Improving the representation of aggregation in a two-moment microphysical scheme with statistics of multi-frequency Doppler radar observations

<p>Aggregation is a key microphysical process for the formation of precipitable ice particles. Its theoretical description involves many parameters and dependencies among different variables that are either insufficiently understood or difficult to accurately represent in bulk microphysics sch...

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Autores principales:	M. Karrer, A. Seifert, D. Ori, S. Kneifel
Formato:	article
Lenguaje:	EN
Publicado:	Copernicus Publications 2021
Materias:	Physics QC1-999 Chemistry QD1-999
Acceso en línea:	https://doaj.org/article/32ffbac391f24e1eae046d555aece1ef
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spelling	oai:doaj.org-article:32ffbac391f24e1eae046d555aece1ef2021-11-25T08:09:13ZImproving the representation of aggregation in a two-moment microphysical scheme with statistics of multi-frequency Doppler radar observations10.5194/acp-21-17133-20211680-73161680-7324https://doaj.org/article/32ffbac391f24e1eae046d555aece1ef2021-11-01T00:00:00Zhttps://acp.copernicus.org/articles/21/17133/2021/acp-21-17133-2021.pdfhttps://doaj.org/toc/1680-7316https://doaj.org/toc/1680-7324<p>Aggregation is a key microphysical process for the formation of precipitable ice particles. Its theoretical description involves many parameters and dependencies among different variables that are either insufficiently understood or difficult to accurately represent in bulk microphysics schemes. Previous studies have demonstrated the valuable information content of multi-frequency Doppler radar observations to characterize aggregation with respect to environmental parameters such as temperature. Comparisons with model simulations can reveal discrepancies, but the main challenge is to identify the most critical parameters in the aggregation parameterization, which can then be improved by using the observations as constraints. In this study, we systematically investigate the sensitivity of physical variables, such as number and mass density, as well as the forward-simulated multi-frequency and Doppler radar observables, to different parameters in a two-moment microphysics scheme. Our approach includes modifying key aggregation parameters such as the sticking efficiency or the shape of the size distribution. We also revise and test the impact of changing functional relationships (e.g., the terminal velocity–size relation) and underlying assumptions (e.g., the definition of the aggregation kernel). We test the sensitivity of the various components first in a single-column “snowshaft” model, which allows fast and efficient identification of the parameter combination optimally matching the observations. We find that particle properties, definition of the aggregation kernel, and size distribution width prove to be most important, while the sticking efficiency and the cloud ice habit have less influence. The setting which optimally matches the observations is then implemented in a 3D model using the identical scheme setup. Rerunning the 3D model with the new scheme setup for a multi-week period revealed that the large overestimation of aggregate size and terminal velocity in the model could be substantially reduced. The method presented is expected to be applicable to constrain other ice microphysical processes or to evaluate and improve other schemes.</p>M. KarrerA. SeifertD. OriS. KneifelCopernicus PublicationsarticlePhysicsQC1-999ChemistryQD1-999ENAtmospheric Chemistry and Physics, Vol 21, Pp 17133-17166 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Physics QC1-999 Chemistry QD1-999
spellingShingle	Physics QC1-999 Chemistry QD1-999 M. Karrer A. Seifert D. Ori S. Kneifel Improving the representation of aggregation in a two-moment microphysical scheme with statistics of multi-frequency Doppler radar observations
description	<p>Aggregation is a key microphysical process for the formation of precipitable ice particles. Its theoretical description involves many parameters and dependencies among different variables that are either insufficiently understood or difficult to accurately represent in bulk microphysics schemes. Previous studies have demonstrated the valuable information content of multi-frequency Doppler radar observations to characterize aggregation with respect to environmental parameters such as temperature. Comparisons with model simulations can reveal discrepancies, but the main challenge is to identify the most critical parameters in the aggregation parameterization, which can then be improved by using the observations as constraints. In this study, we systematically investigate the sensitivity of physical variables, such as number and mass density, as well as the forward-simulated multi-frequency and Doppler radar observables, to different parameters in a two-moment microphysics scheme. Our approach includes modifying key aggregation parameters such as the sticking efficiency or the shape of the size distribution. We also revise and test the impact of changing functional relationships (e.g., the terminal velocity–size relation) and underlying assumptions (e.g., the definition of the aggregation kernel). We test the sensitivity of the various components first in a single-column “snowshaft” model, which allows fast and efficient identification of the parameter combination optimally matching the observations. We find that particle properties, definition of the aggregation kernel, and size distribution width prove to be most important, while the sticking efficiency and the cloud ice habit have less influence. The setting which optimally matches the observations is then implemented in a 3D model using the identical scheme setup. Rerunning the 3D model with the new scheme setup for a multi-week period revealed that the large overestimation of aggregate size and terminal velocity in the model could be substantially reduced. The method presented is expected to be applicable to constrain other ice microphysical processes or to evaluate and improve other schemes.</p>
format	article
author	M. Karrer A. Seifert D. Ori S. Kneifel
author_facet	M. Karrer A. Seifert D. Ori S. Kneifel
author_sort	M. Karrer
title	Improving the representation of aggregation in a two-moment microphysical scheme with statistics of multi-frequency Doppler radar observations
title_short	Improving the representation of aggregation in a two-moment microphysical scheme with statistics of multi-frequency Doppler radar observations
title_full	Improving the representation of aggregation in a two-moment microphysical scheme with statistics of multi-frequency Doppler radar observations
title_fullStr	Improving the representation of aggregation in a two-moment microphysical scheme with statistics of multi-frequency Doppler radar observations
title_full_unstemmed	Improving the representation of aggregation in a two-moment microphysical scheme with statistics of multi-frequency Doppler radar observations
title_sort	improving the representation of aggregation in a two-moment microphysical scheme with statistics of multi-frequency doppler radar observations
publisher	Copernicus Publications
publishDate	2021
url	https://doaj.org/article/32ffbac391f24e1eae046d555aece1ef
work_keys_str_mv	AT mkarrer improvingtherepresentationofaggregationinatwomomentmicrophysicalschemewithstatisticsofmultifrequencydopplerradarobservations AT aseifert improvingtherepresentationofaggregationinatwomomentmicrophysicalschemewithstatisticsofmultifrequencydopplerradarobservations AT dori improvingtherepresentationofaggregationinatwomomentmicrophysicalschemewithstatisticsofmultifrequencydopplerradarobservations AT skneifel improvingtherepresentationofaggregationinatwomomentmicrophysicalschemewithstatisticsofmultifrequencydopplerradarobservations
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Improving the representation of aggregation in a two-moment microphysical scheme with statistics of multi-frequency Doppler radar observations

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