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Level types

Level types are a construct of our atmospheric data models and reflect the layers within a model. Every parameter is generated within a level type which are either single or multi-layered.

Single level types relate to a particular level in the model and are one of the following:

  • atmosphere
  • cloud base (cloudbaseforcloudcover)
  • convective cloud base (convectivecloudbottom)
  • convective cloud top (convectivecloudtop)
  • effective inflow layer base (effinflowlayerbase)
  • effective inflow layer top (effinflowlayertop)
  • ground (or water surface)
  • maximum wind (maxwind)
  • mean sea level (meansea)
  • mixed layer CAPE equilibrium (mixedlayercapeequil)
  • mixing - planetary boundary layer
  • most unstable CAPE equilibrium (mostunstcapeequil)
  • most unstable departure level (mudl)
  • top of atmosphere (atmospheretop) - nominal top of the atmosphere
  • tropopause - the interface between the troposphere and the stratosphere
  • Wet bulb freezing level (wbzeroisotherm)
  • Freezing level (zeroisotherm) - level of the 0 degree C isotherm

Multi level types have many layers in the model and are currently either:

  • Height level or agl (above ground level) which has 34 model levels ranging from 5m to 6000m
  • Pressure level or isbl (isobaric level) which has 33 model levels from 1000hPa to 20hPa
  • Depth level or dbly (depth boundary layer) which has 4 model levels from 0.05m to 2m beneath the surface

In a small number of special cases parameters relate only to a single level of the model but that level is part of the multi-level layers. In these cases whilst the parameter only exists and is selected as single level the parameter is delivered in the api at the specified model level. This is currently true for the following levels:

  • 1.5m - often called screen level and equivalent to 1.5m above ground level
  • (agl) - the height of many measuring stations
  • 10m - often used to measure/ forecast wind parameters and equivalent to 10m agl
  • 700hPa - specifically used to provide a measure of vertical wind velocity and wet bulb potential temperature from the model at the 700hPa pressure level
  • 500, 850 & 925hPa wet bulb potential temperature is also available at these pressure levels - note different levels apply in global and uk model