Towards Improved Agreement between Measured and Calculated Total Scattering of Marine Aerosol: TCAP Airborne Data

 
Poster PDF

Authors

Connor J. Flynn — University of Oklahoma School of Meteorology
Evgueni Kassianov — Pacific Northwest National Laboratory
Mikhail S. Pekour — Pacific Northwest National Laboratory
Larry Berg — Pacific Northwest National Laboratory
Jason Tomlinson — Pacific Northwest National Laboratory
John E Shilling — Pacific Northwest National Laboratory
Duli Chand — Pacific Northwest National Laboratory

Category

Absorbing Aerosol

Description

Many of the science questions address by the ARM and ASR Programs require the use of synergistic data sets. However, successful data integration still represents a challenging task. For example, poor agreement between the measured and calculated total scattering coefficients has been obtained recently for a “simple” marine case with weakly absorbing aerosol measured over the Southeast Pacific Ocean by several research aircraft during the VAMOS Ocean-Cloud-Atmosphere-Land Regional Experiment (VOCALS-Rex). The primary purpose of our work is to answer the following question: What level of agreement between the measured and calculated values of total aerosol scattering can be achieved using airborne data collected by the DOE Gulfstream 1 (G-1) aircraft over the western North Atlantic Ocean and Cape Cod, Massachusetts during the Two-Column Aerosol Project (TCAP)? We start our presentation with a description of the integrated TCAP airborne dataset obtained from a comprehensive suite of instruments, which includes a nephelometer, a particle soot absorption photometer (PSAP), optical particle counters, and an aerosol mass spectrometer (AMS). Similar to the VOCALS-Rex data, the TCAP dataset represents mainly weakly absorbing aerosol. Then we describe an approach for determining improved aerosol size distributions using complementary chemical composition data. The chemical composition data are used to infer the aerosol complex refractive index (RI), which is applied for adjusting size distributions to better account for absorbing aerosol. Once the RI-related adjustments are applied, we are able to improve substantially agreement between the measured and calculated values of total aerosol scattering. Finally, we provide a follow-up of our approach and its expected applications to the available and anticipated airborne data from previous and future ARM supported field campaigns and underline the importance of these observational constrains for climate models.