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DOI	10.5194/acp-21-13099-2021
	A new conceptual model for adiabatic fog
	Toledo F.; Haeffelin M.; Wærsted E.; Dupont J.-C.
发表日期	2021
ISSN	1680-7316
起始页码	13099
结束页码	13117
卷号	21 期号:17
英文摘要	Visibility reduction caused by fog can be hazardous for human activities, especially for the transport sector. Previous studies show that this problem could be mitigated by improving nowcasting of fog dissipation. To address this issue, we propose a new paradigm which could potentially improve our understanding of the life cycle of adiabatic continental fogs and of the conditions that must take place for fog dissipation. For this purpose, adiabatic fog is defined as a layer filled with suspended liquid water droplets, extending from an upper boundary all the way down to the surface, with a saturated adiabatic temperature profile. In this layer, the liquid water path (LWP) must exceed a critical value: the critical liquid water path (CLWP). When the LWP is less than the CLWP, the amount of fog liquid water is not sufficient to extend all the way down to the surface, leading to a surface horizontal visibility greater than 1 km. Conversely, when the LWP exceeds the CLWP, the amount of cloud water is enough to reach the surface, inducing a horizontal visibility of less than 1 km. The excess water with respect to the critical value is defined as the reservoir liquid water path (RLWP). The new fog paradigm is formulated as a conceptual model that relates the liquid water path of adiabatic fog with its thickness and surface liquid water content and allows the critical and reservoir liquid water paths to be computed. Both variables can be tracked in real time using vertical profiling measurements, enabling a real-time diagnostic of fog status. The conceptual model is tested using data from 7 years of measurements performed at the SIRTA observatory, combining cloud radar, microwave radiometer, ceilometer, scatterometer, and weather station measurements. In this time period we found 80 fog events with reliable measurements, with 56 of these lasting more than 3 h. The paper presents the conceptual model and its capability to derive the LWP from the fog top height and surface horizontal visibility with an uncertainty of 10.5 g m-2. The impact of fog liquid water path and fog top height variations on fog life cycle (formation to dissipation) is presented based on four case studies and statistics derived from 56 fog events. Our results, based on measurements and an empirical parametrization for the adiabaticity, validate the applicability of the model. The calculated reservoir liquid water path is consistently positive during the mature phase of fog and starts to decrease quasi-monotonously about 1 h before dissipation, reaching a near-zero value at the time of dissipation. Hence, the reservoir liquid water path and its time derivative could be used as indicators of the life cycle stage, to support nowcasting of fog dissipation. © 2021 The Author(s).
语种	英语
scopus关键词	adiabatic process; cloud water; conceptual framework; dissipation; fog; modeling
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/246610
作者单位	Laboratoire de Météorologie Dynamique, École Polytechnique, Institut Polytechnique de Paris, Palaiseau, 91128, France; Institut Pierre Simon Laplace, École Polytechnique, Cnrs, Institut Polytechnique de Paris, Palaiseau, 91128, France; Institut Pierre-Simon Laplace, École Polytechnique, Uvsq, Université Paris-Saclay, Palaiseau, 91128, France; The Norwegian Meteorological Institute, Henrik Mohns Plass 1, Oslo, 0313, Norway
推荐引用方式 GB/T 7714	Toledo F.,Haeffelin M.,Wærsted E.,et al. A new conceptual model for adiabatic fog[J],2021,21(17).
APA	Toledo F.,Haeffelin M.,Wærsted E.,&Dupont J.-C..(2021).A new conceptual model for adiabatic fog.ATMOSPHERIC CHEMISTRY AND PHYSICS,21(17).
MLA	Toledo F.,et al."A new conceptual model for adiabatic fog".ATMOSPHERIC CHEMISTRY AND PHYSICS 21.17(2021).