On the relationship between Arctic ice clouds and polluted air masses over the North Slope of Alaska in April 2008

Recently, two types of ice clouds (TICs) properties have been characterized using the Indirect and Semi-Direct Aerosol Campaign (ISDAC) airborne measurements (Alaska, April 2008). TIC-2B were characterized by fewer (< 10 L −1 ) and larger (> 110 μm) ice crystals, and a larger ice supersaturati...

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Bibliographic Details
Published in:Atmospheric Chemistry and Physics
Main Authors: C. Jouan, J. Pelon, E. Girard, G. Ancellet, J. P. Blanchet, J. Delanoë
Format: Article in Journal/Newspaper
Language:English
Published: Copernicus Publications 2014
Subjects:
Physics
QC1-999
Chemistry
QD1-999
Arctic
Kamchatka
north slope
Alaska
Siberia
Online Access:https://doi.org/10.5194/acp-14-1205-2014
https://doaj.org/article/f1bdf499387c442d8a6681b9328eb6af
Description
Summary:Recently, two types of ice clouds (TICs) properties have been characterized using the Indirect and Semi-Direct Aerosol Campaign (ISDAC) airborne measurements (Alaska, April 2008). TIC-2B were characterized by fewer (< 10 L −1 ) and larger (> 110 μm) ice crystals, and a larger ice supersaturation (> 15%) compared to TIC-1/2A. It has been hypothesized that emissions of SO 2 may reduce the ice nucleating properties of ice nuclei (IN) through acidification, resulting in a smaller concentration of larger ice crystals and leading to precipitation (e.g., cloud regime TIC-2B). Here, the origin of air masses forming the ISDAC TIC-1/2A (1 April 2008) and TIC-2B (15 April 2008) is investigated using trajectory tools and satellite data. Results show that the synoptic conditions favor air masses transport from three potential SO 2 emission sources into Alaska: eastern China and Siberia where anthropogenic and biomass burning emissions, respectively, are produced, and the volcanic region of the Kamchatka/Aleutians. Weather conditions allow the accumulation of pollutants from eastern China and Siberia over Alaska, most probably with the contribution of acidic volcanic aerosol during the TIC-2B period. Observation Monitoring Instrument (OMI) satellite observations reveal that SO 2 concentrations in air masses forming the TIC-2B were larger than in air masses forming the TIC-1/2A. Airborne measurements show high acidity near the TIC-2B flight where humidity was low. These results support the hypothesis that acidic coating on IN could be at the origin of the formation of TIC-2B.

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