Parameterizations of size distribution and refractive index of biomass burning organic aerosol with black carbon content
<p>Biomass burning organic aerosol (BBOA) impacts significantly on climate directly through scattering and absorbing solar radiation and indirectly through acting as cloud condensation nuclei. However, fundamental parameters in the simulation of BBOA radiative effects and cloud activities such...
| Main Authors: | , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2022-09-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/22/12401/2022/acp-22-12401-2022.pdf |
| Summary: | <p>Biomass burning organic aerosol (BBOA) impacts significantly on climate
directly through scattering and absorbing solar radiation and indirectly
through acting as cloud condensation nuclei. However, fundamental parameters
in the simulation of BBOA radiative effects and cloud activities such as
size distribution and refractive index remain poorly parameterized in
models. In this study, biomass burning events with high combustion
efficiency characterized by a high black carbon (BC) to BBOA ratio (0.22 on
average) were frequently observed during autumn in the Pearl River Delta
region, China. An improved absorption Ångström exponent (AAE) ratio
method considering both variations and spectral dependence of black carbon
AAE was proposed to differentiate brown carbon (BrC) absorptions from total
aerosol absorptions. BBOA size distributions, mass scattering and absorption
efficiency were retrieved based on the changes in aerosol number size
distribution, scattering coefficients and derived BrC absorptions that
occurred with BBOA spikes. Geometric mean diameter of BBOA volume size
distribution <span class="inline-formula"><i>D</i><sub>gv</sub></span> depended largely on combustion conditions, ranging
from 245 to 505 nm, and a linear relationship between <span class="inline-formula"><i>D</i><sub>gv</sub></span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M3" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">Δ</mi><mi mathvariant="normal">BC</mi><mo>/</mo><mi mathvariant="normal">Δ</mi><mi mathvariant="normal">BBOA</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="70pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="e969a3a318043b5907e84ca7235a70d2"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-22-12401-2022-ie00001.svg" width="70pt" height="14pt" src="acp-22-12401-2022-ie00001.png"/></svg:svg></span></span> was achieved. The retrieved real part of the BBOA refractive index
ranges from 1.47 to 1.64, with evidence showing that its variations might
depend largely on combustion efficiency, which is rarely investigated in
existing literature but which however requires further comprehensive investigations.
Retrieved imaginary parts of BBOA refractive index (<span class="inline-formula"><i>m</i><sub>i,BBOA</sub></span>) correlated
highly with <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M5" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">Δ</mi><mi mathvariant="normal">BC</mi><mo>/</mo><mi mathvariant="normal">Δ</mi><mi mathvariant="normal">BBOA</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="70pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="35421c12eb87197632d2ba71f8e0ba37"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-22-12401-2022-ie00002.svg" width="70pt" height="14pt" src="acp-22-12401-2022-ie00002.png"/></svg:svg></span></span> (<span class="inline-formula"><i>R</i><i>></i>0.88</span>) but differ a lot from previous parameterization schemes. The reason behind the inconsistency
might be that single formula parameterizations of <span class="inline-formula"><i>m</i><sub>i,BBOA</sub></span> over the
whole <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M8" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">BC</mi><mo>/</mo><mi mathvariant="normal">BBOA</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="54pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="46496ecdffe248890670b046e4cce32d"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-22-12401-2022-ie00003.svg" width="54pt" height="14pt" src="acp-22-12401-2022-ie00003.png"/></svg:svg></span></span> range were used in previous studies which might deviate
substantially for specific <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M9" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">BC</mi><mo>/</mo><mi mathvariant="normal">BBOA</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="54pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="47e4e3b986dc2b8a159de46f21efacb8"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-22-12401-2022-ie00004.svg" width="54pt" height="14pt" src="acp-22-12401-2022-ie00004.png"/></svg:svg></span></span> ranges. Thus, a new scheme that
parameterizes wavelength-dependent <span class="inline-formula"><i>m</i><sub>i,BBOA</sub></span> was presented, which filled
the gap for field-based BBOA absorptivity parameterizations of
<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M11" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal"></mi><mi mathvariant="normal"></mi><mi mathvariant="normal"></mi><mi mathvariant="normal"></mi><mi mathvariant="normal"></mi><mi mathvariant="normal"></mi><mi mathvariant="normal"></mi><mi mathvariant="normal">BC</mi><mo>/</mo><mi mathvariant="normal">BBOA</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="54pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="a7ec4c358ec753c77c33d21edcbdd7b1"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-22-12401-2022-ie00005.svg" width="54pt" height="14pt" src="acp-22-12401-2022-ie00005.png"/></svg:svg></span></span> <span class="inline-formula"><i>></i>0.1</span>. These findings have significant implications for
simulating BBOA climate effects and suggest that linking both BBOA
refractive index and BBOA volume size distributions to BC content might be a
feasible and a good choice for climate models.</p> |
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| ISSN: | 1680-7316 1680-7324 |