气候变化领域集成服务门户(CCPortal): Enhanced ice nucleation activity of coal fly ash aerosol particles initiated by ice-filled pores

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DOI	10.5194/acp-19-8783-2019
	Enhanced ice nucleation activity of coal fly ash aerosol particles initiated by ice-filled pores
	Umo N.S.; Wagner R.; Ullrich R.; Kiselev A.; Saathoff H.; Weidler P.G.; Cziczo D.J.; Leisner T.; Möhler O.
发表日期	2019
ISSN	16807316
起始页码	8783
结束页码	8800
卷号	19 期号:13
英文摘要	Ice-nucleating particles (INPs), which are precursors for ice formation in clouds, can alter the microphysical and optical properties of clouds, thereby impacting the cloud lifetimes and hydrological cycles. However, the mechanisms with which these INPs nucleate ice when exposed to different atmospheric conditions are still unclear for some particles. Recently, some INPs with pores or permanent surface defects of regular or irregular geometries have been reported to initiate ice formation at cirrus temperatures via the liquid phase in a two-step process, involving the condensation and freezing of supercooled water inside these pores. This mechanism has therefore been labelled pore condensation and freezing (PCF). The PCF mechanism allows formation and stabilization of ice germs in the particle without the formation of macroscopic ice. Coal fly ash (CFA) aerosol particles are known to nucleate ice in the immersion freezing mode and may play a significant role in cloud formation. In our current ice nucleation experiments with a particular CFA sample (CFA-UK), which we conducted in the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) aerosol and cloud simulation chamber at the Karlsruhe Institute of Technology (KIT), Germany, we observed a strong increase (at a threshold relative humidity with respect to ice of 101 %- 105 %) in the ice-active fraction for experiments performed at temperatures just below the homogeneous freezing of pure water. This observed strong increase in the ice-active fraction could be related to the PCF mechanism. To further investigate the potential of CFA particles undergoing the PCF mechanism, we performed a series of temperature-cycling experiments in AIDA. The temperature-cycling experiments involve exposing CFA particles to lower temperatures (down to ∼ 228 K), then warming them up to higher temperatures (238-273 K) before investigating their ice nucleation properties. For the first time, we report the enhancement of the ice nucleation activity of the CFA particles for temperatures up to 263 K, from which we conclude that it is most likely due to the PCF mechanism. This indicates that ice germs formed in the CFA particles' pores during cooling remain in the pores during warming and induce ice crystallization as soon as the pre-activated particles experience ice-supersaturated conditions at higher temperatures; hence, these pre-activated particles show an enhancement in their ice-nucleating ability compared with the scenario where the CFA particles are directly probed at higher temperatures without temporary cooling. The enhancement in the ice nucleation ability showed a positive correlation with the specific surface area and porosity of the particles. On the one hand, the PCF mechanism can play a significant role in mixed-phase cloud formation in a case where the CFA particles are injected from higher altitudes and then transported to lower altitudes after being exposed to lower temperatures. On the other hand, the PCF mechanism could be the prevalent nucleation mode for ice formation at cirrus temperatures rather than the previously acclaimed deposition mode. © 2019 Author(s). This work is distributed under the Creative Commons Attribution 4.0 License.
语种	英语
scopus关键词	aerosol; cloud microphysics; condensation; fly ash; formation mechanism; ice; nucleation; porosity; Germany
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/144292
作者单位	Institute of Meteorology and Climate Research, Atmospheric Aerosol Research, Karlsruhe Institute of Technology, Hermann-von-Helmholtz Platz 1, Eggenstein-Leopoldshafen, 76344, Germany; Institute of Functional Interfaces, Karlsruhe Institute of Technology, Hermann-von-Helmholtz Platz 1, Eggenstein-Leopoldshafen, 76344, Germany; Earth, Atmospheric and Planetary Sciences, Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue 54-1324, Cambridge, MA 02139-4307, United States; Purdue University, Department of Earth, Atmospheric and Planetary Sciences, 550 Lafayette St., West Lafayette, IN 47907, United States
推荐引用方式 GB/T 7714	Umo N.S.,Wagner R.,Ullrich R.,et al. Enhanced ice nucleation activity of coal fly ash aerosol particles initiated by ice-filled pores[J],2019,19(13).
APA	Umo N.S..,Wagner R..,Ullrich R..,Kiselev A..,Saathoff H..,...&Möhler O..(2019).Enhanced ice nucleation activity of coal fly ash aerosol particles initiated by ice-filled pores.Atmospheric Chemistry and Physics,19(13).
MLA	Umo N.S.,et al."Enhanced ice nucleation activity of coal fly ash aerosol particles initiated by ice-filled pores".Atmospheric Chemistry and Physics 19.13(2019).