Comparison of in situ aerosol extinction and scattering coefficient measurements made during the Aerosol Intensive Operating Period

Abstract

[1] In May 2003, the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Program sponsored the Aerosol Intensive Operating Period (AIOP) which was conducted over the ARM Climate Research Facility (ACRF) in central Oklahoma. One new instrument that flew in the AIOP, called Cadenza, employed a cavity ring-down technique to measure extinction coefficient and a reciprocal nephelometer technique to simultaneously measure scattering coefficient. This instrument is described in this paper, and measurements are compared to those of conventional instrumentation. Agreement between Cadenza extinction coefficient and that derived from combining nephelometer scattering and PSAP absorption (Neph + PSAP) was excellent, about 2%. Agreement between Cadenza scattering coefficient and TSI nephelometer scattering was also excellent, about 2%, well within the uncertainty of the nephelometer and Cadenza scattering measurements. Comparisons between these instruments, made for the special case of plumes, showed that Cadenza measured extinction and scattering several percent higher on average than the Neph + PSAP and nephelometer alone. This difference is likely due to differences in the instrument response time: The response time for Cadenza is 1 s while that for the nephelometer is a minimum of 8 s. Plumes, identified as originating from Siberian biomass burning, are characterized. Composite size distributions from wing-mounted probes showed that two of the plumes had significant large particle modes that resulted in high values of the effective radius. The effect of the large particle mode was not seen in the Å ngström coefficient calculated from the in-cabin scattering measurements because of the characteristics of the aircraft inlet.

Error Analysis and Uncertainty in the Determination of Aerosol Optical Properties Using Cavity Ring-Down Spectroscopy, Integrating Nephelometry, and the Extinction-Minus-Scattering Method

“…CRDS was initially focused on the study of gaseous samples (Brown 2003;Berden and Engeln 2009) due to its high sensitivity and ability to measure absolute extinction. It is increasingly applied to the study of aerosols (Smith and Atkinson 2001;Thompson et al 2002Thompson et al , 2008Strawa et al 2003;Pettersson et al 2004;Moosmüller et al 2005;Strawa et al 2006;Butler et al 2007;Miller and Orr-Ewing 2007;Riziq et al 2007Riziq et al , 2008Rudic et al 2007;Dinar et al 2008). CRDS is able to directly measure the total extinction by the sample of particles contained within the optical cavity; this extinction is the sum of scattering and absorption losses.…”

“…The extinction-minus-scattering technique has been used for airborne ambient measurements , characterization of optical properties of biomass burning aerosols (Riziq et al 2007Rudich et al 2007Rudich et al , 2009, retrieving complex refractive indices of humic-like aerosols (Dinar et al 2008), and determining the SSA of isolated aerosol particles (Butler et al 2007;Miller and Orr-Ewing 2007). Instruments have been developed for SSA and aerosol light absorption measurements that combine aerosol cavity ring-down spectrometers (CRDS) and integrating sphere nephelometers using the same laser beam and sample volume (Smith and Atkinson 2001;Thompson et al 2002Thompson et al , 2008Moosmüller et al 2005;Strawa et al 2006). While these integrated CRDS/nephelometer combinations hold great promise, the method employing separate instruments is more common.…”

Initial investigation of the wavelength dependence of optical properties measured with a new multi-pass Aerosol Extinction Differential Optical Absorption Spectrometer (AE-DOAS)

“…A cavity attenuated phase shift (CAPS) spectroscopy instrument has been tested at 445 and 632 nm with an effective path length of 2 km and is reported to have a precision of ∼0.2 Mm −1 , but is limited to a single wavelength per experiment (Massoli et al, 2010). Cavity ring down (CRD) instruments have been built with several wavelength channels or small spectral ranges, including 1550, 1520, 1064, 683, 675, 620, 570-540, 532, 425-385, 390, 355 nm, with excellent precision (Baynard et al, 2007Bulatov et al, 2002;Butler et al, 2009;Dinar et al, 2008;Mellon et al, 2011;Miles et al, 2010b;Moosmüller et al, 2005;Pettersson et al, 2004;Smith and Atkinson, 2001;Spindler et al, 2007;Strawa et al, 2003Strawa et al, , 2006.…”

Sources of Error and Uncertainty in the Use of Cavity Ring Down Spectroscopy to Measure Aerosol Optical Properties

“…A-CRDS is now routinely used in laboratory (Sappey et al 1998;Vander Wal and Ticich 1999;Smith and Atkinson 2001;Bulatov et al 2002Bulatov et al , 2003Bulatov et al , 2006Strawa et al 2003;Pettersson et al 2004;Baynard et al 2006;Garland et al 2007;Riziq et al 2007;Rudić et al 2007;Dinar et al 2008;Riziq et al 2008;Butler et al 2009;Freedman et al 2009;Khalizov et al 2009;Lang-Yona et al 2009Radney et al 2009;Xue et al 2009;Adler et al 2010;Hasenkopf et al 2010;Miles et al 2010aMiles et al , 2010b and field studies (Thompson et al 2002(Thompson et al , 2003Strawa et al 2006;Garland et al 2008;Nakayama et al 2010) to measure extinction by both aerosol ensembles (Vander Wal and Ticich 1999;Thompson et al 2002Thompson et al , 2003Thompson et al , 2008Strawa et al 2003;Pettersson et al 2004;Baynard et al 2006Baynard et al , 2007Garland et al 2007;Riziq et al 2007;Beaver et al 2008;…”