# Code table 4.5 - Fixed surface types and units
0 0 Reserved 
1 sfc Ground or water surface (-)
2 2 Cloud base level (-)
3 3 Level of cloud tops (-)
4 4 Level of 0 degree C isotherm (-)
5 5 Level of adiabatic condensation lifted from the surface (-)
6 6 Maximum wind level (-)
7 7 Tropopause (-)
8 sfc Nominal top of the atmosphere (-)
9 9 Sea bottom (-)
10 10 Entire atmosphere (-)
11 11 Cumulonimbus (CB) base (m)
12 12 Cumulonimbus (CB) top (m)
13 13 Lowest level where vertically integrated cloud cover exceeds the specified percentage (cloud base for a given percentage cloud cover) (%)
14 14 Level of free convection (LFC)
15 15 Convective condensation level (CCL)
16 16 Level of neutral buoyancy or equilibrium level (LNB)
# 17-19 Reserved 
20 20 Isothermal level (K)
21 21 Lowest level where mass density exceeds the specified value (base for a given threshold of mass density) (kg m-3)
22 22 Highest level where mass density exceeds the specified value (top for a given threshold of mass density) (kg m-3)
23 23 Lowest level where air concentration exceeds the specified value (base for a given threshold of air concentration) (Bq m-3)
24 24 Highest level where air concentration exceeds the specified value (top for a given threshold of air concentration) (Bq m-3)
# 25-99 Reserved 
100 pl Isobaric surface (Pa)
101 sfc Mean sea level 
102 102 Specific altitude above mean sea level (m)
103 sfc Specified height level above ground (m)
104 104 Sigma level (sigma value)
105 ml Hybrid level (-)
106 sfc Depth below land surface (m)
107 pt Isentropic (theta) level (K)
108 108 Level at specified pressure difference from ground to level (Pa)
109 pv Potential vorticity surface (K m2 kg-1 s-1)
110 110 Reserved 
111 111 Eta level (-)
112 112 Reserved 
113 113 Logarithmic hybrid level 
114 114 Snow level (Numeric)
115 115 Sigma height level
# 116 Reserved
117 117 Mixed layer depth (m)
118 hhl Hybrid height level (-)
119 hpl Hybrid pressure level (-)
# 120-149 Reserved 
150 150 Generalized vertical height coordinate 
151 sol Soil level (Numeric)
# 152-159 Reserved 
160 160 Depth below sea level (m)
161 161 Depth below water surface (m)
162 162 Lake or river bottom (-)
163 163 Bottom of sediment layer (-)
164 164 Bottom of thermally active sediment layer (-)
165 165 Bottom of sediment layer penetrated by thermal wave (-)
166 166 Mixing layer (-)
167 167 Bottom of root zone (-)
# 168-173 Reserved 
174 174 Top surface of ice on sea, lake or river
175 175 Top surface of ice, under snow cover, on sea, lake or river
176 176 Bottom surface (underside) ice on sea, lake or river
177 sfc Deep soil (of indefinite depth)
# 178 Reserved
179 179 Top surface of glacier ice and inland ice
180 180 Deep inland or glacier ice (of indefinite depth)
181 181 Grid tile land fraction as a model surface
182 182 Grid tile water fraction as a model surface
183 183 Grid tile ice fraction on sea, lake or river as a model surface
184 184 Grid tile glacier ice and inland ice fraction as a model surface
# 185-191 Reserved 
# 192-254 Reserved for local use 
255 255 Missing