气候变化领域集成服务门户(CCPortal): Supercooled liquid fogs over the central Greenland Ice Sheet

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DOI	10.5194/acp-19-7467-2019
	Supercooled liquid fogs over the central Greenland Ice Sheet
	Cox C.J.; Noone D.C.; Berkelhammer M.; Shupe M.D.; Neff W.D.; Miller N.B.; Walden V.P.; Steffen K.
发表日期	2019
ISSN	16807316
起始页码	7467
结束页码	7485
卷号	19 期号:11
英文摘要	Radiation fogs at Summit Station, Greenland (72.58° N, 38.48° W; 3210 m a.s.l.), are frequently reported by observers. The fogs are often accompanied by fogbows, indicating the particles are composed of liquid; and because of the low temperatures at Summit, this liquid is supercooled. Here we analyze the formation of these fogs as well as their physical and radiative properties. In situ observations of particle size and droplet number concentration were made using scattering spectrometers near 2 and 10 m height from 2012 to 2014. These data are complemented by colocated observations of meteorology, turbulent and radiative fluxes, and remote sensing. We find that liquid fogs occur in all seasons with the highest frequency in September and a minimum in April. Due to the characteristics of the boundary-layer meteorology, the fogs are elevated, forming between 2 and 10 m, and the particles then fall toward the surface. The diameter of mature particles is typically 20-25 μm in summer. Number concentrations are higher at warmer temperatures and, thus, higher in summer compared to winter. The fogs form at temperatures as warm as-5 °C, while the coldest form at temperatures approaching-40 °C. Facilitated by the elevated condensation, in winter two-thirds of fogs occurred within a relatively warm layer above the surface when the near-surface air was below-40 °C, as cold as-57 °C, which is too cold to support liquid water. This implies that fog particles settling through this layer of cold air freeze in the air column before contacting the surface, thereby accumulating at the surface as ice without riming. Liquid fogs observed under otherwise clear skies annually imparted 1.5 W m-2 of cloud radiative forcing (CRF). While this is a small contribution to the surface radiation climatology, individual events are influential. The mean CRF during liquid fog events was 26 W m-2, and was sometimes much higher. An extreme case study was observed to radiatively force 5 °C of surface warming during the coldest part of the day, effectively damping the diurnal cycle. At lower elevations of the ice sheet where melting is more common, such damping could signal a role for fogs in preconditioning the surface for melting later in the day. © 2019 Author(s).
语种	英语
scopus关键词	boundary layer; concentration (composition); droplet; fog; low temperature; particle size; particulate matter; physical property; Arctic; Greenland; Greenland Ice Sheet; Summit Station
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/144361
作者单位	Cooperative Institute for Research in Environmental Sciences, Boulder, CO 80309, United States; NOAA Earth System Research Laboratory, Boulder, CO 80305, United States; College of Earth Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, United States; Department of Earth and Environmental Sciences, University of Illinois at Chicago, Chicago, IL 60607, United States; Department of Civil and Environmental Engineering, Washington State University, Pullman, WA 99164, United States; Swiss Federal Research Institute WSL, Birmensdorf, 8903, Switzerland
推荐引用方式 GB/T 7714	Cox C.J.,Noone D.C.,Berkelhammer M.,et al. Supercooled liquid fogs over the central Greenland Ice Sheet[J],2019,19(11).
APA	Cox C.J..,Noone D.C..,Berkelhammer M..,Shupe M.D..,Neff W.D..,...&Steffen K..(2019).Supercooled liquid fogs over the central Greenland Ice Sheet.Atmospheric Chemistry and Physics,19(11).
MLA	Cox C.J.,et al."Supercooled liquid fogs over the central Greenland Ice Sheet".Atmospheric Chemistry and Physics 19.11(2019).