Large-eddy simulation of the planetary boundary layer under baroclinic conditions during daytime and sunset turbulence

Authors


U. Rizza, ISAC-CNR, Istituto di Scienze dell'Atmosfera e del Clima, Consiglio Nazionale delle Ricerche, Strada Provinciale Lecce Monteroni, km.1.2, 73100, Lecce, Italy. E-mail: u.rizza@isac.cnr.it

Abstract

This study investigates the Large-Eddy Simulation (LES) technique in the diurnally varying atmospheric boundary layer in conditions of realistic environmental forcing. The initial settings of meteorological fields are obtained by ‘ingesting’ into the LES domain the vertical profiles of wind, temperature and specific humidity provided by the meteorological model WRF. The surface values of potential temperature and specific humidity from the WRF simulation are used as forcing parameters for the LES runs. These forcing parameters are updated during the runs every 1 h. A methodology is developed to derive the components of the geostrophic wind profile that is used in LES to model the large-scale horizontal mean pressure gradient and treated as an external forcing. This methodology involves the meteorological model WRF. In this context, the WRF model has a dual task: (1) providing realistic atmospheric environmental forcings to LES and (2) providing a very large dataset to investigate possible improvements of the LES setting to make the numerical prediction more realistic.

The principal results obtained by the present study is that the use of geostrophic wind shear profiles improves the prognostic capability of LES in reproducing the wind field pattern in the planetary boundary layer, this is an important parameter for the proper description of the decay of the turbulent kinetic energy at sunset. Copyright © 2012 Royal Meteorological Society

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