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Physicochemical Properties of Free Tropospheric Particles Collected at Pico Mountain Observatory and Their Role in Ice Cloud Formation
NURUN NAHAR LATA, Bo Zhang, Simeon Schum, Lynn Mazzoleni, Claudio Mazzoleni, Swarup China, Pacific Northwest National Laboratory
Abstract Number: 173
Working Group: Aerosol Chemistry
Abstract
Free tropospheric particles after long range transport can contribute to ice nucleation affecting cloud properties and formation. Therefore, detailed physicochemical characterization of ice nucleating particles is fundamental to elucidate their effects on heterogeneous ice nucleation in clouds. In this study, we characterized free tropospheric particles collected from three different events in July, 2014 at the remote Pico Mountain Observatory. Pico Mountain Observatory is located at 2225 m above sea level in the summit caldera of Pico Volcano on Pico Island in the Azores archipelago in the North Atlantic. We performed FLEXPART retroplume modeling to investigate their transport pattern. Utilizing multimodal microscopy and spectroscopic techniques, we analyzed several physicochemical properties of the collected particle and investigate their ice nucleation propensity using a state of the art ice nucleation instrument coupled with an Environmental Scanning Electron Microscope operated at temperature and relative humidity values relevant to mixed phase and cirrus clouds. We conducted single particle as well as bulk analysis of the particles collected from three different sampling periods. The outcomes from both investigations indicates that the chemical compositions of the particles with different aging times are significantly different. Chemical imaging and microanalysis of individual particle using energy dispersive spectroscopy evidance the aging of the organic particles. The identified ice nucleating particles are comprised of mixtures of dust, organic and sulfate coating materials, and other carbonaceous particles. We observed an enhancement of ice nucleation activity for the sample dominated by mineral dust. Altogether, the results from this study provides a better understanding of the role of long range transported free tropospheric particles on ice cloud formation.