Tracers

The tracers to be advected around can be specified via a list of symbols. By default the model evolves temperature and salinity

julia> grid = RegularRectilinearGrid(size=(64, 64, 64), extent=(1, 1, 1));

julia> model = NonhydrostaticModel(grid=grid)
NonhydrostaticModel{CPU, Float64}(time = 0 seconds, iteration = 0)
├── grid: RegularRectilinearGrid{Float64, Periodic, Periodic, Bounded}(Nx=64, Ny=64, Nz=64)
├── tracers: (:T, :S)
├── closure: Nothing
├── buoyancy: SeawaterBuoyancy{Float64, LinearEquationOfState{Float64}, Nothing, Nothing}
└── coriolis: Nothing

whose fields can be accessed via model.tracers.T and model.tracers.S.

julia> model.tracers.T
Field located at (Center, Center, Center)
├── data: OffsetArrays.OffsetArray{Float64, 3, Array{Float64, 3}}, size: (64, 64, 64)
├── grid: RegularRectilinearGrid{Float64, Periodic, Periodic, Bounded}(Nx=64, Ny=64, Nz=64)
└── boundary conditions: west=Periodic, east=Periodic, south=Periodic, north=Periodic, bottom=ZeroFlux, top=ZeroFlux, immersed=ZeroFlux

julia> model.tracers.S
Field located at (Center, Center, Center)
├── data: OffsetArrays.OffsetArray{Float64, 3, Array{Float64, 3}}, size: (64, 64, 64)
├── grid: RegularRectilinearGrid{Float64, Periodic, Periodic, Bounded}(Nx=64, Ny=64, Nz=64)
└── boundary conditions: west=Periodic, east=Periodic, south=Periodic, north=Periodic, bottom=ZeroFlux, top=ZeroFlux, immersed=ZeroFlux

Any number of arbitrary tracers can be appended to this list and passed to a model constructor. For example, to evolve quantities $C_1$, CO₂, and nitrogen as additional passive tracers you could set them up as

julia> model = NonhydrostaticModel(grid=grid, tracers=(:T, :S, :C₁, :CO₂, :nitrogen))
NonhydrostaticModel{CPU, Float64}(time = 0 seconds, iteration = 0)
├── grid: RegularRectilinearGrid{Float64, Periodic, Periodic, Bounded}(Nx=64, Ny=64, Nz=64)
├── tracers: (:T, :S, :C₁, :CO₂, :nitrogen)
├── closure: Nothing
├── buoyancy: SeawaterBuoyancy{Float64, LinearEquationOfState{Float64}, Nothing, Nothing}
└── coriolis: Nothing
Active vs. passive tracers

An active tracer typically denotes a tracer quantity that affects the fluid dynamics through buoyancy. In the ocean temperature and salinity are active tracers. Passive tracers, on the other hand, typically do not affect the fluid dynamics are are passively advected around by the flow field.