Adds a river stub to ClimaLand

src/standalone/Rivers/Rivers.jl

@@ -0,0 +1,103 @@
+module Rivers
+using ClimaLand
+using ClimaCore
+using DocStringExtensions
+import ClimaCore: Fields
+
+import ClimaLand:
+    AbstractExpModel,
+    make_compute_exp_tendency,
+    prognostic_vars,
+    name,
+    prognostic_types,
+    prognostic_domain_names,
+    auxiliary_vars,
+    auxiliary_types,
+    auxiliary_domain_names,
+    make_update_boundary_fluxes,
+    FTfromY
+
+using ClimaLand.Domains
+import ClimaLand.Domains:
+    coordinates
+export RiverModel
+
+abstract type AbstractRiverModel{FT} <: AbstractExpModel{FT} end
+
+abstract type AbstractRiverSimulationMode{FT<: AbstractFloat} end
+
+"""
+    RiverModel{FT, M, D, RD} <: AbstractSurfaceWaterModel{FT}
+
+Interfacer for integrating ClimaLand.jl and ClimaRivers.jl.
+
+$(DocStringExtensions.FIELDS)
+"""
+struct RiverModel{FT, M<: AbstractRiverMode, GD <: Domains.SphericalShell{FT}, BD} <: AbstractRiverModel{FT}
+    "Mode - standalone or prescribed"
+    mode::M
+    "The ClimaCore (grid) domain for the land model; global only"
+    grid_domain::GD
+    "The river basin domain"
+    basin_domain::BD
+    "The river model timestep"
+    Δt_river::FT
+    "time bracket"
+    t_bracket::NTuple{2,FT}
+    "History length"
+    hist_length::Int
+end
+
+ClimaLand.name(model::RiverModel) = :river
+
+ClimaLand.prognostic_vars(model::RiverModel) = (:R_accum,)
+ClimaLand.prognostic_types(model::RiverModel{FT}) where {FT} = (FT,)
+ClimaLand.prognostic_domain_names(model::RiverModel) = (:grid,)
+ClimaLand.auxiliary_vars(model::RiverModel) = (:R_accum_history,:R_inst, :state)
+ClimaLand.auxiliary_types(model::RiverModel{FT}) where {FT} = (NTuple{model.hist_length, FT},FT, FT)
+ClimaLand.auxiliary_domain_names(model::RiverModel) = (:basin,:grid, :basin)
+
+function Domain.coordinates(basin_domain::Vector)
+    return basin_domain
+end
+
+function Domain.coordinates(model::RiverModel)
+    return (:grid = coordinates(model.grid_domain), :basin = coordinates(model.basin_domain))
+end
+
+function ClimaLand.make_compute_exp_tendency(model::RiverModel)
+    function compute_exp_tendency!(dY, Y, p, t)
+        R_inst = p.river.R_inst
+        compute_instantaneous_runoff!(R_inst, model.runoff,Y,p,t)
+        @. dY.river.R_accum = instantaneous_runoff(model.mode,Y,p,t)
+    end
+    return compute_exp_tendency!
+end
+
+
+struct Standalone{FT} <:  AbstractRiverSimulationMode{FT}
+    "Forcing data"
+    forcing_data::FT
+end
+
+struct Integrated{FT} <:  AbstractRiverSimulationMode{FT} end
+
+function compute_instantaneous_runoff!(R_inst, mode::Standalone,Y,p,t)
+    R_inst .= runoff.data(t) # on ClimaCore grid
+end
+
+function compute_instantaneous_runoff!(R_inst, mode::Integrated,Y,p,t)
+    @. R_inst = p.soil.R_s + p.soil.R_ss # on ClimaCore grid
+end
+
+function river_callback!(Y,p,t, t_callback)
+    # if we have stepped a full Δt_river from the previous step
+    if t ≈ t_callback # = t_prev + Δt_river
+        p.river.R_accum_history[1:end-1] .= p.river.R_accum_history[2:end]
+        p.river.R_accum_history[end] .= grid_to_basin(Y.river.R_accum)
+        Y.river.R_accum .= 0
+        update_river_state!(p.river.state, p.river.R_accum_history) # on basin domain
+    else
+        nothing
+    end
+end