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Open AccessEditor’s ChoiceArticle

Cloud Occurrence Frequency at Puy de Dôme (France) Deduced from an Automatic Camera Image Analysis: Method, Validation, and Comparisons with Larger Scale Parameters

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Laboratoire de Météorologie Physique, UMR 6016, CNRS, Université Clermont Auvergne, 63178 Aubière, France
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Observatoire de Physique du Globe de Clermont-Ferrand, UMS 833, CNRS, Université Clermont Auvergne, 63178 Aubière, France
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Laboratoire d’Aérologie, UMR5560, CNRS, Université Paul Sabatier Toulouse III, 31400 Toulouse, France
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Laboratoire de Météorologie Dynamique, UMR8539, CNRS, ENS, Ecole polytechnique, Université Pierre Marie Curie, 75252 Paris, France
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Observatoire OSU-Réunion, UMS3365, CNRS, Université de la Réunion, 97444 Saint Denis de la Réunion, France
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Laboratoire de l’Atmosphère et des Cyclones, UMR8105, CNRS, Météo-France, Université de la Réunion, 97444 Saint Denis de la Réunion, France
*
Author to whom correspondence should be addressed.
Atmosphere 2019, 10(12), 808; https://doi.org/10.3390/atmos10120808
Received: 31 October 2019 / Revised: 2 December 2019 / Accepted: 10 December 2019 / Published: 13 December 2019
(This article belongs to the Special Issue Atmospheric Composition and Cloud Cover Observations)
We present a simple algorithm that calculates the cloud occurrence frequency at an altitude site using automatic camera image analysis. This algorithm was applied at the puy de Dôme station (PUY, 1465 m. a.s.l., France) over 2013–2018. Cloud detection thresholds were determined by direct comparison with simultaneous in situ cloud probe measurements (particulate volume monitor (PVM) Gerber). The cloud occurrence frequency has a seasonal cycle, with higher values in winter (60%) compared to summer (24%). A cloud diurnal cycle is observed only in summer. Comparisons with the larger scale products from satellites and global model reanalysis are also presented. The NASA cloud-aerosol transport system (CATS) cloud fraction shows the same seasonal and diurnal variations and is, on average, 11% higher. Monthly variations of the ECMWF ERA-5 fraction of cloud cover are also highly correlated with the camera cloud occurrence frequency, but the values are 19% lower and up to 40% for some winter months. The METEOSAT-SEVIRI cloud occurrence frequency also follows the same seasonal cycle but with a much smaller decrease in summer. The all-sky imager cloud fraction (CF) presents larger variability than the camera cloud occurrence but also follows similar seasonal variations (67% in winter and 44% in summer). This automatic low-cost detection of cloud occurrence is of interest in characterizing altitude observation sites, especially those that are not yet equipped with microphysical instruments and can be deployed to other high-altitude sites equipped with cameras. View Full-Text
Keywords: cloud occurrence frequency; automatic camera image analysis cloud occurrence frequency; automatic camera image analysis
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MDPI and ACS Style

Baray, J.-L.; Bah, A.; Cacault, P.; Sellegri, K.; Pichon, J.-M.; Deguillaume, L.; Montoux, N.; Noel, V.; Seze, G.; Gabarrot, F.; Payen, G.; Duflot, V. Cloud Occurrence Frequency at Puy de Dôme (France) Deduced from an Automatic Camera Image Analysis: Method, Validation, and Comparisons with Larger Scale Parameters. Atmosphere 2019, 10, 808.

AMA Style

Baray J-L, Bah A, Cacault P, Sellegri K, Pichon J-M, Deguillaume L, Montoux N, Noel V, Seze G, Gabarrot F, Payen G, Duflot V. Cloud Occurrence Frequency at Puy de Dôme (France) Deduced from an Automatic Camera Image Analysis: Method, Validation, and Comparisons with Larger Scale Parameters. Atmosphere. 2019; 10(12):808.

Chicago/Turabian Style

Baray, Jean-Luc; Bah, Asmaou; Cacault, Philippe; Sellegri, Karine; Pichon, Jean-Marc; Deguillaume, Laurent; Montoux, Nadège; Noel, Vincent; Seze, Geneviève; Gabarrot, Franck; Payen, Guillaume; Duflot, Valentin. 2019. "Cloud Occurrence Frequency at Puy de Dôme (France) Deduced from an Automatic Camera Image Analysis: Method, Validation, and Comparisons with Larger Scale Parameters" Atmosphere 10, no. 12: 808.

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