KSEC1 element Contents GRIB octet Recommended GRIB_API keys Coded GRIB_API keys Comments
37 
ECMWF local GRIB use definition identifier.
4 = Ocean model data.
 41 localDefinitionNumber localDefinitionNumber
38 Class 42 class marsClass
39 Type 43 type
 marsType
40 Stream 44-45 stream
 marsStream
41 
Version number or experiment identifier.
(4 ASCII characters, right justified)
 46-49 expver
 experimentVersionNumber
42 Ensemble member number 
50-51, if stream = 1090
50, otherwise
 number
 perturbationNumber
43 Zero 51, unless stream = 1090


- 1 (a flag showing a post-auxiliary array is in use) 52 flagShowingPostAuxiliaryArrayInUse
 flagShowingPostAuxiliaryArrayInUse
44 System number 53 systemNumber
 systemNumber
45 Method number 54 methodNumber
 methodNumber

Used for storing ocean model data in GRIB code. A separate version of code table 2 is used for ocean data: ECMWF local Code Table 2, Version Number 150 or 151 for FM92-VIII.

All coordinates in this local use GRIB definition are given as 4-byte INTEGERs in the following units:

At several points in the definition, there may be a need for a variable amount of supplementary data. This is indicated with '(+info)', and in such cases a supplementary data block is specified at the end of the local use section.

Coordinate structure definition.

The physical meaning of the (x,y,z,t) coordinate system is defined below.

KSEC1 element Contents GRIB octet Recommended GRIB API keys Coded GRIB API keys Comments
46 
Space unit flag (applies only if lengths not otherwise labelled):
 0 = metres
 i<128 = 10**i metres
 i>128 = 10**(i-256) metres
 55 spaceUnitFlag
 spaceUnitFlag
47 
Vertical coordinate definition (z):
 0 = z above origin
 1 = R from origin
 2 = h above mean sea level geopotential
 3 = h above ground surface
 160 = Geopotential depth below mean sea level (mm)
 161 = Ocean isopycnic surface (potential density)
 56 verticalCoordinateDefinition
 verticalCoordinateDefinition
48 
Horizontal coordinate definition (x,y):
 0 = Latitude/longitude (microdegrees)
 1 = Cartesian (fundamental origin)
 2 = Cartesian (shifted, rotated origin) (+info)
 3 = Regular gaussian grid (microdegrees) (+info)
 4 = Polar stereographic (+info)
 5 = Spherical harmonic coefficients (INTEGERs) (+info)
 57 horizontalCoordinateDefinition
 horizontalCoordinateDefinition
49 
Time unit flag:
 0 = Seconds
 1 = Minutes
 2 = Hours
 3 = Days
 4 = Years
 5<i<128 = 10**(i-4) years
 i>128 = 10**(i-256) seconds
 58 timeUnitFlag
 timeUnitFlag
50 
Time coordinate definition (t):
 0 = Real Earth time (UTC)
 1 = Ideal Earth time (360 * 86400s days per year)
 59 timeCoordinateDefinition
 timeCoordinateDefinition

Position definition.

A 2-dimensional field located in 4-dimensional space-time needs 2 coordinates to define where the field is located, and 2 coordinates internal to the field. The locating coordinates are specified first. Each coordinate is identified according to the following table, in this order where possible:

  • 1 = t
  • 2 = z
  • 3 = x
  • 4 = y

    Mixed coordinates

    It is possible to specify mixed coordinates, to allow sections at angles to the coordinate system.

    KSEC1 element Contents GRIB octet Recommended GRIB API keys Coded GRIB API keys Comments
    51 
    Mixed coordinate field flag:
     0 = No mixed coordinates
     1 = x,y coordinates mixed (+info)
     2 = x,z coordinates mixed (+info)
     3 = y,z coordinates mixed (+info)
     4 = x,t coordinates mixed (+info)
     5 = y,t coordinates mixed (+info)
     6 = z,t coordinates mixed (+info)
    		 60 mixedCoordinateFieldFlag
    		 mixedCoordinateFieldFlag
    52 Coordinate 1 flag (usually time). 61 coordinate1Flag
    		 coordinate1Flag
    53 
    Averaging flag:
     0 = no averaging (data on/at level 1)
     1 = inclusive average between level 1 and 2
     2 = exclusive average between level 1 and 2
    		 62 averaging1Flag
    		 averaging1Flag
    54 Position of level 1 63-66 coordinate1Start
    		 coordinate1Start
    55 Position of level 2 (or zero if not used) 67-70 coordinate1End
    		 coordinate1End
    56 Coordinate 2 flag (usually z-coordinate). 71 coordinate2Flag
    		 coordinate2Flag
    57 
    Averaging flag:
     0 = no averaging (data on/at level 1)
     1 = inclusive average between level 1 and 2
     2 = exclusive average between level 1 and 2
    		 72 averaging2Flag
    		 averaging2Flag
    58 Position of level 1 73-76 coordinate2Start
    		 coordinate2Start
    59 Position of level 2 (or zero if not used) 77-80 coordinate2End
    		 coordinate2End
    An inclusive average discards land points when calculating the average, and will produce a value where there is at least one valid ocean point. An exclusive average will only produce a value if all of the points being averaged are valid.

    Data grid definitions

    KSEC1 element Contents GRIB octet Recommended GRIB API keys Coded GRIB API keys Comments
    60 Coordinate 3 flag (x-axis, usually longitude). 81 coordinate3Flag
    		 coordinate3Flag
    61 Coordinate 4 flag (y-axis, usually latitude). 82 coordinate4Flag
    		 coordinate4Flag
    62 Coordinate 4 of first grid point 83-86 coordinate4OfFirstGridPoint
    		 coordinate4OfFirstGridPoint
    63 Coordinate 3 of first grid point 87-90 coordinate3OfFirstGridPoint
    		 coordinate3OfFirstGridPoint
    64 Coordinate 4 of last grid point 91-94 coordinate4OfLastGridPoint
    		 coordinate4OfLastGridPoint
    65 Coordinate 3 of last grid point 95-98 coordinate3OfLastGridPoint
    		 coordinate3OfLastGridPoint
    66 i-increment 99-102 iIncrement
    		 iIncrement
    67 j-increment 103-106 jIncrement
    		 jIncrement
    68 
    Flag for irregular grid coordinate list:
     0 = none
     1 = x-axis values (typically longitude)
     2 = y-axis values (typically latitude)
     3 = first x-axis, then y-axis values given
    		 107 flagForIrregularGridCoordinateList
    		 flagForIrregularGridCoordinateList
    69 
    Flag for normal or staggered grid:
     0 = normal grid (all rows have same x-coordinate system)
     1 = staggered grid (odd and even rows have different x-coordinate systems,
         eg Arakawa grid).
    		 108 flagForNormalOrStaggeredGrid
    		 flagForNormalOrStaggeredGrid

    Auxiliary information

    KSEC1 element Contents GRIB octet Recommended GRIB API keys Coded GRIB API keys Comments
    70 
    Flag for any further information:
     0 = none
     1 = auxiliary array contains x-axis topographic depths/heights.
    		 109 flagForAnyFurtherInformation
    		 flagForAnyFurtherInformation
    71 Number of entries in the horizontal coordinate definition 110 numberInHorizontalCoordinates
    		 numberInHorizontalCoordinates
    72 Number of entries in mixed coordinate definition 111-112 numberInMixedCoordinateDefinition
    		 numberInMixedCoordinateDefinition
    73 Number of entries in the grid coordinate list 113-114 numberInTheGridCoordinateList
    		 numberInTheGridCoordinateList
    74 Number of entries in the auxiliary array 115-116 numberInTheAuxiliaryArray
    		 numberInTheAuxiliaryArray

    The horizontal coordinate definition, the mixed coordinate definition, the grid coordinate list, the auxiliary array and the post-auxiliary-array values are stored in GRIB as 4-byte INTEGERs.

    Horizontal coordinate definition
    KSEC1 element Contents Recommended GRIB API keys Coded GRIB API keys Comments
    A1-nn Horizontal coordinate supplement. Not yet defined. horizontalCoordinateSupplement
    		 horizontalCoordinateSupplement
    		 "numberInHorizontalCoordinates" elements

    Mixed coordinate definition
    KSEC1 element Contents Recommended GRIB API keys Coded GRIB API keys Comments
    B1 
    Flag for regularity of x-y coordinate mixing:
     0 = Mixing is regular and linear
     1 = Mixing is irregular, code given
    		 mixedCoordinateDefinition
    		 mixedCoordinateDefinition
    		 "numberInMixedCoordinateDefinition" elements
    - For regular, linear mixing.


    B2 Alpha *109


    B3 X0


    B4 Y0


    - Irregular mixing with code given.


    B2 Locally defined codes to define section.


    B3 Locally defined codes to define section.


    B4 Locally defined codes to define section.


    Grid coordinate list
    KSEC1 element Contents Recommended GRIB API keys Coded GRIB API keys Comments
    C1-nn 
    Coordinates of irregular x and y-axes.
    The x-axis is given first, then the second x-axis (if staggered grid), and
    then the y-axis. 
    If the x-axis is regular but staggered, the longitude of the first point of
    the second row should be specified as the first entry of this list.
    		 gridCoordinate
    		 gridCoordinate
    		 "numberInTheGridCoordinateList"
    values

    Auxiliary array
    KSEC1 element Contents Recommended GRIB API keys Coded GRIB API keys Comments
    D1-nn Auxiliary array values. auxiliary
    		 auxiliary
    		 "numberInTheAuxiliaryArray" values

    Post-auxiliary array
    KSEC1 element Contents Recommended GRIB API keys Coded GRIB API keys Comments
    E1 Size of post-auxiliary array (number of entries, including E1) sizeOfPostAuxiliaryArrayPlusOne
    		 sizeOfPostAuxiliaryArrayPlusOne
    E2-E4 Array values postAuxiliary
    		 postAuxiliary
    		 "sizeOfPostAuxiliaryArrayPlusOne- 1" valies
    E5-E7 Used for hindcast support if E1 > 4


    E8 Used if E1=8


    E5 Reference date (YYYYMMDD)


    E6 Climate date - from (YYYYMMDD), or zero


    E7 Climate date - to (YYYYMMDD), or zero


    E8 
    Ocean Atmosphere coupling:
    0 = unspecified
    1 = uncoupled
    2 = coupled



    If the post-auxiliary array is not being used, E1 (the value in KSEC1 after the end of the previously defined part of KSEC1) must be explicitly set to zero when coding or else errors may result.

    Comments on setting other GRIB parameters.

    The time and time-range data should be set in the main section, if possible.

    The indicator of type of level should be set to 160 (depth below sea level) for all oceanographic data. The depth in metres should be set to the appropriate value if the field is a horizontal section, and to zero in all other cases.

    It is assumed that the grid description section of the GRIB code corresponds to a latitude/longitude grid, with correct values for the number of points along parallels/meridians, and the coordinates of the first and last data points are in millidegrees (or the appropriate units from this section, divided by 1000).

    The coordinate increments should be given to the extent that the field is regular.