GLOBAL ANALYSIS OF THE RELATIONSHIPS AMONG A VEGETATION INDEX, PRECIPITATION AND LAND-SURFACE TEMPERATURE

This study is designed to examine the spatial variability of the relat ionships among global NDVI (Normalized Difference Vegetation Index) da ta, remotely-sensed land surface temperature data, and gridded station precipitation data as well as to investigate the potential for the co mbined use of NDVI and temperature data for global bioclimate monitori ng. The relationships among the three variables are examined using sin gle and multiple temporal correlations and the analysis is augmented b y the computation of the first annual harmonic of each parameter. In a ddition, the global variability of growing season timing is analysed u sing a proxy for the onset and conclusion of the growing season, based upon slopes of the NDVI time series. The NDVI data set as processed f or this study has significant sources of systematic error, which inclu de aerosol and cloud contamination, orbital drift, and instrument degr adation. This analysis provides insight into the manner in which the r elationships among NDVI, precipitation and remotely-sensed land surfac e temperature vary geographically, in spite of the data noise. Due to excessive systemic error, anomalies of this NDVI data set are not high ly correlated with precipitation, or multiply correlated with temperat ure to precipitation. Greater immediate promise for interannual biocli mate monitoring is contained in the proxies presented here for the gro wing season onset and length.