Assessing the Relationship Between the Standardized Precipitation Evapotranspiration Index (SPEI) and the Normalized Difference Vegetation Index (NDVI) During 1985–2020 in a Mediterranean Area

In the Mediterranean Basin, drought is a significant problem for water resource management. The current study used gridded precipitation and temperature data (10 km × 10 km) for 191 grid points and the MODIS sensor images database from 1985 to 2020 to study drought meteorological conditions described by the SPEI and its relationship with vegetation dynamics described by the NDVI. A statistical analysis of correlation between SPEI and NDVI was performed both at the event scale and for long-term time series. Additionally, an analysis of empirical frequency of occurrence of NDVI values was performed for typical forest and crop cover type. Overall, the results highlighted a weak correlation between drought and vegetation pattern, but improvement in the methodology of analysis with more pronounced phenomenological insights would increase the knowledge of this specific theme.