ElevationChange.cc

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// Copyright (C) 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020, 2021, 2022, 2023, 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.
//
// 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.
//
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// along with PISM; if not, write to the Free Software
// Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 
#include "pism/coupler/surface/ElevationChange.hh"
#include "pism/coupler/util/options.hh"
#include "pism/coupler/util/lapse_rates.hh"
#include "pism/geometry/Geometry.hh"
#include "pism/util/array/Forcing.hh"
#include "pism/util/Logger.hh"
#include "pism/util/io/IO_Flags.hh"
 
namespace pism {
namespace surface {
 
ElevationChange::ElevationChange(std::shared_ptr<const Grid> g, std::shared_ptr<SurfaceModel> in)
  : SurfaceModel(g, in) {
 
  {
    m_smb_lapse_rate = m_config->get_number("surface.elevation_change.smb.lapse_rate",
                                            "(m / s) / m");
    // convert from [m s-1 / m] to [kg m-2 s-1 / m]
    m_smb_lapse_rate *= m_config->get_number("constants.ice.density");
 
    m_smb_exp_factor = m_config->get_number("surface.elevation_change.smb.exp_factor");
  }
 
  {
    auto method = m_config->get_string("surface.elevation_change.smb.method");
    m_smb_method = method == "scale" ? SCALE : SHIFT;
  }
 
  m_temp_lapse_rate = m_config->get_number("surface.elevation_change.temperature_lapse_rate",
                                           "K / m");
 
  {
    ForcingOptions opt(*m_grid->ctx(), "surface.elevation_change");
 
    unsigned int buffer_size = m_config->get_number("input.forcing.buffer_size");
 
    File file(m_grid->com, opt.filename, io::PISM_NETCDF3, io::PISM_READONLY);
 
    m_reference_surface = std::make_shared<array::Forcing>(m_grid, file, "usurf",
                                                           "", // no standard name
                                                           buffer_size, opt.periodic, LINEAR);
    m_reference_surface->metadata(0)
        .long_name("ice surface elevation")
        .units("m")
        .standard_name("surface_altitude");
  }
 
  m_mass_flux    = allocate_mass_flux(g);
  m_temperature  = allocate_temperature(g);
  m_accumulation = allocate_accumulation(g);
  m_melt         = allocate_melt(g);
  m_runoff       = allocate_runoff(g);
}
 
void ElevationChange::init_impl(const Geometry &geometry) {
  using units::convert;
 
  m_input_model->init(geometry);
 
  m_log->message(2,
                 "  [using temperature and mass balance lapse corrections]\n");
 
  m_log->message(2,
                 "   ice upper-surface temperature lapse rate: %3.3f K per km\n",
                 convert(m_sys, m_temp_lapse_rate, "K / m", "K / km"));
 
  if (m_smb_method == SHIFT) {
    double ice_density = m_config->get_number("constants.ice.density");
    m_log->message(2,
                   "   ice-equivalent surface mass balance lapse rate: %3.3f m year-1 per km\n",
                   convert(m_sys, m_smb_lapse_rate, "kg / (m2 second)", "kg / (m2 year)") / ice_density);
  } else {
    m_log->message(2,
                   "   surface mass balance scaling factor with temperature: %3.3f kelvin^-1\n",
                   m_smb_exp_factor);
  }
 
  ForcingOptions opt(*m_grid->ctx(), "surface.elevation_change");
  m_reference_surface->init(opt.filename, opt.periodic);
}
 
void ElevationChange::update_impl(const Geometry &geometry, double t, double dt) {
 
  m_input_model->update(geometry, t, dt);
 
  m_reference_surface->update(t, dt);
  m_reference_surface->interp(t + 0.5*dt);
 
  const array::Scalar &surface = geometry.ice_surface_elevation;
 
  m_temperature->copy_from(m_input_model->temperature());
  lapse_rate_correction(surface, *m_reference_surface,
                        m_temp_lapse_rate, *m_temperature);
 
  m_mass_flux->copy_from(m_input_model->mass_flux());
 
  switch (m_smb_method) {
  case SCALE:
    {
      array::AccessScope list{&surface, m_reference_surface.get(), m_mass_flux.get()};
 
      for (auto p : m_grid->points()) {
        const int i = p.i(), j = p.j();
 
        double dT = -m_temp_lapse_rate * (surface(i, j) - (*m_reference_surface)(i, j));
 
        (*m_mass_flux)(i, j) *= exp(m_smb_exp_factor * dT);
      }
    }
    break;
  default:
  case SHIFT:
    {
      lapse_rate_correction(surface, *m_reference_surface,
                            m_smb_lapse_rate, *m_mass_flux);
    }
    break;
  }
 
  // This modifier changes m_mass_flux, so we need to compute accumulation, melt, and
  // runoff.
  dummy_accumulation(*m_mass_flux, *m_accumulation);
  dummy_melt(*m_mass_flux, *m_melt);
  dummy_runoff(*m_mass_flux, *m_runoff);
 
}
 
const array::Scalar &ElevationChange::mass_flux_impl() const {
  return *m_mass_flux;
}
 
const array::Scalar &ElevationChange::temperature_impl() const {
  return *m_temperature;
}
 
const array::Scalar &ElevationChange::accumulation_impl() const {
  return *m_accumulation;
}
 
const array::Scalar &ElevationChange::melt_impl() const {
  return *m_melt;
}
 
const array::Scalar &ElevationChange::runoff_impl() const {
  return *m_runoff;
}
 
 
} // end of namespace surface
} // end of namespace pism