Raman lidar-derived optical and microphysical properties of ice crystals within thin Arctic clouds during PARCS campaign
<p>Cloud observations in the Arctic are still rare, which requires innovative observation techniques to assess ice crystal properties. We present an original approach using the Raman lidar measurements applied to a case study in northern Scandinavia. The vertical profiles of the optical proper...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2023-12-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://amt.copernicus.org/articles/16/5847/2023/amt-16-5847-2023.pdf |
| Summary: | <p>Cloud observations in the Arctic are still rare, which requires innovative observation techniques to assess ice crystal properties. We present an original approach using the Raman lidar measurements applied to a case study in northern Scandinavia. The vertical profiles of the optical properties, the effective radius of ice crystals and ice water content (IWC) in Arctic semi-transparent clouds were assessed using quantitative ground-based lidar measurements at 355 nm performed from 13 to 26 May 2016 in Hammerfest (north of Norway, 70<span class="inline-formula"><sup>∘</sup></span>39<span class="inline-formula"><sup>′</sup></span>48<span class="inline-formula"><sup>′′</sup></span> N, 23<span class="inline-formula"><sup>∘</sup></span>41<span class="inline-formula"><sup>′</sup></span>00<span class="inline-formula"><sup>′′</sup></span> E). The field campaign was part of the Pollution in the ARCtic System (PARCS) project of the French Arctic Initiative. The presence of low-level semi-transparent clouds was noted on 16 and 17 May. The cloud base was located just above the atmospheric boundary layer where the 0 <span class="inline-formula"><sup>∘</sup></span>C isotherm reached around 800 m above the mean sea level (a.m.s.l.). To ensure the best penetration of the laser beam into the cloud, we selected case studies with cloud optical thickness (COT) lower than 2 and out of supercooled liquid pockets. Lidar-derived multiple scattering coefficients were found to be close to 1 and ice crystal depolarization around 10 %, suggesting that ice crystals were small and had a rather spherical shape. Using Mie computations, we determine effective radii between <span class="inline-formula">∼7</span> and 25 <span class="inline-formula">µm</span> in the clouds for ice water contents between 1 and 8 mg m<span class="inline-formula"><sup>−3</sup></span>, respectively. The uncertainties regarding the effective radii and ice water content are on average 2 <span class="inline-formula">µm</span> and 0.65 mg m<span class="inline-formula"><sup>−3</sup></span>, respectively.</p> |
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| ISSN: | 1867-1381 1867-8548 |