Spatiotemporal Analysis of Vegetation Health Index (VHI) and Drought Patterns in Libya Based on Remote Sensing Time Series

Abstract

Drought is one of the most important and complex climatic and environmental extreme events in terms of measuring, monitoring, and determining the related potential effects and hazards. In this study, a remote sensing–based Vegetation Health Index (VHI) was used to measure the drought conditions in vegetated areas of Libya. In order to ensure the high performance of this index, it was evaluated by a developed ground-based drought index called the Vegetation-Precipitation and Temperature Index (VPTI). The results showed a high level of confidence that VHI is scientifically reliable. The results of our experiment, which used datasets of growth seasons (Sep-May) during 2000–2014, showed that the average VHI did not exceed 43%. Thus, the country was closer to drought conditions. The country has also experienced three major spells of drought (2000–2002, 2009–2011, and 2012–2014), the most severe and prolonged of which was during the 2000/2001 and 2001/2002 seasons, reaching 18 months of moderate drought conditions. The winter and fall dynamics of VHI were responsible for 56% of reported droughts in the season, while the percentage of areas affected by drought reached 46% during the study period. The assessment and analysis of drought risks in Libya using a drought hazard mapping model found that 82% of the areas were subjected to high and very high drought risk.