Comment on acp-2022-496
Rattachement africain : us, br, fr, cn, de, il. Niveau de preuve : code pays fourni par la source.
Le résumé fourni par la source
The southeast Atlantic is home to an expansive smoke aerosol plume overlying a large cloud deck for approximately a third of the year. The aerosol plume is mainly attributed to the extensive biomass burning activity that occurs in southern Africa. Current Earth system models (ESMs) reveal significant differences in their estimates of regional aerosol radiative effects over this region. Such large differences partially stem from uncertainties in the vertical distribution of aerosols in the troposphere. These uncertainties translate into different aerosol optical depths (AOD) in the planetary boundary layer (PBL) and the free troposphere (FT). This study examines differences of AOD fraction in the FT and AOD differences among ESMs (WRF-CAM5, WRF-FINN, GEOS-Chem, EAM-E3SM, ALADIN, GEOS-FP, and MERRA-2) and aircraft-based measurements from the NASA ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES) field campaign. Models frequently define the PBL as the well-mixed surface-based layer, but this definition misses the upper parts of decoupled PBLs, in which most low-level clouds occur. To account for the presence of decoupled boundary layers in the models, the height of maximum vertical gradient of specific humidity profiles from each model is used to define PBL heights. Results indicate that the monthly mean contribution of AOD in the FT to the total-column AOD ranges from 44 % to 74 % in September 2016 and from 54 % to 71 % in August 2017 within the region bounded by 25°S–0° and 15°W–15°E (excluding land) among the ESMs. Using the second-generation High Spectral Resolution Lidar (HSRL-2) to derive an aircraft-based constraint on the AOD and the fractional AOD, we found that WRF-CAM5 produces 40 % less AOD than those from the HSRL-2 measurements, but it performs well at separating AOD fraction between the FT and the PBL. AOD fractions in the FT for GEOS-Chem and EAM-E3SM are, respectively, 10 % and 15 % lower than the AOD fractions from the HSRL-2 and their similarities in the mean AODs are the result of cancellation of high and low AOD biases. GEOS-FP, MERRA-2, and ALADIN produce 24 %–36 % less AOD and tend to misplace more aerosols in the PBL compared to aircraft-based observations. The models generally underestimate AODs for measured AODs that are above 0.8, indicating their limitations at reproducing high AODs. The differences in the absolute AOD, FT AOD, and the vertical apportioning of AOD in different models highlight the need to continue improving the accuracy of modeled AOD distributions. These differences affect the sign and magnitude of the net aerosol radiative forcing, especially when aerosols are in contact with clouds.
Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.
Le contrôle bibliographique ouvert
DOI retrouvé dans Crossref DOI retrouvé ; titre concordant.
- Titre Crossref
- Comment on acp-2022-496
- Date Crossref
- 17/01/2023
- Éditeur
- Copernicus GmbH
- Type
- peer-review
Ce recoupement confirme des métadonnées liées au DOI. Il ne confirme ni la méthode ni les conclusions de l’étude, et il ne compte pas comme une seconde source scientifique indépendante.
Où se fait cette recherche
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University of Oklahoma pays non établi dans la noticeUniversité ou école supérieure
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Ames Research Center pays non établi dans la noticeStructure de recherche
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Bay Area Environmental Research Institute pays non établi dans la noticeOrganisation à but non lucratif
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Cooperative Institute for Research in Environmental Sciences pays non établi dans la noticeStructure de recherche
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University of Washington Cooperative Institute for Climate pays non établi dans la noticeUniversité ou école supérieure
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Cooperative Institute for Climate pays non établi dans la noticeInstitution
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Instituto Nacional de Pesquisas Espaciais pays non établi dans la noticeStructure de recherche
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University of Iowa Center for Global and Regional Environmental Research pays non établi dans la noticeUniversité ou école supérieure
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Goddard Space Flight Center pays non établi dans la noticeStructure de recherche
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University of California Department of Atmospheric and Oceanic Sciences pays non établi dans la noticeUniversité ou école supérieure
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University of Alabama in Huntsville Department of Atmospheric and Earth Science pays non établi dans la noticeUniversité ou école supérieure
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Centre National de la Recherche Scientifique pays non établi dans la noticeOrganisme public
University of Oklahoma, Ames Research Center et Bay Area Environmental Research Institute, avec 9 autres affiliations.
Une affiliation ne permet pas de déduire la nationalité d’un auteur.