| Autor: |
Haspel, Carynelisa, Cuiqi Zhang, Wolf, Martin J., Cziczo, Daniel J., Sela, Maor |
| Zdroj: |
Atmospheric Chemistry & Physics Discussions; 4/24/2023, p1-35, 35p |
| Abstrakt: |
Aerosol particles have both natural and anthropogenic origins and are ubiquitous in the atmosphere. One particularly important type is carbonaceous aerosol, including a specific subset, often termed 'elemental carbon' chemically or 'black carbon' (BC) radiatively. Carbonaceous aerosol particles have implications for atmospheric chemistry, human health, and climate both directly and via their ability to act as site of cloud droplet or ice crystal formation. Laboratory experiments and theory are needed to better understand these particles, specifically their radiative impact. We present here laboratory measurements of side/back scattering of visible radiation by analogues of atmospheric BC aggregates obtained using a depolarizing optical particle counter and accompanying theoretical calculations of scattering by compact and fractal theoretical BC aggregates. We show that with random-orientation, the theoretical calculations reproduce the qualitative behavior of the measurements but are unable to reproduce the highest values of the linear depolarization ratio; we are only able to obtain high values of the linear depolarization ratio using fixed orientation. Thus, we suggest that it is possible that models of scattering by BC aggregates that employ the random orientation assumption/option may underpredict the linear depolarization ratio of actual BC aggregates. Both our measurements and our theoretical calculations point to the possibility that bare (uncoated) BC aggregates, as opposed to the aged/coated BC or soot that was investigated in previous studies, can exhibit higher backscattering linear depolarization than previously assumed. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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