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Ice cloud formation potential by free tropospheric particles from long‐range transport over the Northern Atlantic Ocean
Author(s) -
China Swarup,
Alpert Peter A.,
Zhang Bo,
Schum Simeon,
Dzepina Katja,
Wright Kendra,
Owen R. Chris,
Fialho Paulo,
Mazzoleni Lynn R.,
Mazzoleni Claudio,
Knopf Daniel A.
Publication year - 2017
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2016jd025817
Subject(s) - ice nucleus , troposphere , particle (ecology) , range (aeronautics) , atmospheric sciences , relative humidity , mineral dust , nucleation , environmental science , particle number , aerosol , materials science , chemistry , geology , oceanography , meteorology , geography , physics , plasma , organic chemistry , quantum mechanics , composite material
Long‐range transported free tropospheric particles can play a significant role on heterogeneous ice nucleation. Using optical and electron microscopy we examine the physicochemical characteristics of ice nucleating particles (INPs). Particles were collected on substrates from the free troposphere at the remote Pico Mountain Observatory in the Azores Islands, after long‐range transport and aging over the Atlantic Ocean. We investigate four specific events to study the ice formation potential by the collected particles with different ages and transport patterns. We use single‐particle analysis, as well as bulk analysis to characterize particle populations. Both analyses show substantial differences in particle composition between samples from the four events; in addition, single‐particle microscopy analysis indicates that most particles are coated by organic material. The identified INPs contained mixtures of dust, aged sea salt and soot, and organic material acquired either at the source or during transport. The temperature and relative humidity ( RH ) at which ice formed, varied only by 5% between samples, despite differences in particle composition, sources, and transport patterns. We hypothesize that this small variation in the onset RH may be due to the coating material on the particles. This study underscores and motivates the need to further investigate how long‐range transported and atmospherically aged free tropospheric particles impact ice cloud formation.