Visibility

{
  "reference": {
    "notes": "Coupler identity: this model was serialized with the model-level field `coupletype: \"Visibility\"`, the EarthSciMLBase `CoupleType` metadata tag naming the Julia coupler struct that `EarthSciMLBase.couple2` dispatches on to find this component's pairwise coupling rules. The esm schema defined `coupletype` only before 0.8.0 (\"informational label identifying this system's role in coupling\"); 0.8.0 removed it in favour of explicit coupling — `coupling` entries naming components directly, or `coupling_roles` + `coupling_import` in a coupling-library file (esm-spec §10.9–§10.11). esm 1.0.0 has no model-level coupler-identity field, so the tag is recorded here to keep it recoverable."
  },
  "variables": {
    "Koschmeider_const": {
      "type": "parameter",
      "units": "1",
      "default": 3.912,
      "description": "Koschmeider constant = -ln(0.02) (dimensionless)"
    },
    "one_km": {
      "type": "parameter",
      "units": "m",
      "default": 1000.0,
      "description": "One kilometer in meters"
    },
    "b_ext": {
      "type": "parameter",
      "units": "m^-1",
      "default": 0.0001,
      "description": "Total extinction coefficient"
    },
    "b_sg": {
      "type": "parameter",
      "units": "m^-1",
      "default": 1.32e-05,
      "description": "Rayleigh scattering coefficient (gas)"
    },
    "b_ag": {
      "type": "parameter",
      "units": "m^-1",
      "default": 0.0,
      "description": "Absorption coefficient due to gases (mainly NO2)"
    },
    "x_v": {
      "type": "unknown",
      "units": "m",
      "description": "Visual range"
    },
    "τ_per_km": {
      "type": "unknown",
      "units": "1",
      "description": "Optical depth per kilometer (dimensionless)"
    },
    "b_sp": {
      "type": "unknown",
      "units": "m^-1",
      "description": "Scattering coefficient due to particles"
    }
  },
  "equations": [
    {
      "lhs": "x_v",
      "rhs": {
        "op": "/",
        "args": [
          "Koschmeider_const",
          "b_ext"
        ]
      }
    },
    {
      "lhs": "τ_per_km",
      "rhs": {
        "op": "*",
        "args": [
          "b_ext",
          "one_km"
        ]
      }
    },
    {
      "lhs": "b_sp",
      "rhs": {
        "op": "-",
        "args": [
          {
            "op": "-",
            "args": [
              "b_ext",
              "b_sg"
            ]
          },
          "b_ag"
        ]
      }
    }
  ],
  "tests": [
    {
      "id": "koschmeider_default",
      "description": "Visual range at default parameters (b_ext=1e-4 m^-1): x_v = 3.912 / 1e-4 = 39120 m",
      "time_span": {
        "start": 0.0,
        "end": 0.0
      },
      "assertions": [
        {
          "variable": "x_v",
          "time": 0,
          "expected": 39120.0,
          "tolerance": {
            "abs": 0.01
          }
        }
      ]
    },
    {
      "id": "optical_depth_default",
      "description": "Optical depth per km at default parameters (b_ext=1e-4): tau_per_km = 1e-4 x 1000 = 0.1",
      "time_span": {
        "start": 0.0,
        "end": 0.0
      },
      "assertions": [
        {
          "variable": "τ_per_km",
          "time": 0,
          "expected": 0.1,
          "tolerance": {
            "abs": 1e-10
          }
        }
      ]
    },
    {
      "id": "particle_scattering_default",
      "description": "Particle scattering at defaults: b_sp = 1e-4 - 13.2e-6 - 0 = 8.68e-5 m^-1",
      "time_span": {
        "start": 0.0,
        "end": 0.0
      },
      "assertions": [
        {
          "variable": "b_sp",
          "time": 0,
          "expected": 8.68e-05,
          "tolerance": {
            "abs": 1e-10
          }
        }
      ]
    },
    {
      "id": "rayleigh_clean_atmosphere",
      "description": "Clean Rayleigh atmosphere (S&P p.705): b_ext = b_sg = 13.2e-6 m^-1, x_v = 3.912 / 13.2e-6 = 296363.6 m (~296 km), no particle contribution",
      "time_span": {
        "start": 0.0,
        "end": 0.0
      },
      "parameter_overrides": {
        "b_ext": 1.32e-05,
        "b_sg": 1.32e-05,
        "b_ag": 0.0
      },
      "assertions": [
        {
          "variable": "x_v",
          "time": 0,
          "expected": 296363.636,
          "tolerance": {
            "rel": 0.001
          }
        },
        {
          "variable": "b_sp",
          "time": 0,
          "expected": 0.0,
          "tolerance": {
            "abs": 1e-12
          }
        }
      ]
    },
    {
      "id": "urban_polluted",
      "description": "Urban polluted conditions (b_ext=2e-4 m^-1): x_v = 3.912 / 2e-4 = 19560 m (~20 km), tau_per_km = 0.2",
      "time_span": {
        "start": 0.0,
        "end": 0.0
      },
      "parameter_overrides": {
        "b_ext": 0.0002
      },
      "assertions": [
        {
          "variable": "x_v",
          "time": 0,
          "expected": 19560.0,
          "tolerance": {
            "abs": 0.01
          }
        },
        {
          "variable": "τ_per_km",
          "time": 0,
          "expected": 0.2,
          "tolerance": {
            "abs": 1e-10
          }
        }
      ]
    },
    {
      "id": "gas_absorption_contribution",
      "description": "With NO2 absorption (b_ag=5e-6 m^-1): b_sp = 1e-4 - 13.2e-6 - 5e-6 = 8.18e-5 m^-1",
      "time_span": {
        "start": 0.0,
        "end": 0.0
      },
      "parameter_overrides": {
        "b_ag": 5e-06
      },
      "assertions": [
        {
          "variable": "b_sp",
          "time": 0,
          "expected": 8.18e-05,
          "tolerance": {
            "abs": 1e-10
          }
        }
      ]
    }
  ],
  "analyses": [
    {
      "id": "koschmeider_curve",
      "description": "Koschmeider equation (Eq. 15.36): visual range x_v vs extinction coefficient b_ext. At sea level in a clean Rayleigh atmosphere (b_ext ~13.2e-6 m^-1), maximum visual range is ~296 km. Urban conditions (b_ext ~1e-4 to 1e-3 m^-1) reduce visibility to 4-40 km. Reproduces the characteristic curve from S&P Chapter 15.",
      "initial_state": {},
      "time_span": {
        "start": 0.0,
        "end": 0.0
      },
      "parameter_sweep": {
        "type": "cartesian",
        "dimensions": [
          {
            "parameter": "b_ext",
            "range": {
              "start": 1e-05,
              "stop": 0.001,
              "count": 50,
              "scale": "log"
            }
          }
        ]
      },
      "plots": [
        {
          "id": "visual_range_vs_extinction",
          "type": "line",
          "description": "Visual range x_v (m) vs extinction coefficient b_ext (m^-1), reproducing the Koschmeider relationship (Eq. 15.36).",
          "x": {
            "variable": "b_ext",
            "label": "Extinction coefficient b_ext (m^-1)"
          },
          "y": {
            "variable": "x_v",
            "label": "Visual range x_v (m)"
          }
        }
      ]
    }
  ]
}