Airborne observations of the surface cloud radiative effect during different seasons over sea ice and open ocean in the Fram Strait
<p>This study analyses the cloud radiative effect (CRE) obtained from near-surface observations of three airborne campaigns in the Arctic north-west of Svalbard: Airborne measurements of radiative and turbulent FLUXes of energy and momentum in the Arctic boundary layer (AFLUX, March/April 2019...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2023-06-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/23/7015/2023/acp-23-7015-2023.pdf |
| _version_ | 1797796826017955840 |
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| author | S. Becker A. Ehrlich M. Schäfer M. Wendisch |
| author_facet | S. Becker A. Ehrlich M. Schäfer M. Wendisch |
| author_sort | S. Becker |
| collection | DOAJ |
| description | <p>This study analyses the cloud radiative effect (CRE) obtained from near-surface observations of three airborne campaigns in the Arctic north-west of Svalbard: Airborne measurements of radiative and turbulent FLUXes of energy and momentum in the Arctic boundary layer (AFLUX, March/April 2019), Arctic CLoud Observations Using airborne measurements during polar Day (ACLOUD, May/June 2017), and Multidisciplinary drifting Observatory for the Study of Arctic Climate – Airborne observations in the Central Arctic (MOSAiC-ACA, August/September 2020). The surface CRE quantifies the potential of clouds to modify the radiative energy budget at the surface and is calculated by combining broadband radiation measurements during low-level flight sections in mostly cloudy conditions with radiative transfer simulations of cloud-free conditions. The significance of surface albedo changes due to the presence of clouds is demonstrated, and this effect is considered in the cloud-free simulations. The observations are discussed with respect to differences of the CRE between sea ice and open-ocean surfaces and between the seasonally different campaigns. The results indicate that the CRE depends on cloud, illumination, surface, and thermodynamic properties. The solar and thermal-infrared (TIR) components of the CRE, <span class="inline-formula">CRE<sub>sol</sub></span> and <span class="inline-formula">CRE<sub>TIR</sub></span>, are analysed separately, as well as combined for the study of the total CRE (<span class="inline-formula">CRE<sub>tot</sub></span>). The
inter-campaign differences of <span class="inline-formula">CRE<sub>sol</sub></span> are dominated by the seasonal cycle of the solar zenith angle, with the strongest cooling effect in summer. The lower surface albedo causes a stronger solar cooling effect over open ocean than over sea ice, which amounts to <span class="inline-formula">−</span>259 <span class="inline-formula">W m<sup>−2</sup></span> (<span class="inline-formula">−</span>108 <span class="inline-formula">W m<sup>−2</sup></span>) and <span class="inline-formula">−</span>65 <span class="inline-formula">W m<sup>−2</sup></span> (<span class="inline-formula">−</span>17 <span class="inline-formula">W m<sup>−2</sup></span>), respectively, during summer (spring). Independent of campaign and surface type, <span class="inline-formula">CRE<sub>TIR</sub></span> is only weakly variable and shows values around 75 <span class="inline-formula">W m<sup>−2</sup></span>. In total, clouds show a negative <span class="inline-formula">CRE<sub>tot</sub></span> over open ocean during all campaigns. In contrast, over sea ice, the positive <span class="inline-formula">CRE<sub>tot</sub></span> suggests a warming effect of clouds at the surface, which neutralizes during mid-summer. Given the seasonal cycle of the sea ice distribution, these results imply that clouds in the Fram Strait region cool the surface during the sea ice minimum in late summer, while they warm the surface during the sea ice maximum in spring.</p> |
| first_indexed | 2024-03-13T03:38:53Z |
| format | Article |
| id | doaj.art-da24aefad92247898f7511aa888f377e |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-03-13T03:38:53Z |
| publishDate | 2023-06-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-da24aefad92247898f7511aa888f377e2023-06-23T12:21:13ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242023-06-01237015703110.5194/acp-23-7015-2023Airborne observations of the surface cloud radiative effect during different seasons over sea ice and open ocean in the Fram StraitS. BeckerA. EhrlichM. SchäferM. Wendisch<p>This study analyses the cloud radiative effect (CRE) obtained from near-surface observations of three airborne campaigns in the Arctic north-west of Svalbard: Airborne measurements of radiative and turbulent FLUXes of energy and momentum in the Arctic boundary layer (AFLUX, March/April 2019), Arctic CLoud Observations Using airborne measurements during polar Day (ACLOUD, May/June 2017), and Multidisciplinary drifting Observatory for the Study of Arctic Climate – Airborne observations in the Central Arctic (MOSAiC-ACA, August/September 2020). The surface CRE quantifies the potential of clouds to modify the radiative energy budget at the surface and is calculated by combining broadband radiation measurements during low-level flight sections in mostly cloudy conditions with radiative transfer simulations of cloud-free conditions. The significance of surface albedo changes due to the presence of clouds is demonstrated, and this effect is considered in the cloud-free simulations. The observations are discussed with respect to differences of the CRE between sea ice and open-ocean surfaces and between the seasonally different campaigns. The results indicate that the CRE depends on cloud, illumination, surface, and thermodynamic properties. The solar and thermal-infrared (TIR) components of the CRE, <span class="inline-formula">CRE<sub>sol</sub></span> and <span class="inline-formula">CRE<sub>TIR</sub></span>, are analysed separately, as well as combined for the study of the total CRE (<span class="inline-formula">CRE<sub>tot</sub></span>). The inter-campaign differences of <span class="inline-formula">CRE<sub>sol</sub></span> are dominated by the seasonal cycle of the solar zenith angle, with the strongest cooling effect in summer. The lower surface albedo causes a stronger solar cooling effect over open ocean than over sea ice, which amounts to <span class="inline-formula">−</span>259 <span class="inline-formula">W m<sup>−2</sup></span> (<span class="inline-formula">−</span>108 <span class="inline-formula">W m<sup>−2</sup></span>) and <span class="inline-formula">−</span>65 <span class="inline-formula">W m<sup>−2</sup></span> (<span class="inline-formula">−</span>17 <span class="inline-formula">W m<sup>−2</sup></span>), respectively, during summer (spring). Independent of campaign and surface type, <span class="inline-formula">CRE<sub>TIR</sub></span> is only weakly variable and shows values around 75 <span class="inline-formula">W m<sup>−2</sup></span>. In total, clouds show a negative <span class="inline-formula">CRE<sub>tot</sub></span> over open ocean during all campaigns. In contrast, over sea ice, the positive <span class="inline-formula">CRE<sub>tot</sub></span> suggests a warming effect of clouds at the surface, which neutralizes during mid-summer. Given the seasonal cycle of the sea ice distribution, these results imply that clouds in the Fram Strait region cool the surface during the sea ice minimum in late summer, while they warm the surface during the sea ice maximum in spring.</p>https://acp.copernicus.org/articles/23/7015/2023/acp-23-7015-2023.pdf |
| spellingShingle | S. Becker A. Ehrlich M. Schäfer M. Wendisch Airborne observations of the surface cloud radiative effect during different seasons over sea ice and open ocean in the Fram Strait Atmospheric Chemistry and Physics |
| title | Airborne observations of the surface cloud radiative effect during different seasons over sea ice and open ocean in the Fram Strait |
| title_full | Airborne observations of the surface cloud radiative effect during different seasons over sea ice and open ocean in the Fram Strait |
| title_fullStr | Airborne observations of the surface cloud radiative effect during different seasons over sea ice and open ocean in the Fram Strait |
| title_full_unstemmed | Airborne observations of the surface cloud radiative effect during different seasons over sea ice and open ocean in the Fram Strait |
| title_short | Airborne observations of the surface cloud radiative effect during different seasons over sea ice and open ocean in the Fram Strait |
| title_sort | airborne observations of the surface cloud radiative effect during different seasons over sea ice and open ocean in the fram strait |
| url | https://acp.copernicus.org/articles/23/7015/2023/acp-23-7015-2023.pdf |
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