Guide to WMO Table Driven Code Forms

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Code Table 1.0: GRIB Master Tables Version Number Code figure Meaning 0 Experimental 1 Version implemented on 7 November 2001 2 Version implemented on 4 November 2003 3 Version implemented on 2 November 2005 4 Version implemented on 7 November 2007 5 Pre-operational to be implemented by next amendment 6-254 Future versions 255 Missing value Code Table 1.1: GRIB Local Tables Version Number Code figure Meaning 0 Local tables not used. Only table entries and templates from the current Master table are valid. 1-254 Number of local tables version used 255 Missing The WMO Secretariat maintains all versions of the GRIB Master Table. Octet 10 contains the version number of the Master Table used to generate the data contained in the GRIB message. If octet 10 contains the value 255, however, a local table was used. In this case, the value in octet 11 – Local Table Version Number – is the relevant one. However, to obtain the local table version referred to by octet 11, one must contact the centre that originated the data in the GRIB message as identified by octets 6-7 and 8-9. If local tables were not used, octet 11 will contain the value 0. The meaning of the Reference Time of the Data in GRIB1 was a source of some confusion because it was not clearly defined. In an attempt to be more precise, the Reference Time of the Data in GRIB2 is given in terms of both a date/time and its significance. The significance of the reference time – contained in octet 12 – refers to Code Table 1.2, currently defined as: Code Table 1.2: Significance of Reference Time Code figure Meaning 0 Analysis 1 Start of forecast 2 Verifying time of forecast 3 Observation time 4-191 Reserved 192-254 Reserved for local use 255 Missing This parameter identifies, for example, whether the Reference Date/Time refers to the time of an analysis (octet 12 = 0), the start of a forecast (octet 12 = 1), the verifying time of a forecast (octet 12 = 2), etc. The precise time of the data itself is found by combining the Reference Date/Time itself, contained in octets 13 – 19, with additional time information given in the Product Definition Section (Section 4). 16
Finally, octets 20 and 21 give additional information about the data in the GRIB message via Code Tables 1.3 and 1.4: Code Table 1.3: Production status of data Code figure Meaning 0 Operational products 1 Operational test products 2 Research products 3 Re-analysis products 4-191 Reserved 192-254 Reserved for local use 255 Missing Code Table 1.4: Type of data Code figure Meaning 0 Analysis products 1 Forecast products 2 Analysis and forecast products 3 Control forecast products 4 Perturbed forecast products 5 Control and perturbed forecast products 6 Processed satellite observations 7 Processed radar observations 8-191 Reserved 192-254 Reserved for local use 255 Missing Note: An initialised analysis is considered a zero hour forecast The production status (octet 20) refers to whether the data are an operational product, an operational test product, a research product, etc. The Type of data (octet 21) indicates whether the data are an analysis product, a forecast product, a perturbed forecast products, etc. 2.1.3 Section 2: Local Use Section The purpose of the Local Use Section is just what the Section name implies – information for local use by the originating/generating centre. The originating/generating centre can put anything it desires in this Section. The contents of Section 2 are: Octet No. Contents 1-4 Length of section in octets (nn) 5 Number of Section (“2”) 6-nn Local use 2.1.4 Section 3: Grid Definition Section The purpose of the Grid Definition Section is to define the grid surface and geometry of the data values within the surface for the data contained in the next occurrence of the Data Section. GRIB2 retains the powerful GRIB1 concept of a template in this Section and extends it to the 17
Page 1 and 2: Guide to the WMO Table Driven Code
Page 3 and 4: Layer 1: Basic Aspects of GRIB2 Con
Page 5 and 6: 1.1 Overview Layer 1: Basic Aspects
Page 7 and 8: 1.2 General Description 1.2.1 Code
Page 9 and 10: Section 0: Indicator Section Sectio
Page 11 and 12: 1.2.3.2 Code and Flag Tables A code
Page 13 and 14: 14 Minimum dew point depression K 1
Page 15 and 16: necessary flexibility is available
Page 17 and 18: Layer 2: Structure and Use of GRIB2
Page 19: 15 Month | 16 Day | Reference time
Page 23 and 24: Code Table 3.0: Source of Grid Defi
Page 25 and 26: 2.1.5 Section 4: Product Definition
Page 27 and 28: 2.1.6 Section 5: Data Representatio
Page 29 and 30: The various data compression scheme
Page 31 and 32: 4. Bit 2 of the projection flag is
Page 33 and 34: within the Product Definition Templ
Page 35 and 36: Code Table 4.2 Parameter number by
Page 37 and 38: Code table 4.5: Fixed surface types
Page 39 and 40: 5 Number of Section (“7”) 6-nn
Page 41 and 42: Octet No. Contents 1-4 Length of se
Page 43 and 44: “word” bit-length method. The c
Page 45 and 46: The sub-section set of numbers is t
Page 47 and 48: (increments) themselves are then st
Page 49 and 50: Bit Number Value Meaning 1 0 Points
Page 51 and 52: complex numbers F are stored in the
Page 53 and 54: 2.4 The Structure of GRIB2 Messages
Page 55 and 56: 22-25 59-62 all 1’s There is no s
Page 57 and 58: 2.4.2 Structure of A GRIB2 Message
Page 59 and 60: 22-25 59-62 all 1’s There is no s
Page 61 and 62: 24 227 0 The scale factor of first
Page 63 and 64: 11 417 5 The parameter number is 5
Page 66 and 67: Currently Defined Product Definitio
Page 68 and 69: 0 Vegetation/Biomass 1 Agri-aquacul
Page 70:
3.1 Quasi-regular Grids Layer 3: De
Page 73 and 74:
Now, let us consider the changes th
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68-71 105-108 10000000 The j direct
Page 77 and 78:
generalized as follows: Ph = ah •
Page 79 and 80:
3.3 Data Compression 3.3.1 Complex
Page 81 and 82:
The Grid Point Data - Complex Packi
Page 83 and 84:
Octet No. Contents 1-4 Length of se
Page 85 and 86:
Octet No. Contents 1-4 Length of se
Page 87 and 88:
54600 The order of the spatial diff
Page 89:
3.4 Structure of a GRIB2 Message wi
Page 92 and 93:
22-25 59-62 all 1’s There is no s
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31-34 234-237 36 There are 36 point
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3.4.3 Example of a GRIB2 Message wi
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12 128 0 Since there is no optional
Page 100 and 101:
DIFFERENCE FORMULATION” (Coded ac
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1-4 1574-1577 1000 This Section is
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Guide to WMO Table Driven Code Forms

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