transfer module to compute these temperatures, several simulations were already capable of reproducing the observed superrotation [7] in the modelled atmospheres [8,9,10,11], even if their results vary from case to case, showing a broad variety of zonal wind fields under similar initial conditions These results are qualitatively consistent with the well-known superrotation of Venus’ atmosphere, which is sixty times faster at the cloud top level than at the surface. GCMs have been able to demonstrate the role of the thermal tides in the vertical transportation of angular momentum through the atmosphere [12,13], as well as the role of planetary-scale waves and large-scale gravity waves [11,14]

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Conclusion