             Information about SSMASK - 8 September 2005

The SSMASK program is an interim procedure for generating the OCEANfile,
which is a required input file for CMAQv4.5 when the AERO4 aerosol module
is selected.  The OCEANfile is a time-invariant IOAPI file that has 1
vertical layer and the same columns and rows as the CMAQ model domain.  
The OCEANfile must contain a 2-D field named "OPEN" which represents the
fraction of each grid cell that is covered by open ocean.  The AERO4
module in CMAQ uses the values in this field to compute emissions of sea
salt from each grid cell.

A required input for the SSMASK program is the BEIS3 input file named
LAND_TOTALS.  Two fields in the LAND_TOTALS file are used by the SSMASK
program:
 1. "LAND" - the percent of each grid cell covered by land.
 2. "FIPS_CODE" - the dominant FIPS code within each grid cell.  
    a FIPS code of 377771 is used to designate the Pacific Ocean
               and 377772 is used to designate the Atlantic Ocean.

This program generates a gridded output file called OCEANFILE, containing
3 fields:
 1. MASK = 0 for land or freshwater
           1 for coastline
           2 for sea water
 2. SURF = fraction of grid cell in the surf zone
 3. OPEN = fraction of grid cell that is open ocean

Although the SSMASK program contains logic to estimate surf-zone areas,
those areas not used because surf-zone emissions are neglected in
CMAQv4.5.

Directory Contents:
 README                     this file
 ssmask.F                   source code
 Makefile                   F90 compilation instructions
 ssmask.csh                 run script
 LAND_TOTALS_US36_148X112   sample input file
 OCEANFILE_US36_148X112     sample output file

The Makefile is provided only as an example.  Users must modify this file
so that it is applicable to their local F90 compiler and contains the
correct path names.

Two environment variables in the run script are required by SSMASK:
 1. LAND_TOTALS  the input file name
 2. OUTFILE      the output file name


Acknowledgements:  The SSMASK program was developed at the Environmental
Protection Agency (EPA) and in partnership with the National Oceanic
Atmospheric Administation (NOAA), with contributions from the following
individuals:  G. Pouliot (NOAA), KM Zhang (UC Davis), P. Bhave (NOAA), C.  
Chang (CSC), and M. Mebust (CSC & USEPA).

