Section 4 - Code Table 5 : Fixed surface types and units

Code Tables for Section 4

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Code Meaning
0 Reserved
1 Ground or water surface (-)
2 Cloud base level (-)
3 Level of cloud tops (-)
4 Level of 0 degree 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)
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 Convective condensation level (CCL) (-)
16 Level of neutral buoyancy or equilibrium level (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)
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)
30 Specified radius from the center 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
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 kg-1 s-1)
110 Reserved
111 Eta level (-)
112 Reserved
113 Logarithmic hybrid level
114 Snow level (Numeric)
115 Sigma height level
117 Mixed layer depth (m)
118 Hybrid height level (-)
119 Hybrid pressure level (-)
150 Generalized vertical height coordinate
151 Soil level (Numeric)
152 Sea ice level (Numeric)
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 (kg m-3)
170 Ocean level defined by water potential temperature difference from near-surface to level (K)
174 Top surface of ice on sea, lake or river
175 Top surface of ice, under snow cover, on sea, lake or river
176 Bottom surface (underside) ice on sea, lake or river
177 Deep soil (of indefinite depth)
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
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) 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) 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) 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.

( 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 when using level type 169 or water potential temperature when using level type 170.