WMO Code table 3 - Fixed levels or layers for which the data are included



	Octet 10	Octet 11	Octet 12
Code figure	Meaning	Contents
00	Reserved
01	Ground or water surface	0
02	Cloud base level	0
03	Level of cloud tops	0
04	Level of 0°C isotherm	0
05	Level of adiabatic condensation lifted from the surface	0
06	Maximum wind level	0
07	Tropopause	0
08	Nominal top of atmosphere	0
09	Sea bottom	0
10-19	Reserved
20	Isothermal level	Temperature in 1/100 K
21-99	Reserved
100	Isobaric surface	Pressure in hPa (2 octets)
101	Layer between two isobaric surfaces	Pressure of top in kPa	Pressure of bottom in kPa
102	Mean sea level	0
103	Specified altitude above mean sea level	Altitude in meters (2 octets)
104	Layer between two specified altitudes above mean sea level	Altitude of top in hm	Altitude of bottom in hm
105	Specified height above ground	Height in meters (2 octets)
106	Layer between two specified height levels above ground	Height of top in hm	Height of bottom in hm
107	Sigma level	Sigma value in 1/10000 (2 octets)
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 (2 octets)
110	Layer between two hybrid levels	Level number of top	Level number of bottom
111	Depth below land surface	Depth in centimeters (2 octets)
112	Layer between two depths below land surface	Depth of upper surface in cm	Depth of lower surface in cm
113	Isentropic (theta) level	Potential temperature in K (2 octets)
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 from ground to level	Pressure difference in hPa (2 octets)
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 bottom level in hPa
117	Potential vorticity surface	10-9 K m2 kg-1 s-1
118	Reserved
119	ETA* level	ETA value in 1/10000 (2 octets)
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
122-124
125	Specified height level above ground (high precision)	Height in centimeters (2 octets)
126-127	Reserved
128	Layer between two sigma levels (high precision)	1.1 minus sigma of top in 1/1000 of sigma	1.1 minus sigma of bottom in 1/1000 of sigma
129-140
141	Layer between two isobaric surfaces (mixed precision)	Pressure of top in kPa	1100 hPa minus pressure of bottom in hPa
142-159	Reserved
160	Depth below sea level	Depth in meters (2 octets)
161-199	Reserved
200	Entire atmosphere (considered as a single layer)	0
201	Entire ocean (considered as a single layer)	0
202-254	Reserved
* 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.




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