Measurement report: Comparison of airborne, in situ measured, lidar-based, and modeled aerosol optical properties in the central European background – identifying sources of deviations
<p>A unique data set derived from remote sensing, airborne, and ground-based in situ measurements is presented. This measurement report highlights the known complexity of comparing multiple aerosol optical parameters examined with different approaches considering different states of humidifica...
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| Autores principales: | , , , , , , , , , , , , |
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| Formato: | article |
| Lenguaje: | EN |
| Publicado: |
Copernicus Publications
2021
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| Materias: | |
| Acceso en línea: | https://doaj.org/article/5f0ed27a4232498eb79f490e3fcd1870 |
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| Sumario: | <p>A unique data set derived from remote sensing, airborne, and
ground-based in situ measurements is presented. This measurement report
highlights the known complexity of comparing multiple aerosol optical
parameters examined with different approaches considering different states
of humidification and atmospheric aerosol concentrations. Mie-theory-based
modeled aerosol optical properties are compared with the respective results of airborne and ground-based in situ measurements and remote sensing (lidar and photometer) performed at the rural central European observatory at Melpitz, Germany. Calculated extinction-to-backscatter ratios (lidar ratios) were in the range of previously reported values. However, the lidar ratio is a function of the aerosol type and the relative humidity. The particle lidar ratio (LR) dependence on relative humidity was quantified and followed the trend found in previous studies. We present a fit function for the lidar wavelengths of 355, 532, and 1064 nm with an underlying equation of <span class="inline-formula"><i>f</i><sub>LR</sub></span>(RH, <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M2" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi mathvariant="italic">γ</mi><mo>(</mo><mi mathvariant="italic">λ</mi><mo>)</mo><mo>)</mo><mo>=</mo><msub><mi>f</mi><mi mathvariant="normal">LR</mi></msub><mo>(</mo><mtext>RH</mtext><mo>=</mo><mn mathvariant="normal">0</mn><mo>,</mo><mi mathvariant="italic">λ</mi><mo>)</mo><mo>×</mo><mo>(</mo><mn mathvariant="normal">1</mn><mo>-</mo><mtext>RH</mtext><msup><mo>)</mo><mrow><mo>-</mo><mi mathvariant="italic">γ</mi><mo>(</mo><mi mathvariant="italic">λ</mi><mo>)</mo></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="176pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="458f9952503443f938b0cb23d6a4d7ed"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-16745-2021-ie00001.svg" width="176pt" height="16pt" src="acp-21-16745-2021-ie00001.png"/></svg:svg></span></span>, with the derived estimates of <span class="inline-formula"><i>γ</i></span>(355 nm) <span class="inline-formula">=</span> 0.29 (<span class="inline-formula">±0.01</span>), <span class="inline-formula"><i>γ</i></span>(532 nm) <span class="inline-formula">=</span> 0.48 (<span class="inline-formula">±0.01</span>), and <span class="inline-formula"><i>γ</i></span>(1064 nm) <span class="inline-formula">=</span> 0.31 (<span class="inline-formula">±0.01</span>) for central European aerosol. This parameterization might be used in the data analysis of elastic-backscatter lidar observations or lidar-ratio-based aerosol typing efforts. Our study shows that the used aerosol model could reproduce the in situ measurements of the aerosol particle light extinction coefficients (measured at dry conditions) within 13 %. Although the model reproduced the in situ measured aerosol particle light absorption coefficients within a reasonable range, we identified many sources for significant uncertainties in the simulations, such as the unknown aerosol mixing state, brown carbon (organic material) fraction, and the unknown aerosol mixing state wavelength-dependent refractive index. The modeled ambient-state aerosol particle light extinction and backscatter coefficients were smaller than the measured ones. However, depending on the prevailing aerosol conditions, an overlap of the uncertainty ranges of both approaches was achieved.</p> |
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