气候变化领域集成服务门户(CCPortal): How frequent is natural cloud seeding from ice cloud layers ( &-35&°C) over Switzerland?

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DOI	10.5194/acp-21-5195-2021
	How frequent is natural cloud seeding from ice cloud layers ( &-35&°C) over Switzerland?
	Proske U.; Bessenbacher V.; Dedekind Z.; Lohmann U.; Neubauer D.
发表日期	2021
ISSN	1680-7316
起始页码	5195
结束页码	5216
卷号	21 期号:6
英文摘要	Clouds and cloud feedbacks represent one of the largest uncertainties in climate projections. As the ice phase influences many key cloud properties and their lifetime, its formation needs to be better understood in order to improve climate and weather prediction models. Ice crystals sedimenting out of a cloud do not sublimate immediately but can survive certain distances and eventually fall into a cloud below. This natural cloud seeding can trigger glaciation and has been shown to enhance precipitation formation. However, to date, an estimate of its occurrence frequency is lacking. In this study, we estimate the occurrence frequency of natural cloud seeding over Switzerland from satellite data and sublimation calculations. We use the DARDAR (radar lidar) satellite product between April 2006 and October 2017 to estimate the occurrence frequency of multi-layer cloud situations, where a cirrus cloud at T <-35 °C can provide seeds to a lower-lying feeder cloud. These situations are found to occur in 31% of the observations. Of these, 42% have a cirrus cloud above another cloud, separated, while in 58% the cirrus is part of a thicker cloud, with a potential for in-cloud seeding. Vertical distances between the cirrus and the lower-lying cloud are distributed uniformly between 100m and 10 km. They are found to not vary with topography. Seasonally, winter nights have the most multi-layer cloud occurrences, in 38% of the measurements. Additionally, in situ and liquid origin cirrus cloud size modes can be identified according to the ice crystal mean effective radius in the DARDAR data. Using sublimation calculations, we show that in a significant number of cases the seeding ice crystals do not sublimate before reaching the lower-lying feeder cloud. Depending on whether bullet rosette, plate-like or spherical crystals were assumed, 10 %, 11% or 20% of the crystals, respectively, could provide seeds after sedimenting 2 km. The high occurrence frequency of seeding situations and the survival of the ice crystals indicate that the seeder-feeder process and natural cloud seeding are widespread phenomena over Switzerland. This hints at a large potential for natural cloud seeding to influence cloud properties and thereby the Earth's radiative budget and water cycle, which should be studied globally. Further investigations of the magnitude of the seeding ice crystals' effect on lower-lying clouds are necessary to estimate the contribution of natural cloud seeding to precipitation. © 2021 American Institute of Physics Inc.. All rights reserved.
语种	英语
scopus关键词	cloud seeding; hydrological cycle; ice crystal; precipitation (climatology); radiation budget; satellite data; sublimation; Switzerland
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/247001
作者单位	Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland
推荐引用方式 GB/T 7714	Proske U.,Bessenbacher V.,Dedekind Z.,et al. How frequent is natural cloud seeding from ice cloud layers ( &-35&°C) over Switzerland?[J],2021,21(6).
APA	Proske U.,Bessenbacher V.,Dedekind Z.,Lohmann U.,&Neubauer D..(2021).How frequent is natural cloud seeding from ice cloud layers ( &-35&°C) over Switzerland?.ATMOSPHERIC CHEMISTRY AND PHYSICS,21(6).
MLA	Proske U.,et al."How frequent is natural cloud seeding from ice cloud layers ( &-35&°C) over Switzerland?".ATMOSPHERIC CHEMISTRY AND PHYSICS 21.6(2021).