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Title: Airborne Aerosol in Situ Measurements during TCAP: A Closure Study of Total Scattering

We present here a framework for calculating the total scattering of both non-absorbing and absorbing aerosol at ambient conditions from aircraft data. The synergistically employed aircraft data involve aerosol microphysical, chemical, and optical components and ambient relative humidity measurements. Our framework is developed emphasizing the explicit use of the complementary chemical composition data for estimating the complex refractive index (RI) of particles, and thus obtaining improved ambient size spectra derived from Optical Particle Counter (OPC) measurements. The feasibility of our framework for improved calculations of total aerosol scattering is demonstrated for different ambient conditions with a wide range of relative humidities (from 5 to 80%) using three types of data collected by the U.S. Department of Energy (DOE) G-1 aircraft during the recent Two-Column Aerosol Project (TCAP). Namely, these three types of data employed are: (1) size distributions measured by an Ultra High Sensitivity Aerosol Spectrometer (UHSAS; 0.06-1 µm), a Passive Cavity Aerosol Spectrometer (PCASP; 0.1-3 µm) and a Cloud and Aerosol Spectrometer (CAS; 0.6- >10 µm), (2) chemical composition data measured by an Aerosol Mass Spectrometer (AMS; 0.06-0.6 µm) and a Single Particle Soot Photometer (SP2; 0.06-0.6 µm), and (3) the dry total scattering coefficient measured by a TSImore » integrating nephelometer at three wavelengths (0.45, 0.55, 0.7 µm) and scattering enhancement factor measured with a humidification system at three RHs (near 45%, 65% and 90%) at a single wavelength (0.525 µm). We demonstrate that good agreement (~10% on average) between the observed and calculated scattering at these three wavelengths can be obtained using the best available chemical composition data for the RI-based correction of the OPC-derived size spectra. We also demonstrate that ignoring the RI-based correction and using non-representative RI values can cause a substantial underestimation (~40% on average) and overestimation (~35% on average) of the calculated total scattering, respectively.« less
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [2] ;  [3] ;  [1]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  2. University of Nevada, Reno, NV (United States)
  3. Brookhaven National Laboratory, Upton, NY (United States)
Publication Date:
Report Number(s):
PNNL-SA-110601; BNL-108230-2015-JA
Journal ID: ISSN 2073-4433; ATMOCZ; KP1701000
Grant/Contract Number:
AC05-76RL01830; SC00112704
Type:
Accepted Manuscript
Journal Name:
Atmosphere (Basel)
Additional Journal Information:
Journal Name: Atmosphere (Basel); Journal Volume: 6; Journal Issue: 8; Journal ID: ISSN 2073-4433
Publisher:
MDPI
Research Org:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Secretary of Energy (S)
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; 14 SOLAR ENERGY; aircraft measurements of aerosol microphysical, chemical, and optical components and ambient relative humidity; Ultra-High Sensitivity Aerosol Spectrometer (UHSAS); Passive Cavity Aerosol Spectrometer (PCASP); Cloud and Aerosol Spectrometer (CAS); Aerosol Mass Spectrometer (AMS); Single Particle Soot Photometer (SP2); integrating nephelometer; humidification system; Two-Column Aerosol Project (TCAP)
OSTI Identifier:
1209863
Alternate Identifier(s):
OSTI ID: 1213372