get_PDDs get_snow_accumulation get_timeseries_length pdd_threshold_temp PDDMassBalance precip_as_snow refreeze_ice_melt step Tmax Tmin ~PDDMassBalance

step() PDDMassBalance::Changes pism::surface::PDDMassBalance::step ( const DegreeDayFactors &  ddf, double  PDDs, double  thickness, double  old_firn_depth, double  old_snow_depth, double  accumulation  ) virtual Compute the surface mass balance at a location from the number of positive degree days and the accumulation amount in a time interval. This is a PDD scheme. The input parameter ddf.snow is a rate of melting per positive degree day for snow. accumulation has units "meter / second". a fraction of the melted snow and ice refreezes, conceptualized as superimposed ice, and this is controlled by parameter ddf.refreeze_fraction the excess number of PDDs is used to melt both the ice that came from refreeze and then any ice which is already present. Ice melts at a constant rate per positive degree day, controlled by parameter ddf.ice. The scheme here came from EISMINT-Greenland [RitzEISMINT], but is influenced by R. Hock (personal communication). Implements pism::surface::LocalMassBalance. Definition at line 194 of file localMassBalance.cc. References pism::surface::LocalMassBalance::Changes::firn_depth, pism::surface::LocalMassBalance::DegreeDayFactors::ice, pism::array::max(), pism::surface::LocalMassBalance::Changes::melt, pism::array::min(), pism::surface::LocalMassBalance::DegreeDayFactors::refreeze_fraction, refreeze_ice_melt, pism::surface::LocalMassBalance::Changes::runoff, pism::surface::LocalMassBalance::Changes::smb, pism::surface::LocalMassBalance::DegreeDayFactors::snow, and pism::surface::LocalMassBalance::Changes::snow_depth.