Design Document for GETWATER

GETWATER

AUTHOR: Tim Baltzer

Functional Summary:

Get the most accurate global water vapor image available for a given timeframe.

Comments:

Background:

Initially GETWATER was written to just access the TOVS dataset. However, since NASA Goddard was grossly negligent in making TOVS available in a near-real-time timeframe, another water vapor data source was identified (NCEP). GETWATER now needs to be modified so that it will:
  • get an NCEP image if available for the day of interest
  • otherwise get a TOVS image for the day of interest
  • otherwise get a TOVS climatology image for the day of interest
  • Overall design:

    Algorithm:

  • Attempt to get an NCEP image for the designated date and time (GETNCEP).
  • If failure, attempt to get a TOVS image for the designated date and direction (ascending/descending) (GETTOVS).
  • If failure, attempt to get a TOVS climatology image for the designated date and direction (ascending/descending) (GETTOVS).

  • Module Design(s):

    GETNCEP:

    Get an NCEP global water vapor image if available

    PARAMETERS:

    HOUR
    Acquisition hour used to determine which NCEP model to retrieve

    MONTH
    Month of output image

    DAY
    Day of output image

    YEAR
    Four digit year of output image

    SILOBASEDIR
    Base SILO directory

    WATERBASEDIR
    Base water vapor directory (climatology)

    OUT
    Filled water vapor output image

    QC
    Quality Control output image

    ALGORITHM:

  • Determine which of the NCEP models we want to use for this day ( 00 06 12 18 Z hour)
  • If the image exists on the silo, return it as well as:
  • RETURN VALUE(S):

    SUCCESS Successfully returned NCEP image
    FAILURE Didn't return NCEP image
    

    GETTOVS:

    Get a TOVS global water vapor image

    PARAMETERS:

    MONTH
    Month of output image

    DAY
    Day of output image

    YEAR
    Four digit year of output image

    SATID
    Satellite identifier number

    SILOBASEDIR
    Base SILO directory

    WATERBASEDIR
    Base water vapor directory (climatology)

    OUT
    Filled water vapor output image

    QC
    Quality Control output image

    TIMEFLAG
    Time flag ("am","pm")

    ALGORITHM:

  • Return TOVS image data using the following priority until the entire image for the day of interest has been filled:
  • - An individual acquisition for the day of interest - Daily climatology - Monthly climatology - Fill using NN technique
  • Along with the TOVS image data, return the following as well: 0: pixel value from individual acquisition 1: pixel value from daily climatology 2: pixel value from monthly climatology 3: pixel value was interpolated
  • RETURN VALUE(S):

    SUCCESS Successfully returned TOVS image
    FAILURE Didn't return TOVS image