Open AccessTrans‐Pacific transport of Saharan dust to western North America: A case study
Author(s) -
McKendry Ian G.,
Strawbridge Kevin B.,
O'Neill Norman T.,
Macdonald Anne Marie,
Liu Peter S. K.,
Leaitch W. Richard,
Anlauf Kurt G.,
Jaegle Lyatt,
Fairlie T. Duncan,
Westphal Douglas L.
Publication year - 2007
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2006jd007129
Subject(s) - angstrom exponent , aerosol , mineral dust , atmospheric sciences , particulates , asian dust , altitude (triangle) , lidar , chemical transport model , climatology , environmental science , boundary layer , storm , geology , oceanography , geography , meteorology , physics , ecology , geometry , mathematics , remote sensing , biology , thermodynamics
The first documented case of long‐range transport of Saharan dust over a pathway spanning Asia and the Pacific to western North America is described. Crustal material generated by North African dust storms during the period 28 February to 3 March 2005 reached western Canada on 13–14 March 2005 and was observed by lidar and sunphotometer in the Vancouver region and by high‐altitude aerosol instrumentation at Whistler Peak. Global chemical models (GEOS‐Chem and NRL NAAPS) confirm the transport pathway and suggest source attribution was simplified in this case by the distinct, and somewhat unusual, lack of dust activity over Eurasia (Gobi and Takla Makan deserts) at this time. Over western North America the dust layer, although subsiding close to the boundary layer, did not appear to contribute to boundary layer particulate matter concentrations. Furthermore, sunphotometer observations (and associated inversion products) suggest that the dust layer had only subtle optical impact (aerosol optical thickness ( τ a500 ) and Ångström exponent ( α 440–870 ) were 0.1 and 1.2, respectively) and was dominated by fine particulate matter (modes in aerodynamic diameter at 0.3 and 2.5 μ m). High‐altitude observations at Whistler, British Columbia, confirm the crustal origin of the layer (rich in Ca ++ ions) and the bimodal size distribution. Although a weak event compared to the Asian trans‐Pacific dust events of 1998 and 2001, this novel case highlights the possibility that Saharan sources may contribute episodically to the aerosol burden in western North America.