A method to assess the cloud-aerosol transition zone from ceilometer measurements
dc.contributor.author
dc.date.accessioned
2024-09-09T06:52:27Z
dc.date.available
2024-09-09T06:52:27Z
dc.date.issued
2024-11-01
dc.identifier.issn
0169-8095
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dc.description.abstract
Cloud and aerosol contribution to the Earth's radiative budget constitutes one of the most significant uncertainties in future climate projections. To distinguish between clouds and cloud-free air, atmospheric scientists have been using a wide range of instruments, techniques, and algorithms with various detection thresholds. However, since the change from a cloudy to a cloud-free atmosphere may be gradual and, in some cases, far from obvious, recent research is questioning where the threshold between both phases should be established. These considerations lead to contemplate a transition zone (TZ) between cloud and cloud-free conditions. In the present study, backscatter profiles obtained by a Vaisala CL31 ceilometer were processed to assess the transition zone. First, two widely used cloud detection algorithms were applied and compared: the method provided by the ceilometer manufacturer (Vaisala) and Cloudnetpy, the algorithm from ACTRIS Cloudnet, a project devoted to aerosol, clouds, and trace gases research. Second, a sensitivity analysis was applied to the backscatter and signal-to-noise ratio thresholds used for cloud detection in Cloudnetpy. This methodology has allowed us to assess the vertical distribution of clouds, aerosols, the TZ, and its frequency of occurrence. Results indicate a gradual transition in backscatter retrievals from cloud to cloud-free, where particles detected near cloud boundaries induced higher backscatter values than those found further away. Depending on the thresholds used, we observed a 9.3% (with an estimated range of uncertainty of 5.4[sbnd]20%) variation in cloud occurrence which can be attributed to TZ conditions. Analysing the whole backscatter profile, we found as many TZ conditions as cloudy values, which emphasises the importance of studying the vertical distribution of the TZ. Moreover, the analysis of TZ occurrence in height and time revealed that such conditions concentrate below 800 m during night periods, although annual height-hour distributions involve a remarkable variability among seasons. These findings highlight the importance of either including an additional phase between ‘pure clouds’ and ‘pure aerosols’ or treating them as a continuum of suspended particles in the atmosphere
dc.description.sponsorship
This study has been funded through project NUBESOL-2 (PID2019-105901RB-I00) of the Spanish Ministry of Science and Innovation (MICINN). Jaume Ruiz de Morales is supported by an IFUdG-AE 2022 fellowship
Open Access funding provided thanks to the CRUE-CSIC agreement with Elsevier
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application/pdf
dc.language.iso
eng
dc.publisher
Elsevier
dc.relation
PID2019-105901RB-I00
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Reproducció digital del document publicat a: https://doi.org/10.1016/j.atmosres.2024.107623
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© Atmospheric Research, 2024, vol. 310, art.núm. 107623
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Articles publicats (D-F)
dc.rights
Attribution 4.0 International
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dc.subject
dc.title
A method to assess the cloud-aerosol transition zone from ceilometer measurements
dc.type
info:eu-repo/semantics/article
dc.rights.accessRights
info:eu-repo/semantics/openAccess
dc.relation.projectID
info:eu-repo/grantAgreement/AEI/Plan Estatal de Investigación Científica y Técnica y de Innovación 2017-2020/PID2019-105901RB-I00/ES/CONDICIONES FRONTERA ENTRE NUBE Y AEROSOL: TRATAMIENTO EN MODELOS RADIATIVOS Y ATMOSFERICOS/
dc.type.version
info:eu-repo/semantics/publishedVersion
dc.identifier.doi
dc.identifier.idgrec
039135
dc.contributor.funder
dc.type.peerreviewed
peer-reviewed
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dc.relation.ProjectAcronym