A cloud-patch technique for identification and removal of no-rain clouds from satellite infrared imagery

Liming Xu, Soroosh Sorooshian, Xiaogang Gao, Hoshin Vijai Gupta

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

A new cloud-patch method for the identification and removal of no-rain cold clouds from infrared (IR) imagery is presented. A cloud patch is defined as a cluster of connected IR imagery pixels that are colder than a given IR brightness temperature threshold. The threshold is derived through a combination of the rainfall field estimated from microwave observations and the IR data closely coincident with microwave sensor satellite overpasses. Seven cloud-patch features are used to describe cloud-top properties, including six IR based and one VIS based. The ID3 algorithm is used to extract structural knowledge from a training dataset and to produce classification rules expressed explicitly on the values of various patch features; these rules can be used to explain the physical principles underlying the cloud classification. The method was evaluated for the Japanese islands and surrounding oceans using AIP/1 data for June (training period) and July-August (evaluation period) 1989. The results of identifying no-rain cloud patches are very good for both periods in spite of the change in rainfall regime from frontal to subtropical convective. Nearly 20% of the total pixels and 60% of the no-rain cloud pixels were removed with negligible rain losses due to misclassification. Moreover, visible data were found to be useful for enhancing the no-rain cold patch identification and thereby reducing the rain loss.

Original languageEnglish (US)
Pages (from-to)1170-1181
Number of pages12
JournalJournal of Applied Meteorology
Volume38
Issue number8
StatePublished - Aug 1999

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infrared imagery
satellite imagery
pixel
cloud classification
rainfall
satellite sensor
brightness temperature
removal
rain
ocean
cold

ASJC Scopus subject areas

  • Atmospheric Science

Cite this

A cloud-patch technique for identification and removal of no-rain clouds from satellite infrared imagery. / Xu, Liming; Sorooshian, Soroosh; Gao, Xiaogang; Gupta, Hoshin Vijai.

In: Journal of Applied Meteorology, Vol. 38, No. 8, 08.1999, p. 1170-1181.

Research output: Contribution to journalArticle

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abstract = "A new cloud-patch method for the identification and removal of no-rain cold clouds from infrared (IR) imagery is presented. A cloud patch is defined as a cluster of connected IR imagery pixels that are colder than a given IR brightness temperature threshold. The threshold is derived through a combination of the rainfall field estimated from microwave observations and the IR data closely coincident with microwave sensor satellite overpasses. Seven cloud-patch features are used to describe cloud-top properties, including six IR based and one VIS based. The ID3 algorithm is used to extract structural knowledge from a training dataset and to produce classification rules expressed explicitly on the values of various patch features; these rules can be used to explain the physical principles underlying the cloud classification. The method was evaluated for the Japanese islands and surrounding oceans using AIP/1 data for June (training period) and July-August (evaluation period) 1989. The results of identifying no-rain cloud patches are very good for both periods in spite of the change in rainfall regime from frontal to subtropical convective. Nearly 20{\%} of the total pixels and 60{\%} of the no-rain cloud pixels were removed with negligible rain losses due to misclassification. Moreover, visible data were found to be useful for enhancing the no-rain cold patch identification and thereby reducing the rain loss.",
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