Characterization of aerosol particles at Cabo Verde close to sea level and at the cloud level – Part 2: Ice-nucleating particles in air, cloud and seawater
<p>Ice-nucleating particles (INPs) in the troposphere can form ice in clouds via heterogeneous ice nucleation. Yet, atmospheric number concentrations of INPs (<span class="inline-formula"><i>N</i><sub>INP</sub></span>) are not well characterized, a...
| Main Authors: | , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-02-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/20/1451/2020/acp-20-1451-2020.pdf |
| _version_ | 1828895947340382208 |
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| author | X. Gong H. Wex M. van Pinxteren N. Triesch K. W. Fomba J. Lubitz C. Stolle C. Stolle T.-B. Robinson T. Müller H. Herrmann F. Stratmann |
| author_facet | X. Gong H. Wex M. van Pinxteren N. Triesch K. W. Fomba J. Lubitz C. Stolle C. Stolle T.-B. Robinson T. Müller H. Herrmann F. Stratmann |
| author_sort | X. Gong |
| collection | DOAJ |
| description | <p>Ice-nucleating particles (INPs) in the troposphere can form ice in clouds via heterogeneous ice nucleation. Yet, atmospheric number concentrations of INPs (<span class="inline-formula"><i>N</i><sub>INP</sub></span>) are not well characterized, and, although there is some understanding of their sources, it is still unclear to what extend different sources contribute or if all sources are known. In this work, we examined properties of INPs at Cabo Verde (a.k.a. Cape Verde) from different environmental compartments: the oceanic sea surface microlayer (SML), underlying water (ULW), cloud water and the atmosphere close to both sea level and cloud level.</p>
<p>Both enrichment and depletion of <span class="inline-formula"><i>N</i><sub>INP</sub></span> in SML compared to ULW were observed. The enrichment factor (EF) varied from roughly 0.4 to 11, and there was no clear trend in EF with ice-nucleation temperature.</p>
<p><span class="inline-formula"><i>N</i><sub>INP</sub></span> values in PM<span class="inline-formula"><sub>10</sub></span> sampled at Cape Verde Atmospheric Observatory (CVAO) at any particular ice-nucleation temperature spanned around 1 order of magnitude below <span class="inline-formula">−15</span> <span class="inline-formula"><sup>∘</sup></span>C, and about 2 orders of magnitude at warmer temperatures (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M7" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>></mo><mo>-</mo><mn mathvariant="normal">12</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="32pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="a7f9da50f44ff0b2e27748f108bed98d"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-20-1451-2020-ie00001.svg" width="32pt" height="10pt" src="acp-20-1451-2020-ie00001.png"/></svg:svg></span></span> <span class="inline-formula"><sup>∘</sup></span>C). Among the 17 PM<span class="inline-formula"><sub>10</sub></span> samples at CVAO, three PM<span class="inline-formula"><sub>10</sub></span> filters showed elevated <span class="inline-formula"><i>N</i><sub>INP</sub></span> at warm temperatures, e.g., above 0.01 L<span class="inline-formula"><sup>−1</sup></span> at <span class="inline-formula">−10</span> <span class="inline-formula"><sup>∘</sup></span>C. After heating samples at 95 <span class="inline-formula"><sup>∘</sup></span>C for 1 h, the elevated <span class="inline-formula"><i>N</i><sub>INP</sub></span> at the warm temperatures disappeared, indicating that these highly ice active INPs were most likely biological particles.</p>
<p>INP number concentrations in PM<span class="inline-formula"><sub>1</sub></span> were generally lower than those in PM<span class="inline-formula"><sub>10</sub></span> at CVAO. About <span class="inline-formula">83±22</span> %, <span class="inline-formula">67±18</span> % and <span class="inline-formula">77±14</span> % (median<span class="inline-formula">±</span>standard deviation) of INPs had a diameter <span class="inline-formula">>1</span> <span class="inline-formula">µ</span>m at ice-nucleation temperatures of <span class="inline-formula">−12</span>, <span class="inline-formula">−15</span> and <span class="inline-formula">−18</span> <span class="inline-formula"><sup>∘</sup></span>C, respectively. PM<span class="inline-formula"><sub>1</sub></span> at CVAO did not show such elevated <span class="inline-formula"><i>N</i><sub>INP</sub></span> at warm temperatures. Consequently, the difference in <span class="inline-formula"><i>N</i><sub>INP</sub></span> between PM<span class="inline-formula"><sub>1</sub></span> and PM<span class="inline-formula"><sub>10</sub></span> at CVAO suggests that biological ice-active particles were present in the supermicron size range.</p>
<p><span class="inline-formula"><i>N</i><sub>INP</sub></span> in PM<span class="inline-formula"><sub>10</sub></span> at CVAO was found to be similar to that on Monte Verde (MV, at 744 m a.s.l.) during noncloud events. During cloud events, most INPs on MV were activated to cloud droplets. When highly ice active particles were present in PM<span class="inline-formula"><sub>10</sub></span> filters at CVAO, they were not observed in PM<span class="inline-formula"><sub>10</sub></span> filters on MV but in cloud water samples instead. This is direct evidence that these INPs, which are likely biological, are activated to cloud droplets during cloud events.</p>
<p>For the observed air masses, atmospheric <span class="inline-formula"><i>N</i><sub>INP</sub></span> values in air fit well to the concentrations observed in cloud water. When comparing concentrations of both sea salt and INPs in both seawater and PM<span class="inline-formula"><sub>10</sub></span> filters, it can be concluded that sea spray aerosol (SSA) only contributed a minor fraction to the atmospheric <span class="inline-formula"><i>N</i><sub>INP</sub></span>. This latter conclusion still holds when accounting for an enrichment of organic carbon in supermicron particles during sea spray generation as reported in literature.</p> |
| first_indexed | 2024-12-13T14:35:23Z |
| format | Article |
| id | doaj.art-87ace2b22fdd469f82469969a436181e |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-13T14:35:23Z |
| publishDate | 2020-02-01 |
| publisher | Copernicus Publications |
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| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-87ace2b22fdd469f82469969a436181e2022-12-21T23:41:44ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242020-02-01201451146810.5194/acp-20-1451-2020Characterization of aerosol particles at Cabo Verde close to sea level and at the cloud level – Part 2: Ice-nucleating particles in air, cloud and seawaterX. Gong0H. Wex1M. van Pinxteren2N. Triesch3K. W. Fomba4J. Lubitz5C. Stolle6C. Stolle7T.-B. Robinson8T. Müller9H. Herrmann10F. Stratmann11Leibniz Institute for Tropospheric Research, Leipzig, GermanyLeibniz Institute for Tropospheric Research, Leipzig, GermanyLeibniz Institute for Tropospheric Research, Leipzig, GermanyLeibniz Institute for Tropospheric Research, Leipzig, GermanyLeibniz Institute for Tropospheric Research, Leipzig, GermanyLeibniz Institute for Tropospheric Research, Leipzig, GermanyLeibniz Institute for Baltic Sea Research Warnemünde (IOW), Rostock, GermanyInstitute for Chemistry and Biology of the Marine Environment, University of Oldenburg, Wilhelmshaven, GermanyInstitute for Chemistry and Biology of the Marine Environment, University of Oldenburg, Wilhelmshaven, GermanyLeibniz Institute for Tropospheric Research, Leipzig, GermanyLeibniz Institute for Tropospheric Research, Leipzig, GermanyLeibniz Institute for Tropospheric Research, Leipzig, Germany<p>Ice-nucleating particles (INPs) in the troposphere can form ice in clouds via heterogeneous ice nucleation. Yet, atmospheric number concentrations of INPs (<span class="inline-formula"><i>N</i><sub>INP</sub></span>) are not well characterized, and, although there is some understanding of their sources, it is still unclear to what extend different sources contribute or if all sources are known. In this work, we examined properties of INPs at Cabo Verde (a.k.a. Cape Verde) from different environmental compartments: the oceanic sea surface microlayer (SML), underlying water (ULW), cloud water and the atmosphere close to both sea level and cloud level.</p> <p>Both enrichment and depletion of <span class="inline-formula"><i>N</i><sub>INP</sub></span> in SML compared to ULW were observed. The enrichment factor (EF) varied from roughly 0.4 to 11, and there was no clear trend in EF with ice-nucleation temperature.</p> <p><span class="inline-formula"><i>N</i><sub>INP</sub></span> values in PM<span class="inline-formula"><sub>10</sub></span> sampled at Cape Verde Atmospheric Observatory (CVAO) at any particular ice-nucleation temperature spanned around 1 order of magnitude below <span class="inline-formula">−15</span> <span class="inline-formula"><sup>∘</sup></span>C, and about 2 orders of magnitude at warmer temperatures (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M7" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>></mo><mo>-</mo><mn mathvariant="normal">12</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="32pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="a7f9da50f44ff0b2e27748f108bed98d"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-20-1451-2020-ie00001.svg" width="32pt" height="10pt" src="acp-20-1451-2020-ie00001.png"/></svg:svg></span></span> <span class="inline-formula"><sup>∘</sup></span>C). Among the 17 PM<span class="inline-formula"><sub>10</sub></span> samples at CVAO, three PM<span class="inline-formula"><sub>10</sub></span> filters showed elevated <span class="inline-formula"><i>N</i><sub>INP</sub></span> at warm temperatures, e.g., above 0.01 L<span class="inline-formula"><sup>−1</sup></span> at <span class="inline-formula">−10</span> <span class="inline-formula"><sup>∘</sup></span>C. After heating samples at 95 <span class="inline-formula"><sup>∘</sup></span>C for 1 h, the elevated <span class="inline-formula"><i>N</i><sub>INP</sub></span> at the warm temperatures disappeared, indicating that these highly ice active INPs were most likely biological particles.</p> <p>INP number concentrations in PM<span class="inline-formula"><sub>1</sub></span> were generally lower than those in PM<span class="inline-formula"><sub>10</sub></span> at CVAO. About <span class="inline-formula">83±22</span> %, <span class="inline-formula">67±18</span> % and <span class="inline-formula">77±14</span> % (median<span class="inline-formula">±</span>standard deviation) of INPs had a diameter <span class="inline-formula">>1</span> <span class="inline-formula">µ</span>m at ice-nucleation temperatures of <span class="inline-formula">−12</span>, <span class="inline-formula">−15</span> and <span class="inline-formula">−18</span> <span class="inline-formula"><sup>∘</sup></span>C, respectively. PM<span class="inline-formula"><sub>1</sub></span> at CVAO did not show such elevated <span class="inline-formula"><i>N</i><sub>INP</sub></span> at warm temperatures. Consequently, the difference in <span class="inline-formula"><i>N</i><sub>INP</sub></span> between PM<span class="inline-formula"><sub>1</sub></span> and PM<span class="inline-formula"><sub>10</sub></span> at CVAO suggests that biological ice-active particles were present in the supermicron size range.</p> <p><span class="inline-formula"><i>N</i><sub>INP</sub></span> in PM<span class="inline-formula"><sub>10</sub></span> at CVAO was found to be similar to that on Monte Verde (MV, at 744 m a.s.l.) during noncloud events. During cloud events, most INPs on MV were activated to cloud droplets. When highly ice active particles were present in PM<span class="inline-formula"><sub>10</sub></span> filters at CVAO, they were not observed in PM<span class="inline-formula"><sub>10</sub></span> filters on MV but in cloud water samples instead. This is direct evidence that these INPs, which are likely biological, are activated to cloud droplets during cloud events.</p> <p>For the observed air masses, atmospheric <span class="inline-formula"><i>N</i><sub>INP</sub></span> values in air fit well to the concentrations observed in cloud water. When comparing concentrations of both sea salt and INPs in both seawater and PM<span class="inline-formula"><sub>10</sub></span> filters, it can be concluded that sea spray aerosol (SSA) only contributed a minor fraction to the atmospheric <span class="inline-formula"><i>N</i><sub>INP</sub></span>. This latter conclusion still holds when accounting for an enrichment of organic carbon in supermicron particles during sea spray generation as reported in literature.</p>https://www.atmos-chem-phys.net/20/1451/2020/acp-20-1451-2020.pdf |
| spellingShingle | X. Gong H. Wex M. van Pinxteren N. Triesch K. W. Fomba J. Lubitz C. Stolle C. Stolle T.-B. Robinson T. Müller H. Herrmann F. Stratmann Characterization of aerosol particles at Cabo Verde close to sea level and at the cloud level – Part 2: Ice-nucleating particles in air, cloud and seawater Atmospheric Chemistry and Physics |
| title | Characterization of aerosol particles at Cabo Verde close to sea level and at the cloud level – Part 2: Ice-nucleating particles in air, cloud and seawater |
| title_full | Characterization of aerosol particles at Cabo Verde close to sea level and at the cloud level – Part 2: Ice-nucleating particles in air, cloud and seawater |
| title_fullStr | Characterization of aerosol particles at Cabo Verde close to sea level and at the cloud level – Part 2: Ice-nucleating particles in air, cloud and seawater |
| title_full_unstemmed | Characterization of aerosol particles at Cabo Verde close to sea level and at the cloud level – Part 2: Ice-nucleating particles in air, cloud and seawater |
| title_short | Characterization of aerosol particles at Cabo Verde close to sea level and at the cloud level – Part 2: Ice-nucleating particles in air, cloud and seawater |
| title_sort | characterization of aerosol particles at cabo verde close to sea level and at the cloud level part 2 ice nucleating particles in air cloud and seawater |
| url | https://www.atmos-chem-phys.net/20/1451/2020/acp-20-1451-2020.pdf |
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