DryDepositionGas

{
  "reference": {
    "citation": "Seinfeld, J. H., & Pandis, S. N. (2006). Atmospheric Chemistry and Physics: From Air Pollution to Climate Change (2nd ed.), Ch. 19, Eq. 19.2 (gas deposition velocity) and Eq. 19.1 (deposition flux). John Wiley & Sons, Inc.",
    "notes": "source_ref: AtmosphericDeposition.jl@e4468c79c8dd4aae88646cd16d6bcf290874742c:src/seinfeld_pandis_ch19.jl:416\n\nUpstream `DryDepositionGas` is an MTK `@component` that composes three subsystems -- `@named aero = AerodynamicResistance()`, `@named qlam = QuasiLaminarResistanceGas()`, `@named surf = SurfaceResistance()` -- via `System(eqs, t; systems=[aero, qlam, surf])`, with its own `@variables` (u_star, C, G, T_s, r_t, v_d, F) and seven coupling equations. Migrated as a subsystem-composed model (ESS spec section 4.7), the convention of the sibling composed migrations water_vapor_thermo.esm (esm-tfh2) and radiation_fundamentals.esm: the `aero`, `qlam` and `surf` subsystems inline the `variables` + `equations` of the already-migrated standalone components aerodynamic_resistance.esm (esm-x8pg), quasi_laminar_gas.esm (esm-t3wp) and surface_resistance.esm (esm-ug1i). The seven upstream coupling equations are carried as the model's top-level `equations`; subsystem variables are referenced by full dotted path from the model name (spec section 4.6), bare names resolve to the top-level system.\n\nRe-typing. In the standalone `.esm` files a component's connected inputs are typed `parameter` (no governing equation within the standalone component). In the composed model the parent coupling equations govern four of those inputs -- `aero.u_star` (by `aero.u_star ~ u_star`), `qlam.u_star` (by `qlam.u_star ~ u_star`), `surf.G` (by `surf.G ~ G`) and `surf.T_s` (by `surf.T_s ~ T_s`) -- so those four are re-typed `parameter` -> `state` here, because a `parameter` cannot be an equation LHS. Their upstream-test default values (u_star = 0.4 m/s, G = 300 W/m^2, T_s = 298.15 K) are kept as the state defaults. All other subsystem `parameter`s (aero.kappa/z/z_0, qlam.nu/D_g, and surf's land-use resistances and empirical constants) keep their `parameter` type and standalone-file default values. The top-level u_star, C, G and T_s are the model's input `parameter`s; r_t, v_d and F are its algebraic `state` outputs.\n\nVariable mapping. The upstream component declares 7 `@variables`: u_star, C, G, T_s are flagged `input = true` (connected, no defining equation) and migrate as top-level `type: parameter` -- the connected-input-variable convention of [[esm-input-variable-to-parameter]] and the standalone sibling files. r_t, v_d, F each carry a defining top-level equation and migrate as `type: state`. The upstream test `5.1 Gas Deposition System Compilation` confirms the input set by compiling the component with `mtkcompile(gas_dep; inputs = [u_star, C, G, T_s])`.\n\nEquations (migrated verbatim from the upstream `eqs` vector). Four coupling equations feed the inputs into the subsystems (aero.u_star ~ u_star, qlam.u_star ~ u_star, surf.G ~ G, surf.T_s ~ T_s); the remaining three are the diagnostic outputs: r_t ~ aero.r_a + qlam.r_b + surf.r_c (Eq. 19.2, the three resistances in series), v_d ~ 1/r_t (Eq. 19.2, deposition velocity), and F ~ -v_d*C (Eq. 19.1, the downward dry-deposition flux; the negative sign marks the flux as toward the surface). The subsystem equations are copied verbatim from the three standalone `.esm` files.\n\nThe flattened system is 16 algebraic equations in 16 states (the 4 coupled subsystem inputs aero.u_star/qlam.u_star/surf.G/surf.T_s, the subsystem outputs aero.r_a, qlam.Sc/r_b, surf.T_s_C/G_factor/T_factor/r_st/r_m/r_c, and the top-level r_t/v_d/F), fully explicit and triangular: each input flows to its subsystem, each subsystem computes its resistance, the three resistances sum to r_t, and v_d and F follow by direct substitution. `system_kind` is left unset (zero differential states), consistent with the composed sibling water_vapor_thermo.esm and the three standalone Ch. 19 components. No `examples` block: `tools/render_example_plots.py` resolves algebraic models on the top-level model only and does not descend into `subsystems`, so combined-diagnostic plots cannot be rendered -- matching water_vapor_thermo.esm / radiation_fundamentals.esm; verification is via the inline-test gate, which flattens subsystems.\n\nSingularities and domain. Eq. 19.14 is singular at u_star = 0 (r_a) and the stomatal temperature factor of Eq. 19.51 is singular at T_s_C = 0 (T_s = 273.15 K) and T_s_C = T_max (T_s = 313.15 K); every test keeps u_star > 0 and T_s strictly interior to the 273.15-313.15 K stomatal-function window, so r_t is finite and positive and v_d = 1/r_t is well-defined throughout.\n\nTolerance rationale (model-level rel=1e-6): an explicit triangular algebraic system with no ODE integration, matching the standalone Ch. 19 siblings and water_vapor_thermo.esm (all rel=1e-6). The pinned `expected` values are the Float64 evaluation of the same equation chain the runner walks (a logarithm, a fractional power, several reciprocal sums, two divisions); rel=1e-6 covers float64 round-off across that chain with wide margin. No assertion is near zero (r_a, r_b, r_c, r_t are O(10)-O(600) s/m and v_d is O(1e-3) m/s, all strictly positive; F is O(1e-9) and strictly negative), so a relative tolerance alone is sufficient."
  },
  "tolerance": {
    "rel": 1e-06
  },
  "variables": {
    "u_star": {
      "type": "parameter",
      "units": "m/s",
      "default": 0.4,
      "description": "Friction velocity characterizing surface-layer turbulence -- input to the composite, fed to the aero and qlam subsystems by the coupling equations aero.u_star ~ u_star and qlam.u_star ~ u_star. Default 0.4 m/s (the upstream Ch. 19 test reference value)."
    },
    "C": {
      "type": "parameter",
      "units": "mol/m^3",
      "default": 1e-06,
      "description": "Gas concentration at the reference height -- input to the composite, scales the dry-deposition flux via F = -v_d*C (Eq. 19.1). Default 1e-6 mol/m^3, a representative near-surface molar concentration of a depositing trace gas."
    },
    "G": {
      "type": "parameter",
      "units": "W/m^2",
      "default": 300.0,
      "description": "Solar irradiance reaching the surface -- input to the composite, fed to the surf subsystem by the coupling equation surf.G ~ G. Default 300 W/m^2 (matches the surface_resistance.esm reference case)."
    },
    "T_s": {
      "type": "parameter",
      "units": "K",
      "default": 298.15,
      "description": "Surface temperature -- input to the composite, fed to the surf subsystem by the coupling equation surf.T_s ~ T_s. Default 298.15 K, 25 degC (matches the surface_resistance.esm reference case)."
    },
    "r_t": {
      "type": "unknown",
      "units": "s/m",
      "description": "Total dry-deposition resistance: the series sum r_a + r_b + r_c of the aerodynamic, quasi-laminar and surface resistances (Eq. 19.2)."
    },
    "v_d": {
      "type": "unknown",
      "units": "m/s",
      "description": "Gas dry-deposition velocity, the reciprocal of the total series resistance v_d = 1/r_t (Eq. 19.2)."
    },
    "F": {
      "type": "unknown",
      "units": "mol/(m^2*s)",
      "description": "Gas dry-deposition flux F = -v_d*C (Eq. 19.1); the negative sign marks the flux as downward, toward the surface."
    }
  },
  "subsystems": {
    "aero": {
      "variables": {
        "kappa": {
          "type": "parameter",
          "units": "1",
          "default": 0.4,
          "description": "Von Karman constant (dimensionless), upstream @constant KAPPA. Sets the slope of the neutral-stability logarithmic wind profile."
        },
        "z": {
          "type": "parameter",
          "units": "m",
          "default": 10.0,
          "description": "Reference height above the surface at which the resistance is evaluated. Default: 10 m (S&P upstream test 2.1 canonical case)."
        },
        "z_0": {
          "type": "parameter",
          "units": "m",
          "default": 0.1,
          "description": "Surface roughness length. Default: 0.1 m, open cropland / tall grass (S&P upstream test 2.1 canonical case)."
        },
        "u_star": {
          "type": "unknown",
          "units": "m/s",
          "default": 0.4,
          "description": "Friction velocity -- coupled input, driven by the parent coupling equation aero.u_star ~ u_star (re-typed parameter -> state for the composed model)."
        },
        "r_a": {
          "type": "unknown",
          "units": "s/m",
          "description": "Aerodynamic resistance to dry deposition through the surface layer under neutral atmospheric stability (Eq. 19.14)."
        }
      },
      "equations": [
        {
          "_comment": "Eq. 19.14 -- neutral-stability aerodynamic resistance: r_a = (1/(kappa*u_star)) * ln(z/z_0).",
          "lhs": "r_a",
          "rhs": {
            "op": "*",
            "args": [
              {
                "op": "/",
                "args": [
                  1,
                  {
                    "op": "*",
                    "args": [
                      "kappa",
                      "u_star"
                    ]
                  }
                ]
              },
              {
                "op": "log",
                "args": [
                  {
                    "op": "/",
                    "args": [
                      "z",
                      "z_0"
                    ]
                  }
                ]
              }
            ]
          }
        }
      ]
    },
    "qlam": {
      "variables": {
        "nu": {
          "type": "parameter",
          "units": "m^2/s",
          "default": 1.5e-05,
          "description": "Kinematic viscosity of air (upstream input @parameter; default 1.5e-5 m^2/s is the value for air near 298 K used in the upstream test suite)."
        },
        "D_g": {
          "type": "parameter",
          "units": "m^2/s",
          "default": 1.5e-05,
          "description": "Molecular diffusivity of the depositing gas in air (upstream input @parameter; default 1.5e-5 m^2/s is an O3-like diffusivity giving a Schmidt number of 1.0)."
        },
        "u_star": {
          "type": "unknown",
          "units": "m/s",
          "default": 0.4,
          "description": "Friction velocity -- coupled input, driven by the parent coupling equation qlam.u_star ~ u_star (re-typed parameter -> state for the composed model)."
        },
        "Sc": {
          "type": "unknown",
          "units": "1",
          "description": "Schmidt number Sc = nu/D_g, the dimensionless ratio of momentum to mass diffusivity (algebraic output)."
        },
        "r_b": {
          "type": "unknown",
          "units": "s/m",
          "description": "Quasi-laminar (boundary-layer) resistance for the gas, Eq. 19.17 (algebraic output)."
        }
      },
      "equations": [
        {
          "_comment": "Schmidt number Sc = nu/D_g -- the ratio of the kinematic viscosity of air to the molecular diffusivity of the depositing gas.",
          "lhs": "Sc",
          "rhs": {
            "op": "/",
            "args": [
              "nu",
              "D_g"
            ]
          }
        },
        {
          "_comment": "Eq. 19.17 -- quasi-laminar resistance for gases, r_b = 5 * Sc^(2/3) / u_star. The exponent 2/3 is the AST node {op:/,args:[2,3]} (float division). Julia's left-associative `5 * Sc^(2/3) / u_star` parses as (5*Sc^(2/3))/u_star, mirrored here by the outer / node over the 5*Sc^(2/3) product.",
          "lhs": "r_b",
          "rhs": {
            "op": "/",
            "args": [
              {
                "op": "*",
                "args": [
                  5,
                  {
                    "op": "^",
                    "args": [
                      "Sc",
                      {
                        "op": "/",
                        "args": [
                          2,
                          3
                        ]
                      }
                    ]
                  }
                ]
              },
              "u_star"
            ]
          }
        }
      ]
    },
    "surf": {
      "variables": {
        "T_ref": {
          "type": "parameter",
          "units": "K",
          "default": 273.15,
          "description": "Celsius-to-Kelvin offset applied to the surface temperature (upstream @constant)."
        },
        "G_ref": {
          "type": "parameter",
          "units": "W/m^2",
          "default": 200.0,
          "description": "Reference solar irradiance in the stomatal light response, Eq. 19.51 (upstream @constant)."
        },
        "G_offset": {
          "type": "parameter",
          "units": "W/m^2",
          "default": 0.1,
          "description": "Small irradiance offset that keeps the light factor finite at G = 0 (upstream @constant)."
        },
        "T_coeff": {
          "type": "parameter",
          "units": "K^2",
          "default": 400.0,
          "description": "Temperature coefficient of the stomatal temperature factor, Eq. 19.51 (upstream @constant)."
        },
        "T_max": {
          "type": "parameter",
          "units": "K",
          "default": 40.0,
          "description": "Upper temperature bound (Celsius-equivalent) of stomatal function in Eq. 19.51 (upstream @constant)."
        },
        "H_coeff": {
          "type": "parameter",
          "units": "m/s",
          "default": 0.00033,
          "description": "Henry's-law coefficient of the mesophyll resistance, Eq. 19.52 (upstream @constant)."
        },
        "f_coeff": {
          "type": "parameter",
          "units": "m/s",
          "default": 100.0,
          "description": "Reactivity coefficient of the mesophyll resistance, Eq. 19.52 (upstream @constant)."
        },
        "H_star": {
          "type": "parameter",
          "units": "1",
          "default": 100000.0,
          "description": "Effective Henry's-law constant of the depositing gas (dimensionless, normalized; S&P Table 19.4). Default: SO2."
        },
        "f_0": {
          "type": "parameter",
          "units": "1",
          "default": 0.0,
          "description": "Chemical reactivity factor of the depositing gas, 0-1 (S&P Table 19.4). Default: SO2."
        },
        "D_ratio": {
          "type": "parameter",
          "units": "1",
          "default": 1.9,
          "description": "Ratio of water-vapor to gas molecular diffusivity, D_H2O/D_gas (S&P Table 19.4). Default: SO2."
        },
        "r_i": {
          "type": "parameter",
          "units": "s/m",
          "default": 70.0,
          "description": "Minimum bulk-canopy stomatal resistance (Wesely 1989 land-use table). Default: deciduous forest, midsummer."
        },
        "r_lu": {
          "type": "parameter",
          "units": "s/m",
          "default": 2000.0,
          "description": "Cuticular / outer-canopy-surface resistance (Wesely 1989 land-use table). Default: deciduous forest, midsummer."
        },
        "r_dc": {
          "type": "parameter",
          "units": "s/m",
          "default": 100.0,
          "description": "Lower-canopy buoyant-convection resistance (Wesely 1989 land-use table). Default: representative midsummer value."
        },
        "r_cl": {
          "type": "parameter",
          "units": "s/m",
          "default": 2000.0,
          "description": "Lower-canopy exposed-surfaces uptake resistance (Wesely 1989 land-use table). Default: deciduous forest, midsummer, SO2."
        },
        "r_ac": {
          "type": "parameter",
          "units": "s/m",
          "default": 2000.0,
          "description": "In-canopy aerodynamic resistance (Wesely 1989 land-use table). Default: deciduous forest, midsummer."
        },
        "r_gs": {
          "type": "parameter",
          "units": "s/m",
          "default": 500.0,
          "description": "Ground-surface uptake resistance (Wesely 1989 land-use table). Default: deciduous forest, midsummer, SO2."
        },
        "G": {
          "type": "unknown",
          "units": "W/m^2",
          "default": 300.0,
          "description": "Solar irradiance reaching the surface -- coupled input, driven by the parent coupling equation surf.G ~ G (re-typed parameter -> state for the composed model)."
        },
        "T_s": {
          "type": "unknown",
          "units": "K",
          "default": 298.15,
          "description": "Surface temperature -- coupled input, driven by the parent coupling equation surf.T_s ~ T_s (re-typed parameter -> state for the composed model)."
        },
        "T_s_C": {
          "type": "unknown",
          "units": "K",
          "description": "Surface temperature offset from the 273.15 K reference (Celsius-equivalent magnitude carried with a K unit)."
        },
        "G_factor": {
          "type": "unknown",
          "units": "1",
          "description": "Dimensionless irradiance factor of the stomatal resistance, 1 + (G_ref/(G+G_offset))^2 (Eq. 19.51)."
        },
        "T_factor": {
          "type": "unknown",
          "units": "1",
          "description": "Dimensionless temperature factor of the stomatal resistance, T_coeff/(T_s_C*(T_max-T_s_C)) (Eq. 19.51)."
        },
        "r_st": {
          "type": "unknown",
          "units": "s/m",
          "description": "Bulk-canopy stomatal resistance (Eq. 19.51)."
        },
        "r_m": {
          "type": "unknown",
          "units": "s/m",
          "description": "Mesophyll resistance (Eq. 19.52)."
        },
        "r_c": {
          "type": "unknown",
          "units": "s/m",
          "description": "Total surface (canopy) resistance to gaseous dry deposition along four parallel pathways (Eq. 19.50)."
        }
      },
      "equations": [
        {
          "_comment": "Temperature offset from the 273.15 K reference: T_s_C = T_s - T_ref.",
          "lhs": "T_s_C",
          "rhs": {
            "op": "-",
            "args": [
              "T_s",
              "T_ref"
            ]
          }
        },
        {
          "_comment": "Eq. 19.51 light factor: G_factor = 1 + (G_ref/(G + G_offset))^2.",
          "lhs": "G_factor",
          "rhs": {
            "op": "+",
            "args": [
              1,
              {
                "op": "^",
                "args": [
                  {
                    "op": "/",
                    "args": [
                      "G_ref",
                      {
                        "op": "+",
                        "args": [
                          "G",
                          "G_offset"
                        ]
                      }
                    ]
                  },
                  2
                ]
              }
            ]
          }
        },
        {
          "_comment": "Eq. 19.51 temperature factor: T_factor = T_coeff/(T_s_C*(T_max - T_s_C)).",
          "lhs": "T_factor",
          "rhs": {
            "op": "/",
            "args": [
              "T_coeff",
              {
                "op": "*",
                "args": [
                  "T_s_C",
                  {
                    "op": "-",
                    "args": [
                      "T_max",
                      "T_s_C"
                    ]
                  }
                ]
              }
            ]
          }
        },
        {
          "_comment": "Eq. 19.51 stomatal resistance: r_st = D_ratio*r_i*G_factor*T_factor.",
          "lhs": "r_st",
          "rhs": {
            "op": "*",
            "args": [
              "D_ratio",
              "r_i",
              "G_factor",
              "T_factor"
            ]
          }
        },
        {
          "_comment": "Eq. 19.52 mesophyll resistance: r_m = 1/(H_coeff*H_star + f_coeff*f_0).",
          "lhs": "r_m",
          "rhs": {
            "op": "/",
            "args": [
              1,
              {
                "op": "+",
                "args": [
                  {
                    "op": "*",
                    "args": [
                      "H_coeff",
                      "H_star"
                    ]
                  },
                  {
                    "op": "*",
                    "args": [
                      "f_coeff",
                      "f_0"
                    ]
                  }
                ]
              }
            ]
          }
        },
        {
          "_comment": "Eq. 19.50 total surface resistance: four parallel deposition pathways.",
          "lhs": "r_c",
          "rhs": {
            "op": "/",
            "args": [
              1,
              {
                "op": "+",
                "args": [
                  {
                    "op": "/",
                    "args": [
                      1,
                      {
                        "op": "+",
                        "args": [
                          "r_st",
                          "r_m"
                        ]
                      }
                    ]
                  },
                  {
                    "op": "/",
                    "args": [
                      1,
                      "r_lu"
                    ]
                  },
                  {
                    "op": "/",
                    "args": [
                      1,
                      {
                        "op": "+",
                        "args": [
                          "r_dc",
                          "r_cl"
                        ]
                      }
                    ]
                  },
                  {
                    "op": "/",
                    "args": [
                      1,
                      {
                        "op": "+",
                        "args": [
                          "r_ac",
                          "r_gs"
                        ]
                      }
                    ]
                  }
                ]
              }
            ]
          }
        }
      ]
    }
  },
  "equations": [
    {
      "_comment": "Couple the input friction velocity into the aerodynamic-resistance subsystem (upstream: aero.u_star ~ u_star).",
      "lhs": "DryDepositionGas.aero.u_star",
      "rhs": "u_star"
    },
    {
      "_comment": "Couple the input friction velocity into the quasi-laminar-resistance subsystem (upstream: qlam.u_star ~ u_star).",
      "lhs": "DryDepositionGas.qlam.u_star",
      "rhs": "u_star"
    },
    {
      "_comment": "Couple the input solar irradiance into the surface-resistance subsystem (upstream: surf.G ~ G).",
      "lhs": "DryDepositionGas.surf.G",
      "rhs": "G"
    },
    {
      "_comment": "Couple the input surface temperature into the surface-resistance subsystem (upstream: surf.T_s ~ T_s).",
      "lhs": "DryDepositionGas.surf.T_s",
      "rhs": "T_s"
    },
    {
      "_comment": "Eq. 19.2 -- total resistance: the aerodynamic, quasi-laminar and surface resistances act in series, r_t = r_a + r_b + r_c.",
      "lhs": "r_t",
      "rhs": {
        "op": "+",
        "args": [
          "DryDepositionGas.aero.r_a",
          "DryDepositionGas.qlam.r_b",
          "DryDepositionGas.surf.r_c"
        ]
      }
    },
    {
      "_comment": "Eq. 19.2 -- gas dry-deposition velocity is the reciprocal of the total series resistance, v_d = 1/r_t.",
      "lhs": "v_d",
      "rhs": {
        "op": "/",
        "args": [
          1,
          "r_t"
        ]
      }
    },
    {
      "_comment": "Eq. 19.1 -- gas dry-deposition flux F = -v_d*C; the negative sign marks the flux as downward, toward the surface.",
      "lhs": "F",
      "rhs": {
        "op": "-",
        "args": [
          {
            "op": "*",
            "args": [
              "v_d",
              "C"
            ]
          }
        ]
      }
    }
  ],
  "tests": [
    {
      "id": "default_conditions",
      "description": "Component defaults: u_star = 0.4 m/s, G = 300 W/m^2, T_s = 298.15 K, C = 1e-6 mol/m^3, with the aero subsystem at its 10 m / 0.1 m neutral-stability defaults, qlam at an O3-like diffusivity (Schmidt number 1.0) and surf at the SO2 deciduous-forest land-use defaults. The three series resistances are r_a = 28.782 s/m (Eq. 19.14), r_b = 12.5 s/m (Eq. 19.17) and r_c = 159.835 s/m (Eq. 19.50), summing to a total resistance r_t = 201.117 s/m; the deposition velocity is v_d = 1/r_t = 4.9722e-3 m/s and the flux F = -v_d*C = -4.9722e-9 mol/(m^2*s). Verifies the full coupling chain end to end. v_d and F are re-checked at t = 1 s to confirm the algebraic system is time-invariant.",
      "time_span": {
        "start": 0.0,
        "end": 1.0
      },
      "assertions": [
        {
          "variable": "DryDepositionGas.aero.r_a",
          "time": 0.0,
          "expected": 28.78231366242557
        },
        {
          "variable": "DryDepositionGas.qlam.Sc",
          "time": 0.0,
          "expected": 1.0
        },
        {
          "variable": "DryDepositionGas.qlam.r_b",
          "time": 0.0,
          "expected": 12.5
        },
        {
          "variable": "DryDepositionGas.surf.r_c",
          "time": 0.0,
          "expected": 159.83485089186416
        },
        {
          "variable": "DryDepositionGas.r_t",
          "time": 0.0,
          "expected": 201.11716455428973
        },
        {
          "variable": "DryDepositionGas.v_d",
          "time": 0.0,
          "expected": 0.004972226026635629
        },
        {
          "variable": "DryDepositionGas.F",
          "time": 0.0,
          "expected": -4.972226026635629e-09
        },
        {
          "variable": "DryDepositionGas.v_d",
          "time": 1.0,
          "expected": 0.004972226026635629
        },
        {
          "variable": "DryDepositionGas.F",
          "time": 1.0,
          "expected": -4.972226026635629e-09
        }
      ]
    },
    {
      "id": "coherent_so2_deposition",
      "description": "A coherent SO2 deposition case: the surf subsystem is already at its SO2 land-use defaults, and the qlam diffusivity D_g is overridden to nu/1.3 = 1.1538e-5 m^2/s so the Schmidt number Sc = nu/D_g = 1.3 matches SO2 in air near 298 K. The quasi-laminar resistance rises to r_b = 5*1.3^(2/3)/0.4 = 14.889 s/m (above the Sc=1.0 default), so r_t = 203.506 s/m and v_d falls slightly to 4.9139e-3 m/s -- a slower-diffusing gas deposits marginally slower.",
      "parameter_overrides": {
        "DryDepositionGas.qlam.D_g": 1.1538461538461538e-05
      },
      "time_span": {
        "start": 0.0,
        "end": 1.0
      },
      "assertions": [
        {
          "variable": "DryDepositionGas.qlam.Sc",
          "time": 0.0,
          "expected": 1.3
        },
        {
          "variable": "DryDepositionGas.qlam.r_b",
          "time": 0.0,
          "expected": 14.88923031495541
        },
        {
          "variable": "DryDepositionGas.r_t",
          "time": 0.0,
          "expected": 203.50639486924513
        },
        {
          "variable": "DryDepositionGas.v_d",
          "time": 0.0,
          "expected": 0.004913850499108443
        }
      ]
    },
    {
      "id": "ozone_deposition",
      "description": "Ozone over the midsummer deciduous forest: the surf subsystem is overridden to the O3 Table 19.4 properties (D_ratio = 1.6, H_star = 0.01, f_0 = 1.0). O3 is weakly soluble but highly reactive, so the mesophyll resistance collapses and the stomatal resistance drops, giving r_c = 139.431 s/m -- below the SO2 default r_c = 159.835 s/m. The total resistance falls to r_t = 180.713 s/m and the deposition velocity rises to v_d = 5.5336e-3 m/s: a reactive gas deposits faster than a soluble-only gas over the same canopy.",
      "parameter_overrides": {
        "DryDepositionGas.surf.D_ratio": 1.6,
        "DryDepositionGas.surf.H_star": 0.01,
        "DryDepositionGas.surf.f_0": 1.0
      },
      "time_span": {
        "start": 0.0,
        "end": 1.0
      },
      "assertions": [
        {
          "variable": "DryDepositionGas.surf.r_st",
          "time": 0.0,
          "expected": 172.52758312300134
        },
        {
          "variable": "DryDepositionGas.surf.r_c",
          "time": 0.0,
          "expected": 139.43055397838557
        },
        {
          "variable": "DryDepositionGas.r_t",
          "time": 0.0,
          "expected": 180.71286764081114
        },
        {
          "variable": "DryDepositionGas.v_d",
          "time": 0.0,
          "expected": 0.005533640260679289
        }
      ]
    },
    {
      "id": "strong_turbulence",
      "description": "Strong surface-layer turbulence: the input friction velocity u_star is raised to 1.0 m/s. The coupling equations carry it into both the aero and qlam subsystems, where Eq. 19.14 and Eq. 19.17 each make their resistance inversely proportional to u_star -- r_a falls to 11.513 s/m and r_b to 5.0 s/m. The surface resistance r_c is unchanged (it does not depend on u_star), so r_t drops to 176.348 s/m and the deposition velocity rises to v_d = 5.6706e-3 m/s.",
      "parameter_overrides": {
        "DryDepositionGas.u_star": 1.0
      },
      "time_span": {
        "start": 0.0,
        "end": 1.0
      },
      "assertions": [
        {
          "variable": "DryDepositionGas.aero.r_a",
          "time": 0.0,
          "expected": 11.51292546497023
        },
        {
          "variable": "DryDepositionGas.qlam.r_b",
          "time": 0.0,
          "expected": 5.0
        },
        {
          "variable": "DryDepositionGas.r_t",
          "time": 0.0,
          "expected": 176.3477763568344
        },
        {
          "variable": "DryDepositionGas.v_d",
          "time": 0.0,
          "expected": 0.005670613038956216
        }
      ]
    },
    {
      "id": "calm_conditions",
      "description": "Calm, weakly turbulent conditions: u_star is lowered to 0.1 m/s. Because both r_a and r_b scale as 1/u_star, each grows fourfold relative to the 0.4 m/s default -- r_a = 115.129 s/m and r_b = 50.0 s/m -- so the aerodynamic and quasi-laminar pathways now dominate the total. r_t rises to 324.964 s/m and the deposition velocity falls to v_d = 3.0773e-3 m/s.",
      "parameter_overrides": {
        "DryDepositionGas.u_star": 0.1
      },
      "time_span": {
        "start": 0.0,
        "end": 1.0
      },
      "assertions": [
        {
          "variable": "DryDepositionGas.aero.r_a",
          "time": 0.0,
          "expected": 115.12925464970228
        },
        {
          "variable": "DryDepositionGas.qlam.r_b",
          "time": 0.0,
          "expected": 50.0
        },
        {
          "variable": "DryDepositionGas.r_t",
          "time": 0.0,
          "expected": 324.9641055415664
        },
        {
          "variable": "DryDepositionGas.v_d",
          "time": 0.0,
          "expected": 0.0030772629436517543
        }
      ]
    },
    {
      "id": "smooth_surface",
      "description": "A smooth surface: the aero roughness length z_0 is overridden to 0.01 m (mown grass / snow). The smaller roughness widens the height ratio z/z_0 inside the logarithm of Eq. 19.14, raising the aerodynamic resistance to r_a = 43.173 s/m above the 0.1 m default. Only the aero subsystem is affected; r_b and r_c are unchanged. r_t rises to 215.508 s/m and v_d falls to 4.6402e-3 m/s.",
      "parameter_overrides": {
        "DryDepositionGas.aero.z_0": 0.01
      },
      "time_span": {
        "start": 0.0,
        "end": 1.0
      },
      "assertions": [
        {
          "variable": "DryDepositionGas.aero.r_a",
          "time": 0.0,
          "expected": 43.17347049363835
        },
        {
          "variable": "DryDepositionGas.r_t",
          "time": 0.0,
          "expected": 215.5083213855025
        },
        {
          "variable": "DryDepositionGas.v_d",
          "time": 0.0,
          "expected": 0.004640192051847475
        }
      ]
    },
    {
      "id": "coupling_propagation",
      "description": "Exercises the coupling equations directly: the three top-level inputs are overridden together (u_star = 0.7 m/s, G = 500 W/m^2, T_s = 290 K) and the coupled subsystem inputs are asserted equal to them -- aero.u_star = qlam.u_star = u_star = 0.7 and surf.G = G = 500, surf.T_s = T_s = 290 -- confirming each coupling equation propagates its input correctly. The downstream resistances follow: r_a = 16.447 s/m, r_b = 7.143 s/m, r_c = 129.933 s/m, giving v_d = 6.5137e-3 m/s.",
      "parameter_overrides": {
        "DryDepositionGas.u_star": 0.7,
        "DryDepositionGas.G": 500.0,
        "DryDepositionGas.T_s": 290.0
      },
      "time_span": {
        "start": 0.0,
        "end": 1.0
      },
      "assertions": [
        {
          "variable": "DryDepositionGas.aero.u_star",
          "time": 0.0,
          "expected": 0.7
        },
        {
          "variable": "DryDepositionGas.qlam.u_star",
          "time": 0.0,
          "expected": 0.7
        },
        {
          "variable": "DryDepositionGas.surf.G",
          "time": 0.0,
          "expected": 500.0
        },
        {
          "variable": "DryDepositionGas.surf.T_s",
          "time": 0.0,
          "expected": 290.0
        },
        {
          "variable": "DryDepositionGas.aero.r_a",
          "time": 0.0,
          "expected": 16.4470363785289
        },
        {
          "variable": "DryDepositionGas.qlam.r_b",
          "time": 0.0,
          "expected": 7.142857142857143
        },
        {
          "variable": "DryDepositionGas.surf.r_c",
          "time": 0.0,
          "expected": 129.93319240743807
        },
        {
          "variable": "DryDepositionGas.v_d",
          "time": 0.0,
          "expected": 0.0065136783432272645
        }
      ]
    },
    {
      "id": "flux_scales_with_concentration",
      "description": "The dry-deposition flux F = -v_d*C (Eq. 19.1) is linear in the gas concentration C. With C doubled to 2e-6 mol/m^3 and every resistance at its default, the deposition velocity v_d is unchanged at 4.9722e-3 m/s (it depends only on the resistances, not on C), while the flux doubles to F = -9.9445e-9 mol/(m^2*s) -- exactly twice the default-case flux. Confirms C enters only the flux equation and not the velocity.",
      "parameter_overrides": {
        "DryDepositionGas.C": 2e-06
      },
      "time_span": {
        "start": 0.0,
        "end": 1.0
      },
      "assertions": [
        {
          "variable": "DryDepositionGas.v_d",
          "time": 0.0,
          "expected": 0.004972226026635629
        },
        {
          "variable": "DryDepositionGas.F",
          "time": 0.0,
          "expected": -9.944452053271258e-09
        }
      ]
    },
    {
      "id": "low_irradiance_high_canopy_resistance",
      "description": "Low-light conditions: the solar irradiance G is lowered to 50 W/m^2 (heavy overcast / near-dusk). The stomatal light factor of Eq. 19.51 is G_factor = 1 + (G_ref/(G+G_offset))^2 = 16.936, an order of magnitude above the 300 W/m^2 default, driving the stomatal resistance up to r_st = 2402.7 s/m and the total surface resistance to r_c = 557.9 s/m. The total resistance rises to r_t = 599.2 s/m and the deposition velocity collapses to v_d = 1.6689e-3 m/s -- stomatal closure in low light strongly suppresses gas dry deposition.",
      "parameter_overrides": {
        "DryDepositionGas.G": 50.0
      },
      "time_span": {
        "start": 0.0,
        "end": 1.0
      },
      "assertions": [
        {
          "variable": "DryDepositionGas.surf.G_factor",
          "time": 0.0,
          "expected": 16.936191489276933
        },
        {
          "variable": "DryDepositionGas.surf.r_st",
          "time": 0.0,
          "expected": 2402.6810326120876
        },
        {
          "variable": "DryDepositionGas.surf.r_c",
          "time": 0.0,
          "expected": 557.9152406948829
        },
        {
          "variable": "DryDepositionGas.r_t",
          "time": 0.0,
          "expected": 599.1975543573085
        },
        {
          "variable": "DryDepositionGas.v_d",
          "time": 0.0,
          "expected": 0.0016688986674396344
        }
      ]
    }
  ]
}