Relationship between the Vertical Velocity Skewness and Kurtosis Observed during Sea-Breeze Convection

S. Alberghi ISAC-CNR, Bologna, Italy

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A. Maurizi ISAC-CNR, Bologna, Italy

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F. Tampieri ISAC-CNR, Bologna, Italy

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Abstract

Fourth-order moments of vertical velocity in the convective boundary layer (CBL) are seldom available because the unsteady nature of atmospheric flows makes time statistics unreliable for the evaluation of high-order moments. In this paper, sound detection and ranging (sodar) measurements in well-developed, almost steady convective conditions are selected and analyzed to investigate the relationship between skewness and kurtosis. Moments of vertical velocity up to the fourth order are computed with special attention to the assessment of the errors connected to the number of independent data and to the inherent spatial and temporal filtering of the measuring system. Results show that a significant correlation between skewness and kurtosis exists in the lower half of the CBL, and a quadratic relationship is proposed that is similar to the one valid for alongwind velocity in shear-dominated boundary layers.

Corresponding author address: A. Maurizi, ISAC-CNR, via Gobetti 101, I-40129 Bologna, Italy. a.maurizi@isac.cnr.it

Abstract

Fourth-order moments of vertical velocity in the convective boundary layer (CBL) are seldom available because the unsteady nature of atmospheric flows makes time statistics unreliable for the evaluation of high-order moments. In this paper, sound detection and ranging (sodar) measurements in well-developed, almost steady convective conditions are selected and analyzed to investigate the relationship between skewness and kurtosis. Moments of vertical velocity up to the fourth order are computed with special attention to the assessment of the errors connected to the number of independent data and to the inherent spatial and temporal filtering of the measuring system. Results show that a significant correlation between skewness and kurtosis exists in the lower half of the CBL, and a quadratic relationship is proposed that is similar to the one valid for alongwind velocity in shear-dominated boundary layers.

Corresponding author address: A. Maurizi, ISAC-CNR, via Gobetti 101, I-40129 Bologna, Italy. a.maurizi@isac.cnr.it

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