Universität zu Köln

Griewank, Philipp J., Heus, Thijs ORCID: 0000-0003-2650-2423 and Neggers, Roel A. J. (2022). Size-Dependent Characteristics of Surface-Rooted Three-Dimensional Convective Objects in Continental Shallow Cumulus Simulations. J. Adv. Model. Earth Syst., 14 (3). WASHINGTON: AMER GEOPHYSICAL UNION. ISSN 1942-2466

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Abstract

A segmentation algorithm is applied to high resolution simulations of shallow continental convection to identify individual convective 3D objects within the convective boundary layer, in order to investigate which properties of the objects vary with the object width. The study analyses the geometry of the objects, along with their profiles of vertical velocity and total water, to assess various assumptions often used in spectral mass-flux convection schemes. The methodology of this paper is unique in that we use (a) a novel application of the watershed algorithm to detect individual objects in the constantly evolving continental boundary layer efficiently, and (b) an unprecedentedly large number of simulations being analyzed. In total, 26 days of LASSO simulations at the Atmospheric Radiation Measurement Southern Great Plains site are analyzed, yielding roughly one million objects. Plume-like surface-rooted objects are found to be omnipresent, the vertical extent of which is strongly dependent on the object width. The vertical velocity and moisture anomaly profiles of the widest objects are roughly consistent with the classic buoyancy-driven rising plume model. The kinematic and thermodynamic properties of the objects vary with object width. This width dependence is strongest above cloud base, but much weaker below. Finally the impact of neglecting the contribution of covariances to the vertical moisture flux, which is commonly used in mass-flux parameterizations, is investigated. The average effect of neglecting covariances increases linearly with object width, leading to a 20% flux underestimation for 2 km wide objects. Implications of the results for spectral convection scheme development are briefly discussed.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Griewank, Philipp J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Heus, Thijs UNSPECIFIED orcid.org/0000-0003-2650-2423 UNSPECIFIED Neggers, Roel A. J. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-676291
DOI:	10.1029/2021MS002612
Journal or Publication Title:	J. Adv. Model. Earth Syst.
Volume:	14
Number:	3
Date:	2022
Publisher:	AMER GEOPHYSICAL UNION
Place of Publication:	WASHINGTON
ISSN:	1942-2466
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language LARGE-EDDY SIMULATION; COHERENT STRUCTURES; BOUNDARY-LAYER; CLOUD ENSEMBLE; PARAMETERIZATION; TURBULENCE; REPRESENTATION; STATISTICS; RESOLUTION; DYNAMICS Multiple languages Meteorology & Atmospheric Sciences Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/67629