Tracers

Note

Usage: Enable tracers using a keyword argument in the AtmosModel specification
- tracers = NoTracer()
- tracers = NTracers{N, FT}(δ_χ) where N is the number of tracers required.
FT is the float-type and $\delta_{\chi}$ is an SVector of diffusivity scaling coefficients

Note

Hyperdiffusion is currently not supported with tracers. Laplacian diffusion coefficients may still be specified. (See above)

In tracers.jl, we define the equation sets governing tracer dynamics. Specifically, we address the the equations of tracer motion in conservation form,

export NoTracers, NTracers

Equations

$$$\frac{\partial \rho\chi}{\partial t} + \nabla \cdot ( \rho\chi u) = \nabla \cdot (\rho\delta_{D\chi}\mathrm{D_{T}}\nabla\chi) + \rho \mathrm{S}$$$

where $\chi$ represents the tracer species, $\mathrm{S}$ represents the tracer source terms and $\delta_{D\chi} \mathrm{D_{T}}$ represents the scaled turbulent eddy diffusivity for each tracer. Currently a default scaling of 1 is supported. The equation as written above corresponds to a single scalar tracer, but can be extended to include multiple independent tracer species.

We first define an abstract tracer type, and define the default function signatures. Two options are currently supported. NoTracers, and NTracers.

Abstract Tracer Type

Default stub functions for a generic tracer type are defined here.

abstract type TracerModel <: BalanceLaw end

vars_state(::TracerModel, ::AbstractStateType, FT) = @vars()

function atmos_init_aux!(
::TracerModel,
::AtmosModel,
aux::Vars,
geom::LocalGeometry,
)
nothing
end
function atmos_nodal_update_auxiliary_state!(
::TracerModel,
m::AtmosModel,
state::Vars,
aux::Vars,
t::Real,
)
nothing
end
function flux_tracers!(
::TracerModel,
atmos::AtmosModel,
state::Vars,
aux::Vars,
t::Real,
)
nothing
end
::TracerModel,
diffusive::Vars,
state::Vars,
aux::Vars,
t::Real,
)
nothing
end
function flux_second_order!(
::TracerModel,
state::Vars,
diffusive::Vars,
aux::Vars,
t::Real,
D_t,
)
nothing
end
::TracerModel,
transform::Vars,
state::Vars,
aux::Vars,
t::Real,
)
nothing
end

NoTracers

The default tracer type in both the LES and GCM configurations is the no tracer model. (This means no state variables for tracers are being carried around). For the purposes of this model, moist variables are considered separately in moisture.jl.

NTracers

Allows users to specify an integer corresponding to the number of tracers required. Note that tracer naming is not currently supported, i.e. the user must track each tracer variable based on its numerical index. Sources can be added to each tracer based on the corresponding numerical vector index. Initial profiles must be specified using the init_state_prognostic! hook at the experiment level.

ClimateMachine.Atmos.NTracersType
NTracers{N, FT} <: TracerModel

Currently the simplest way to get n-tracers in an AtmosModel run using the existing machinery. Model input: SVector of diffusivity scaling coefficients. Length of SVector allows number of tracers to be inferred. Tracers are currently identified by indices.

Fields

• δ_χ

N-component SVector with scaling ratios for tracer diffusivities

source