README -- Contents of /pub/geos-chem/data/GEOS_2x2.5/TOMS_200701/
03 Mar 2010
Bob Yantosca and Claire Carouge
geos-chem-support@g.harvard.edu


Data Download:
===============================================================================

The files in this directory may be accessed by FTP download:

   ftp ftp.as.harvard.edu
   cd pub/geos-chem/data/GEOS_2x2.5/TOMS_200701/

You may also use "wget" download:

   wget -r -nH "ftp://ftp.as.harvard.edu/pub/geos-chem/data/GEOS_2x2.5/TOMS_200701/"


Files:
===============================================================================

TOMS_O3col_1985.geos.2x25  -- Binary punch (bpch) files containing 12 months
TOMS_O3col_1986.geos.2x25     of TOMS/SBUV data on the GEOS-Chem 2x25 grid.
TOMS_O3col_1987.geos.2x25 
TOMS_O3col_1988.geos.2x25     The data comes from the raw data file
TOMS_O3col_1989.geos.2x25     "toms_sbuv.v8.mod_v3.78-06.5x10.rev3.txt",
TOMS_O3col_1990.geos.2x25     which is available from the website
TOMS_O3col_1991.geos.2x25     hyperion.gsfc.nasa.gov/Data_services/merged/data/
TOMS_O3col_1992.geos.2x25    
TOMS_O3col_1993.geos.2x25     The data are then split into individual monthly
TOMS_O3col_1994.geos.2x25     files with ~bmy/archive/data/IDL/cut.pro.
TOMS_O3col_1995.geos.2x25 
TOMS_O3col_1996.geos.2x25     Then the data are regridded and saved to binary
TOMS_O3col_1997.geos.2x25     punch format with the IDL program
TOMS_O3col_1998.geos.2x25     ~bmy/archive/data/IDL/reader_10x5.pro.
TOMS_O3col_1999.geos.2x25
TOMS_O3col_2000.geos.2x25     Currently we have data from 1979-2005.  More
TOMS_O3col_2001.geos.2x25     data may be added as it becomes available.
TOMS_O3col_2002.geos.2x25
TOMS_O3col_2003.geos.2x25     These data files are used by "toms_mod.f"
TOMS_O3col_2004.geos.2x25     of the GEOS-Chem source code.
TOMS_O3col_2005.geos.2x25
TOMS_O3col_2006.geos.2x25
TOMS_O3col_2007.geos.2x25


Data source and version:
===============================================================================

1985 - 2005 are taken from:

  http://code916.gsfc.nasa.gov/Data_services/merged/index.html

  TOMS/SBUV MERGED TOTAL OZONE DATA, Version 8, Revision 3.
  Resolution:  5 x 10 deg.

  Contact person for the merged data product:
  Stacey Hollandsworth Frith (smh@hyperion.gsfc.nasa.gov)

2006 and 2007 are taken from:

   http://code916.gsfc.nasa.gov/Data_services/merged/index.html

   Version 8 Merged Ozone Data Sets
   Revision 04 
   DATA THROUGH: SEP 2008
   LAST MODIFIED: 20 OCT 2008


Methodology:
===============================================================================

FAST-J comes with its own default O3 column climatology (from McPeters 1992
& Nagatani 1991), which is stored in the input file "jv_atms.dat".  These 
"FAST-J default" O3 columns are used in the computation of the actinic flux 
and other optical quantities for the FAST-J photolysis.  

The TOMS/SBUV O3 columns and 1/2-monthly O3 trends (contained in the 
TOMS_200701 directory) are read to GEOS-Chem by routine READ_TOMS in 
"toms_mod.f".  Missing values (i.e. locations where there are no data) in the 
TOMS/SBUV O3 columns are defined by the flag -999.  

After being read from disk in routine READ_TOMS, the TOMS/SBUV O3 data are then
passed to the FAST-J routine "set_prof.f".  In "set_prof.f", a test is done
to make sure that the TOMS/SBUV O3 columns and 1/2-monthly trends do not have
any missing values for (lat,lon) location for the given month.  If so, then
the TOMS/SBUV O3 column data is interpolated to the current day and is used to
weight the "FAST-J default" O3 column.  This essentially "forces" the
"FAST-J default" O3 column values  to better match the observations, as
defined by TOMS/SBUV.

If there are no TOMS/SBUV O3 columns (and 1/2-monthly trends) at a (lat,lon)
location for given month, then FAST-J will revert to its own "default" 
climatology for that location and month.  Therefore, the TOMS O3 can be 
thought of as an  "overlay" data -- it is only used if it exists.

Note that there are no TOMS O3 columns at the higher latitudes.  At these
latitudes, the code will revert to using the "FAST-J default" O3 columns.

As of February 2007, we have TOMS/SBUV data for 1979 thru 2005.  2006 
TOMS/SBUV data is incomplete as of this writing.  For years 2006 and onward, 
we use 2005 TOMS O3 columns.

This methodology was originally adopted by Mat Evans.  Symeon Koumoutsaris
was responsible for creating the downloading and processing the TOMS O3 data 
files from 1979 thru 2005 in the TOMS_200701 directory.