A test of ice self-collection kernels using aircraft data

• Published in: Journal of the atmospheric sciences Vol. 63; no. 2; pp. 651 - 666
• Main Authors: FIELD, P. R, HEYMSFIELD, A. J, BANSEMER, A
• Format: Journal Article
• Language: English
• Published: Boston, MA American Meteorological Society 01.02.2006
• Subjects: Aircraft; Cloud physics; Clouds; Drop size distribution; Earth, ocean, space; Exact sciences and technology; External geophysics; Ice; Meteorology; Particle size; Relative humidity; Aggregation; Relative humidity; Kernel function; Ice crystals; Particle size distribution; Cirrus; Aircraft observation; tropical zone; Convective cloud; troposphere; Ice cloud; storms
• ISSN: 0022-4928; 1520-0469
• DOI: 10.1175/jas3653.1

Aircraft observations from the Cirrus Regional Study of Tropical Anvils and Cirrus Layers (CRYSTAL)-Florida Area Cirrus Experiment (FACE) campaign obtained in the anvil of a large convective storm from 26 July 2002 are presented. During this flight a Lagrangian spiral descent was made, allowing the evolution of the ice particle size distribution to be followed. Relative humidities during 61 km (from -11' to -3'C) of the descent were within 4% of ice saturation. It was assumed that the ice particle size distribution was evolving through the process of aggregation alone. Three idealized ice-ice collection kernels were used in a model of ice aggregation and compared to the observed ice particle size distribution evolution: a geometric sweep-out kernel, a Golovin (sum of particle masses) kernel, and a modified-Golovin kernel (sum of particle masses raised to a power). The Golovin kernel performed worst. The sweep-out kernel produced good agreement with the observations when a constant aggregation efficiency of 0.09 was used. The modified-Golovin kernel performed the best and implied that the aggregation efficiency of sub-300-km particles was greater than unity when compared with a geometric sweep-out kernel.