Stable atmospheric surface layer in modelling with constant ground temperature

Influence of the surface roughness, geostrophic wind speed and initial stable stratification on surface layer scales, namely the friction velocity, temperature scale and the Monin-Obukhov length, and on non-dimensional profiles has been studied in quasi-stationary PIAPBLM ((P) under bar rague (I) under bar nstitute of (A) under bar tmospheric (P) under bar hysics (B) under bar oundary (L) under bar ayer (M) under bar odel) runs. Modifications of the stability functions, of the non-local mixing length concept, and of surface layer parametrization have improved the model results. With the ground temperature kept constant in time, the boundary layer is subjected to a turbulent cooling induced by surface roughness and to a counteracting turbulent heat transfer directed downwards. If the wind speed is lower, a rather mixed layer capped by a more stable layer. The estimated Monin-Obukhov length then slightly increases and the non-dimensional gradients overpredict the empirical values even more.