Abstract
We simulate the 3D ozone distribution of a tidally locked Earth-like exoplanet using the high-resolution, 3D chemistry-climate model CESM1(WACCM) and study how the ozone layer of a tidally locked Earth (TLE) ( $$\Omega _{\mathrm{TLE}}= 1/365$$ days) differs from that of our present-day Earth (PDE) ( $$\Omega _{\mathrm{PDE}}= 1/1$$ day). The middle atmosphere reaches a steady state asymptotically within the first 80 days of the simulation. An upwelling, centred on the subsolar point, is present on the day side while a downwelling, centred on the antisolar point, is present on the night side. In the mesosphere, we find similar global ozone distributions for the TLE and the PDE, with decreased ozone on the day side and enhanced ozone on the night side. In the lower mesosphere, a jet stream transitions into a large-scale vortex around a low-pressure system, located at low latitudes of the TLE night side. In the middle stratosphere, the concentration of odd oxygen is approximately equal to that of the ozone [( $${\mathrm{O}}_{x}$$ ) $$\approx$$ ( $${\mathrm{O}}_{3}$$ )]. At these altitudes, the lifetime of odd oxygen is $$\mathrm \sim$$ 16 h and the transport processes significantly contribute to the global distribution of stratospheric ozone. Compared to the PDE, where the strong Coriolis force acts as a mixing barrier between low and high latitudes, the transport processes of the TLE are governed by jet streams variable in the zonal and meridional directions. In the middle stratosphere of the TLE, we find high ozone values on the day side, due to the increased production of atomic oxygen on the day side, where it immediately recombines with molecular oxygen to form ozone. In contrast, the ozone is depleted on the night side, due to changes in the solar radiation distribution and the presence of a downwelling. As a result of the reduced Coriolis force, the tropical and extratropical air masses are well mixed and the global temperature distribution of the TLE stratosphere has smaller horizontal gradients than the PDE. Compared to the PDE, the total ozone column global mean is reduced by $$\mathrm \sim$$ 19.3 %. The day side and the night side total ozone column means are reduced by 23.21 and 15.52 %, respectively. Finally, we present the total ozone column (TOC) maps as viewed by a remote observer for four phases of the TLE during its revolution around the star. The mean TOC values of the four phases of the TLE vary by up to 23 %.
Highlights
In this study, we simulate and analyse the middle atmospheric ozone distribution of a tidally locked Earth-like exoplanet orbiting a Sun-like star (TLE) using a realistic, high-resolution, 3D chemistry-climate model
We discussed and compared the 3D ozone distributions of the present-day Earth (PDE) and a tidally locked Earthlike exoplanet revolving around a Sun-like star (TLE)
We demonstrated that it is possible to simulate the middle atmosphere of a TLE using the realistic, high-resolution, 3D chemistry-climate model (CESM1(WACCM))
Summary
We simulate and analyse the middle atmospheric ozone distribution of a tidally locked Earth-like exoplanet orbiting a Sun-like star (TLE) using a realistic, high-resolution, 3D chemistry-climate model. Yang et al (2014) studied the dependence of a planet’s habitability on its rotation rate using two 3D models, the CAM3 and the CCSM3. The CCSM3’s atmospheric components are the CAM3 or the CAM4 They are able to simulate the marine stratus, layered, shallow convective and deep convective clouds as well as liquid and ice condensates. The study of Yang et al (2014) focused on the troposphere of the simulated planets They demonstrated that a slow rotating Earth-like planet (rotation speed = 1 rotation/243 days), located at a distance of 0.7 AU away from a Sun-like star, would be habitable. They determined that an Earth-like planet rotating at a rate of 1 rotation/day required half the stellar flux compared to an Earth-like planet rotating at a rate of 1 rotation/243 days to maintain an Earth-like climate
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