  The present study examined a multi-year reanalysis dataset (ERA5-Land)
including numerous drought events across the Iberian Peninsula, with a specific
emphasis on the 2005 episode. The mechanisms underlying the transition from
meteorological to agricultural drought and its features were investigated.
Various non-parametric standardized drought indices were utilized. For
meteorological droughts, the Standardized Precipitation-Evapotranspiration
Index (SPEI) was employed, while the Standardized Soil Moisture Index (SSI),
Multivariate Standardized Drought Index (MSDI), and Standard Precipitation,
Evapotranspiration and Soil Moisture Index (SPESMI) were utilized for
agricultural droughts, while their ability to identify relative vegetation
stress in areas affected by severe droughts was investigated using the Fraction
of Absorbed Photosynthetically Active Radiation (FAPAR) Anomaly provided by the
Copernicus European Drought Observatory (EDO). A statistical approach based on
run theory was employed to analyze several characteristics of drought
propagation, such as response time scale, propagation probability, and lag time
at monthly, seasonal, and six-month time scales. The retrieved response time
scale was fast, about 1-2 months, and the probability of occurrence increased
with the severity of the originating meteorological drought. The duration of
agricultural drought was shorter than that of meteorological drought, with a
delayed onset but the same term. The results obtained by multi-variate indices
showed a more rapid propagation process and a tendency to identify more severe
events than uni-variate indices. In general terms, agricultural indices were
found to be effective in assessing vegetation stress in the Iberian Peninsula.
A newly developed combined agricultural drought index was found to balance the
characteristics of the other adopted indices and may be useful for future
studies.
