1Chemistry Department, Portland State University, Portland, OR, 97207-0751, USA
2University of Colorado, Cooperative Institute for Research in Environmental Sciences, Boulder, CO, 80309, USA
3NOAA Earth System Research Laboratory, Chemical Science Division, Boulder, CO, 80305, USA
4CARTEL, Département de géomatique appliqueé, Université de Sherbrooke, Sherbrooke, Quebec, J1K 2R1, Canada
5NOAA Pacific Marine Environment Laboratory, 7600 Sand Point Way NE, Seattle, WA, 98115, USA
6Department of Atmospheric Sciences, Texas A & M University, College Station, TX, 77843, USA
7Earth and Atmospheric Sciences Department, University of Houston, Houston, TX, 77204-5007, USA
*now at: Aerodyne Research, Inc. Billerica, MA, 01821, USA
Received: 09 Jul 2009 – Discussion started: 20 Aug 2009
Abstract. During the 2006 Texas Air Quality Study and Gulf of Mexico Atmospheric Composition and Climate Study (TexAQS-GoMACCS 2006), the optical, chemical and microphysical properties of atmospheric aerosols were measured on multiple mobile platforms and at ground based stations. In situ measurements of the aerosol light extinction coefficient (σep) were performed by two multi-wavelength cavity ring-down (CRD) instruments, one located on board the NOAA R/V Ronald H. Brown (RHB) and the other located at the University of Houston, Moody Tower (UHMT). An AERONET sunphotometer was also located at the UHMT to measure the columnar aerosol optical depth (AOD). The σep data were used to extract the extinction Ångström exponent (åep), a measure of the wavelength dependence of σep. There was general agreement between the åep (and to a lesser degree σep) measurements by the two spatially separated CRD instruments during multi-day periods, suggesting a regional scale consistency of the sampled aerosols. Two spectral models are applied to the σep and AOD data to extract the fine mode fraction of extinction (η) and the fine mode effective radius (Reff,f). These two parameters are robust measures of the fine mode contribution to total extinction and the fine mode size distribution, respectively. The results of the analysis are compared to Reff,f values extracted using AERONET V2 retrievals and calculated from in situ particle size measurements on the RHB and at UHMT. During a time period when fine mode aerosols dominated the extinction over a large area extending from Houston/Galveston Bay and out into the Gulf of Mexico, the various methods for obtaining Reff,f agree qualitatively (showing the same temporal trend) and quantitatively (pooled standard deviation = 28 nm).
Revised: 29 Nov 2009 – Accepted: 09 Dec 2009 – Published: 06 Jan 2010
Atkinson, D. B., Massoli, P., O'Neill, N. T., Quinn, P. K., Brooks, S. D., and Lefer, B.: Comparison of in situ and columnar aerosol spectral measurements during TexAQS-GoMACCS 2006: testing parameterizations for estimating aerosol fine mode properties, Atmos. Chem. Phys., 10, 51-61, doi:10.5194/acp-10-51-2010, 2010.