engleski

Mixing length-scale for inclined stable boundary layers

It has been recognized for quite some time that current numerical mesoscale models often represent stable atmospheric boundary layers (SABL) poorly in terms of the SABL depth, near-surface inversion characteristics, low-level wind profiles and overall mixing properties. Since the SABL structures are far from being fully understood today, their parameterizations or explicit treatment are still usually very sketchy in most mesoscale and climate models. Typically an over- diffusion through the SABL occurs in most of numerical models. The mixing length-scale within the SABL, i.e. in the „ z-less“ regime, as often parameterized in mesoscale models with higher- order closure turbulence schemes, is addressed. We intend to improve this length-scale by including shear effects explicitly. With the “ z-less” mixing length-scale proposed here the over- diffusion is absent but sharp gradients still exist. Moreover, the mesoscale MIUU model used gave results similar to those from an improved Prandtl model (also addressed by L. Gutman), i.e. katabatic flow occupying the lower and more active part of the SABL developed in both models. The corresponding low-level jet (LLJ) that is imbedded in the strong near-surface inversion (NSI) appears similar in both models. Certain details about the corresponding LLJ and NSI vary simply because of very different nature of the models deployed. The results could be used in different types of numerical modelling, parameterizations of the SABL, further development of analytical models and data interpretation.

Low-level jet; MIUU mesoscale model; Monin-Obukhov length; Prandtl model; turbulence; Temperature inversion;

Prof.dr.sc. Branko Grisogono bio je član međunarodnog programskog odbora konferencije, a pozvan je sa strane voditelja sekcije: Arakela Petrosyana i Sergeja Zilitinkevicha.