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Nonlinear Processes in Geophysics An interactive open-access journal of the European Geosciences Union
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Volume 21, issue 2
Nonlin. Processes Geophys., 21, 489–501, 2014
https://doi.org/10.5194/npg-21-489-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Nonlinear processes of Air-Sea/Land interaction: from observations...

Nonlin. Processes Geophys., 21, 489–501, 2014
https://doi.org/10.5194/npg-21-489-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 11 Apr 2014

Research article | 11 Apr 2014

The role of subsidence in a weakly unstable marine boundary layer: a case study

I. M. Mazzitelli1, M. Cassol2, M. M. Miglietta3, U. Rizza3, A. M. Sempreviva4,5, and A. S. Lanotte3,6 I. M. Mazzitelli et al.
  • 1Dip. Ingegneria dell'Innovazione, Univ. del Salento, 73100 Lecce, Italy
  • 2Multidisciplinary Institute, Fed. Rur. Univ. of Rio de Janeiro, Nova Iguaçu-RJ, CEP 26020-740, Brazil
  • 3CNR-ISAC Institute of Atmospheric Sciences and Climate, UOS di Lecce, 73100 Lecce, Italy
  • 4CNR-ISAC Institute of Atmospheric Sciences and Climate, UOS di Lamezia Terme, 88046 Lamezia Terme, Italy
  • 5Technical University of Denmark, Wind Energy Department, Risoe Campus, Roskilde, Denmark
  • 6INFN, Sez. di Lecce, 73100 Lecce, Italy

Abstract. The diurnal evolution of a cloud free, marine boundary layer is studied by means of experimental measurements and numerical simulations. Experimental data belong to an investigation of the mixing height over inner Danish waters. The mixed-layer height measured over the sea is generally nearly constant, and does not exhibit the diurnal cycle characteristic of boundary layers over land. A case study, during summer, showing an anomalous development of the mixed layer under unstable and nearly neutral atmospheric conditions, is selected in the campaign. Subsidence is identified as the main physical mechanism causing the sudden decrease in the mixing layer height. This is quantified by comparing radiosounding profiles with data from numerical simulations of a mesoscale model, and a large-eddy simulation model. Subsidence not only affects the mixing layer height, but also the turbulent fluctuations within it. By analyzing wind and scalar spectra, the role of subsidence is further investigated and a more complete interpretation of the experimental results emerges.

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