GRIB2 - CODE TABLE 4.5

FIXED SURFACE TYPES AND UNITS

In Section 4, Octets 23 and 29

Revised 09/18/2025
Red text depicts changes made since 10/24/2023


Code Figure Meaning
0
 Reserved
1
 Ground or Water Surface
2
 Cloud Base Level
3
 Level of Cloud Tops
4
 Level of 0o 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 Base (CB) m
12 Cumulonimbus Top (CT) m
13 Lowest level where vertically integrated cloud cover exceeds the specified percentage
(cloud base for a given percentage cloud cover)		 %
14 Level of free convection (LFC)
15 Convection condensation level (CCL)
16 Level of neutral buoyancy or equilibrium (LNB)
17 Departure level of the most unstable parcel of air (MUDL)
18 Departure level of a mixed layer parcel of air with specified layer depth Pa
19
 Lowest level where cloud cover exceeds the specified percentage (see Note 9) %
20
 Isothermal Level
 K
21 Lowest level where mass density exceeds the specified value
(base for a given threshold of mass density)		 kg m-3
22 Highest level where mass density exceeds the specified
value (top for a given threshold of mass density)		 kg m-3
23 Lowest level where air concentration exceeds the specified
value (base for a given threshold of air concentration		 Bq m-3
24 Highest level where air concentration exceeds the specified
value (top for a given threshold of air concentration)		 Bq m-3
25 Highest level where radar reflectivity exceeds the specified
value (echo top for a given threshold of reflectivity)		 dBZ
26 Convective cloud layer base m
27 Convective cloud layer top m
28-29
 Reserved
30 Specified radius from the centre of the Sun m
31 Solar photosphere
32 Ionospheric D-region level
33 Ionospheric E-region level
34 Ionospheric F1-region level
35 Ionospheric F2-region level
36 Stratopause
37-99
 Reserved
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
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 kg-1 s-1
110
 Reserved
111
 Eta Level
112 Reserved
113 Logarithmic Hybrid Level
114 Snow Level Numeric
115 Sigma height level (see Note 4)
116 Reserved
117
 Mixed Layer Depth
 m
118 Hybrid Height Level
119 Hybrid Pressure Level
120-149
 Reserved
150 Generalized Vertical Height Coordinate (see Note 4)
151 Soil level (See Note 5) Numeric
152 Sea-ice level (see Note 8) Numeric
153-159 Reserved
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
167 Bottom of Root Zone
168 Ocean Model Level Numeric
169 Ocean level defined by water density (sigma-theta)
difference from near-surface to level (see Note 7)		 kg m-3
170 Ocean level defined by water potential temperature
difference from near-surface to level (see Note 7)		 K
171 Ocean level defined by vertical eddy diffusivity difference from near-surface to level (see Note 7) m2 s-1
172 Ocean level defined by water density (rho) difference from near-surface to level m
173 Top of Snow Over Sea Ice on Sea, Lake or River
174 Top Surface of Ice on Sea, Lake or River
175 Top Surface of Ice, under Snow, on Sea, Lake or River
176 Bottom Surface (underside) Ice on Sea, Lake or River
177 Deep Soil (of indefinite depth)
178 Reserved
179 Top Surface of Glacier Ice and Inland Ice
180 Deep Inland or Glacier Ice (of indefinite depth)
181 Grid Tile Land Fraction as a Model Surface
182 Grid Tile Water Fraction as a Model Surface
183 Grid Tile Ice Fraction on Sea, Lake or River as a Model Surface
184 Grid Tile Glacier Ice and Inland Ice Fraction as a Model Surface
185 Roof Level
186 Wall level
187 Road Level
188 Melt pond Top Surface
189 Melt Pond Bottom Surface
190 Reserved
191 Abstract Level with no Vertical Localization (see Note 10)
192-254
 Reserved for Local Use
200
 Entire atmosphere (considered as a single layer)
201
 Entire ocean (considered as a single layer)
204
 Highest tropospheric freezing level
206
 Grid scale cloud bottom level
207
 Grid scale cloud top level
209
 Boundary layer cloud bottom level
210
 Boundary layer cloud top level
211
 Boundary layer cloud layer
212
 Low cloud bottom level
213
 Low cloud top level
214
 Low cloud layer
215
 Cloud ceiling
216 Effective Layer Top Level m
217 Effective Layer Bottom Level m
218 Effective Layer m
220 Planetary Boundary Layer
221 Layer Between Two Hybrid Levels
222
 Middle cloud bottom level
223
 Middle cloud top level
224
 Middle cloud layer
232
 High cloud bottom level
233
 High cloud top level
234
 High cloud layer
235
 Ocean Isotherm Level (1/10 ° C)
236
 Layer between two depths below ocean surface

237
 Bottom of Ocean Mixed Layer (m)
238
 Bottom of Ocean Isothermal Layer (m)
239
 Layer Ocean Surface and 26C Ocean Isothermal Level
240
 Ocean Mixed Layer
241
 Ordered Sequence of Data
242
 Convective cloud bottom level
243
 Convective cloud top level
244
 Convective cloud layer
245
 Lowest level of the wet bulb zero
246
 Maximum equivalent potential temperature level
247
 Equilibrium level
248
 Shallow convective cloud bottom level
249
 Shallow convective cloud top level
251
 Deep convective cloud bottom level
252
 Deep convective cloud top level
253
 Lowest bottom level of supercooled liquid water layer
254
 Highest top level of supercooled liquid water layer
255 Missing


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)* orog
(k=1,..., NLevels; orog=orography; z(k)=height in meters at level(k)

(3)  Hybrid pressure level, for which code figure 119 shall be used insteaf of 105, can be defined as:
p(k)=A(k) + B(k) * sp
(k=1,...,NLevels, sp=surface pressure; p(k)=pressure at level (k)

(4)  Sigma height level is the vertical model level of the height-based terrain-following coordinate (Gal-Chen and Somerville, 1975). The value of the level = (height of the level – height of the terrain) / (height of the top level – height of the terrain), which is ≥ 0 and ≤ 1.

(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 meters (see Notes for section 4), i.e., this GRIB message will contain the field with discipline = 0, category = 3, parameterm = 6 (Geometric height).

(6)  The soil level represents a model level for which the depth is not constant across the model domain. The depth in metres of the level is provided by another GRIB message with the parameter "Soil Depth" with discipline 2, category 3 and parameter number 27.

(7)  The level is defined by a water property difference from the near-surface to the level. The near-surface is typically chosen at 10 m depth. The physical quantity used to compute the difference can be water density (δΘ) when using level type 169 or water potential temperature (Θ) when using level type 170.

(8)  The sea-ice level represents a sea-ice model level for which the depth is not constant across the model domains. The depth in metres of the level is provided by another GRIB message with the parameter “sea-ice thickness” with discipline 10, category 2 and parameter number 1.

(9)  This level differs from entry 13 which is vertically accumulated from the surface while this entry is not.

(10)  This level has no defined location along the vertical axis. Scale factor and scaled values of first and second fixed surface should be set to 'missing' if not used.


Back