Some news about the Venus Climate Database: version 3.1

Introduction

The Venus Climate Database is a tool designed to provide to the scientific and engineer community working on projects linked to Venus a realistic description of its atmospheric climatology, based on simulations of the Venus PCM [1,2]. The current version, VCD v2.3, was released in late 2023 and is now used by roughly 180 users from 21 countries.

One of the main goal is to provide a robust assessment of the thermosphere of Venus, for aerobraking studies, in particular in relation to current mission projects such as EnVision. Thanks to ESA funding, our team has worked to investigate some processes that are source of uncertainty in the thermospheric circulation, as well as to include new scenarios from other GCMs.

Updates of the Venus PCM simulations

Some modifications have been implemented in the Venus PCM to improve some parameterizations. This includes :

• adjustments of the gravity wave parameterization scheme: the polar regions now benefit from GW oriented in all directions. The transition between E-W orientation and full random is done around 45-55° of latitude. This modification is based on observations of GW orientations in the polar region at cloud level and above.

• A new molecular diffusion scheme has been implemented.

• Modifications have been done in the photochemistry, with some cross section updates (SO, S₂), addition of OSSO isomers, ClSO and Cl₂SO₂. All these modifications are affecting composition up to 100-130 km, but not above.

These modifications lead to a small reduction of the tuning needed on oxygen atom production, and the main impact is visible in the temperature structure of the polar thermosphere. It also affected the variability on the thermospheric density, in particular on the night side where this variability is highest.

New concept: scenarios from additional GCMs

The main change in this new version of the VCD is the possibility to access scenarios that are built from simulations of other GCMs. Invitations were sent to other models of the Venusian atmosphere to provide the needed simulations so that the VCD team can produce scenarios based on these results. In VCD v3.1, we have included scenarios based on the AFES-Venus model [3], with a scenario associated to a free run, and a second one based on data assimilation [4]. Additional models may be included in the future. The protocole for the production of needed simulations is available on demand by contacting the VCD team. This feature allows for comparison between models, and help the user to build a more robust view of the model dependency of the provided climate and variabilities.

In practice, new flags have been implemented to label the different scenarios in an intuitive way. Undefined values are output for any variable or location that is not present in the requested scenario. Some examples are provided in Figures 1 and 2.

Figure 1: Example of zonal wind profiles in VCD v3.1, with Venus PCM scenario 11 (basic albedo and EUV) and AFES-V scenarios 101 (free run) and 102 (data assimilation run).

 

Figure 2: Zonal and temporal averages for temperature and zonal wind fields, in three different scenarios of the VCD v3.1.

An additional improvement that should be useful to users: some code re-engineering has been done in order to improve significantly the speed of successive queries, in particular in the case of the tracking of atmospheric fields along a spacecraft trajectory.

The VCD v3.1 should be released to the public before the end of the year 2026.

References

[1] Martinez A. et al. (2023) Icarus 389, 115272, 10.1016/j.icarus.2022.115272.

[2] Martinez A. et al. (2024) Icarus 415, 116035, 10.1016/j.icarus.2024.116035

[3] Sugimoto N. et al. (2014) J. of Geophys. Res. Planets 119, 1950-1968, 10.1002/2014JE004624

[4] Sugimoto N. et al. (2017) Sci. Reports 7, 9321, 10.1038/s41598-017-09461-1