A multi-year study of lower tropospheric aerosol variability and systematic relationships from four North American regions

Abstract. Hourly averaged aerosol optical properties (AOPs) measured over the years 2010–2013 at four continental North American NOAA Earth System Research Laboratory (NOAA/ESRL) cooperative aerosol network sites – Southern Great Plains near Lamont, OK (SGP), Bondville, IL (BND), Appalachian State University in Boone, NC (APP), and Egbert, Ontario, Canada (EGB) are analyzed. Aerosol optical properties measured over 1996–2009 at BND and 1997–2009 at SGP are also presented. The aerosol sources and types in the four regions differ enough so as to collectively represent rural, anthropogenically perturbed air conditions over much of eastern continental North America. Temporal AOP variability on monthly, weekly, and diurnal timescales is presented for each site. Differences in annually averaged AOPs and those for individual months at the four sites are used to examine regional AOP variability. Temporal and regional variability are placed in the context of reported aerosol chemistry at the sites, meteorological measurements (wind direction, temperature), and reported regional mixing layer heights. Basic trend analysis is conducted for selected AOPs at the long-term sites (BND and SGP). Systematic relationships among AOPs are also presented. Seasonal variability in PM1 (sub-1 μm particulate matter) scattering and absorption coefficients at 550 nm (σsp and σap, respectively) and most of the other PM1 AOPs is much larger than day of week and diurnal variability at all sites. All sites demonstrate summer σsp and σap peaks. Scattering coefficient decreases by a factor of 2–4 in September–October and coincides with minimum single-scattering albedo (ω0) and maximum hemispheric backscatter fraction (b). The co-variation of ω0 and b lead to insignificant annual cycles in top-of-atmosphere direct radiative forcing efficiency (DRFE) at APP and SGP. Much larger annual DRFE cycle amplitudes are observed at EGB (~ 40 %) and BND (~ 25 %), with least negative DRFE in September–October at both sites. Secondary winter peaks in σsp are observed at all sites except APP. Amplitudes of diurnal and weekly cycles in σap at the sites are larger for all seasons than those of σsp, with the largest differences occurring in summer. The weekly and diurnal cycle amplitudes of most intensive AOPs (e.g., those derived from ratios of measured σsp and σap) are minimal in most cases, especially those related to parameterizations of aerosol size distribution. Statistically significant trends in σsp (decreasing), PM1 scattering fraction (decreasing), and b (increasing) are found at BND from 1996 to 2013 and at SGP from 1997 to 2013. A statistically significant decreasing trend in PM10 scattering Angstrom exponent is also observed for SGP but not BND. Most systematic relationships among AOPs are similar for the four sites and are adequately described for individual seasons by annually averaged relationships, although relationships involving absorption Angstrom exponent vary with site and season.

[1]  William C. Malm,et al.  Spatial and monthly trends in speciated fine particle concentration in the United States , 2004 .

[2]  S. Howell,et al.  Biomass burning and pollution aerosol over North America: Organic components and their influence on spectral optical properties and humidification response , 2007 .

[3]  T. Eck,et al.  Accuracy assessments of aerosol optical properties retrieved from Aerosol Robotic Network (AERONET) Sun and sky radiance measurements , 2000 .

[4]  Y. Kaufman,et al.  Dynamic aerosol model: Urban/industrial aerosol , 1998 .

[5]  Oleg Dubovik,et al.  Angstrom exponent and bimodal aerosol size distributions , 2006 .

[6]  Shao-Meng Li,et al.  Primary and secondary organic aerosols in urban air masses intercepted at a rural site , 2010 .

[7]  Two-year observations of fine carbonaceous particles in variable sampling intervals , 2011 .

[8]  M. Chin,et al.  A review of measurement-based assessments of the aerosol direct radiative effect and forcing , 2005 .

[9]  David J. Delene,et al.  Variability of Aerosol Optical Properties at Four North American Surface Monitoring Sites , 2002 .

[10]  George C. Holzworth,et al.  ESTIMATES OF MEAN MAXIMUM MIXING DEPTHS IN THE CONTIGUOUS UNITED STATES , 1964 .

[11]  J. Ogren Comment on “Calibration and Intercomparison of Filter-Based Measurements of Visible Light Absorption by Aerosols” , 2010 .

[12]  L. D. Monache,et al.  In situ aerosol profiles over the Southern Great Plains cloud and radiation test bed site: 2. Effects of mixing height on aerosol properties , 2004 .

[13]  R. Gehrig,et al.  Long‐term trend analysis of aerosol variables at the high‐alpine site Jungfraujoch , 2007 .

[14]  M. Zheng,et al.  Biomass burning impact on PM 2.5 over the southeastern US during 2007: integrating chemically speciated FRM filter measurements, MODIS fire counts and PMF analysis , 2010 .

[15]  Jenny L. Hand,et al.  Seasonal composition of remote and urban fine particulate matter in the United States , 2012 .

[16]  Thomas Trautmann,et al.  Thermal IR radiative properties of mixed mineral dust and biomass aerosol during SAMUM-2 , 2011 .

[17]  J. Ogren,et al.  Determining Aerosol Radiative Properties Using the TSI 3563 Integrating Nephelometer , 1998 .

[18]  Hans Moosmüller,et al.  Observations of OM/OC and specific attenuation coefficients (SAC) in ambient fine PM at a rural site in central Ontario, Canada , 2010 .

[19]  G. Hidy,et al.  Chemical climatology of the southeastern United States, 1999–2013 , 2014 .

[20]  A. Goldstein,et al.  Biogenic carbon and anthropogenic pollutants combine to form a cooling haze over the southeastern United States , 2009, Proceedings of the National Academy of Sciences.

[21]  Shao-Meng Li,et al.  Temperature response of the submicron organic aerosol from temperate forests , 2011 .

[22]  J. Chow,et al.  Aerosol properties at a midlatitude Northern Hemisphere continental site , 2001 .

[23]  Tami C. Bond,et al.  Calibration and Intercomparison of Filter-Based Measurements of Visible Light Absorption by Aerosols , 1999 .

[24]  A. Jefferson,et al.  Spatial variability of submicrometer aerosol radiative properties over the Indian Ocean during INDOEX , 2002 .

[25]  David S. Covert,et al.  Variability of aerosol optical properties derived from in situ aircraft measurements during ACE‐Asia , 2003 .

[26]  J. Ogren,et al.  Observations of the vertical and regional variability of aerosol optical properties over central and eastern North America , 1999 .

[27]  Oleg Dubovik,et al.  Recent trends in aerosol optical properties derived from AERONET measurements , 2014 .

[28]  W. Malm,et al.  Decreases in elemental carbon and fine particle mass in the United States , 2011 .

[29]  J. Pichon,et al.  Characterization and intercomparison of aerosol absorption photometers: result of two intercomparison workshops , 2010 .

[30]  A. Smirnov,et al.  AERONET-a federated instrument network and data archive for aerosol Characterization , 1998 .

[31]  P. Palmer,et al.  Estimates of global terrestrial isoprene emissions using MEGAN (Model of Emissions of Gases and Aerosols from Nature) , 2006 .

[32]  J. Schauer,et al.  Hourly and Daily Patterns of Particle-Phase Organic and Elemental Carbon Concentrations in the Urban Atmosphere , 2004, Journal of the Air & Waste Management Association.

[33]  V. Ramanathan,et al.  Atmospheric Chemistry and Physics Discussions Interactive comment on “ Relating aerosol absorption due to soot , organic carbon , and dust to emission sources determined from in-situ chemical measurements ” , 2022 .

[34]  D. Winker,et al.  Vertical profiles of aerosol optical properties over central Illinois and comparison with surface and satellite measurements , 2012 .

[35]  Qi Zhang,et al.  Long-term measurements of submicrometer aerosol chemistry at the Southern Great Plains (SGP) using an Aerosol Chemical Speciation Monitor (ACSM) , 2015 .

[36]  J. Hansen,et al.  Radiative forcing and climate response , 1997 .

[37]  T. Eck,et al.  Global evaluation of the Collection 5 MODIS dark-target aerosol products over land , 2010 .

[38]  P. Laj,et al.  Climatology of aerosol radiative properties in the free troposphere , 2011 .

[39]  Jian Wang,et al.  Aircraft observations of aerosol composition and ageing in New England and Mid‐Atlantic States during the summer 2002 New England Air Quality Study field campaign , 2007 .

[40]  W. Malm,et al.  Particulate sulfate ion concentration and SO 2 emission trends in the United States from the early 1990s through 2010 , 2012 .

[41]  P. Massoli,et al.  Uncertainty in Light Scattering Measurements by TSI Nephelometer: Results from Laboratory Studies and Implications for Ambient Measurements , 2009 .

[42]  A. Kokhanovsky,et al.  Trend analysis of aerosol optical thickness and Ångström exponent derived from the global AERONET spectral observations , 2011 .

[43]  Mark J. Rood,et al.  Impact of particulate organic matter on the relative humidity dependence of light scattering: A simplified parameterization , 2005 .

[44]  Harald Flentje,et al.  Aerosol decadal trends - Part 1: In-situ optical measurements at GAW and IMPROVE stations , 2012 .

[45]  J. Seinfeld,et al.  Atmospheric Chemistry and Physics: From Air Pollution to Climate Change , 1998 .

[46]  W. Malm,et al.  Widespread reductions in haze across the United States from the early 1990s through 2011 , 2014 .

[47]  R. Martin,et al.  Characterization of a large biogenic secondary organic aerosol event from eastern Canadian forests , 2009 .

[48]  Gregory J. Frost,et al.  Weekly patterns of aerosol in the United States , 2008 .

[49]  Warren J. Wiscombe,et al.  The backscattered fraction in two-stream approximations. , 1976 .

[50]  J. D. Wheeler,et al.  Aerosol backscatter fraction and single scattering albedo: Measured values and uncertainties at a coastal station in the Pacific Northwest , 1999 .

[51]  T. Eck,et al.  Variability of Absorption and Optical Properties of Key Aerosol Types Observed in Worldwide Locations , 2002 .

[52]  Tracey Holloway,et al.  Seasonality of speciated aerosol transport over the Great Lakes region , 2009 .

[53]  Tami C. Bond,et al.  Spectral absorption properties of atmospheric aerosols , 2007 .

[54]  P. Massoli,et al.  Absorption Enhancement of Coated Absorbing Aerosols: Validation of the Photo-Acoustic Technique for Measuring the Enhancement , 2009 .

[55]  H. V. Hulst Light Scattering by Small Particles , 1957 .

[56]  W. Arnott,et al.  In situ aerosol optics in Reno, NV, USA during and after the summer 2008 California wildfires and the influence of absorbing and non-absorbing organic coatings on spectral light absorption , 2009 .

[57]  U. Lohmann,et al.  An Intensive Study of the Size and Composition of Submicron Atmospheric Aerosols at a Rural Site in Ontario, Canada , 2005 .

[58]  Tim Elliott,et al.  Four Years of Continuous Surface Aerosol Measurements from the Department of Energy's Atmospheric Radiation Measurement Program Southern Great Plains Cloud and Radiation Testbed Site , 2022 .

[59]  Beat Schmid,et al.  Comparison of methods for deriving aerosol asymmetry parameter , 2006 .

[60]  Jenny L. Hand,et al.  Spatial and Temporal Trends in PM2.5 Organic and Elemental Carbon across the United States , 2013 .

[61]  J. Seinfeld,et al.  Atmospheric Chemistry and Physics: From Air Pollution to Climate Change , 1997 .

[62]  J. Haywood,et al.  The effect of anthropogenic sulfate and soot aerosol on the clear sky planetary radiation budget , 1995 .

[63]  Philip B. Russell,et al.  Wavelength Dependence of the Absorption of Black Carbon Particles: Predictions and Results from the TARFOX Experiment and Implications for the Aerosol Single Scattering Albedo , 2002 .

[64]  Gian Paolo Gobbi,et al.  Identification of key aerosol populations through their size and composition resolved spectral scattering and absorption , 2012 .

[65]  David S. Covert,et al.  Bias in Filter-Based Aerosol Light Absorption Measurements Due to Organic Aerosol Loading: Evidence from Ambient Measurements , 2008 .

[66]  Steven G. Brown,et al.  Analysis and Apportionment of Organic Carbon and Fine Particulate Matter Sources at Multiple Sites in the Midwestern United States , 2007, Journal of the Air & Waste Management Association.

[67]  Douglas R Lawson,et al.  Differences between Weekday and Weekend Air Pollutant Levels in Atlanta; Baltimore; Chicago; Dallas–Fort Worth; Denver; Houston; New York; Phoenix; Washington, DC; and Surrounding Areas , 2008, Journal of the Air & Waste Management Association.

[68]  R. Ferrare,et al.  In situ aerosol profiles over the Southern Great Plains cloud and radiation test bed site: 1. Aerosol optical properties , 2004 .

[69]  James B. Burkholder,et al.  Bias in Filter-Based Aerosol Light Absorption Measurements Due to Organic Aerosol Loading: Evidence from Laboratory Measurements , 2008 .

[70]  Karl Ropkins,et al.  openair - An R package for air quality data analysis , 2012, Environ. Model. Softw..

[71]  Matthew West,et al.  A characterization of volatile organic compounds and secondary organic aerosol at a mountain site in the Southeastern United States , 2015, Journal of Atmospheric Chemistry.

[72]  Meinrat O. Andreae,et al.  Strong present-day aerosol cooling implies a hot future , 2005, Nature.