Drought characterization across Peru and Ecuador and its relationship with ocean-atmospheric indices

Peru and Ecuador have suffered high economic losses because of extreme events (Floods and Droughts). The analysis of the meteorological droughts and their drivers is of paramount importance for water resources management and risk assessment in these countries. This study aims to characterize the spatiotemporal variability of droughts across Peru and Ecuador over the last four decades (1981-2020) and evaluate the relationship with the ocean-atmospheric circulation patterns. The Rain for Peru and Ecuador (RAIN4PE) gridded precipitation dataset was used to estimate the Standardized Precipitation Index (SPI) at time scales of 3 and 12 months to assess short and long-term droughts, respectively. Droughts were characterized by the number of events, duration, intensity, and severity, and the relationship was evaluated by computing the Pearson correlation to identify the leading oceanic-atmospheric indices: E (Eastern Pacific SST anomalies), C (Central Pacific SST anomalies), PDO (Pacific Decadal Oscillation), SOI (Southern Oscillation Index), MEI2 (Multivariate Enso Index), TPI (Tripole Index for the Interdecadal Pacific Oscillation), TNA (Tropical North Atlantic index), and TSA (Tropical Southern Atlantic Index).

The results show high spatiotemporal variability of drought characteristics with the high frequency of extreme droughts over the southern Peruvian Andes in Peru and the eastward of the Andes in Ecuador. The ranking of the extremeness of drought events based on the areal extent, duration, and intensity identified that three of the four more extreme events match ENSO conditions in Peru (1992/02, 1988/08, 1990/01) and Ecuador (1985/04, 1990/01, 1995/04). Finally, strong relationships between ocean-atmospheric indices and droughts in Peru and Ecuador were identified. Droughts in Peru evidence significant correlations with E, C, and TNA indices. Similarly, droughts in Ecuador show high correlations with E, C, PDO, TPI, and SOI indices. These results provide more insights into the characteristics of droughts and the possible drivers, information that is useful for water resource management decisions and can help as the basis for developing drought forecasts.