source: issm/trunk/src/m/mech/robintemperature.py@ 17806

import numpy as npy
from scipy.special import erf

def robintemperature(heatflux,accumrate,thickness,surftemp,z):
        '''
        Compute vertical temperature profile of an ice sheet (Robin, 1955)

        This routine computes the vertical temperature profile of an ice sheet
        according to the solution of Robin (1955), neglecting friction and
        horizontal advection.  The solution is thus most appropriate at an ice
        divide.

        The coordinate system for the solution runs from z=0 at the base 
        to z=H at the surface of the ice.

        Parameters (SI units):
                -heatflux       Geothermal heat flux (W m^-2)
                -accumrate      Surface accumulation rate (m s^-1 ice equivalent)
                -thickness      Ice thickness (m)
                -surftemp       Surface temperature (K)
                -z                              Vertical position at which to calculate temperature
                                                (z can be a scalar or a vector)

        Returns a vector the same length as z containing the temperature in K

        Usage:
                tprofile=robintemperature(heatflux,accumrate,thickness,surftemp,z)
        '''

        # some constants (from Holland and Jenkins, 1999)
        alphaT=1.14e-6 # thermal diffusivity (m^2 s^-1)
        c=2009. # specific heat capacity (J kg^-1 K^-1)
        rho=917.  # ice density (kg m^-3)
        
        #create vertical coordinate variable
        zstar=npy.sqrt(2.*alphaT*thickness/accumrate)
        
        tprofile=surftemp+npy.sqrt(2.*thickness*npy.pi/accumrate/alphaT)*(-heatflux)/2./rho/c*(erf(z/zstar)-erf(thickness/zstar))
        
        # difference between surface and base temperature for check (Cuffey2010 p412):
        # print tprofile-surftemp