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Clustering, randomness, and regularity in cloud fields. 4: Stratocumulus cloud fieldsTo complete the analysis of the spatial distribution of boundary layer cloudiness, the present study focuses on nine stratocumulus Landsat scenes. The results indicate many similarities between stratocumulus and cumulus spatial distributions. Most notably, at full spatial resolution all scenes exhibit a decidedly clustered distribution. The strength of the clustering signal decreases with increasing cloud size; the clusters themselves consist of a few clouds (less than 10), occupy a small percentage of the cloud field area (less than 5%), contain between 20% and 60% of the cloud field population, and are randomly located within the scene. In contrast, stratocumulus in almost every respect are more strongly clustered than are cumulus cloud fields. For instance, stratocumulus clusters contain more clouds per cluster, occupy a larger percentage of the total area, and have a larger percentage of clouds participating in clusters than the corresponding cumulus examples. To investigate clustering at intermediate spatial scales, the local dimensionality statistic is introduced. Results obtained from this statistic provide the first direct evidence for regularity among large (more than 900 m in diameter) clouds in stratocumulus and cumulus cloud fields, in support of the inhibition hypothesis of Ramirez and Bras (1990). Also, the size compensated point-to-cloud cumulative distribution function statistic is found to be necessary to obtain a consistent description of stratocumulus cloud distributions. A hypothesis regarding the underlying physical mechanisms responsible for cloud clustering is presented. It is suggested that cloud clusters often arise from 4 to 10 triggering events localized within regions less than 2 km in diameter and randomly distributed within the cloud field. As the size of the cloud surpasses the scale of the triggering region, the clustering signal weakens and the larger cloud locations become more random.
Document ID
19950045731
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Lee, J. (South Dakota School of Mines and Technology, Rapid City, SD United States)
Chou, J. (South Dakota School of Mines and Technology, Rapid City, SD United States)
Weger, R. C. (South Dakota School of Mines and Technology, Rapid City, SD United States)
Welch, R. M. (South Dakota School of Mines and Technology, Rapid City, SD United States)
Date Acquired
August 16, 2013
Publication Date
July 20, 1994
Publication Information
Publication: Journal of Geophysical Research
Volume: 99
Issue: D7
ISSN: 0148-0227
Subject Category
METEOROLOGY AND CLIMATOLOGY
Funding Number(s)
CONTRACT_GRANT: NSF ATM-92-24513
CONTRACT_GRANT: NSF ATM-88-16052
CONTRACT_GRANT: NAG1-542
Distribution Limits
Public
Copyright
Other