- Altitude above Mean Seal Level or other datum
- Elevation above the land surface (actual, or sometimes a coarse Digital Terrain Model used by a specific Numerical Weather Prediction model)
- Pressure levels, measured in hectoPascals (which have the same numerical values as milliBars)
- Potential Temperature levels (the potential temperature of a parcel of air is the temperature it would be if brought down to the surface or a standard pressure level, using the adiabatic gas laws)
- Isopycnic levels below the sea surface, where the coordinate is density. This is useful because both temperature and salinity affect density.
- Sigma levels, which are the pressure level values normalised by the surface pressure, in the range (0,1), with 1 at the surface and 0 at the top of the atmosphere.
- Oceanographic sigma levels, which may be normalised density values.
- Hybrid sigma levels (sometimes called eta levels), which are linear combinations of sigma and scaled altitude.
- etc

02 Cloud base level

03 Level of cloud tops

04 Level of 0°C isotherm

05 Level of adiabatic condensation lifted from the surface

06 Maximum wind level

07 Tropopause

08 Nominal top of atmosphere

09 Sea bottom

20 Isothermal level, Temperature in 1/100 K

100 Isobaric surface, Pressure in hPa

101 Layer between two isobaric surfaces, Pressure of top in kPa, Pressure of bottom in kPa

102 Mean Sea Level

103 Specified altitude above Mean Sea Level, in metres

104 Layer between two specified altitudes above mean sea level, Altitude of top in hm, Altitude of bottom in hm

105 Specified height level above ground, in metres

106 Layer between two specified height levels above ground, Height of top in hm, Height of bottom in hm

107 Sigma level, value in 1/10 000

108 Layer between two sigma levels, Sigma value of top in 1/100, Sigma value of bottom in 1/100

109 Hybrid level, Level number

110 Layer between two hybrid levels, Level number of top, Level number of bottom

111 Depth below land surface, in centimetres

112 Layer between two depths below land, Depth of upper surface in cm, Depth of lower surface surface in cm

113 Isentropic (theta) level, Potential temperature in K

114 Layer between two isentropic levels, 475 K minus theta of top in K, 475 K minus theta of bottom in K

115 Level at specified pressure difference, Pressure difference in hPa from ground to level

116 Layer between two levels at specified pressure differences from ground to level, Pressure difference from ground to top level in hPa, Pressure difference from ground to to bottom level in hPa

117 Potential vorticity surface, in 109K m2 kg1 s1

119 ETA level, ETA value in 1/10000

120 Layer between two ETA levels, ETA value at top of layer in 1/100, ETA value at bottom of layer in 1/100

121 Layer between two isobaric surfaces (high precision), 1100 hPa minus pressure of top in hPa, 1100 hPa minus pressure of bottom in hPa 4.2 Review of above. Four types identified:

4.2.1 Single levels, though some are not easily defined

4.2.2 Multiple levels, each identified by a single coordinate value

4.2.3 Multiple layers, each identified by two coordinate values, each layer assumed to be relatively homogeneous

4.2.4 Single layer encompassing a significant depth or height 4.3 Grib Edition 2 Notes

(1) Coordinate values are intended to document the vertical discretization associated with model data on hybrid coordinate vertical levels. A number of zero in octets 6-7 indicates that no such values are present. Otherwise the number corresponds to the whole set of values.

(2) Hybrid systems, in this context, employ a means of representing vertical coordinates in terms of a mathematical combination of pressure and sigma coordinates. When used in conjunction with a surface pressure field and an appropriate mathematical expression, the vertical coordinate parameters may be used to interpret the hybrid vertical coordinate.

(3) Hybrid coordinate values, if present, should be encoded in IEEE 32-bit floating point format. They are intended to be encoded as pairs.

(4) Two distinct pressure-based hybrid coordinate formulations can be expressed in GRIB Edition 2. If the hybrid coordinate being used is based on pressure, then level type 105 (Code table 4.5) shall be used to specify the vertical level type. If the formulation is based on the natural logarithm of pressure then level type 113 (Code table 4.5) shall be used. In both cases Notes 1 to 3 (above) apply fully.

(5) In the case of a generalized vertical height coordinate (fixed surface type 150), no pairs of coordinate values follow after the template, but six sets of additional information (each 4 octets long and encoded in IEEE 32-bit floating point format) follow, starting with the number of vertical levels and the identification number of the used vertical system in the additional GRIB2 message with the 3D vertical system. This identification number together with an UUID (Universally Unique IDentifier) in four parts allows a unique identification of the grid.

[xx+1][xx+4] Number of vertical levels

[xx+5][xx+8] Identification number of 3D vertical grid GRIB2 message (defined by originating centre)

[xx+9][xx+12] UUID part 1 of 4

[xx+13][xx+16] UUID part 2 of 4

[xx+17][xx+20] UUID part 3 of 4

[xx+21][xx+24] UUID part 4 of 4

63 Physical meaning of vertical coordinate (see Code table 3.15)

64 Vertical dimension coordinate values definition (see Code table 3.21)

6566 NCnumber of coefficients or values used to specify vertical coordinates

67(66+NCx4) Coefficients to define vertical dimension coordinate values in functional form, or the explicit coordinate values (IEEE 32-bit floating-point values)

40 Vertical dimension coordinate values definition (see Code table 3.21)

4142 NCnumber of coefficients or values used to specify vertical coordinates

43(42+NCx4) Coefficients to define vertical dimension coordinate values in functional form, or the explicit coordinate values (IEEE 32-bit floating-point values)

Product definition template 4.1 individual ensemble forecast, control and perturbed, at a horizontal level or in a horizontal layer at a point in time

Product definition template 4.2 derived forecasts based on all ensemble members at a horizontal level or in a horizontal layer at a point in time

Product definition template 4.3 derived forecasts based on a cluster of ensemble members over a rectangular area at a horizontal level or in a horizontal layer at a point in time

Product definition template 4.4 derived forecasts based on a cluster of ensemble members over a circular area at a horizontal level or in a horizontal layer at a point in time

Product definition template 4.5 probability forecasts at a horizontal level or in a horizontal layer at a point in time

Product definition template 4.6 percentile forecasts at a horizontal level or in a horizontal layer at a point in time

Product definition template 4.7 analysis or forecast error at a horizontal level or in a horizontal layer at a point in time

Product definition template 4.8 average, accumulation and/or extreme values or other statistically processed values at a horizontal level or in a horizontal layer in a continuous or non-continuous time interval

Product definition template 4.9 probability forecasts at a horizontal level or in a horizontal layer in a continuous or non-continuous time interval

Product definition template 4.10 percentile forecasts at a horizontal level or in a horizontal layer in a continuous or non-continuous time interval

Product definition template 4.11 individual ensemble forecast, control and perturbed, at a horizontal level or in a horizontal layer in a continuous or non-continuous time interval

Product definition template 4.12 derived forecasts based on all ensemble members at a horizontal level or in a horizontal layer in a continuous or non-continuous time interval

Product definition template 4.13 derived forecasts based on a cluster of ensemble members over a rectangular area at a horizontal level or in a horizontal layer in a continuous or non-continuous time interval

Product definition template 4.14 derived forecasts based on a cluster of ensemble members over a circular area at a horizontal level or in a horizontal layer in a continuous or non-continuous time interval

Product definition template 4.15 average, accumulation, extreme values, or other statistically processed values over a spatial area at a horizontal level or in a horizontal layer at a point in time

Product definition template 4.40 analysis or forecast at a horizontal level or in a horizontal layer at a point in time for atmospheric chemical constituents

Product definition template 4.41 individual ensemble forecast, control and perturbed, at a horizontal level or in a horizontal layer at a point in time for atmospheric chemical constituents

Product definition template 4.42 average, accumulation, and/or extreme values or other statistically processed values at a horizontal level or in a horizontal layer in a continuous or non-continuous time interval for atmospheric chemical constituents

Product definition template 4.43 individual ensemble forecast, control and perturbed, at a horizontal level or in a horizontal layer in a continuous or non-continuous time interval for atmospheric chemical constituents

Product definition template 4.44 analysis or forecast at a horizontal level or in a horizontal layer at a point in time for aerosol

Product definition template 4.45 individual ensemble forecast, control and perturbed, at a horizontal level or in a horizontal layer at a point in time for aerosol

Product definition template 4.46 average, accumulation, and/or extreme values or other statistically processed values at a horizontal level or in a horizontal layer in a continuous or non-continuous time interval for aerosolProduct definition template 4.47 individual ensemble forecast, control and perturbed, at a horizontal level or in a horizontal layer in a continuous or non-continuous time interval for aerosolProduct definition template 4.48 analysis or forecast at a horizontal level or in a horizontal layer at a point in time for optical properties of aerosol

Product definition template 4.51 categorical forecasts at a horizontal level or in a horizontal layer at a point in time

Product definition template 4.53 partitioned parameters at a horizontal level or in a horizontal layer at a point in time

Product definition template 4.54 individual ensemble forecast, control and perturbed, at a horizontal level or in a horizontal layer at a point in time for partitioned parameters

Product definition template 4.91 categorical forecasts at a horizontal level or in a horizontal layer in a continuous or non-continuous time interval

Product definition template 4.1100 Hovmφller-type grid with no averaging or other statistical processing

+2 Scale factor of first fixed surface

+3-7 Scaled value of first fixed surface

+8 Type of second fixed surface (see Code table 4.5)

+9 Scale factor of second fixed surface

+10-13 Scaled value of second fixedsurface

100 Pressure Pa

101 Pressure deviation from mean sea level Pa

102 Altitude above mean sea level m

103 Height above ground (see Note 1) m

104 Sigma coordinate

105 Hybrid coordinate

106 Depth below land surface m

107 Potential temperature (theta) K

108 Pressure deviation from ground to level Pa

109 Potential vorticity K m2 kg1 s1

110 Geometrical height m

111 Eta coordinate (see Note 2)

112 Geopotential height gpm

113 Logarithmic hybrid coordinate 160 Depth below sea level m

Notes:

(1) Negative values associated to this coordinate will indicate depth below ground surface. If values are all below surface, use of entry 106 is recommended, with positive coordinate values instead.

(2) The Eta vertical coordinate system involves normalizing the pressure at some point on a specific level by the mean sea level pressure at that point.

0 Explicit coordinate values set

1 Linear coordinates

f(1) = C1

f(n) = f(n1) + C2

11 Geometric coordinates

f(1) = C1

f(n) = C2 Χ f(n1)

1 Ground or water surface

2 Cloud base level

3 Level of cloud tops

4 Level of 0°C isotherm

5 Level of adiabatic condensation lifted from the surface

6 Maximum wind level

7 Tropopause

8 Nominal top of the atmosphere

9 Sea bottom

10 Entire atmosphere

11 Cumulonimbus (CB) base m

12 Cumulonimbus (CB) top m

20 Isothermal level K

100 Isobaric surface Pa

101 Mean sea level

102 Specific altitude above mean sea level m

103 Specified height level above ground m

104 Sigma level sigma value

105 Hybrid level

106 Depth below land surface m

107 Isentropic (theta) level K

108 Level at specified pressure difference from ground to level Pa

109 Potential vorticity surface K m2 kg1 s1

111 Eta level

113 Logarithmic hybrid level

114 Snow level Numeric

117 Mixed layer depth m

118 Hybrid height level

119 Hybrid pressure level

150 Generalized vertical height coordinate (see Note 5)

160 Depth below sea level m

161 Depth below water surface m

162 Lake or river bottom

163 Bottom of sediment layer

164 Bottom of thermally active sediment layer

165 Bottom of sediment layer penetrated by thermal wave

166 Mixing layer Notes:

(1) The Eta vertical coordinate system involves normalizing the pressure at some point on a specific level by the mean sea level pressure at that point.

(2) Hybrid height level (Code figure 118) can be defined as:

z(k) = A(k) + B(k) x orog(k = 1,...,NLevels; orog = orography; z(k) = height in metres at level k)

(3) Hybrid pressure level, for which Code figure 119 shall be used instead of 105, can be defined as:

p(k) = A(k) + B(k) x sp

(k = 1,...,NLevels; sp = surface pressure; p(k) = pressure at level k)

(4) Ice internal pressure or stress (Pa m) is the integrated pressure across the vertical thickness of a layer of ice. It is produced when concentrated ice reacts to external forces such as wind and ocean currents.

(5) The definition of a generalized vertical height coordinate implies the absence of coordinate values in Section 4 but the presence of an external 3D-GRIB message that specifies the height of every model grid point in metres (see Notes to Section 4 in the section above entitled Specification of Octet Contents), i.e., this GRIB message will

contain the field with discipline = 0, category = 3, parameter = 6 (Geometric height).

090 Elevation in increments of 100 m

254 Clouds

255 Missing

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