An analysis of AERONET aerosol absorption properties and classifications representative of aerosol source regions

Abstract

[1] Partitioning of mineral dust, pollution, smoke, and mixtures using remote sensing techniques can help improve accuracy of satellite retrievals and assessments of the aerosol radiative impact on climate. Spectral aerosol optical depth (t) and single scattering albedo (w o ) from Aerosol Robotic Network (AERONET) measurements are used to form absorption (i.e., w o and absorption Ångström exponent (a abs )) and size (i.e., extinction Ångström exponent (a ext ) and fine mode fraction of t) relationships to infer dominant aerosol types. Using the long-term AERONET data set (1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010), 19 sites are grouped by aerosol type based on known source regions to (1) determine the average w o and a abs at each site (expanding upon previous work), (2) perform a sensitivity study on a abs by varying the spectral w o , and (3) test the ability of each absorption and size relationship to distinguish aerosol types. The spectral w o averages indicate slightly more aerosol absorption (i.e., a 0.0 < dw o ≤ 0.02 decrease) than in previous work, and optical mixtures of pollution and smoke with dust show stronger absorption than dust alone. Frequency distributions of a abs show significant overlap among aerosol type categories, and at least 10% of the a abs retrievals in each category are below 1.0. Perturbing the spectral w o by AE0.03 induces significant a abs changes from the unperturbed value by at least $AE0.6 for Dust, $AE0.2 for Mixed, and $AE0.1 for Urban/Industrial and Biomass Burning. The w o440nm and a ext440-870nm relationship shows the best separation among aerosol type clusters, providing a simple technique for determining aerosol type from surface-and future space-based instrumentation.

Systematic analysis of tropospheric NO&lt;sub&gt;2&lt;/sub&gt; long-range transport events detected in GOME-2 satellite data

“…NO 2 and glyoxal (CHOCHO) from large bush fires such as the Black Saturday fires are routinely observed in satellite data (Wittrock et al, 2006;Vrekoussis et al, 2009) and GOME-2 data show elevated NO 2 vertical column densities over southwestern Australia on 25 and 26 April 2008 -on the order of 3 × 10 15 molecules cm −2 , a factor 2 higher than background levels. It is likely, that our data product underestimates these values due to a lowered air-mass factor in the presence of black carbon aerosol in bush fire smoke plumes (Martin et al, 2003;Leitão et al, 2010;Giles et al, 2012). An origin in bush fires would also explain the necessary lifting of the NO 2 from the planetary boundary layer into the free troposphere in the absence of a frontal system (see Labonne et al, 2007).…”

AERONET-based models of smoke-dominated aerosol near source regions and transported over oceans, and implications for satellite retrievals of aerosol optical depth

“…Biomass burning at Moscow during the period considered (summers of 2002 and 2010) was influenced more strongly by peat burning than the other boreal sites, although forest burning contributed in some cases (Gorchakov et al, 2004;Chubarova et al, 2011); 90 % of the inversions obtained at Moscow were from intense (predominantly peat) burning during summer 2002. A complication for Moscow is that it is a large city and thus there will be an additional contribution from local aerosol sources, which may also lead to scatter in the parametrisations.…”

“…surface reflectance inputs; Eck et al, 2008). Giles et al (2012) also examined a few of these sites, although that study was focussed on characterising global aerosol absorption properties from a variety of types, rather than creation of microphysical/optical models to represent these aerosols. State/country information for each site is provided the first time a site is discussed in the text.…”

Relating aerosol absorption due to soot, organic carbon, and dust to emission sources determined from in-situ chemical measurements

“…Russell et al (2010) highlighted that many recent studies have shown the persistent connections between aerosol absorbing species and the wavelength dependence of absorption. Thus, numerous studies have classified absorbing aerosol types from optical properties measured on ground stations (Eck et al, 1999;Dubovik et al, 2002;Collaud Coen et al, 2004;Fialho et al, 2005;Meloni et al, 2006;Kalapureddy et al, 2009;Mielonen et al, 2009;Giles et al, 2011Giles et al, , 2012 and from satellites (Higurashi and Nakajima, 2002;Barnaba and Gobbi, 2004;Jeong and Li, 2005;Kaufman et al, 2005;Torres et al, 2005;Kaskaoutis et al, 2007;Kim et al, 2007;Yu et al, 2009). In this study, in-situ optical properties and single particle chemical composition measured during three aircraft field campaigns are combined in order to validate a methodology for the estimation of absorbing aerosol types using spectral optical properties.…”