If you are using data from TAM, please cite Lora et al. (2015) and the relevant configuration paper.
The following is a list and description of configurations of TAM that have been used to investigate various aspects of Titan’s climate system. In some cases, different configurations are applicable to similar scientific questions and the choice of configuration depends more on model complexity and computational expense considerations than on the requirement for specific representations of certain physical processes. Appropriate references to papers wherein more detailed descriptions can be found are listed in the right column.
TAM Configurations
| TAM with Simple Hydrology | Atmosphere–land model including parameterizations for: – radiative transfer – boundary layer – surface fluxes of sensible heat, methane (latent heat), and momentum – surface temperature (including subsurface conduction) – methane moist processes: large-scale condensation and simplified quasi-equilibrium moist convection – a simple surface “bucket” scheme that tracks surface liquid but ignores any horizontal liquid flow This configuration is the original set-up. Initialization of the surface methane boundary condition is arbitrary, but the model must run for many decades for the hydroclimate to equilibrate. This configuration produces a realistic climate, but ignores some processes related to hydrology. | Lora et al. (2015) |
| TAM “Aquaplanet” | This configuration is idealized, and produces a climate that is not particularly realistic compared to Titan. Same configuration as TAM with Simple Hydrology, except that surface liquids are prescribed to be infinite. This therefore simulates a climate with a global “ocean” of methane, but one where there are no currents (alternatively, this has been referred to as a “swamp-planet”). This is comparable to the well-established terrestrial aquaplanet idealized setup. This configuration is idealized, and produces a climate that is not particularly realistic compared to Titan. | Lora et al. (2015) |
| TAM “Wetlands” | Same configuration as TAM with Simple Hydrology, except that surface liquids in the bucket model are prescribed to be infinite at polar latitudes, and an imposed “infiltration” causes standing surface methane liquids to decay at lower latitudes. This configuration spins up relatively quickly because the surface liquids do not need to evolve to an equilibrium state. This configuration is idealized, and produces a climate that is representative of Titan’s, but with substantial simplifications. | Lora & Mitchell (2015); Mitchell & Lora (2016) |
| Dry version | Same configuration as above, but without surface fluxes of methane (latent heat), methane moist processes, or the surface bucket model. This configuration spins up very quickly and ignores the methane cycle (note, though, that a static, prescribed atmospheric methane profile is still considered for the radiative transfer). This configuration is idealized, and produces a climate that is not particularly realistic compared to Titan. | MacKenzie et al. (2019) |
| TAM with Coupled Hydrology | Fully coupled atmosphere–land–hydrology configuration that enables a fully self-consistent simulation of the methane cycle. The simple “bucket” scheme is replaced with a full (albeit still simple) land hydrology model that includes: – runoff, routed by steepest descent – a subsurface methane table underlain by an impermeable equipotential surface – infiltration and seepage to/from the subsurface methane table – subsurface liquid flow – groundmethane evaporation This configuration enables our most realistic simulation of Titan’s full climate system, including the distribution of surface liquids (and interaction with topography). Initialization of the total methane budget (i.e., the depth to the impermeable basement) is arbitrary, and the model must run for many decades for the hydroclimate to equilibrate. | Faulk et al. (2020); Lora et al. (2022) |
| Middle Atmosphere | Middle atmosphere configuration, which includes several parameterizations that improve the stability and realism of the simulated stratosphere and mesosphere. These are: – radiative heating from seasonally dependent molecular abundance and haze opacity profiles from the Seasonally Varying Radiative Species (SVRS) dataset. SVRS is a dataset of trace molecule abundance and aerosol opacity derived from Cassini CIRS and ISS observations that have been interpolated across latitude, pressure, and solar longitude – a Kelvin-Helmholtz mixing parameterization at pressures below 1 Pa. This is a local parameterization that mixes wind and temperature between two vertical levels where the Richardson number exceeds a threshold value – an energy-conserving Rayleigh damping of the zonal eddy components of the zonal wind and temperature (adapted from the MiMA model) at pressures below 0.5 Pa This configuration enables the best simulations of Titan’s middle atmosphere, including the seasonal behavior of the zonal jets, the formation and dissipation of the polar vortices, and the maintenance of superrotation by waves. | Lombardo & Lora (2023a) |