Code table 4.5 - Fixed surface types and units



Code figure	Meaning	Units
0	Reserved
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	-
10-19	Reserved
20	Isothermal level	K
21-99	Reserved
100	Isobaric surface	Pa
101	Mean sea level	-
102	Specific altitude above mean sea level	m
103	Specific height level above ground	m
104	Sigma level	"sigma" value
105	Hybrid level	-
106	Depth below land suface	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	-
112-116	Reserved
117	Mixed layer depth	m
118-159	Reserved
160	Depth below sea level	m
161-191	Reserved
192-254	Reserved for local use
255	Missing




Note*

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