Modelling the Stable Boundary Layer in Operational Weather Forecasting: Current Issues

Accurate parametrization of processes in the stable boundary layer (SBL) is important for the forecasting of meteorological fields at night, and especially the near-surface air temperature. Traditionally, the modelling of the SBL has been considered problematic and turbulence schemes with enhanced mixing are employed in operational forecasting models.

The parametrization of turbulent mixing is only one process of relevance to the SBL and the nocturnal surface flux budget is also greatly affected by other aspects of the forecasting model, such as its representation of cloud cover. Improved representation of such associated processes facilitates the introduction of more realistic turbulence schemes, without causing a loss of performance. Recently, a sharp-tailed mixing scheme has been introduced into high-resolution operational forecasting at the Met Office, leading to lower and more realistic minimum temperatures on clear nights. However, a general warm bias still persists.

We present a review of the current position, including illustrative forecasts. Comparisons with field observations and remotely sensed data are used to assess these forecasts and suggest areas for future development. The importance of land-surface processes in further improving forecasts is emphasized.