Runoff_SMB.cc

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// Copyright (C) 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2021, 2022, 2023, 2024, 2025 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.
//
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// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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// details.
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// along with PISM; if not, write to the Free Software
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#include <cmath>
 
#include "pism/coupler/ocean/Runoff_SMB.hh"
#include "pism/util/ScalarForcing.hh"
#include "pism/util/Logger.hh"
 
namespace pism {
namespace ocean {
 
Runoff_SMB::Runoff_SMB(std::shared_ptr<const Grid> g, std::shared_ptr<OceanModel> in)
  : OceanModel(g, in) {
 
  m_forcing.reset(new ScalarForcing(*g->ctx(),
                                    "ocean.runoff_to_ocean_melt",
                                    "delta_T",
                                    "kelvin",
                                    "kelvin",
                                    "air temperature offsets"));
 
  m_temp_to_runoff_a       = m_config->get_number("surface.temp_to_runoff_a");
  m_runoff_to_ocean_melt_b = m_config->get_number("ocean.runoff_to_ocean_melt.b");
 
  m_runoff_to_ocean_melt_power_alpha = m_config->get_number("ocean.runoff_to_ocean_melt.power_alpha");
  m_runoff_to_ocean_melt_power_beta  = m_config->get_number("ocean.runoff_to_ocean_melt.power_beta");
 
  m_shelf_base_mass_flux = allocate_shelf_base_mass_flux(g);
}
 
Runoff_SMB::~Runoff_SMB() {
  // empty
}
 
void Runoff_SMB::init_impl(const Geometry &geometry) {
 
  m_input_model->init(geometry);
 
  m_log->message(2,
                 "* Initializing ice shelf base mass flux forcing using scalar multiplier...\n"
                 "*   derived from delta_T air temperature modifier\n");
}
 
void Runoff_SMB::update_impl(const Inputs &inputs, double t, double dt) {
  m_input_model->update(inputs, t, dt);
 
  mass_flux(m_forcing->value(t + 0.5 * dt), *m_shelf_base_mass_flux);
}
 
void Runoff_SMB::mass_flux(double delta_T, array::Scalar &result) const {
 
  // short-cuts, just to make the formula below easier to read
  double
    a            = m_temp_to_runoff_a,
    B            = m_runoff_to_ocean_melt_b,
    alpha        = m_runoff_to_ocean_melt_power_alpha,
    beta         = m_runoff_to_ocean_melt_power_beta,
    scale_factor = 1.0;
 
  /*
    This parameterization only works if delta_T > 0 because
    negative numbers cannot be raised to a fractional power
    so we do not scale the forcing if delta_T < 0
  */
  if (delta_T > 0.0) {
    scale_factor = 1 + B * pow(a * delta_T, alpha) * pow(delta_T, beta);
  }
  result.scale(scale_factor);
}
 
} // end of namespace ocean
} // end of namespace pism