Relationship between Interannual Variations in Satellite-based Vegetation Index and ENSO Phase over Tropical Forests

Abstract

　Carbon cycle of tropical ecosystems may respond from climate variations related to El Nino-Southern Oscillation (ENSO). Although models and atmospheric studies have demonstrated the relationship, few studies have been conducted using direct observations on large spatial scales. In the present study, the interannual variations associated with ENSO period in the satellite-based Normalized Difference Vegetation Index (NDVI) data over low latitudinal zones (30ﾟN to 30ﾟS) from 1981 to 2000 were analyzed using Singular Spectrum Analysis (SSA), which is an effective method to extract the variations from short-term noisy time-series data.
　The NDVI variations over tropical rainforest are characterized by a high proportion of variances explained by ENSO time-scale mode, although the original NDVI data also contained the seasonal variations. In addition, these variations show a high correlation with Southern Oscillation Index (SOI) variation.
　We concluded that the long-term satellite observation also shows the impact of ENSO-related climate variations on terrestrial vegetation activities.