Browsing by Author "Keim, Barry D."
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Item Manual synoptic climate classification for the East Coast of New England (USA) with an application to PM2.5 concentration(Inter-Research, 2005-03-16) Keim, Barry D.; Meeker, Loren David; Slater, John F.This study presents a manual synoptic climate classification for the East Coast of New England with an application to regional pollution. New England weather was classified into 9 all-inclusive weather types: Canadian High, Modified High, Gulf of Maine Return, New England High, Atlantic Return, Frontal Atlantic Return, Frontal Overrunning-Continental, Frontal Overrun-ning-Marine, and Tropical Disturbance. Canadian High and Modified High weather are the domi-nant weather patterns at Boston, Massachusetts, while Tropical Disturbance, Gulf of Maine Return, and New England High weather types are the least frequent. Properties of the weather types were determined at 07:00 h Local Standard Time (LST) each day in Boston. The coldest and driest weather type is the Canadian High, while the hottest, most humid weather is generated by Frontal Atlantic Return. The synoptic weather classification system, applied to airborne fine particle mass concentra-tions with an aerodynamic diameter ≤2.5 μm (PM2.5), showed significant differences in concentra-tions between weather types: transport from the north and northwest had low PM2.5, while transport from the south and southwest had high PM2.5 concentrations. This climate classification system also has potential applications ranging from studies of insect migration to analyses of climate change.Item Relationships between synoptic-scale transport and interannual variability of inorganic cations in surface snow at Summit, Greenland: 1992-1996(American Geophysical Union, 2001-09-27) Slater, John F.; Dibb, Jack E.; Keim, Barry D.; Kahl, Jonathan D. W.To fully utilize the long-term chemical records retrieved from central Greenland ice cores, specific relationships between atmospheric circulation and the variability of chemical species in the records need to be better understood. This research examines associations between the variability of surface snow inorganic cation chemistry at Summit, Greenland (collected during 1992-1996 summer field seasons) and changes in air mass transport pathways and source regions, as well as variations in aerosol source strength. Transport patterns and source regions are determined through 10-day isentropic backward air mass trajectories during a 1 month (late May to late June) common season over the 5 years. Changes in the extent of exposed continental surfaces in source regions are evaluated to estimate aerosol-associated calcium and magnesium ion source strength, while forest fire activity in the circumpolar north is investigated to estimate aerosol ammonium ion source strength. During the 1995 common season, 3 times more calcium and magnesium accumulated in the snowpack than the other study years. Also, an increasing trend of ammonium concentration was noted throughout the 5 years. Anomalous transport pathways and velocities were observed during 1995, which likely contributed to the high levels of calcium and magnesium. Increased forest fire activity in North America was concurrent with increased levels of ammonium and potassium, except for 1996, when ion levels were above average and forest fire activity was below average. Because of the ubiquitous nature of soluble ions, we conclude that it is very difficult to establish a quantitative link between the ion content of snow and firn at Summit and changes in aerosol source regions and source strength.