13 One dimensional and 3D Models as Planetary Habitability Assessment Tools

13 one dimensional and 3d models as planetary

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13. One-dimensional and 3D Models as Planetary Habitability Assessment Tools Until recently, virtually all exoplanet habitability studies had been performed using single-column (1D) radiative-convective climate models. This has changed in recent years, however, as a wide array of 1D (including energy balance) (e.g., [ 2 , 50 , 51 , 55 , 132 , 148 , 216 , 251 255 ]) and 3D (e.g., [ 27 , 30 , 161 , 237 , 239 , 240 , 244 246 , 256 , 257 ]) models are now being used to assess exoplanet habitability. The reason for this trend is because both 1D and 3D climate models have complementary advantages and disadvantages. One-dimensional models are computationally cheap, which allows quick exploration of parameter space, the incorporation of more detailed radiative transfer, and the consideration of a larger number of greenhouse gases. One-dimensional models are also more easily coupled to other (e.g., interior, escape stellar, photochemical, and other 1D) models. In contrast, 3D models can calculate more atmospheric processes self-consistently than can be done with 1D models, which must make more simplifying assumptions regarding dynamics, relative humidity, and clouds. Thus, 3D models can assess the subtleties of atmospheres in greater detail, which includes evaluating complex circulation patterns. Thus, both 1D and 3D models will remain essential for studying planetary habitability, including studies of the habitable zone. One previous opinion is that 3D models are the future of theoretical habitability studies [ 153 , 258 ]. However, recent years are instead unveiling a future dominated by both 1D and 3D models. Although 3D modeling studies have increased, 1D models, including coupled 1D models, have also been on the rise. For instance, coupled 1D atmospheric and magma ocean models can compute volatile retention and O 2 build up [ 55 , 116 ] and estimate pre-main-sequence HZ inner edge boundaries (e.g., [ 50 , 254 ]). Single-column radiative–convective and energy balance models are also coupled to evaluate processes in multiple dimensions (e.g., [ 79 , 216 , 251 , 252 ]). Coupled climate-photochemical calculations, which have been popular for many years (e.g., [ 170 , 259 ]), remain in high use, particularly for the calculation of atmospheric biosignatures (e.g., [ 255 , 260 , 261 ]). Given the lack of detailed exoplanetary observations that are needed to fully utilize the potential of 3D models, plus limitations in computer power, simpler 1D models will remain crucial for advancing our knowledge and testing new ideas (e.g., [ 134 , 216 , 262 ]). For example, 1D models that can treat clouds semi-consistently already exist (e.g., [ 263 ]), as do coupled radiative–convective climate and energy balance models that can emulate the dynamical behavior of idealized slab ocean GCMs (e.g., [ 252 , 264 ]). However, 3D models are also improving. For instance, once the sole domain of 1D models, 3D models are beginning to make preliminary biosignature predictions (e.g., [ 30 ]). Although most 3D modeling of the inner edge of the HZ has been performed using idealized slab ocean GCMs (e.g., [ 27 , 239 , 240 ]), these lack a realistic treatment of equator to poleward heat transfer (e.g., [ 241 ]).
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