AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
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Evaluating the Consistency of Submicron Aerosol Mass during the Atmospheric Tomography Mission (ATom): A Focus on the Aerosol Mass Spectrometer Quantification
HONGYU GUO, Pedro Campuzano-Jost, Benjamin A. Nault, Douglas Day, Christina Williamson, Agnieszka Kupc, Charles Brock, Gregory Schill, Karl D. Froyd, Daniel Murphy, Eric Scheuer, Jack Dibb, Joseph Katich, Jose-Luis Jimenez, CIRES, University of Colorado, Boulder
Abstract Number: 651 Working Group: Instrumentation and Methods
Abstract The Aerodyne high-resolution time-of-flight Aerosol Mass Spectrometer (AMS) is a widely used real-time-response instrument that provides quantifiable mass and size products of non-refractory submicron chemical species. Although good agreements have been found in past field studies when intercomparing with other instruments, concerns regarding the AMS calibration have recently been discussed in the literature. This study aims to provide a critical evaluation of AMS quantification through comparisons to other well characterized and operated instruments in NASA Atmospheric Tomography Mission (ATom). These aircraft campaigns, which sampled the remote marine troposphere from 65°S to 80°N over different seasons, offer a unique opportunity to evaluate AMS quantification over a very wide range of aerosol concentrations and compositions. The NOAA particle size spectrometers (NMASS+UHSAS+LAS; measure 4nm-5µm particle number size distributions), a Particle Analysis by Laser Mass Spectrometer (PALMS; provides size-resolved particle composition when coupled with the size distributions), and a Soluble Acidic Gases and Aerosols (SAGA-IC&filters; measures inorganic ions concentrations) are included in the intercomparisons. Special attention was paid to characterize the AMS size-dependent transmission with in-field calibrations; this provides crucial context when comparing to instruments with very different size cuts. Good agreement was found between the AMS calculated volumes (including SP2 black carbon) and the submicron volume derived from the NOAA particle size spectrometers over three orders-of-magnitude concentrations (slope = 0.97 and 0.88, r2 = 0.93 and 0.87, for ATom-1 and -2, respectively). A comprehensive evaluation was performed on the different sources of uncertainty and their impact on the comparison. Good agreement was also found between SAGA, PALMS, and AMS sulfate and between the PALMS apportioned organic aerosol (OA) and AMS OA. These results suggest the absence of important unknown quantification biases for AMS total mass, sulfate, and OA for the mostly aged air masses encountered in ATom.