HR: 0800h
AN: B41B-0110    [Abstracts]
TI: Identification of the Interrelationship Between the Interannual Variation in Vegetation Activity and Climate Over Tropics
AU: * Nagai, S
EM: s010116d@mbox.nagoya-u.ac.jp
AF: Graduate School of Environmental Studies, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601 Japan
AU: Ichii, K
EM: kichiijp@yahoo.co.jp
AF: San Jose State University, One Washington Square, San Jose, CA 95192 United States
AU: Morimoto, H
EM: e43468a@cc.nagoya-u.ac.jp
AF: Graduate School of Environmental Studies, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601 Japan
AB: Clarification of the global terrestrial carbon cycle is essential to appreciate the green house effect. In special, tropical ecosystems have been influenced by the climate variations such as ENSO. Therefore, estimating the correlation between interannual variability in vegetation activities and the climate system is important. Although many studies have shown the relationship between the vegetation activities and ENSO events, they are not enough to evaluate the interannual variability and each response between the vegetation activities and climate parameters in the system. In this study, we used the 10 days composite Normalized Difference Vegetation Index (NDVI) originated from the Advanced Very High Resolution Radiometers (AVHRR) on the NOAA satellites from 1981 to 2000. Firstly, we estimated the variation associated with ENSO period using Singular Spectrum Analysis (SSA), which is useful method to extract a low frequency component from short-term noisy time-series. Secondly, we proposed the multivariable linear system model using the ENSO-related variation in NDVI, Multivariate ENSO Index (MEI) and the atmospheric CO2 growth ratio, and then investigated their mutual responses and feedback system in the model. Although the NDVI time-series over tropics contain many noisy elements due to cloud contamination or sensor degradation, the principal components ENSO-associated cycle explained a certain proportion of variance and the reconstructed fluctuation showed high correlation with Southern Oscillation Index (SOI), MEI, and ENSO-connected climate variations (precipitation, temperature, and incoming surface solar radiation) on a seasonal basis. Our model results showed that the regions correlated well with ENSO activities are inclined to coincide with the interannual vegetation variation. Our conclusion is that the NDVI time-series over tropics, where have been affected by ENSO activities, contain the ENSO-related component and link with the interannual CO2 growing variation. Future of our studies are to improve the NDVI data set to predict future well and to compare ENSO-associated variation in NDVI with NPP or GPP derived from the biochemical model.
DE: 1600 GLOBAL CHANGE (New category)
DE: 1640 Remote sensing
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting