Formulation of the Thermal Internal Boundary Layer in a Mesoscale Model

Mesoscale models using a non-local K-scheme for parameterixation of boundary-layer processes require an estimate of the planetary boundary layer (PBL) height z, at all times. In this paper, two-dimensional sea-breeze experiments are carried out to evaluate three different formulations for the advective contribution in the zi prognostic equation of Deardorff (1974). Poor representation of the thermal internal boundary layer in the sea breeze is obtained when zi is advected by the wind at level zi. However, significantly better results are produced if the mean PBL wind is used for the advecting velocity, or if z, is determined simply by checking for the first ‘sufficiently’ stable layer above the ground. A Lagrangian particle model is used to demonstrate the effect of each formulation on plume dispersion by the sea breeze.