30-year vegetation trend analysis: Global and Regional

Space observations of land surface obtained from the Advanced Very High Resolution Radiometer (AVHRR) has the longest (30 year) and continues (daily) global records. The AVHRR-based datasets has already been used for climate studies and will be used in the future. The NDVI derived from AVHRR is a proxy for greenness and vigor of plant canopy and consequently for photosynthetic activities and has been extensively used for trend analysis of vegetation. The satellite NDVI records begun in July 1981 and extends to the present time. These records were aggregated to a 4 km (Global Area Coverage-GAC) spatial and 7-day composite temporal data set called GVI-x. These records were collected from six NOAA afternoon satellites (NOAA-7, 9, 11, 14, 16 & 18). They were pre- and post-launch calibrated and high frequency noise related to short-term changes in the atmosphere and land surface were removed using statistical filtering procedure. In addition the data were processed to remove large-scale disturbances such as volcanoes, orbit degradation and differences in response function. This paper presents briefly the processing procedure and analysis the trends in NDVI time series. These trends were compared to the trend analysis of other global AVHRR-based data sets (Global Inventory Modeling and Mapping Studies (GIMMS) and Land Long Term Data Record (LTDR) over the period 1982-1999.