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An analysis of the threshold method for measuring area-average rainfallExperimental evidence shows that the area-average rain rate and the fractional area covered by rain rate exceeding a fixed threshold are highly correlated; that is, are highly linearly related. A precise theoretical explanation of this fact is given. The explanation is based on the observation that rain rate has a mixed distribution, one that is a mixture of a discrete distribution and a continuous distribution. Under a homogeneity assumption, the slope of the linear relationship depends only on the continuous part of the distribution and as such is found to be markedly immune to parameter changes. This is illustrated by certain slope surfaces obtained from three specific distributions. The threshold level can be chosen in an optimal way by minimizing a certain distance function defined over the threshold range. In general, the threshold level should be not too far from the mean rain rate conditional on rain. The so-called threshold method advocates measuring rainfall from fractional area exploiting the observed linear relationship of the later with the area average rain rate. The method is potentially useful for the estimation of rainfall from space via satellites.
Document ID
19900037418
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Kedem, Benjamin
(Maryland, University College Park, United States)
Chiu, Long S.
(Applied Research Corp. Landover, MD, United States)
Karni, Zvi
(Interdisciplinary Science Applications Rockville, MD, United States)
Date Acquired
August 14, 2013
Publication Date
January 1, 1990
Publication Information
Publication: Journal of Applied Meteorology
Volume: 29
ISSN: 0894-8763
Subject Category
Meteorology And Climatology
Accession Number
90A24473
Distribution Limits
Public
Copyright
Other

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