During this working session some topics, especially from the main lectures of the workshop, were analysed in more detail. The discussion focused on these important topics:

Laminar layer

Introduction of a new layer (laminar layer) nearest the surface can improve the vertical structure of turbulent fluxes (idea of Harald Seidl). Implementation raises technical difficulties in the current structure of ALADIN.

Richardson number

Computation of this variable is very sensitive to meteorological situations, especially wind shear. André Simon analysed the contribution of the tuning parameters USURID , USURIDE to the critical Richardson number, which has direct influence on the turbulent fluxes computation. For cyclogenesis and atmospheric inversion the opposite effect on the Richardson number has been observed.

PBL depth

Vertical oscillations of turbulent fluxes have been observed in the PBL. Spatial and temporal resolution (ALADIN-ARPEGE) dependence is visible. The temperature fields nearest the surface were studied for this reason (by Martina Tudor). Improvement is expected from tuning the anti-fibrillation scheme.

Shallow convection

Discussion about cloudiness problem (Harald Seidl and Jean-Marcel Piriou). Stratocumulus clouds are sometimes represented by one model layer, which triggers model representation difficulties. It is convenient to find more case studies for analyses of model behaviour compared with reality.

Turbulent Kinetic Energy

TKE as prognostic variable can solve some current problems (anti-fibrillation scheme, ...). Discussion was about initialization and implementation of this variable to the ALADIN structure (half or full level ...).

Collaboration

To improve the scientific possibilities, communication is necessary.

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