High-resolution nesting simulations for the EDL stage of China’s first Mars exploration mission (Tianwen-1)

China’s first Mars rover “Zhurong” successfully landed (on July 15, 2021，07:18 CST) at the pre-selected landing area on Utopia Planitia of Mars. The “Entrance, Descending, and Landing (EDL)” process was the most challenging and highly dependent on the accurate prediction of the atmospheric conditions all along the descending trajectory and around the landing site.

In this study, a series of five-domain nested simulations were conducted using MarsWRF GCM, with the top of the domains at ~90 km and the highest horizontal resolution of ~3.6 km. Especially, modified fully-interactive dust lifting and radiation feedback (hereafter “inter-active dust”) schemes were used in all nested domains as a “control” experiment. The results can reasonably represent the Martian atmospheric features based on MCS-MRO observations and MCD5.3 re-analysis data (e.g., the “thermal tide”, meridional circulations, semi-spherical and local topographic flows, and mesoscale structures around landing site). The advantages of our nesting simulation compared to MCD5.3 data included: 1) the suspended dust was more “elevated” at some regions; 2) it can resolve the topographic gravity waves and even convection-like structures in the boundary layer.

In consideration of the uncertainties caused by the dust and radiation processes, besides the control experiment, three more nesting simulations with different dust distributions and radiation feedback schemes were also conducted to give an ensemble prediction with a certain spread, which confirmed the engineering meteorological thresholds provided by CAST. Finally, the model predictions were validated by the EDL retrieved profiles, showing that the temperature and wind speed profiles were well predicted. Especially, only the “inter-active dust” experiments showed the easterlies between 20~30km altitudes as reported by the EDL data. However, the density profiles of both the model and MCD5.3 re-analysis were underestimated below 30 km altitude.