UebSnow.hpp

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// SPDX-License-Identifier: Apache-2.0

 
#pragma once
#include <string>
#include <vector>
 
namespace openswmm::surface::ueb {
enum class TemperatureMethod { ModifiedForceRestore, Equilibrium };
struct Parameters {
    TemperatureMethod temperature = TemperatureMethod::ModifiedForceRestore;
    double rain_temperature = 3, snow_temperature = -1, emissivity = .99;
    double roughness = .01, measurement_height = 2, snow_density = 200, soil_density = 1700;
    double soil_heat_capacity = 2.09, active_soil_depth = .1;
    double liquid_retention = .02, drainage_conductivity = 200; // m/h, reference parameter units
    double equilibrium_conductance = .02;                       // m/h
    double snow_conductivity = .33, soil_conductivity = 6.5;    // kJ/(m K h)
    double low_frequency = .0654, amplitude = 1, stability = 1;
    double ground_albedo = .25, visible_albedo = .85, infrared_albedo = .65;
    double new_snow_depth = .002, age_dust = .03;
    double visible_age = .2, infrared_age = .5;
    double max_step = 3600; // seconds; kernel subdivides longer forcing intervals
    std::string validate() const;
};

struct Site {
    double forest = 0, drift = 1, pressure = 101325, ground_heat = 0, extinction_depth = .1;
};

struct Forcing {
    double seconds = 0, precipitation = 0, temperature = 0, wind = 0, humidity = .5;
    double shortwave = 0, longwave = 0, cosine = 0; // W/m2; cosine of incident sun angle
    double snow_catch = 1;
    double snow_fraction = -1; // -1 uses UEB temperature partition; [0,1] prescribes it
};

struct ThermalSample {
    double seconds = 0, surface = 0, bulk = 0;
};

struct State {
    double energy = 0, water = 0, age = 0, refreezing_depth = 0, total_refreezing_depth = 0;
    std::vector<ThermalSample> history; // at most the preceding 24 hours, duration weighted
};

struct Fluxes {
    double rain = 0, snow = 0, liquid = 0,
           sublimation = 0;                          // integrated m; sublimation may be negative
    double net_energy = 0, outgoing_melt_energy = 0; // integrated kJ/m2
    double surface_temperature = 0, bulk_temperature = 0, albedo = 0;
    double water_residual = 0, energy_residual = 0;
    int steps = 0, retries = 0, diagnostics = 0;
};

std::string advance(State& state, const Parameters& parameters, const Site& site,
                    const Forcing& forcing, Fluxes& output);
double bulkTemperature(const State& state, const Parameters& parameters) noexcept;
}