emcsfc_ice_blend  1.4.0
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Functions/Subroutines
emcsfc_ice_blend.f90 File Reference

Create blended ice product for gfs/gdas cycles. More...

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Functions/Subroutines

program emcsfc_ice_blend
 Create a global 5-minute blended ice concentration dataset for use by GDAS/GFS. More...
 

Detailed Description

Create blended ice product for gfs/gdas cycles.

Author
George Gayno NCEP/EMC
Date
2014-03-20

Definition in file emcsfc_ice_blend.f90.

Function/Subroutine Documentation

program emcsfc_ice_blend ( )

Create a global 5-minute blended ice concentration dataset for use by GDAS/GFS.

This blend is created from National Ice Center Interactive Multisensor Snow and Ice Mapping System (IMS) data, and the NCEP/MMAB global 5-minute ice concentration data.

Program History Log

  • 2014-03-20 Initial version.
  • 2014-10-20 Use grib2 for all i/o. Mask out 'land' points in the blended analysis using a bitmap instead of the '1.57' flag.

input files:

  • fort.11 - NH IMS ice data, interpolated to the 5-minute grid (grib 2)
  • fort.15 - global 5-minute MMAB ice concentration file (grib 2)
  • fort.17 - global 5-minute MMAB land mask file (grib 2).

output files:

  • fort.51 - global 5-minute blended ice concentration file (grib 2)

condition codes:

  • 0 - normal run
  • 1 - bad open of 5-minute MMAB land mask file
  • 2 - bad read of 5-minute MMAB land mask grib record
  • 5 - bad open of IMS ice file
  • 7 - bad read of IMS ice grib record
  • 8 - bad open of 5-minute MMAB ice concentration file
  • 9 - bad read of 5-minute MMAB ice concentration grib header
  • 10 - bad read of 5-minute MMAB ice concentration grib record
  • 16 - bad open of 5-minute blended ice concentration file
  • 17 - bad write of 5-minute blended ice concentration file

This program creates a sea ice concentration file suitable for use by the GFS global cycle program. The 5-minute ice concentration file from MMAB can't be used 'as is' because the MMAB data can't give a reliable analysis for small lakes now resolved by the GFS land mask.

This program creates an ice concentration file on the same 5-minute grid as the MMAB data using IMS data from the National Ice Center to fill in small lakes. The IMS data is NH only and is a yes/no flag (not a concentration). The IMS data is on a 4km polar stereographic grid and must be interpolated to the MMAB 5-minute grid (NCEP grid 173) before ingest to this program. This interpolation may be done using copygb2 as follows:

 grid173="0 0 0 0 0 0 0 0 4320 2160 0 0 89958000 42000 48 -89958000 359958000 83000 83000 0"
 copygb2 -x -i3 -g "$grid173" ims.icec.grib2 ims.icec.5min.grib2

When using the "budget" interpolation option (-i3), the IMS yes/no flag will be converted to a pseudo ice concentration.

The IMS data contains a land/water mask. Ice concentration is only specified at 'water' points.

The 5-minute data mask contains 'land', 'coast' and 'water' points. Ice concentration is specified at 'coast' and 'water', but 'coast' points have error and are not used here.

The blending process is as follows in the NH:

  1. If IMS indicates 'land', then the blended value is set to 'land' and is bitmapped out.
  2. If the IMS is 'water', and the MMAB data point is 'coast' or 'land', the IMS ice concentration is used as the blended value.
  3. If IMS and MMAB indicate a point as water, then
    • The blended value is set to zero if the IMS concentration is less than 50%.
    • If the IMS concentration is >=50%, then the neighboring 5-minute data is checked for ice.
      • If the 5-minute point is ice free, but at least one of its neighbors has ice, the blended value is set to the IMS ice concentration. Examination of the 5-minute showed isolated open water points within large areas of ice. This logic attempts to remove these likely wrong points.
      • If (i) is false, then the blended value is set to the 5-minute value or 15%, whichever is greater. 15% is the lower threshold in the MMAB 5-minute product.

In the SH, the blended value is simply the 5-minute ice concentration at 'water' points. 'Coast' and 'land' points are bitmapped out.

Returns
0 for success, error code otherwise.
Author
George Gayno NCEP/EMC

Definition at line 93 of file emcsfc_ice_blend.f90.