Japan Geoscience Union Meeting 2015

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International Session (Oral)

Symbol A (Atmospheric and Hydrospheric Sciences) » A-CG Complex & General

[A-CG09] Satellite Earth Environment Observation

Thu. May 28, 2015 2:15 PM - 4:00 PM 301B (3F)

Convener:*Riko Oki(Japan Aerospace Exploration Agency), Tadahiro Hayasaka(Graduate School of Science, Tohoku University), Kaoru Sato(Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo), Masaki Satoh(Atmosphere and Ocean Research Institute, The University of Tokyo), Nobuhiro Takahashi(National Institute of Information and Communications Technology), Yoshiaki HONDA(Center for Environmental Remote Sensing, Chiba University), Kenlo Nasahara(Faculty of Life and Environmental Sciences, University of Tsukuba), Takashi Nakajima(Tokai University, School of Information Science & Technology, Dept. of Human & Information Science), Taikan Oki(Institute of Industrial Science, The University of Tokyo), Tatsuya Yokota(National Institute for Environmental Studies), Yukari Takayabu(Atmosphere and Ocean Research Institute, the University of Tokyo), Hiroshi Murakami(Earth Observation Research Center, Japan Aerospace Exploration Agency), Hajime Okamoto(Kyushu University), Chair:Hiroshi Murakami(Earth Observation Research Center, Japan Aerospace Exploration Agency)

2:30 PM - 2:45 PM

[ACG09-27] Harmonic analysis of desertification processes measured by vegetation greenness data from GIMMS3g NDVI

*Narumasa TSUTSUMIDA1, Heiko Balzter2 (1.Graduate School of Global Environmental Studies, Kyoto University, 2.Centre for Landscape and Climate Research, Department of Geography, University of Leicester)

Keywords:Desertification, GIMMS3g, NDVI, Harmonic analysis

Desertification is a spatio-temporal process caused by both natural climate changes (e.g. drought) and anthropogenic disturbances (e.g. overgrazing and excessive agricultural developments). To monitor this, long-term remote sensing observations are useful for finding vegetation activities using by vegetation indices such as Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI). Previous remote sensing studies have sometimes ignored detailed desertification processes. As unstable vegetation conditions on the edge of deserts, the observed time series data in those areas tend to produce anomalies. To overcome this issue, it is beneficial to focus on phonological process by vegetation indices because such anomalies may represent the vegetation conditions on land. The aim of this study is therefore to understand the desertification process by identifying phenological events using long-term historical remotely sensed imagery. Harmonic analysis is applied to Global Inventory Modeling and Mapping Studies (GIMMS) 3g NDVI time series for 1981-2012. GIMMS3G data is an update version of GIMMS NDVI data covering recent 31 years. Harmonic analysis is a decomposition technique which allows extracting individual harmonic oscillation terms from time series data. This model can assess the statistical significance of each decomposed wave term through Fisher’s test and has a great advantage compared to related models such as the seasonal-trend decomposition model and structural time series models. Using these methods, we investigate vegetation phenological signals around the boundary of deserts. The harmonic analysis approach provides insights into long-term desertification processes from the interpretation of the amplitude and phase terms of the individual harmonic terms.