The Atmospheric Boundary Layer

The correct representation of the turbulence in the boundary layer, typically the lowest kilometre of the atmosphere, is critical in providing good weather forecasts and climate predictions.

The boundary layer is defined as that part of the atmosphere that directly feels the effect of the earth's surface.  Its depth can range from just a few metres to several kilometres depending on the local meteorology.  Turbulence is generated in the boundary layer as the wind blows over the earth's surface and by thermals, such as those rising from land as it is heated by the sun, but also thermals associated with clouds.  All this turbulence redistributes heat, moisture and the drag on the wind within the boundary layer, as well as pollutants and other constituents of the atmosphere.  In so doing it plays a crucial role in modulating the weather (temperature, humidity, wind strength, air quality, etc) as we experience it, living on the surface.  The strength of turbulent mixing is extremely variable  and understanding that variability is a key aspect of boundary layer research at the Met Office.  Much of this is modulated through interactions with the surface and so close links are maintained with those working on surface processes.

Much of our research involves the use of very high resolution numerical modelling of the boundary layer using the Large Eddy Model which allows us to explore sensitivities and so improve understanding.  An important aspect of that work is confronting these models with observations, often made by Met Office staff in Observations Based Research, or through international model intercomparison projects such as those run by GCSS and GABLS.

Key aims

  • to improve forecasts of near-surface weather parameters (such as temperature, wind speed, visibility, etc) and boundary layer clouds through an improved representation of boundary layer turbulent transports in the Met Office Unified Model 

  • to improve our understanding of physical processes in the atmospheric boundary layer

Current projects

  • Improving forecasts of near-surface temperatures and boundary layer cloud over the UK and the uncertainty in those predictions

  • Evaluation of alternative closure models for boundary layer turbulence at high resolution, in collaboration with JMA

  • Understanding cloud responses under climate change, in collaboration with GCSS BLCWG (Boundary Layer Cloud Working Group) and CFMIP

  • Improving the representation of boundary layer heterogeneity and fog in complex terrain, including close collaboration with Observation Based Research (OBR) through the COLPEX campaign

  • Improving the representation of mesoscale horizontal structures in stratocumulus clouds, comparing UM simulations of stratocumulus clouds at a variety of resolutions with  detailed observations in the SE Pacific from the VOCALS campaign.

Last updated: 3 September 2013