Atmospheric Radiation Measurements Aerosol Intensive Operating Period: Comparison of Aerosol Scattering during Coordinated Flights

[1] In May 2003, a Twin Otter airplane, equipped with instruments for making in situ measurements of aerosol optical properties, was deployed during the Atmospheric Radiation Measurements (ARM) Program's Aerosol Intensive Operational Period in Oklahoma. Several of the Twin Otter flights were flown in formation with an instrumented light aircraft (Cessna 172XP) that makes routine in situ aerosol profile flights over the site. This paper presents comparisons of measured scattering coefficients at 467 nm, 530 nm, and 675 nm between identical commercial nephelometers aboard each aircraft. Overall, the agreement between the two nephelometers decreases with longer wavelength. During the majority of the flights, the Twin Otter flew with a diffuser inlet while the Cessna had a 1 μm impactor, allowing for an estimation of the fine mode fraction aloft. The fine mode fraction aloft was then compared to the results of a ground-based nephelometer. Comparisons are also provided in which both nephelometers operated with identical 1 μm impactors. These scattering coefficient comparisons are favorable at the longer wavelengths (i.e., 530 nm and 675 nm), yet differed by approximately 30% at 467 nm. Mie scattering calculations were performed using size distribution measurements, made during the level flight legs. Results are also presented from Cadenza, a new continuous wave cavity ring-down (CW-CRD) instrument, which compared favorably (i.e., agreed within 2%) with data from other instruments aboard the Twin Otter. With this paper, we highlight the significant implications of coarse mode (larger than 1 μm) aerosol aloft with respect to aerosol optical properties.

[1]  Daniel M. Murphy,et al.  Wind Tunnel Tests of a Shrouded Aircraft Inlet , 1998 .

[2]  G. Meijer,et al.  Cavity Ringdown Spectroscopy , 1998, Technical Digest. 1998 EQEC. European Quantum Electronics Conference (Cat. No.98TH8326).

[3]  Beat Schmid,et al.  Evaluation of daytime measurements of aerosols and water vapor made by an operational Raman lidar over the Southern Great Plains , 2006 .

[4]  H. Jonsson,et al.  Comparison of in situ aerosol extinction and scattering coefficient measurements made during the Aerosol Intensive Operating Period , 2006 .

[5]  P. Quinn,et al.  A comparison and summary of aerosol optical properties as observed in situ from aircraft, ship, and land during ACE‐Asia , 2005 .

[6]  Beat Schmid,et al.  Clear-Column Radiative Closure During ACE-Asia: Comparison of Multiwavelength Extinction Derived from Particle Size and Composition with Results from Sun Photometry , 2002 .

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

[8]  J. Seinfeld,et al.  In situ aerosol-size distributions and clear-column radiative closure during ACE-2 , 2000 .

[9]  Young-Joon Kim,et al.  An overview of ACE‐Asia: Strategies for quantifying the relationships between Asian aerosols and their climatic impacts , 2003 .

[10]  A. Clarke,et al.  Aircraft studies of size‐dependent aerosol sampling through inlets , 1992 .

[11]  M. L. Laucks,et al.  An Evaluation of the Community Aerosol Inlet for the NCAR C-130 Research Aircraft , 2001 .

[12]  I. Tang,et al.  Water activities, densities, and refractive indices of aqueous sulfates and sodium nitrate droplets of atmospheric importance , 1994 .

[13]  M. Wendisch,et al.  Particle scattering, backscattering, and absorption coefficients: An in situ closure and sensitivity study , 2002 .

[14]  Barry J. Huebert,et al.  Size distributions and mixtures of dust and black carbon aerosol in Asian outflow: Physiochemistry and optical properties , 2004 .

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

[16]  W. Wiscombe.  Improved Mie scattering algorithms. , 1980, Applied optics.

[17]  W. G. Collins,et al.  Dust and pollution transport on global scales: Aerosol measurements and model predictions , 2001 .

[18]  H. Jonsson,et al.  Determination of the Transmission Efficiency of an Aircraft Aerosol Inlet , 2005 .

[19]  A Lacis,et al.  Climate forcings in the industrial era. , 1998, Proceedings of the National Academy of Sciences of the United States of America.

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

[21]  Anthony W. Strawa,et al.  The Measurement of Aerosol Optical Properties Using Continuous Wave Cavity Ring-Down Techniques , 2003 .

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

[23]  J. Houghton,et al.  Climate change 2001 : the scientific basis , 2001 .

[24]  Haflidi H. Jonsson,et al.  Ocean Sciences: UNOLS Now Oversees Research Aircraft Facilities for Ocean Science , 2004 .

[25]  M. Krämer,et al.  Sampling characteristics of inlets operated at low U/U0 ratios: new insights from computational fluid dynamics (CFX) modeling , 2004 .

[26]  Anders Ångström,et al.  On the Atmospheric Transmission of Sun Radiation and on Dust in the Air , 1929 .

[27]  Alexander Smirnov,et al.  How well do State-of-the-Art Techniques Measuring the Vertical Profile of Tropospheric Aerosol Extinction Compare? , 2006 .

[28]  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 .

[29]  B. Huebert,et al.  Sea-salt vertical profiles over the Southern and tropical Pacific oceans : Microphysics, optical properties, spatial variability, and variations with wind speed , 2004 .

[30]  J. Ogren,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 , 2001 .

[31]  Beat Schmid,et al.  The Reno Aerosol Optics Study: An Evaluation of Aerosol Absorption Measurement Methods , 2005 .

[32]  V. Ramanathan,et al.  Evidence of surface cooling from absorbing aerosols , 2002 .

[33]  G. McFarquhar,et al.  Parameterizations of INDOEX microphysical measurements and calculations of cloud susceptibility: Applications for climate studies , 2001 .

[34]  P. Novelli,et al.  Long‐range transport of Siberian biomass burning emissions and impact on surface ozone in western North America , 2004 .

[35]  B. Huebert,et al.  Airborne aerosol inlet passing efficiency measurement , 1990 .

[36]  W. Arnott,et al.  Toward an ideal integrating nephelometer. , 2003, Optics letters.

[37]  B. Huebert,et al.  PELTI: Measuring the Passing Efficiency of an Airborne Low Turbulence Aerosol Inlet , 2004 .

[38]  Eric P. Shettle,et al.  Atmospheric Aerosols: Global Climatology and Radiative Characteristics , 1991 .

[39]  R. Charlson,et al.  Radiative Properties of the Background Aerosol: Absorption Component of Extinction , 1985, Science.

[40]  Nelson P. Bryner,et al.  Radiometric model of the transmission cell-reciprocal nephelometer , 1994 .

[41]  Robert J. Charlson,et al.  Performance Characteristics of a High-Sensitivity, Three-Wavelength, Total Scatter/Backscatter Nephelometer , 1996 .

[42]  J. Smith,et al.  A portable pulsed cavity ring-down transmissometer for measurement of the optical extinction of the atmospheric aerosol. , 2001, The Analyst.

[43]  H. Jonsson,et al.  Aerosol Chemistry, and Light-Scattering and Hygroscopicity Budgets during Outflow from East Asia , 2003 .

[44]  Kenneth W. Busch,et al.  Cavity-ringdown spectroscopy : an ultratrace-absorption measurement technique , 1999 .

[45]  A. O’Keefe,et al.  Cavity ring‐down optical spectrometer for absorption measurements using pulsed laser sources , 1988 .

[46]  S. Schwartz,et al.  The Atmospheric Radiation Measurement (ARM) Program: Programmatic Background and Design of the Cloud and Radiation Test Bed , 1994 .

[47]  D. Romanini,et al.  CW cavity ring down spectroscopy , 1997 .

[48]  A. Wiedensohler,et al.  Sampling Characteristics of an Aircraft-Borne Aerosol Inlet System , 2001 .

[49]  H. Jonsson,et al.  The cloud, aerosol and precipitation spectrometer: a new instrument for cloud investigations , 2001 .

[50]  A. Stohl,et al.  Around the world in 17 days - hemispheric-scale transport of forest fire smoke from Russia in May 2003 , 2004 .

[51]  James E. Dye,et al.  Performance of a focused cavity aerosol spectrometer for measurements in the stratosphere of particle size in the 0.06-2.0-micrometer-diameter range , 1995 .