Trace Gases

ClimaAtmos implements two modes each for ozone and carbon dioxide: one time varying and one time invariant. These are only relevant for radiative transfer, and only when RRTMGP is used. All other atmospheric gases are held fixed with default values from RRTMGP that can be changed in the toml file.

Time Invariant Ozone Profile

The time invariant type of ozone uses the idealized_ozone function to compute an idealized ozone profile based on the work of [20]. This option is the default.

The idealized_ozone function returns the ozone concentration in volume mixing ratio (VMR) at a given altitude z.

ClimaAtmos.idealized_ozone — Function

idealized_ozone(z::FT)

Returns idealized ozone volume mixing ratio (VMR) from Wing et al. 2018.

The ozone profile is calculated as a function of altitude z using the following formula:

\[O_3(z) = g_1 p^{g_2} e^{(-p / g_3)}\]

where:

O_3(z) is the ozone concentration in volume mixing ratio (VMR) at altitude z.
p is the pressure at altitude z calculated using the hydrostatic equation: p = P_0 exp(-z / H_{Earth}), where P_0 is the surface pressure and H_{Earth} is the scale height of the Earth's atmosphere (assumed to be 7000 meters).
g_1, g_2, and g_3 are empirical constants.

References

Wing, A. A., et al. (2018). Radiative-convective equilibrium model intercomparison project. Geoscientific Model Development, 11(2), 663-690.

source

This function looks like

using CairoMakie
import ClimaAtmos

z = range(0, 60000, length = 100)
ozone = ClimaAtmos.idealized_ozone.(z)

fig = Figure()
ax = Axis(fig[1, 1]; xlabel = "Ozone (VMR)", ylabel = "Altitude (m)")
lines!(ax, ozone, z)
save("idealized_ozone.png", fig);

Idealized ozone profile

Time Varying Ozone Profile

The time varying ozone profile uses CMIP6 forcing data to prescribe ozone as read from files. A high-resolution, multi-year file is available in the ozone_concentrations artifact. This file is not small, so you have to obtain it independently. Please refer to ClimaArtifacts for more information. If the file is not found, a low-resolution, single-year version is used. This is not advised for production simulations. This option is enabled by adding "O3" to the time_varying_trace_gases config argument list, i.e.: time_varying_trace_gases: ["O3"].

We interpolate the file data in time whenever radiation is called. The interpolation used is LinearInterpolation from ClimaUtilities (linear in time between file snapshots).

Time Invariant CO2 Profile

By default, CO2 concentrations are set to 397.547 ppm. This value can be changed with the CO2_fixed_value parameter in the toml file.

Time Varying CO2 Profile

ClimaAtmos can prescribe CO2 concentration using data from Mauna Loa CO2 measurements. This option is enabled by adding "CO2" to the time_varying_trace_gases config argument list, i.e.: time_varying_trace_gases: ["CO2"].