Runoff_SMB.hh

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#ifndef _PO_RUNOFF_SMB_H_
#define _PO_RUNOFF_SMB_H_
 
#include "pism/coupler/OceanModel.hh"
 
namespace pism {
 
class ScalarForcing;
 
namespace ocean {
 
/** Modify the shelf base mass flux using a function of air temperature changes.
 *
 * This modifier multiplies the input shelf base mass flux by a factor
 * @f$ F @f$, which depends on the change in the global average
 * near-surface air temperature =delta_T= read from an input file.
 *
 * The parameterization described below is inspired by [@ref Xu2013]
 * with the relationship between air temperatures and subglacial
 * runoff flux parameterized using a linear function (a fit to
 * results of GCM simulations).
 *
 * @f[ F(\Delta T) = 1 + B \times (a \Delta T)^\alpha \times (\Delta T)^\beta. @f]
 *
 * Here @f$ a @f$, @f$ B @f$, @f$ \alpha @f$, and @f$ \beta @f$ are constants.
 *
 * The paper [@ref Xu2013] approximates the sub-shelf melt rate as a
 * function of *ocean* temperature above the freezing point and the
 * subglacial runoff.
 *
 * We assume that the lag between the air and ocean temperatures is
 * negligible and a change in air temperature is directly translated
 * into a change in ocean temperature.
 */
class Runoff_SMB : public OceanModel
{
public:
  Runoff_SMB(std::shared_ptr<const Grid> g, std::shared_ptr<OceanModel> in);
  virtual ~Runoff_SMB();
 
private:
  void init_impl(const Geometry &geometry);
 
  void update_impl(const Geometry &geometry, double t, double dt);
 
  void mass_flux(double delta_T, array::Scalar &result) const;
 
  // @brief constant in the parameterization of the subglacial
  // runoff flux as a function of air temperature
  double m_temp_to_runoff_a;
 
  // Constants in the parameterization of the sub-shelf melt rate.
  double m_runoff_to_ocean_melt_b;
  double m_runoff_to_ocean_melt_power_alpha;
  double m_runoff_to_ocean_melt_power_beta;
 
  std::shared_ptr<array::Scalar> m_shelf_base_mass_flux;
  std::unique_ptr<ScalarForcing> m_forcing;
};
 
} // end of namespace ocean
} // end of namespace pism
 
#endif /* _PO_RUNOFF_SMB_H_ */