IMAPP MODIS Direct Broadcast Near-Infrared Total 
   Column Water Vapor (WVNIR) Product Description
   -------------------------------------------

     The IMAPP WVNIR software produces retrievals at 1 km
     resolution over all pixels.  It should be noted
     that this is not the algorithm used in the official DAAC
     MOD05 water vapor product.

     The NIR water vapor algorithm can only produce reasonable
     results above bright surfaces. Therefore, over ocean the
     retrieved water vapor content will most of the time be wrong.
     However, water pixels have not been generally flagged out in
     order to allow the use of the product above sunglint regions.
     A land/sea mask is contained in the MOD03 geolocation (.geo.hdf)
     files.

     Also, please make sure to mask out cloudy pixels (using e.g.
     the MOD35 cloud mask) prior to any interpretation of the
     retrieved product.
     Multiple scattering at cloud droplets has not been accounted
     for during algorithm development, and results for cloudy
     pixels are unpredictable. The combined effects of reflection
     (i.e. shading of lower atmospheric levels)and multiple scattering
     can lead to increased or decreased results compared to the true
     integrated columnar water vapor.

     For a description of the algorithm, please see:

     P. ALBERT, R. BENNARTZ, R. PREUSKER, R. LEINWEBER, AND J. FISCHER,
      2005:  Remote Sensing of Atmospheric Water Vapor Using the Moderate
      Resolution Imaging Spectroradiometer.  Journal of Atmospheric and
      Oceanic Technology, Vol. 22, 309-314.

     The user can choose the output format type, either HDF or
     binary.  If you are using the modis_level2.csh script,
     you set the OUTPUT_TYPE environmental variable in the
     imapp_modisl2/env scripts to:

               1 = binary only
               2 = hdf only
               3 = binary and hdf


--------------------------------------------------------------------------
BINARY OUTPUT FILE
  The near-infrared water vapor output product consists of a separate
  .img file in flat binary format, and accompanying header file.

  The wvnir.img file is a 1 float band interleaved product at 1 km 
  pixel resolution. Please see a list of these bands below.
  The test output file that you create from the input aqua test data 
  sets contains the nominal MODIS swath size 1354 elements and 
  2890 lines.  In FORTRAN, it would be read as wvnir(1354,2890).
  This would be reversed in C - wvnir(2890,1354).  

--------------------------------------------------------------------------
   MODIS Direct Broadcast Near-Infared Water Vapor
          Output Product Description
   -------------------------------------------
   Four byte float data
   1 parameter
   1 km-pixel resolution

band names = {
band  1: WVNIR_LAND
}
band units = {
band  1: kg/m^2
}

--------------------------------------------------------------------------
HDF OUTPUT FILE
  The HDF output file (*wvnir.hdf) contains 3 arrays.  Latitude, Longitude and 
    the Near-Infrared Retrieved Water Vapor field in units of kilograms
    per square meter.

  (Example ncdump -h of an IMAPP wvnir HDF file)

dimensions:
        Cell_Along_Swath_5km = 578 ;
        Cell_Across_Swath_5km = 270 ;
        Cell_Along_Swath_1km = 2890 ;
        Cell_Across_Swath_1km = 1354 ;

variables:
        float Latitude(Cell_Along_Swath_5km, Cell_Across_Swath_5km) ;
                Latitude:_FillValue = -999.98999f ;
        float Longitude(Cell_Along_Swath_5km, Cell_Across_Swath_5km) ;
                Longitude:_FillValue = -999.98999f ;
        float Water_Vapor_Direct_Broadcast_Near_Infrared(Cell_Along_Swath_1km,
Cell_Across_Swath_1km) ;
                Water_Vapor_Direct_Broadcast_Near_Infrared:units = "kg/m2" ;
                Water_Vapor_Direct_Broadcast_Near_Infrared:scale_factor = 1. ;
                Water_Vapor_Direct_Broadcast_Near_Infrared:add_offset = 0. ;
                Water_Vapor_Direct_Broadcast_Near_Infrared:_FillValue = -1.f ;