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Running gnumake in this directory will create an executable named
"definesurf".  Its function is to compute required CAM initial dataset
variables SGH, PHIS, LANDFRAC, and LANDM from a high-resolution topography
dataset, then add or replace the values on an existing initial dataset. SGH
is the standard deviation of PHIS used in the gravity wave drag scheme.
PHIS is the geopotential height.  LANDFRAC is land fraction. 
LANDM is a field derived from LANDFRAC which is required by the prognostic cloud 
water parameterization.

The high resolution topography dataset used by definesurf is named topo.nc
and is included as part of the CAM distribution in the datasets tar
file. topo.nc was derived from the U.S. Navy Global Elevation 10-MIN dataset
DS754.0 Please refer to the following NCAR website for more information:

http://www.scd.ucar.edu/dss/catalogs/geo.html

The algorithms within this code should be considered experimental.  For
example, a 1-2-1 smoothing operator (sm121, called from subroutine sghphis)
is applied twice in succession to the topography variance field regardless of
horizontal resolution.  The SGH field (sqare root of the variance) is then
set to zero (in subroutine fmain) over all points which are not land.  Also,
a spectral filter will be applied to the PHIS field within the CAM at model
startup if PHIS was defined from the high resolution topography dataset.  The
model determines this by checking for the presence of netcdf attribute
"from_hires" on initial dataset variable PHIS.
