气候变化领域集成服务门户(CCPortal): Supercooled drizzle development in response to semi-coherent vertical velocity fluctuations within an orographic-layer cloud

CCPortal

DOI	10.5194/acp-20-5035-2020
	Supercooled drizzle development in response to semi-coherent vertical velocity fluctuations within an orographic-layer cloud
	Majewski A.; French J.R.
发表日期	2020
ISSN	1680-7316
起始页码	5035
结束页码	5054
卷号	20 期号:8
英文摘要	Observations of supercooled liquid water are nearly ubiquitous within wintertime orographic-layer clouds over the Intermountain West; however, observations of regions containing supercooled drizzle drops (SCDDs) are much rarer and the factors controlling SCDD development and location less well understood. As part of the Seeded and Natural Orographic Wintertime clouds-the Idaho Experiment (SNOWIE) and its goal of improving understanding of natural cloud structure, this study examines the role of finescale (sub-kilometer) vertical velocity fluctuations on the microphysical evolution and location of SCDDs within the observed mixed-phase, wintertime orographic clouds from one research flight in SNOWIE. For the case examined, SCDDs developed in an elevated, postfrontal-layer cloud with cold cloud tops (T-30 C) and low number concentrations of both ice (less than 0.5 L-1) and cloud droplets (less than 30 cm-3). Regions of supercooled drizzle at flight level extended more than a kilometer along the mean wind direction and were first located at and below layers of semi-coherent vertical velocity fluctuations (SCVVFs) embedded within the cloud and subsequently below cloud top. The microphysical development of SCDDs in this environment is catalogued using size and mass distributions derived from in situ probe measurements. Regions corresponding to hydrometeor growth are determined from radar reflectivity profiles retrieved from an airborne W-band cloud radar. Analysis suggests that SCVVF layers are associated with local SCDD development in response to the kinematic perturbation pattern. This drizzle development and subsequent growth by collision-coalescence is inferred from vertical reflectivity enhancements (-20 dBZ km-1), with drizzle production confirmed by in situ measurements within one of these SCVVF layers. The SCDD production and growth occurs embedded within cloud over shallow (km or less) layers before transitioning to drizzle production at cloud top further downwind, indicating that wind shear and resultant vertical velocity fluctuations may act to enhance or speed up SCDD development compared to classic cloud top broadening mechanisms in orographic (or similarly sheared) cloud environment(s). © 2020 Copernicus GmbH. All rights reserved.
语种	英语
scopus关键词	atmospheric convection; cloud microphysics; drizzle; flow velocity; research work; wind velocity; winter
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/247819
作者单位	Department of Atmospheric Science, University of Wyoming, Laramie, 82070, United States
推荐引用方式 GB/T 7714	Majewski A.,French J.R.. Supercooled drizzle development in response to semi-coherent vertical velocity fluctuations within an orographic-layer cloud[J],2020,20(8).
APA	Majewski A.,&French J.R..(2020).Supercooled drizzle development in response to semi-coherent vertical velocity fluctuations within an orographic-layer cloud.ATMOSPHERIC CHEMISTRY AND PHYSICS,20(8).
MLA	Majewski A.,et al."Supercooled drizzle development in response to semi-coherent vertical velocity fluctuations within an orographic-layer cloud".ATMOSPHERIC CHEMISTRY AND PHYSICS 20.8(2020).