Near-surface and lower tropospheric aerosol characteristics have been determined at several remote sites near Orogrande, New Mexico, using a variety of methods and sensors including quartz fiber filter samplers, hi-vol samplers, ground-based and aircraft-mounted light-scattering aerosol counters, an aerosol counter equipped with a heated inlet, and an aethalometer (a device that measures aerosol absorption). The results of these measurements, which have been taken sporadically over the last 15 years but with a higher density of measurements during 1989-1991, suggest that regardless of season, aerosol consists of two modes: a submicron fraction composed primarily of ammonium/acid sulfates and elemental black carbon (BC) and a supermicron fraction composed mainly of quartz and clay minerals of soil origin. Aerosol mass concentrations determined from weekly or biweekly samples are dominated by wind-derived aerosol of soil origin and typically range from • 10/xg m -3 in the fall rainy season (August-October) to • 100/xg m -3 during the spring windy season (February-June). The mass concentration frequency of occurrence of both total aerosol and BC are well approximated by -3 lognormal probability distributions. Geometric mean masses of aerosol range from 16 to 32/xg m and are smaller for mountain sites than for basin sites; geometric mean BC mass concentrations at a single basin site are •0.15 /xg m -3. Aerosol loadings decrease slightly from 1975-1977 to 1990 measurement periods, whereas BC concentrations, within statistical error, remain unchanged. However, a statistically significant increase in BC did occur from 1990 to 1991. The fraction of (visible spectrum) aerosol absorption attributable to BC has a yearly mean value of •0.84, although during dusty conditions occurring in spring or early summer, non-BC aerosol absorption contributes up to •30% of the total. Sulfate and BC aerosol concentrations are sometimes highly correlated, suggesting they have a common source and may be internally mixed. Limited aircraft measurements in the lowest few kilometers of the troposphere reveal a well-mixed aerosol for a neutral atmospheric condition, and a significant decrease in aerosol concentration with altitude for a stable atmospheric condition. INTRODUCTION Previous measurements of the physiochemical properties of natural aerosol in the arid southwestern United States have been directed toward determination of aerosol composition [Hoidale and Blanco, 1969; Lindberg, 1975; Reagan et al., 1984; P. J. Sheridan et al., unpublished manuscript, 1992] and size distribution [Twomey, 1976; Patterson and Gillette, 1977a; Reagan et al., 1980], characteristic morphologies [Gillette and Walker, 1977], average refractive index [Grams et al., 1974; Herman et al., 1975; Lindberg and Gillespie, 1977], effect on visibility [Patterson et al., 1976; Patterson, 1977; Patterson and Gillette, 1977b], vertical structure [Spinhirne et al., 1980; Schwiesow et al., 1981; Reagan et al., 1984], backscatter to extinction ratios [Reagan et al., 1988], w...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.