Estimating marine aerosol particle volume and number from Maritime Aerosol Network data 1Goddard Earth Sciences Technology And Research (GESTAR), Universities Space Research Association (USRA), Columbia, Maryland, USA
28 Sep 2012
2NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
3Sigma Space Corporation, Lanham, Maryland, USA
4Science Systems Applications Inc., Lanham, Maryland, USA
Received: 21 May 2012 – Published in Atmos. Chem. Phys. Discuss.: 12 Jun 2012Abstract. As well as spectral aerosol optical depth (AOD), aerosol composition and
concentration (number, volume, or mass) are of interest for a variety of
applications. However, remote sensing of these quantities is more difficult
than for AOD, as it is more sensitive to assumptions relating to aerosol
composition. This study uses spectral AOD measured on Maritime Aerosol
Network (MAN) cruises, with the additional constraint of a microphysical
model for unpolluted maritime aerosol based on analysis of Aerosol Robotic
Network (AERONET) inversions, to estimate these quantities over open ocean.
When the MAN data are subset to those likely to be comprised of maritime
aerosol, number and volume concentrations obtained are physically reasonable.
Attempts to estimate surface concentration from columnar abundance, however,
are shown to be limited by uncertainties in vertical distribution. Columnar
AOD at 550 nm and aerosol number for unpolluted maritime cases are
also compared with Moderate Resolution Imaging Spectroradiometer (MODIS)
data, for both the present Collection 5.1 and forthcoming Collection 6. MODIS
provides a best-fitting retrieval solution, as well as the average for
several different solutions, with different aerosol microphysical models. The
"average solution" MODIS dataset agrees more closely with MAN than the
"best solution" dataset. Terra tends to retrieve lower aerosol number
than MAN, and Aqua higher, linked with differences in the aerosol models
commonly chosen. Collection 6 AOD is likely to agree more closely with MAN
over open ocean than Collection 5.1. In situations where spectral AOD is
measured accurately, and aerosol microphysical properties are reasonably
well-constrained, estimates of aerosol number and volume using MAN or similar
data would provide for a greater variety of potential comparisons with
aerosol properties derived from satellite or chemistry transport model data.
However, without accurate AOD data and prior knowledge of microphysical
properties, such attempts are fraught with high uncertainties.
Revised: 27 Aug 2012 – Accepted: 13 Sep 2012 – Published: 28 Sep 2012
Citation: Sayer, A. M., Smirnov, A., Hsu, N. C., Munchak, L. A., and Holben, B. N.: Estimating marine aerosol particle volume and number from Maritime Aerosol Network data, Atmos. Chem. Phys., 12, 8889-8909, doi:10.5194/acp-12-8889-2012, 2012.