# Local definition 4: Ocean model data

## Local definitions

- Local definition 1
- Local definition 2
- Local definition 3
- Local definition 4
- Local definition 5
- Local definition 6
- Local definition 7
- Local definition 8
- Local definition 9
- Local definition 10
- Local definition 11
- Local definition 12
- Local definition 13
- Local definition 14
- Local definition 15
- Local definition 16
- Local definition 17
- Local definition 18
- Local definition 19
- Local definition 20
- Local definition 21
- Local definition 22
- Local definition 23
- Local definition 24
- Local definition 25
- Local definition 26
- Local definition 27
- Local definition 28
- Local definition 29
- Local definition 30
- Local definition 31
- Local definition 32
- Local definition 36
- Local definition 37
- Local definition 38
- Local definition 39
- Local definition 49
- Local definition 50
- Local definition 190
- Local definition 191
- Local definition 192

Octets | Key | Type | Contents |

41 | localDefinitionNumber | unsigned | ECMWF local GRIB use definition identifier. 4 = Ocean model data. |

42 | class | codetable | Class |

43 | type | codetable | Type |

44-45 | stream | codetable | Stream |

46-49 | experimentVersionNumber | ksec1expver | Version number or experiment identifier. (4 ASCII characters, right justified) |

50-51, if stream = 109; 050, otherwise | perturbationNumber | unsigned | Ensemble member number |

51, unless stream = 1090 | Zero | ||

52 | flagShowingPostAuxiliaryArrayInUse | unsigned | 1 (a flag showing a post-auxiliary array is in use) |

53 | systemNumber | unsigned | System number |

54 | methodNumber | unsigned | Method number |

55 | spaceUnitFlag | unsigned | Space unit flag (applies only if lengths not otherwise labelled): 0 = metres i<128 = 10**i metres i>128 = 10**(i-256) metres |

56 | verticalCoordinateDefinition | unsigned | 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) |

57 | horizontalCoordinateDefinition | unsigned | 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) |

58 | timeUnitFlag | unsigned | Time unit flag:
0 = Seconds
1 = Minutes
2 = Hours
3 = Days
4 = Years
5128 = 10**(i-256) seconds |

59 | timeCoordinateDefinition | unsigned | Time coordinate definition (t): 0 = Real Earth time (UTC) 1 = Ideal Earth time (360 * 86400s days per year) |

60 | mixedCoordinateFieldFlag | unsigned | 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) |

61 | coordinate1Flag | unsigned | Coordinate 1 flag (usually time). |

62 | averaging1Flag | unsigned | 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 |

63-66 | coordinate1Start | signed | Position of level 1 |

67-70 | coordinate1End | signed | Position of level 2 (or zero if not used) |

71 | coordinate2Flag | unsigned | Coordinate 2 flag (usually z-coordinate). |

72 | averaging2Flag | unsigned | 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 |

73-76 | coordinate2Start | signed | Position of level 1 |

77-80 | coordinate2End | signed | Position of level 2 (or zero if not used) |

81 | coordinate3Flag | unsigned | Coordinate 3 flag (x-axis, usually longitude). |

82 | coordinate4Flag | unsigned | Coordinate 4 flag (y-axis, usually latitude). |

83-86 | coordinate4OfFirstGridPoint | signed | Coordinate 4 of first grid point |

87-90 | coordinate3OfFirstGridPoint | signed | Coordinate 3 of first grid point |

91-94 | coordinate4OfLastGridPoint | signed | Coordinate 4 of last grid point |

95-98 | coordinate3OfLastGridPoint | signed | Coordinate 3 of last grid point |

99-102 | iIncrement | signed | i-increment |

103-106 | jIncrement | signed | j-increment |

107 | flagForIrregularGridCoordinateList | codeflag | 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 |

108 | flagForNormalOrStaggeredGrid | codeflag | 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). |

109 | flagForAnyFurtherInformation | codeflag | Flag for any further information: 0 = none 1 = auxiliary array contains x-axis topographic depths/heights. |

110 | numberInHorizontalCoordinates | unsigned | Number of entries in the horizontal coordinate definition |

111-112 | numberInMixedCoordinateDefinition | unsigned | Number of entries in mixed coordinate definition |

113-114 | numberInTheGridCoordinateList | unsigned | Number of entries in the grid coordinate list |

115-116 | numberInTheAuxiliaryArray | unsigned | Number of entries in the auxiliary array |

A1-nn | horizontalCoordinateSupplement | unsigned | Horizontal coordinate definition |

B1-nn | mixedCoordinateDefinition | unsigned | Mixed coordinate definition |

C1-nn | gridCoordinate | unsigned | Grid coordinate list |

D1-nn | auxiliary | unsigned | Auxiliary array |

E1-nn | postAuxiliary | unsigned | Post-auxiliary array |

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

( 2) 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.

( 3) 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).

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