A review of biomass burning emissions part III: intensive optical properties of biomass burning particles

Abstract

Abstract. Because of its wide coverage over much of the globe, biomass burning has been widely studied in the context of direct radiative forcing. Such study is warranted as smoke particles scatter and at times absorb solar radiation efficiently. Further, as much of what is known about smoke transport and impacts is based on remote sensing measurements, the optical properties of smoke particles have far reaching effects into numerous aspects of biomass burning studies. Global estimates of direct forcing have been widely varying, ranging from near zero to −1 W m −2 . A significant part of this difference can be traced to varying assumptions on the optical properties of smoke. This manuscript is the third part of four examining biomass-burning emissions. Here we review and discuss the literature concerning measurement and modeling of optical properties of biomassburning particles. These include available data from published sensitivity studies, field campaigns, and inversions from the Aerosol Robotic Network (AERONET) of Sun photometer sites. As a whole, optical properties reported in the literature are varied, reflecting both the dynamic nature of fires, variations in smoke aging processes and differences in measurement technique. We find that forward modeling or "internal closure" studies ultimately are of little help in resolving outstanding measurement issues due to the high degree of degeneracy in solutions when using "reasonable" input parameters. This is particularly notable with respect to index of refraction and the treatment of black carbon. Consequently, previous claims of column closure may in fact be more ambiguous. Differences between in situ and retrieved ω o values have implications for estimates of mass scattering and mass absorption efficiencies. In this manuscript we Correspondence to: J. S. Reid (reidj@nrlmry.navy.mil) review and discuss this community dataset. Strengths and lapses are pointed out, future research topics are prioritized, and best estimates and uncertainties of key smoke particle parameters are provided.

Separation of the optical and mass features of particle components in different aerosol mixtures by using POLIPHON retrievals in synergy with continuous polarized Micro-Pulse Lidar (P-MPL) measurements

“…For instance, a k SM = 4.5 ± 1.4 m 2 g −1 is derived for fine smoke particles at 06:00 UTC (see Table 3). This value is in good agreement with that reported for Canadian forest fire smoke aerosols (Ichoku and Kaufman, 2005;Reid et al, 2005). However, a rather lower MEE value is obtained for the coarse-mode NS particles (k NS = 2.4 ± 0.5 m 2 g −1 ) at the same time.…”

“…Particular MEE values derived for smoke particles, k SM = 4.5 ± 1.1 and 1.9 ± 0.4 m 2 g −1 , are obtained at 06:00 and 14:00 UTC. These results would indicate that smoke plumes detected in the first scenario are predominantly composed of relatively pure fine biomassburning particles, with similar MEE values to those reported for Canadian boreal forest fire aged smoke particles (Ichoku and Kaufman, 2005;Reid et al, 2005). However, those observed in the second one would represent a mixed state of smoke particles with an enhanced coarse mode, thus decreasing their MEE.…”

“…Table 3 shows the AERONET parameters involved in the extinction-to-mass conversion (VC c,f , τ c,f ) at selected times for each aerosol case together with those typical particle densities Pd for each aerosol component. In particular, Pd values assumed for each type of aerosols are 2.60 g cm −3 for dust (Ansmann et al, 2012), 1.30 g cm −3 for smoke (Reid et al, 2005) and 0.92 g cm −3 for pollen (Platanus) particles (Jackson and Lyford, 1999;Zhang et al, 2014). For the other components, the particle density is obtained from the OPAC database .…”

Retrieving the height of smoke and dust aerosols by synergistic use of VIIRS, OMPS, and CALIOP observations

“…However, it would be challenging to apply the algorithm to aerosol events originating from multiple source regions that can show variable optical properties within a granule, dust or smoke layers mixed with other aerosol types or each other, and/or the aerosols of which optical properties significantly differ from the assumed aerosol models. It is also known that the optical properties of smoke (both SSA and AE) can change rapidly during the aging process [Reid et al, 2005]. In addition, the present algorithm showed a weakness for multilayered aerosol events, for which it tends to report intermediate heights between the layers, due to the limited sensitivity of passive sensors to such cases.…”

Mixing state of biomass burning particles by single particle aerosol mass spectrometer in the urban area of PRD, China

“…Up to 38% of the total emissions of black carbon in China have been attributed to biomass burning (Streets et al, 2001). Moreover, biomass burning particles can effectively scatter and absorb solar radiation, and are good cloud condensation nuclei (Reid et al, 2005a(Reid et al, , 2005b. Therefore, biomass burning has always been of interest to scientists.…”