DEBMSimplePointwise.hh

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// Copyright (C) 2009--2023 PISM Authors
//
// This file is part of PISM.
//
// PISM is free software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the Free Software
// Foundation; either version 3 of the License, or (at your option) any later
// version.
//
// PISM is distributed in the hope that it will be useful, but WITHOUT ANY
// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
// FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
// details.
//
// You should have received a copy of the GNU General Public License
// along with PISM; if not, write to the Free Software
// Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 
#ifndef PISM_DEBM_SIMPLE_POINTWISE_H
#define PISM_DEBM_SIMPLE_POINTWISE_H
 
#include <memory>
#include <array>
 
#include "pism/util/Mask.hh"
#include "pism/util/ScalarForcing.hh"
 
namespace pism {
 
class Context;
class Time;
 
namespace surface {
 
class DEBMSimpleMelt {
public:
  DEBMSimpleMelt();
 
  double temperature_melt;
  double insolation_melt;
  double offset_melt;
  double total_melt;
};
 
//! A dEBM-simple implementation
/*!
 * This class implements dEBM-simple, the simple diurnal energy balance model described in
 *
 * M. Zeitz, R. Reese, J. Beckmann, U. Krebs-Kanzow, and R. Winkelmann, “Impact of the
 * melt–albedo feedback on the future evolution of the Greenland Ice Sheet with
 * PISM-dEBM-simple,” The Cryosphere, vol. 15, Art. no. 12, Dec. 2021.
*/
class DEBMSimplePointwise {
public:
  DEBMSimplePointwise(const Context &ctx);
 
  double albedo(double melt_rate, MaskValue cell_type) const;
 
  struct OrbitalParameters {
    double declination;
    double distance_factor;
  };
 
  OrbitalParameters orbital_parameters(double time) const;
 
  DEBMSimpleMelt melt(double declination,
                      double distance_factor,
                      double dt,
                      double T_std_deviation,
                      double T,
                      double surface_elevation,
                      double lat,
                      double albedo) const;
 
  class Changes {
  public:
    Changes();
 
    double snow_depth;
    double melt;
    double runoff;
    double smb;
  };
 
  Changes step(double ice_thickness,
               double max_melt,
               double snow_depth,
               double accumulation) const;
 
  // public because it is a diagnostic field
  double atmosphere_transmissivity(double elevation) const;
 
  double insolation(double declination,
                    double distance_factor,
                    double latitude_degrees) const;
 
private:
  double eccentricity(double time) const;
  double obliquity(double time) const;
  double perihelion_longitude(double time) const;
 
  //! refreeze melted ice
  bool m_refreeze_ice_melt;
  //! refreeze fraction
  double m_refreeze_fraction;
  //! threshold temperature for the computation of temperature-driven melt
  double m_positive_threshold_temperature;
 
  double m_ice_density;
  double m_water_density;
 
  double m_albedo_max;
  double m_albedo_min;
  double m_albedo_ocean;
 
  //! slope used in the linear parameterization of the albedo as a function of melt
  double m_albedo_slope;
 
  //! slope used in the linear parameterization of transmissivity
  double m_transmissivity_slope;
  double m_transmissivity_intercept;
 
  // tuning parameters of the melt equation
  double m_melt_c1;
  double m_melt_c2;
 
  // threshold air temperature (no melt at temperatures below this)
  double m_melt_threshold_temp;
 
  //! latent heat of fusion
  double m_L;
  //! the solar constant
  double m_solar_constant;
 
  //! minimum solar elevation angle above which melt is possible
  double m_phi;
 
  std::unique_ptr<ScalarForcing> m_eccentricity;
  std::unique_ptr<ScalarForcing> m_obliquity;
  std::unique_ptr<ScalarForcing> m_perihelion_longitude;
 
  bool m_paleo;
  bool m_use_paleo_file;
 
  double m_constant_eccentricity;
  double m_constant_perihelion_longitude;
  double m_constant_obliquity;
 
  std::shared_ptr<const Time> m_time;
};
 
} // end of namespace surface
} // end of namespace pism
 
#endif  /* PISM_DEBM_SIMPLE_POINTWISE_H */