TemperatureIndex.hh

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// Copyright (C) 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2021, 2022, 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.
//
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// 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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#ifndef _PSTEMPERATUREINDEX_H_
#define _PSTEMPERATUREINDEX_H_
 
#include <memory>
 
#include "pism/coupler/SurfaceModel.hh"
#include "pism/coupler/surface/localMassBalance.hh"
 
namespace pism {
namespace surface {
 
//! @brief A class implementing a temperature-index (positive degree-day) scheme
//! to compute melt and runoff, and thus surface mass balance, from
//! precipitation and air temperature.
/*! 
  Temperature-index schemes are far from perfect as a way of modeling surface mass
  balance on ice sheets which experience surface melt, but they are known to have
  reasonable data requirements and to do a good job when tuned appropriately
  [@ref Hock05].
*/
class TemperatureIndex : public SurfaceModel {
public:
  TemperatureIndex(std::shared_ptr<const Grid> g, std::shared_ptr<atmosphere::AtmosphereModel> input);
  virtual ~TemperatureIndex() = default;
 
  // diagnostics (for the last time step)
  const array::Scalar& firn_depth() const;
  const array::Scalar& snow_depth() const;
  // these represent totals (not rates) over the time step
  const array::Scalar& air_temp_sd() const;
 
protected:
  virtual void init_impl(const Geometry &geometry);
  virtual void update_impl(const Geometry &geometry, double t, double dt);
  virtual MaxTimestep max_timestep_impl(double t) const;
 
  virtual void define_model_state_impl(const File &output) const;
  virtual void write_model_state_impl(const File &output) const;
 
  virtual DiagnosticList diagnostics_impl() const;
 
  virtual const array::Scalar& mass_flux_impl() const;
  virtual const array::Scalar& temperature_impl() const;
  
  virtual const array::Scalar& accumulation_impl() const;
  virtual const array::Scalar& melt_impl() const;
  virtual const array::Scalar& runoff_impl() const;
 
  double compute_next_balance_year_start(double time);
protected:
  //! mass balance scheme to use
 
  std::unique_ptr<LocalMassBalance> m_mbscheme;
 
  //! if not NULL then user wanted fausto PDD stuff
  std::unique_ptr<FaustoGrevePDDObject> m_faustogreve;
 
  //! holds degree-day factors in location-independent case
  LocalMassBalance::DegreeDayFactors m_base_ddf;
 
  //! K; daily amount of randomness
  double m_base_pddStdDev;
 
  double m_next_balance_year_start;
 
  //! cached surface mass balance rate
  array::Scalar m_mass_flux;
 
  std::shared_ptr<array::Scalar> m_temperature;
 
  //! firn depth
  array::Scalar m_firn_depth;
 
  //! snow depth (reset once a year)
  array::Scalar m_snow_depth;
 
  //! standard deviation of the daily variability of the air temperature
  std::shared_ptr<array::Forcing> m_air_temp_sd;
 
  //! total accumulation during the last time step
  std::shared_ptr<array::Scalar> m_accumulation;
 
  //! total melt during the last time step
  std::shared_ptr<array::Scalar> m_melt;
 
  //! total runoff during the last time step
  std::shared_ptr<array::Scalar> m_runoff;
 
  bool m_sd_use_param, m_sd_file_set;
  double m_sd_param_a, m_sd_param_b;
};
 
} // end of namespace surface
} // end of namespace pism
 
#endif /* _PSTEMPERATUREINDEX_H_ */