Impact of bidirectional reflectance distribution function on modis vegetation indices in southeast Asia tropical forests

Tran, NN; Huete, A; Hardtke, L

Impact of bidirectional reflectance distribution function on modis vegetation indices in southeast Asia tropical forests

Tran, NN Huete, A

Hardtke, L

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Publication Type:: Conference Proceeding
Citation:: 38th Asian Conference on Remote Sensing - Space Applications: Touching Human Lives, ACRS 2017, 2017, 2017-October
Issue Date:: 2017-01-01

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Field	Value	Language
dc.contributor.author	Tran, NN	en_US
dc.contributor.author	Huete, A https://orcid.org/0000-0003-2809-2376	en_US
dc.contributor.author	Hardtke, L https://orcid.org/0000-0001-7107-1218	en_US
dc.date.issued	2017-01-01	en_US
dc.identifier.citation	38th Asian Conference on Remote Sensing - Space Applications: Touching Human Lives, ACRS 2017, 2017, 2017-October	en_US
dc.identifier.uri	http://hdl.handle.net/10453/127391
dc.description.abstract	Copyright © 2017 ISRS, All Rights Reserved. Tropical forests play important roles on global climate and biodiversity. The Moderate Resolution Imaging Spectroradiometer (MODIS), with high temporal resolution, provide a useful tool to study tropical forest dynamics, including seasonality and inter-annual variation. However, optical satellite data have cloud, aerosol and bidirectional reflectance distribution function (BRDF) effects, that create uncertainty in tropical forest studies. In the Amazon, some researchers demonstrated the difficulties in separating true forest dynamics from BRDF artefacts and seasonal cloud and aerosol influences. Lastly, optical reflectance saturation in dense tropical forests may restrict the retrieval of phenology information. In this study, we investigated the impact of BRDF effects on MODIS vegetation indices (VI) in Southeast Asia (SEA) tropical forests, the least studied area compared to other major tropical forests (South America and Central Africa). Moreover, unlike Amazon tropical forests, VI seasonality in SEA forests is not synchronous with sun-sensor geometries. We used 10-year data of daily MODIS BRDF (MCD43A1) collection 6 product, a kernel-driven model product that allows us to retrieve VI values for a range of fixed solar zenith angles (SZA). We compared these with the standard VI products (MOD13A1, MYD13A1) to analyse BRDF influences. The results show significant BRDF effects in all forest sites. Generally, smaller SZA yielded higher VI signals in forests. We found tradeoff's between VI robustness to BRDF effects and saturation that impacted upon the retrievals of phenology parameters.	en_US
dc.relation.ispartof	38th Asian Conference on Remote Sensing - Space Applications: Touching Human Lives, ACRS 2017	en_US
dc.title	Impact of bidirectional reflectance distribution function on modis vegetation indices in southeast Asia tropical forests	en_US
dc.type	Conference Proceeding
utslib.citation.volume	2017-October	en_US
utslib.for	0909 Geomatic Engineering	en_US
pubs.embargo.period	Not known	en_US
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Faculty of Science
pubs.organisational-group	/University of Technology Sydney/Faculty of Science/School of Life Sciences
pubs.organisational-group	/University of Technology Sydney/Strength - CAMGIS - Centre for Advanced Modelling and Geospatial lnformation Systems
utslib.copyright.status	open_access
pubs.publication-status	Published	en_US
pubs.volume	2017-October	en_US

Abstract:

Copyright © 2017 ISRS, All Rights Reserved. Tropical forests play important roles on global climate and biodiversity. The Moderate Resolution Imaging Spectroradiometer (MODIS), with high temporal resolution, provide a useful tool to study tropical forest dynamics, including seasonality and inter-annual variation. However, optical satellite data have cloud, aerosol and bidirectional reflectance distribution function (BRDF) effects, that create uncertainty in tropical forest studies. In the Amazon, some researchers demonstrated the difficulties in separating true forest dynamics from BRDF artefacts and seasonal cloud and aerosol influences. Lastly, optical reflectance saturation in dense tropical forests may restrict the retrieval of phenology information. In this study, we investigated the impact of BRDF effects on MODIS vegetation indices (VI) in Southeast Asia (SEA) tropical forests, the least studied area compared to other major tropical forests (South America and Central Africa). Moreover, unlike Amazon tropical forests, VI seasonality in SEA forests is not synchronous with sun-sensor geometries. We used 10-year data of daily MODIS BRDF (MCD43A1) collection 6 product, a kernel-driven model product that allows us to retrieve VI values for a range of fixed solar zenith angles (SZA). We compared these with the standard VI products (MOD13A1, MYD13A1) to analyse BRDF influences. The results show significant BRDF effects in all forest sites. Generally, smaller SZA yielded higher VI signals in forests. We found tradeoff's between VI robustness to BRDF effects and saturation that impacted upon the retrievals of phenology parameters.

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http://hdl.handle.net/10453/127391