PROGRAM snow_to_obs

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$Id: snow_to_obs.html 6341 2013-07-31 14:24:51Z nancy $


MODIS Snowcover Fraction Observation Converter


There are several satellite sources for snow observations. Generally the data is distributed in HDF-EOS format. The converter code in this directory DOES NOT READ HDF FILES as input. It expects the files to have been preprocessed to contain text, one line per observation, with northern hemisphere data only.


not sure.


The snow_to_obs.f90 file is the source for the main converter program.

To compile and test, go into the work subdirectory and run the quickbuild.csh script to build the converter and a couple of general purpose utilities. advance_time helps with calendar and time computations, and the obs_sequence_tool manipulates DART observation files once they have been created.

This converter creates observations of the "MODIS_SNOWCOVER_FRAC" type.

There is another program in this directory called snow_to_obs_netcdf.f90 which is a prototype for reading netcdf files that contain some metadata and presumably have been converted from the original HDF. THIS HAS NOT BEEN TESTED but if you have such data, please contact for more assistance. If you write something that reads the HDF-EOS MODIS files directly, please, please contact us! Thanks.


This namelist is read from the file input.nml. Namelists start with an ampersand '&' and terminate with a slash '/'. Character strings that contain a '/' must be enclosed in quotes to prevent them from prematurely terminating the namelist.

  longrid         = 360,
  latgrid         = 90, 
  year            = 2000, 
  doy             = 1,
  snow_input_file = 'snowdata.input', 
  missing_value   = -20.0, 
  debug           = .false.
Item Type Description
longrid integer The number of divisions in the longitude dimension.
latgrid integer The number of divisions in the latitude dimension. This converter assumes the data is for the northern hemisphere only. A namelist item could be added to select northern verses southern hemisphere if needed.
year integer The year number of the data.
doy integer The day number in the year. Valid range 1 to 365 in a non-leap year, 1 to 366 in a leap year.
snow_input_file character(len=128) The name of the input file.
missing_value real(r8) The value used to mark missing data.
debug logical If set to .true. the converter will print out more information as it does the conversion.


This program is hardcoded to read only northern hemisphere data. It should handle global values.


This program should use the HDF-EOS libraries to read the native MODIS granule files. Right now the ascii intermediate files contain no metadata, so if the namelist values don't match the actual division of the globe, bad things will happen.

Terms of Use

DART software - Copyright 2004 - 2013 UCAR.
This open source software is provided by UCAR, "as is",
without charge, subject to all terms of use at

Contact: nancy collins
Revision: $Revision: 6341 $
Source: $URL: $
Change Date: $Date: 2013-07-31 08:24:51 -0600 (Wed, 31 Jul 2013) $
Change history:  try "svn log" or "svn diff"