Sodar Detected Top-Down Convection in a Nocturnal Cloud-Topped Boundary Layer: A Case Study

Authors: P. Martano¹; D. Cava²; G. Mastrantonio²; S. Argentini³; A. Viola³

Source: Boundary-Layer Meteorology, Volume 115, Number 1, April 2005 , pp. 85-103(19)

Publisher: Springer

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Abstract:

Nocturnal convection, originating in a well-mixed marine cloud-topped boundary layer, advected onshore, was observed using a Doppler sodar on the Tyrrhenian coast in Italy. The horizontal and vertical dimensions of the downdrafts were evaluated. The oscillation frequency triggered by the downdrafts at the inversion layer, derived from the harmonic analysis of the sodar measured vertical velocity (w), is compared with the Brunt-Vaisala frequency, obtained from the rawinsonde temperature profile. A similarity function for the sigma

²_w vertical profile was used to fit the sodar experimental data and to retrieve the depth of the mixing layer and the sensible heat flux at the top of the cloud layer. The results are in agreement with the convection layer depth observed in the sodar echoes facsimile record, and with the energy budget evaluated at the top of the cloud layer using the rawinsonde profiles.

Keywords: cloud-topped boundary layer; cloud-top radiative cooling; doppler sodar; entrainment; nocturnal convection

Document Type: Research article

DOI: http://dx.doi.org/10.1007/s10546-004-3648-9

Affiliations: 1: ISAC – Institute of Atmosphere and Climate Sciences, National Research Council, Section of Lecce, Italy, Email: p.martano@isac.cnr.it 2: ISAC – Institute of Atmosphere and Climate Sciences, National Research Council, Section of Lecce, Italy, 3: ISAC – Institute of Atmosphere and Climate Sciences, National Research Council, Section of Roma, Italy,

Publication date: 2005-04-01