Development of simple equations to estimate net rainfall under closed tree canopies

Many interception models have been developed. These models, however, are complex, data-demanding, and often usable only for a specific vegetation type. The focus of this study was to develop and validate a two- and a three-coefficient equation for full canopies for oil palm, rubber, and pine trees...

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Main Author:	Chong, Siam Yee
Format:	Thesis
Language:	English
Published:	2012
Subjects:	Rain and rainfall - Mathematical models Forest canopies Rain and rainfall
Online Access:	http://psasir.upm.edu.my/id/eprint/31621/1/FP%202012%2054R.pdf
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id	my-upm-ir.31621
record_format	uketd_dc
spelling	my-upm-ir.316212015-02-02T05:26:00Z Development of simple equations to estimate net rainfall under closed tree canopies 2012-12 Chong, Siam Yee Many interception models have been developed. These models, however, are complex, data-demanding, and often usable only for a specific vegetation type. The focus of this study was to develop and validate a two- and a three-coefficient equation for full canopies for oil palm, rubber, and pine trees. Throughfall and stemflow data from seven past studies were used to determine the best-fit coefficients for the two equations. The three-coefficient equation was Pn = Pg x exp [- (0.3443 – (Pg / (58.9748 + Pg)) x 0.1639)] and the two-coefficient equation was Pn = 0.7724 x Pg – 0.5845 (R2 = 0.91), where Pn and Pg are net and gross rainfall, respectively. To validate these two equations, field data were collected. Rain gauges were used for rainfall measurement and recorded in five minutes interval by data loggers. Ten rain gauges were used for throughfall measurement and arranged along the North-South direction with a 10-m interval. Three sampled trees were selected randomly for stemflow measurement and one rain gauge was installed at a nearby open area. Two error indexes were used as a goodness-of-fit measure, namely: index of agreement and normalized mean absolute error. Results showed that both the two and three-coefficient equations performed nearly equally well. The equations predicted net rainfall with errors between 12 to 23% (ranked as “Fair” to “Good” in terms of overall equation accuracy) and with an index of agreement of more than 90%. Results showed that these two equations can be used with fairly accurate estimations of throughfall and net rainfall, and, to a lesser degree, stemflow. The estimation errors were most probably because the canopy and rainfall characteristics were not taken into account in the two equations. Rain and rainfall - Mathematical models Forest canopies Rain and rainfall 2012-12 Thesis http://psasir.upm.edu.my/id/eprint/31621/ http://psasir.upm.edu.my/id/eprint/31621/1/FP%202012%2054R.pdf application/pdf en public masters Universiti Putra Malaysia Rain and rainfall - Mathematical models Forest canopies Rain and rainfall Faculty of Agriculture
institution	Universiti Putra Malaysia
collection	PSAS Institutional Repository
language	English
topic	Rain and rainfall - Mathematical models Forest canopies Rain and rainfall
spellingShingle	Rain and rainfall - Mathematical models Forest canopies Rain and rainfall Chong, Siam Yee Development of simple equations to estimate net rainfall under closed tree canopies
description	Many interception models have been developed. These models, however, are complex, data-demanding, and often usable only for a specific vegetation type. The focus of this study was to develop and validate a two- and a three-coefficient equation for full canopies for oil palm, rubber, and pine trees. Throughfall and stemflow data from seven past studies were used to determine the best-fit coefficients for the two equations. The three-coefficient equation was Pn = Pg x exp [- (0.3443 – (Pg / (58.9748 + Pg)) x 0.1639)] and the two-coefficient equation was Pn = 0.7724 x Pg – 0.5845 (R2 = 0.91), where Pn and Pg are net and gross rainfall, respectively. To validate these two equations, field data were collected. Rain gauges were used for rainfall measurement and recorded in five minutes interval by data loggers. Ten rain gauges were used for throughfall measurement and arranged along the North-South direction with a 10-m interval. Three sampled trees were selected randomly for stemflow measurement and one rain gauge was installed at a nearby open area. Two error indexes were used as a goodness-of-fit measure, namely: index of agreement and normalized mean absolute error. Results showed that both the two and three-coefficient equations performed nearly equally well. The equations predicted net rainfall with errors between 12 to 23% (ranked as “Fair” to “Good” in terms of overall equation accuracy) and with an index of agreement of more than 90%. Results showed that these two equations can be used with fairly accurate estimations of throughfall and net rainfall, and, to a lesser degree, stemflow. The estimation errors were most probably because the canopy and rainfall characteristics were not taken into account in the two equations.
format	Thesis
qualification_level	Master's degree
author	Chong, Siam Yee
author_facet	Chong, Siam Yee
author_sort	Chong, Siam Yee
title	Development of simple equations to estimate net rainfall under closed tree canopies
title_short	Development of simple equations to estimate net rainfall under closed tree canopies
title_full	Development of simple equations to estimate net rainfall under closed tree canopies
title_fullStr	Development of simple equations to estimate net rainfall under closed tree canopies
title_full_unstemmed	Development of simple equations to estimate net rainfall under closed tree canopies
title_sort	development of simple equations to estimate net rainfall under closed tree canopies
granting_institution	Universiti Putra Malaysia
granting_department	Faculty of Agriculture
publishDate	2012
url	http://psasir.upm.edu.my/id/eprint/31621/1/FP%202012%2054R.pdf
_version_	1747811619878993920

Development of simple equations to estimate net rainfall under closed tree canopies

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