Experimental Evaluation of Collection and Coalescence Efficiencies of Cloud Drops

Zev Levin Dept. of Environmental Sciences, Tel-Aviv University, Ramat Aviv, Israel

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Morris Neiburger Dept. of Meteorology, University of California, Los Angeles

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Lawrence Rodriguez Dept. of Meteorology, University of California, Los Angeles

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Abstract

Collection efficiencies of drops of radius A less than 120 µm falling through clouds of drop radius a for which the size ratio p=a/A was between 0.18 and 0.23 were found experimentally to be considerably lower than the corresponding theoretically computed collision efficiency. Assuming the difference to be due to failure of some of the colliding drops to coalesce, the coalescence efficiency was computed and found to decrease with increasing p, in qualitative agreement with the results of Whelpdale and List obtained for much larger collector drops.

Abstract

Collection efficiencies of drops of radius A less than 120 µm falling through clouds of drop radius a for which the size ratio p=a/A was between 0.18 and 0.23 were found experimentally to be considerably lower than the corresponding theoretically computed collision efficiency. Assuming the difference to be due to failure of some of the colliding drops to coalesce, the coalescence efficiency was computed and found to decrease with increasing p, in qualitative agreement with the results of Whelpdale and List obtained for much larger collector drops.

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