Table 4.5 https://www.nco.ncep.noaa.gov/pmb/docs/grib2/grib2_doc/grib2_table4-5.shtml Ground or Water Surface Cloud Base Level Level of Cloud Tops Level of 0o C Isotherm Level of Adiabatic Condensation Lifted from the Surface Maximum Wind Level Tropopause Nominal Top of the Atmosphere Sea Bottom Entire Atmosphere Cumulonimbus Base (CB) Cumulonimbus Top (CT) Lowest level where vertically integrated cloud cover exceeds the specified percentage (cloud base for a given percentage cloud cover) Level of free convection (LFC) Convection condensation level (CCL) Level of neutral buoyancy or equilibrium (LNB) Isothermal Level Lowest level where mass density exceeds the specified value (base for a given threshold of mass density) Highest level where mass density exceeds the specified value (top for a given threshold of mass density) Lowest level where air concentration exceeds the specified value (base for a given threshold of air concentration Highest level where air concentration exceeds the specified value (top for a given threshold of air concentration) Highest level where radar reflectivity exceeds the specified value (echo top for a given threshold of reflectivity) Isobaric Surface Mean Sea Level Specific Altitude Above Mean Sea Level Specified Height Level Above Ground Sigma Level Hybrid Level Depth Below Land Surface Isentropic (theta) Level Level at Specified Pressure Difference from Ground to Level Potential Vorticity Surface Eta Level Logarithmic Hybrid Level Snow Level Sigma height level (see Note 4) Mixed Layer Depth Hybrid Height Level Hybrid Pressure Level Generalized Vertical Height Coordinate (see Note 4) Soil level (See Note 5) Depth Below Sea Level Depth Below Water Surface Lake or River Bottom Bottom Of Sediment Layer Bottom Of Thermally Active Sediment Layer Bottom Of Sediment Layer Penetrated By Thermal Wave Mixing Layer Bottom of Root Zone Ocean Model Level Ocean level defined by water density (sigma-theta) difference from near-surface to level (see Note 7) Ocean level defined by water potential temperature difference from near-surface to level (see Note 7) Top Surface of Ice on Sea, Lake or River Top Surface of Ice, under Snow, on Sea, Lake or River Bottom Surface (underside) Ice on Sea, Lake or River Deep Soil (of indefinite depth) Top Surface of Glacier Ice and Inland Ice Deep Inland or Glacier Ice (of indefinite depth) Grid Tile Land Fraction as a Model Surface Grid Tile Water Fraction as a Model Surface Grid Tile Ice Fraction on Sea, Lake or River as a Model Surface Grid Tile Glacier Ice and Inland Ice Fraction as a Model Surface Entire atmosphere (considered as a single layer) Entire ocean (considered as a single layer) Highest tropospheric freezing level Grid scale cloud bottom level Grid scale cloud top level Boundary layer cloud bottom level Boundary layer cloud top level Boundary layer cloud layer Low cloud bottom level Low cloud top level Low cloud layer Cloud ceiling Planetary Boundary Layer Layer Between Two Hybrid Levels Middle cloud bottom level Middle cloud top level Middle cloud layer High cloud bottom level High cloud top level High cloud layer Ocean Isotherm Level (1/10 C) Layer between two depths below ocean surface Bottom of Ocean Mixed Layer (m) Bottom of Ocean Isothermal Layer (m) Layer Ocean Surface and 26C Ocean Isothermal Level Ocean Mixed Layer Ordered Sequence of Data Convective cloud bottom level Convective cloud top level Convective cloud layer Lowest level of the wet bulb zero Maximum equivalent potential temperature level Equilibrium level Shallow convective cloud bottom level Shallow convective cloud top level Deep convective cloud bottom level Deep convective cloud top level Lowest bottom level of supercooled liquid water layer Highest top level of supercooled liquid water layer Missing