GRIB2 - PRODUCT DEFINITION TEMPLATE 4.55

Spatio-temporal changing tiles
at a horizontal level or horizontal layer at a point in time

Created 06/03/2019


Octet No. Contents
10
Parameter category (see Code table 4.1)
11 Parameter number (see Code table 4.2)
12 Tile classification (see Code table 4.242)
13 Total number (NT) of tile/attribute pairs (see Notes 1 and 2)
14 Number of used spatial tiles (NUT) (see Notes 1 and 2)
15 Tile index (ITN={1,...,NUT}) (see Note 1)
16 Number of used tile attributes (NAT) for tile ITN (see Note 1)
17 Attribute of tile (see Code table 4.241) (A={A(1),...,A(NAT(ITN))}) (see Note 1)
18 Type of generating process (see Code table 4.3)
19 Background generating process identifier (defined by originating centre)
20 Analysis or forecast generating process identifier (see Code ON388 Table A)
21-22 Hours of observational data cut-off after reference time (see Note 3)
23 Minutes of observational data cut-off after reference
24 Indicator of unit of time range (see Code table 4.4)
25-28 Forecast time in units defined by octet 24
29 Type of first fixed surface (see Code table 4.5)
30 Scale factor of first fixed surface
31-34 Scaled value of first fixed surface
35 Type of second fixed surfaced (see Code table 4.5)
36 Scale factor of second fixed surface
37-40 Scaled value of second fixed surfaces


Notes:

(1)   NUT is the number of used different spatial tiles, defining the cover structure of point. As each of these tiles has one or more different tile attributes A(NAT(ITN)), where (ITN=1,...,NUT), for example, (unmodified, snow-covered,...), there are NT=∑ITN=1NUT NAT(ITN) fields (that is, the total number of tile attribute pairs, defined in (octet 13) with indices (ITN,IAN) with the following meaning (IAN={1,...,ITN)}):
    1,1                                    First tile - first attribute (e.g. unmodified) attribute
    ...                           ...
    1,NAT(1)                         First tile - NAT of first tile (last, e.g. snow-covered) attribute
    2,1                                    Second tile - first attribute (e.g. unmodified)
    ...                          ...
    2,NAT(2)                         Second tile - NAT of second tile (last, e.g. snow-covered) attribute
    ...                          ...
    ...                          ...
    NUT,1                             NUT tile - first attribute (e.g. unmodified)
    ...                          ...
    NUT,NAT(NUT)          NUT tile - NAT of last attribute (last) attribute


A single tile attribute index (ITN,IAN) with spatial tile index ITN(1,...,NUT) and attribute A(IAN) with (IAN=1,...,NAT(ITN)) is represented in the template. All NT partitions are linked by the normalization formula, which states that the sum of all partions must be equal to normalization term (N=1 for fractions and N = 100 for percentage) on each point of the grid.

The fields "tile class" and "tile fraction" must be provided in order to obtain the tile structure of each grid point. Please note that the field "tile fraction" is time-dependent in the case of defined attribute, whereas the field "tile class" is not affected by attribute (NT=NUT).

(2)   For more informtion, see Part B, GRIB Attachment IV.

(3)   Hours greater than 65534 will be coded as 65534.


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