Radiation.hpp

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// SPDX-License-Identifier: Apache-2.0
//
// Copyright 2026 Caleb Buahin
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

 
#ifndef OPENSWMM_ENGINE_HYDROLOGY_RADIATION_HPP
#define OPENSWMM_ENGINE_HYDROLOGY_RADIATION_HPP
#include <string>
#include "surface/UebSnow.hpp"
 
namespace openswmm {
struct SimulationContext;
struct SolarConfig;
struct CloudConfig;
}
 
namespace openswmm::climate {
 
enum class RadiationOrigin { Computed, Timeseries, MetFile, LegacyHeat };
struct RadiationState {
    double shortwave = 0, longwave = 0; // W/m², horizontal
    double cosine = 0, horizontal = 0, transmittance = 0, cloud = 0;
    double temperature = 0, humidity = .5, wind = 0; // °C, fraction, m/s
    double pressure = 101325;
    double declination = 0, hour_angle = 0, latitude = 0;
    double date = 0, seconds = 0;
    RadiationOrigin shortwave_source = RadiationOrigin::Computed;
    RadiationOrigin longwave_source = RadiationOrigin::Computed;
    bool shared_heat_forcing = false;
};

std::string resolveRadiation(SimulationContext& ctx, double date, double seconds,
                             RadiationState& output);
std::string initializeRadiation(SimulationContext& ctx);
std::string resolveUebForcing(SimulationContext& ctx, double date, double seconds, double slope,
                              double aspect, surface::ueb::Forcing& forcing, double& pressure);

inline constexpr double kSolarConstant = 1367.0;

inline constexpr double kStdPressureMb = 1013.25;

struct SolarPosition {
    double declination_deg = 0.0; 
    double eq_time_min = 0.0;     
    double hour_angle_deg = 0.0;  
    double zenith_deg = 90.0;     
    double cos_zenith = 0.0;      
    double elevation_deg = 0.0;   
    double eccentricity = 1.0;
};

SolarPosition solarPosition(int day_of_year, double hour_local, double lat_deg, double lon_deg,
                            double tz_hours) noexcept;

double airMass(double zenith_deg) noexcept;

double pressureFromElevation(double elevation_m) noexcept;

double birdClearSkyGHI(const SolarPosition& pos, double pressure_mb,
                       const SolarConfig& cfg) noexcept;

double cloudShortwaveFactor(double cloud_fraction, double k, double n) noexcept;

double cloudLongwaveFactor(double cloud_fraction, double k_lw) noexcept;

void updateSolarForcing(SimulationContext& ctx, double seconds = 1);
void updateSolarForcing(SimulationContext& ctx, double seconds, bool mesh_enabled);
 
} // namespace openswmm::climate
 
#endif // OPENSWMM_ENGINE_HYDROLOGY_RADIATION_HPP