Clouds over Hyytiälä, Finland : an algorithm to classify clouds based on solar radiation and cloud base height measurements

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dc.contributor.author Ylivinkka, Ilona
dc.contributor.author Kaupinmäki, Santeri
dc.contributor.author Virman, Meri
dc.contributor.author Peltola, Maija
dc.contributor.author Taipale, Ditte
dc.contributor.author Petäjä, Tuukka
dc.contributor.author Kerminen, Veli-Matti
dc.contributor.author Kulmala, Markku
dc.contributor.author Ezhova, Ekaterina
dc.date.accessioned 2020-11-26T11:13:02Z
dc.date.available 2020-11-26T11:13:02Z
dc.date.issued 2020-10-22
dc.identifier.citation Ylivinkka , I , Kaupinmäki , S , Virman , M , Peltola , M , Taipale , D , Petäjä , T , Kerminen , V-M , Kulmala , M & Ezhova , E 2020 , ' Clouds over Hyytiälä, Finland : an algorithm to classify clouds based on solar radiation and cloud base height measurements ' , Atmospheric Measurement Techniques , vol. 13 , no. 10 , pp. 5595-5619 . https://doi.org/10.5194/amt-13-5595-2020
dc.identifier.other PURE: 150926456
dc.identifier.other PURE UUID: c85aca88-b5d2-4d67-9d62-63272aaa5b2f
dc.identifier.other WOS: 000584479000001
dc.identifier.other ORCID: /0000-0002-5591-4876/work/84257926
dc.identifier.other ORCID: /0000-0002-7046-3057/work/84258581
dc.identifier.other ORCID: /0000-0003-2770-9143/work/84258795
dc.identifier.other ORCID: /0000-0002-2023-2461/work/84259628
dc.identifier.other ORCID: /0000-0002-1881-9044/work/102822647
dc.identifier.uri http://hdl.handle.net/10138/321980
dc.description.abstract We developed a simple algorithm to classify clouds based on global radiation and cloud base height measured by pyranometer and ceilometer, respectively. We separated clouds into seven different classes (stratus, stratocumulus, cumulus, nimbostratus, altocumulus + altostratus, cirrus + cirrocumulus + cirrostratus and clear sky + cirrus). We also included classes for cumulus and cirrus clouds causing global radiation enhancement, and we classified multilayered clouds, when captured by the ceilometer, based on their height and characteristics (transmittance, patchiness and uniformity). The overall performance of the algorithm was nearly 70% when compared with classification by an observer using total-sky images. The performance was best for clouds having well-distinguishable effects on solar radiation: nimbostratus clouds were classified correctly in 100% of the cases. The worst performance corresponds to cirriform clouds (50 %). Although the overall performance of the algorithm was good, it is likely to miss the occurrences of high and multilayered clouds. This is due to the technical limits of the instrumentation: the vertical detection range of the ceilometer and occultation of the laser pulse by the lowest cloud layer. We examined the use of clearness index, which is defined as a ratio between measured global radiation and modeled radiation at the top of the atmosphere, as an indicator of clear-sky conditions. Our results show that cumulus, altocumulus, altostratus and cirriform clouds can be present when the index indicates clear-sky conditions. Those conditions have previously been associated with enhanced aerosol formation under clear skies. This is an important finding especially in the case of low clouds coupled to the surface, which can influence aerosol population via aerosol-cloud interactions. Overall, caution is required when the clearness index is used in the analysis of processes affected by partitioning of radiation by clouds. en
dc.format.extent 25
dc.language.iso eng
dc.relation.ispartof Atmospheric Measurement Techniques
dc.rights cc_by
dc.rights.uri info:eu-repo/semantics/openAccess
dc.subject 114 Physical sciences
dc.subject PARTICLE FORMATION EVENTS
dc.subject VERTICAL STRUCTURE
dc.subject LONG-TERM
dc.subject ATMOSPHERIC NUCLEATION
dc.subject STATISTICAL-MODEL
dc.subject CLEAR-SKY
dc.subject CLASSIFICATION
dc.subject BOREAL
dc.subject CEILOMETER
dc.subject AEROSOLS
dc.title Clouds over Hyytiälä, Finland : an algorithm to classify clouds based on solar radiation and cloud base height measurements en
dc.type Article
dc.contributor.organization Global Atmosphere-Earth surface feedbacks
dc.contributor.organization INAR Physics
dc.contributor.organization Aerosol-Cloud-Climate -Interactions (ACCI)
dc.contributor.organization Institute for Atmospheric and Earth System Research (INAR)
dc.contributor.organization Department of Physics
dc.description.reviewstatus Peer reviewed
dc.relation.doi https://doi.org/10.5194/amt-13-5595-2020
dc.relation.issn 1867-1381
dc.rights.accesslevel openAccess
dc.type.version publishedVersion

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