气候变化领域集成服务门户(CCPortal): Preconditioning of overcast-To-broken cloud transitions by riming in marine cold air outbreaks

CCPortal

DOI	10.5194/acp-21-12049-2021
	Preconditioning of overcast-To-broken cloud transitions by riming in marine cold air outbreaks
	Tornow F.; Ackerman A.S.; Fridlind A.M.
发表日期	2021
ISSN	1680-7316
起始页码	12049
结束页码	12067
卷号	21 期号:15
英文摘要	Marine cold air outbreaks (CAOs) commonly form overcast cloud decks that transition into broken cloud fields downwind, dramatically altering the local radiation budget. In this study, we investigate the impact of frozen hydrometeors on these transitions. We focus on a CAO case in the NW Atlantic, the location of the multi-year flight campaign ACTIVATE (Aerosol Cloud meTeorology Interactions oVer the western ATlantic Experiment). We use MERRA-2 (Modern-Era Retrospective analysis for Research and Applications, version 2) reanalysis fields to drive large eddy simulations with mixed-phase two-moment microphysics in a Lagrangian framework. We find that transitions are triggered by substantial rain (rainwater paths >25ĝ€¯gm-2), and only simulations that allow for aerosol depletion result in sustained breakups, as observed. Using a range of diagnostic ice nucleating particle concentrations, Ninp, we find that increasing ice progressively accelerates transitions, thus abbreviating the overcast state. Ice particles affect the cloud-Topped boundary layer evolution, primarily through riming-related processes prior to substantial rain, leading to (1) a reduction in cloud liquid water, (2) early consumption of cloud condensation nuclei, and (3) early and light precipitation cooling and moistening below cloud. We refer to these three effects collectively as "preconditioning by riming". Greater boundary layer aerosol concentrations available as cloud condensation nuclei (CCN) delay the onset of substantial rain. However, cloud breakup and low CCN concentration final stages are found to be inevitable in this case, due, primarily, to liquid water path buildup. An ice-modulated cloud transition speed suggests the possibility of a negative cloud-climate feedback. To address prevailing uncertainties in the model representation of mixed-phase processes, the magnitude of ice formation and riming impacts and, thereby, the strength of an associated negative cloud-climate feedback process, requires further observational evaluation by targeting riming hot spots with in situ imaging probes that allow for both the characterization of ice particles and abundance of supercooled droplets. © Copyright:
语种	英语
scopus关键词	atmospheric convection; cloud condensation nucleus; cloud microphysics; cold air; concentration (composition); hydrometeorology; satellite data; satellite imagery
来源期刊	ATMOSPHERIC CHEMISTRY AND PHYSICS
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/246661
作者单位	Center for Climate Systems Research, Earth Institute, Columbia University, New York, NY 10025, United States; NASA Goddard Institute for Space Sciences, New York, NY 10025, United States
推荐引用方式 GB/T 7714	Tornow F.,Ackerman A.S.,Fridlind A.M.. Preconditioning of overcast-To-broken cloud transitions by riming in marine cold air outbreaks[J],2021,21(15).
APA	Tornow F.,Ackerman A.S.,&Fridlind A.M..(2021).Preconditioning of overcast-To-broken cloud transitions by riming in marine cold air outbreaks.ATMOSPHERIC CHEMISTRY AND PHYSICS,21(15).
MLA	Tornow F.,et al."Preconditioning of overcast-To-broken cloud transitions by riming in marine cold air outbreaks".ATMOSPHERIC CHEMISTRY AND PHYSICS 21.15(2021).