Naslov
Comparison of different configurations of the TOUCANS system of turbulence parametrizations

Autori
Hrastinski, Mario ; Horvath, Kristian ; Tudor, Martina ; Kovačić, Tomislav ; Odak Plenković, Iris

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Skup
34th International Conference on Alpine Meteorology (ICAM)

Mjesto i datum
Reykjavík, Island, 18.06.2017. - 24.06.2017

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
TOUCANS ; turbulence parametrization ; turbulence kinetic energy (TKE) ; turbulence total energy (TTE) ; TKE budget ; emulation ; tower measurements ; mixing length ;

Sažetak
Third Order moments Unified Condensation Accounting and N-dependent Solver – TOUCANS is a compact 2.5 level parametrization of turbulence, which integrates several ideas into its framework: non existence of critical Richardson number (Ricr), anisotropy of turbulence, prognostic treatment of Turbulent Kinetic Energy (TKE) and Total Turbulent Energy (TTE), inclusion of moisture influence on turbulence, as well as the possibility of prognostic treatment of mixing length and 3D turbulence parametrization. TOUCANS is based on the framework of four free parameters which influence the basic properties of the scheme and three functional dependencies which define the shape of stability functions. By adjusting the scheme parameters and modifying the stability component in functional dependencies, TOUCANS is able to emulate more advanced turbulence parametrizations like Quas-Normal Scale Elimination (QNSE) and Energy- and Flux-Budget (EFB). On the other hand, TOUCANS is able to go step backwards, i.e. it can emulate its long term predecessor – diagnostic Louis scheme. In this work we use the emulation property of the TOUCANS system and compare the performance of turbulence parametrizations mentioned above, focusing on the TKE and covariances, along with the terms of the TKE budget equation. For this purpose we run the non-hydrostatic regional NWP ALADIN-HR 2 km horizontal grid spacing model with 37 vertical levels during the episode of bora downslope windstorm. Furthermore, we compare the performance of the currently operational Geleyn-Cedilnik mixing length formulation against TKE-based formulations, e.g. Bougeault-Lacarrere and Deardorff. Model outputs are verified against the three level (10, 22 and 40 m AGL) 3D 5 Hz ultrasonic tower measurements at the top of Pometeno Brdo (≈ 600 ASL) in the hinterland of Split, Croatia. Additionally, the results are compared to the WRF-LES simulations. The observational and model analysis suggests dominant contribution of mechanic production and TKE dissipation terms of the TKE budget, but large portion of TKE also originates from the non-local turbulence. We discuss the applicability of the simplified 1D TKE budget equation to this bora case, as well as the impact of different configurations of the TOUCANS system to the TKE forecast, with an emphasis on the link between the TKE and mixing length.

Izvorni jezik
Engleski

Znanstvena područja
Geofizika

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