Unidata transcribe WMO306_Vol_I.2_2010_en.pdf Ground or water surface surface Cloud base level cloud_base Level of cloud tops cloud_tops Level of 0deg C isotherm zeroDegC_isotherm Level of adiabatic condensation lifted from the surface adiabatic_condensation_lifted Maximum wind level maximum_wind Tropopause tropopause Nominal top of the atmosphere atmosphere_top Sea bottom sea_bottom Isothermal level isotherm K Isobaric surface isobaric hPa Layer between 2 isobaric levels layer_between_two_isobaric hPa true Mean sea level msl Altitude above mean sea level altitude_above_msl m mean sea level true Layer between 2 altitudes above msl layer_between_two_altitudes_above_msl m true true Specified height level above ground height_above_ground m ground true Layer between 2 specified height level above ground layer_between_two_heights_above_ground m ground true true Sigma level sigma sigma Layer between 2 sigma levels layer_between_two_sigmas sigma true Hybrid level hybrid Layer between 2 hybrid levels layer_between_two_hybrids true Depth below land surface depth_below_surface cm ground Layer between 2 depths below land surface layer_between_two_depths_below_surface cm ground true Isentropic theta level isentrope K Layer between 2 isentropic levels layer_between_two_isentrope K true Level at specified pressure difference from ground to level pressure_difference hPa ground Layer between 2 level at pressure difference from ground to level layer_between_two_pressure_difference_from_ground hPa ground true Potential vorticity surface potential_vorticity_surface 1.0E-9 K.kg-1.m2.s-1 Eta level eta Layer between 2 Eta levels layer_between_two_eta true Layer between 2 isobaric levels layer_between_two_isobaric_surfaces hPa true Specified height level above ground height_above_ground cm ground true Layer between 2 sigma levels (hi precision) layer_between_two_sigmas_hi sigma true Layer between 2 isobaric surfaces (mixed precision) layer_between_two_isobaric_surfaces hPa true Depth below sea level depth_below_sea m sea level Entire atmosphere (considered as a single layer) entire_atmosphere Entire ocean (considered as a single layer) entire_ocean Isobaric surface (high precision) isobaric_surface Pa