Phase matrix characterization of long-range-transported Saharan dust using multiwavelength-polarized polar imaging nephelometry
<p>This work investigates scattering matrix elements during different Saharan dust outbreaks over Granada (southeast Spain) in 2022 using a polarized imaging nephelometer (PI-Neph) capable of measuring continuously the phase function (<span class="inline-formula"><i>F<...
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| Main Authors: | , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2025-06-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/25/6325/2025/acp-25-6325-2025.pdf |
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| Summary: | <p>This work investigates scattering matrix elements during different Saharan dust outbreaks over Granada (southeast Spain) in 2022 using a polarized imaging nephelometer (PI-Neph) capable of measuring continuously the phase function (<span class="inline-formula"><i>F</i><sub>11</sub></span>) and the polarized phase function (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M2" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><msub><mi>F</mi><mn mathvariant="normal">12</mn></msub><mo>/</mo><msub><mi>F</mi><mn mathvariant="normal">11</mn></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="46pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="a6e3f1eb3299ee1cf773cb5249d5f2b9"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-25-6325-2025-ie00001.svg" width="46pt" height="14pt" src="acp-25-6325-2025-ie00001.png"/></svg:svg></span></span>) at three different wavelengths (405, 515 and 660 nm) in the range 5–175°. The focus is on two extreme dust events (PM<span class="inline-formula"><sub>10</sub></span> <span class="inline-formula"><i>></i></span> 1000 <span class="inline-formula">µ</span>g m<span class="inline-formula"><sup>−3</sup></span>) in March 2022. During the peaks of these events <span class="inline-formula"><i>F</i><sub>11</sub></span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M8" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><msub><mi>F</mi><mn mathvariant="normal">12</mn></msub><mo>/</mo><msub><mi>F</mi><mn mathvariant="normal">11</mn></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="46pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="eb7bfb3856e0976d3ae203346717101b"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-25-6325-2025-ie00002.svg" width="46pt" height="14pt" src="acp-25-6325-2025-ie00002.png"/></svg:svg></span></span> show the classical patterns observed for dust samples in laboratory measurements available in the Granada–Amsterdam Light Scattering Database at all wavelengths. However, for the moments prior to and after the peaks the results reveal important sensitivity in <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M9" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><msub><mi>F</mi><mn mathvariant="normal">12</mn></msub><mo>/</mo><msub><mi>F</mi><mn mathvariant="normal">11</mn></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="46pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="a1251db68b6a7deb25e36c9406ccfa2b"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-25-6325-2025-ie00003.svg" width="46pt" height="14pt" src="acp-25-6325-2025-ie00003.png"/></svg:svg></span></span> at 405 nm. For the other wavelengths, however, this difference in <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M10" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><msub><mi>F</mi><mn mathvariant="normal">12</mn></msub><mo>/</mo><msub><mi>F</mi><mn mathvariant="normal">11</mn></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="46pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="54ea5d92af68558ddf67c927269fa877"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-25-6325-2025-ie00004.svg" width="46pt" height="14pt" src="acp-25-6325-2025-ie00004.png"/></svg:svg></span></span> is not evident. Moreover, no remarkable changes are found in <span class="inline-formula"><i>F</i><sub>11</sub></span>, which is always characterized by strong predominance of forward scattering. The analyses of more frequent and moderate events recorded in summer 2022 (PM<span class="inline-formula"><sub>10</sub></span> between 50 and 100 <span class="inline-formula">µ</span>g m<span class="inline-formula"><sup>−3</sup></span>) revealed <span class="inline-formula"><i>F</i><sub>11</sub></span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M16" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><msub><mi>F</mi><mn mathvariant="normal">12</mn></msub><mo>/</mo><msub><mi>F</mi><mn mathvariant="normal">11</mn></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="46pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="d0eb8a74480392a1e8346d3ad295ed0f"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-25-6325-2025-ie00005.svg" width="46pt" height="14pt" src="acp-25-6325-2025-ie00005.png"/></svg:svg></span></span> patterns like those observed prior to and after the extreme events. The combination of PI-Neph measurements with additional in situ instrumentation allowed a typing classification that revealed the peaks in the extreme dust events as pure dust, while for the rest of cases it remarked a mixture of dust with urban background pollution. In addition, simulations with the Generalized Retrieval of Atmosphere and Surface Properties (GRASP) code explain the different patterns in <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M17" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><msub><mi>F</mi><mn mathvariant="normal">12</mn></msub><mo>/</mo><msub><mi>F</mi><mn mathvariant="normal">11</mn></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="46pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="4b3a52d979b51bf2696ecfd96fa30942"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-25-6325-2025-ie00006.svg" width="46pt" height="14pt" src="acp-25-6325-2025-ie00006.png"/></svg:svg></span></span>, with changes in the refractive indexes and with the different contributions of the fine and coarse mode.</p> |
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| ISSN: | 1680-7316 1680-7324 |