1#Code table 4.5: Fixed surface types and units 20 0 Reserved 31 sfc Ground or water surface 42 2 Cloud base level 53 3 Level of cloud tops 64 4 Level of 0 degree C isotherm 75 5 Level of adiabatic condensation lifted from the surface 86 6 Maximum wind level 97 sfc Tropopause 108 sfc Nominal top of the atmosphere 119 9 Sea bottom 1210 10 Entire atmosphere 1311 11 Cumulonimbus (CB) base (m) 1412 12 Cumulonimbus (CB) top (m) 15# 13-19 Reserved 1620 20 Isothermal level (K) 17#21-99 Reserved 18100 pl Isobaric surface (Pa) 19101 sfc Mean sea level 20102 102 Specific altitude above mean sea level (m) 21103 sfc Specified height level above ground (m) 22104 104 Sigma level (sigma value) 23105 ml Hybrid level 24106 sfc Depth below land surface (m) 25107 pt Isentropic (theta) level (K) 26108 108 Level at specified pressure difference from ground to level (Pa) 27109 pv Potential vorticity surface (K m2 kg-1 s-1) 28110 110 Reserved 29111 111 Eta level 30# 112-116 Reserved 31117 117 Mixed layer depth (m) 32118 hhl Hybrid height level 33119 hpl Hybrid pressure level 34# 120-159 Reserved 35160 160 Depth below sea level (m) 36#161-191 Reserved 37#192-254 Reserved for local use 38255 255 Missing 39