NEW ARM VAP Aerosol Optical Properties (AOP): Explanation, Assessment, and Comparisons
Authors
Connor J. Flynn — University of Oklahoma School of Meteorology
Annette S. Koontz — Pacific Northwest National Laboratory
Brian D Ermold — Pacific Northwest National Laboratory
Stephen R. Springston — Brookhaven National Laboratory
Arthur J Sedlacek — Brookhaven National Laboratory
Elisabeth Andrews — University of Colorado
Timothy B Onasch — Aerodyne Research, Inc.
Category
Absorbing aerosol
Description
Aerosols occupy critical roles in Earth’s climate processes with impacts on radiation, on cloud processes, and also on quality of life. ARM operates Aerosol Observation Systems (AOS) to measure local aerosol properties at each fixed site and mobile facility. The aerosol optical properties of absorption and scattering represent key AOS measurements that relate specifically to the radiative effects of aerosols. Instruments measuring these properties are operated 24/7 in conjunction with a size-selecting impactor and processed autonomously by the ARM Data Center. The new Aerosol Optical Properties (AOP) VAP produces a c-level product of _science-ready_ measurements on same-day basis.
The Aerosol Optical Properties VAP computes 60-second averaged PM1 and PM10 absorption, scattering, and extinction at nominal red, green, and blue wavelengths. The filter-based absorption measurements incorporate published corrections described in Bond 1999, Ogren 2010, and Virkkula 2010. The scattering properties incorporate size-dependent truncation corrections described in Anderson & Ogren 1998, reported under STP conditions, and are converted to wavelengths corresponding to the absorption measurements. Intensive properties computed from these bulk extensive properties include scattering angstrom exponents (AE), backscatter fraction (bsf), asymmetry parameter (g), absorption angstrom exponent (AAE), and single scattering albedo (SSA). In addition, a separate daily file contains hourly-averaged quantities including super-micron scattering and absorption fractions.
We present a survey of AOP results from the ASI, ENA, MAO, and SGP ARM facilities where comparison is possible with comparable measurements, especially aethalometers and CAPS instruments.
