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Title: The Mechanism of First Raindrops Formation in Deep Convective Clouds

Abstract

The formation of first raindrops in deep convective clouds is investigated. A combination of observational data analysis and 2-D and 3-D numerical bin microphysical simulations of deep convective clouds suggests that the first raindrops form at the top of undiluted or slightly diluted cores. It is shown that droplet size distributions in these regions are wider and contain more large droplets than in diluted volumes. The results of the study indicate that the initial raindrop formation is determined by the basic microphysical processes within ascending adiabatic volumes. It allows one to predict the height of the formation of first raindrops considering the processes of nucleation, diffusion growth and collisions. The results obtained in the study explain observational results reported by Freud and Rosenfeld (2012) according to which the height of first raindrop formation depends linearly on the droplet number concentration at cloud base. The results also explain why a simple adiabatic parcel model can reproduce this dependence. The present study provides a physical basis for retrieval algorithms of cloud microphysical properties and aerosol properties using satellites proposed by Rosenfeld et al. ( 2012). The study indicates that the role of mixing and entrainment in the formation of the first raindropsmore » is not of crucial importance. It is also shown that low variability of effective and mean volume radii along horizontal traverses, as regularly observed by in situ measurements, can be simulated by high-resolution cloud models, in which mixing is parameterized by a traditional 1.5 order turbulence closure scheme.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1094915
Report Number(s):
PNNL-SA-92209
KP1701000
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Journal of Geophysical Research. D. (Atmospheres), 118(16):9123-9140
Additional Journal Information:
Journal Name: Journal of Geophysical Research. D. (Atmospheres), 118(16):9123-9140
Country of Publication:
United States
Language:
English
Subject:
mechanism; rain; formation; deep; cumulus; clouds

Citation Formats

Khain, Alexander, Prabha, Thara, Benmoshe, Nir, Pandithurai, G., and Ovchinnikov, Mikhail. The Mechanism of First Raindrops Formation in Deep Convective Clouds. United States: N. p., 2013. Web. doi:10.1002/jgrd.50641.
Khain, Alexander, Prabha, Thara, Benmoshe, Nir, Pandithurai, G., & Ovchinnikov, Mikhail. The Mechanism of First Raindrops Formation in Deep Convective Clouds. United States. https://doi.org/10.1002/jgrd.50641
Khain, Alexander, Prabha, Thara, Benmoshe, Nir, Pandithurai, G., and Ovchinnikov, Mikhail. 2013. "The Mechanism of First Raindrops Formation in Deep Convective Clouds". United States. https://doi.org/10.1002/jgrd.50641.
@article{osti_1094915,
title = {The Mechanism of First Raindrops Formation in Deep Convective Clouds},
author = {Khain, Alexander and Prabha, Thara and Benmoshe, Nir and Pandithurai, G. and Ovchinnikov, Mikhail},
abstractNote = {The formation of first raindrops in deep convective clouds is investigated. A combination of observational data analysis and 2-D and 3-D numerical bin microphysical simulations of deep convective clouds suggests that the first raindrops form at the top of undiluted or slightly diluted cores. It is shown that droplet size distributions in these regions are wider and contain more large droplets than in diluted volumes. The results of the study indicate that the initial raindrop formation is determined by the basic microphysical processes within ascending adiabatic volumes. It allows one to predict the height of the formation of first raindrops considering the processes of nucleation, diffusion growth and collisions. The results obtained in the study explain observational results reported by Freud and Rosenfeld (2012) according to which the height of first raindrop formation depends linearly on the droplet number concentration at cloud base. The results also explain why a simple adiabatic parcel model can reproduce this dependence. The present study provides a physical basis for retrieval algorithms of cloud microphysical properties and aerosol properties using satellites proposed by Rosenfeld et al. ( 2012). The study indicates that the role of mixing and entrainment in the formation of the first raindrops is not of crucial importance. It is also shown that low variability of effective and mean volume radii along horizontal traverses, as regularly observed by in situ measurements, can be simulated by high-resolution cloud models, in which mixing is parameterized by a traditional 1.5 order turbulence closure scheme.},
doi = {10.1002/jgrd.50641},
url = {https://www.osti.gov/biblio/1094915}, journal = {Journal of Geophysical Research. D. (Atmospheres), 118(16):9123-9140},
number = ,
volume = ,
place = {United States},
year = {Thu Aug 22 00:00:00 EDT 2013},
month = {Thu Aug 22 00:00:00 EDT 2013}
}