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Open AccessArticle

A Statistical Method for Determining Optical and Geometrical Characteristics of Cirrus Clouds

1
Department of Physics, SCSVMV University, Enathur, Kancheepuram, Tamil Nadu 631561, India
2
Department of Materials Science and Engineering, City University of Hong Kong, Hong Kong 999077, China
*
Author to whom correspondence should be addressed.
Climate 2019, 7(5), 72; https://doi.org/10.3390/cli7050072
Received: 12 April 2019 / Revised: 16 May 2019 / Accepted: 23 May 2019 / Published: 27 May 2019
Altitude occurrences of cirrus clouds, their base, mid, and top heights are identified by using a powerful statistical approach called the Variance Centroid Method (VCM). This method is effective in determining the geometrical properties of cirrus clouds at a height range of 8 km to 20 km. This statistical method provides in-depth information on Generation Circulation Models (GCM’s) because of its significant role in the radiative balance of the earth’s atmosphere. The output related to geometrical and optical properties of cirrus clouds obtained from this statistical method for the years 2014 and 2015 are studied. Altitude distributions of base, mid, top, and thickness of tropical cirrus clouds are analyzed in terms of percentage occurrences. For the year 2014, it was found that 14.8%, 75.2%, and 9.9% of cirrus clouds were sub-visual, thin, and thick clouds and for the year 2015, 71.2% and 28.7% of cirrus clouds were found to be thin and thick clouds, and sub-visual types of clouds were not observed. The interdependence of optical depth with the depolarization ratio is discussed and it is observed that the correlation is negative (−0.0303) for the year 2014 and positive (0.1311) for the year 2015. High optical depths with values from 0.502 to 0.849 are observed in the height regions from 9 km to 15 km (for 2014) and for the year 2015, the observed value ranges from 0.514 to 0.822 for the height regions from 9 km to 11 km. Statistical variation of characteristics of tropical cirrus clouds is presented for the period of study. The characterization of these cirrus clouds is highly useful for climate modeling studies, and their impact plays a vital role in the Earth’s radiation budget at the top of the atmosphere. View Full-Text
Keywords: cirrus clouds; depolarization ratio; lidar; optical depth; radiation cirrus clouds; depolarization ratio; lidar; optical depth; radiation
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Nellore, M.K.; Kannan, V.; Vellaisamy, A.L.R. A Statistical Method for Determining Optical and Geometrical Characteristics of Cirrus Clouds. Climate 2019, 7, 72.

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