AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Merging Multiple Instrument Measurements of Aerosol Size Distributions into a Best Estimate Aerosol Size Distribution
JASON TOMLINSON, Fan Mei, Don Collins, Gunnar Senum, Stephen Springston, Chen Song, Jacqueline Wilson, Alla Zelenyuk, Jennifer Comstock, John Hubbe, John Shilling, Duli Chand, Mikhail Pekour, Beat Schmid, Larry Berg, Pacific Northwest National Laboratory
Abstract Number: 577 Working Group: Instrumentation and Methods
Abstract The Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Aerial Facility (AAF) utilizes three optically based aerosol probes, mounted on under-wing pylons, to measure the aerosol ambient size distribution aboard the DOE AAF G-1 aircraft. The Ultra High Sensitivity Aerosol Spectrometer – Airborne (UHSAS-A), Passive Cavity Aerosol Spectrometer (PCASP), and the Cloud Aerosol Spectrometer (CAS) each measure a subset of the ambient aerosol size distribution from 0.06 micro-meter to greater than 10 micro-meter at a sampling frequency of 1 Hz. These optically-based instruments are used aboard an aircraft because they provide the desired sampling rates. However, the instruments have known problems stemming from poor collection efficiency at certain sizes, noisy data, and difficulty in accurate sizing of the aerosol if its composition is different from the calibration aerosol. In addition, the merging of size distributions is not always straightforward. These problems can lead to difficulty when conducting closure studies or in modeling studies.
The DOE AAF has recently released a Best Estimate Aerosol Size Distribution to remedy the aforementioned problems. Errors in the measured size distributions are quantified and the size distributions for the three probes are recovered, merged, and smoothed using a kernel-based Twomey algorithm. The fidelity of the merged size distribution will be presented through lab studies, comparison with vacuum aerodynamic size distributions measured by single particle mass spectrometers (SPLAT II and mini-SPLAT, and a comparison with ground based measurements during the Two-Column Aerosol Project intensive operation periods in July 2012 and February 2013.