Global vegetative drought trend and variability analysis from long-term remotely sensed data

With several decadal accumulations of remotely sensed data and products and advances in satellite based vegetative drought detection methods, the global and regional characteristics of drought are expected be discovered from those long-term historical inventory data. In this study, we investigate the trend and variability of global vegetative drought using bf 1981-2017 NOVAA/AVHRR weekly VHI products. We proposed a methodological framework to perform trend and variability analysis from overall trend test to trend location detection to trend magnitude estimate. Accounting for the effect of the global geographical heterogeneity on trend analysis, we aggregated the VHI dataset on designated zones in view of latitude ranges and climate zones. We found that: (1) although the overall trends are not obvious for some cases, the local trends are significant in some specific periods, and (2) the trends of vegetative drought in the north hemisphere is better than that in the south hemisphere.