Linking El Niño Southern Oscillation for early drought detection in tropical climates: The Ecuadorian coast

Abstract

El Niño Southern Oscillation (ENSO) is the most determining climate pattern in the tropics of the Pacific coast of America that regulate flood and drought periods. Over the last decades, Ecuador has incurred in significant economic losses due to drought events, around 4% of the GDP, mainly in the agricultural and livestock sectors and the hydropower generation. The use of Drought Indicators and the Early Drought Detection can contribute to reduce the impacts of these events. A drought forecasting system, based on ENSO and Drought Indicators, is presented to determine the possibility of appearance of drought events in Manabí River Basin District (MRBD). This system can help to the decision makers, in December (short-term drought, seasonal) and in May (long-term drought, annual), to activate the drought measures in the following months.Six climate indices are used for ENSO: Oceanic Niño Index (ONI), Southern Oscillation Index (SOI), and Sea Surface Temperature (SST) for Niño regions: 4, 3.4, 3 and 1 + 2. On the other hand, two drought indices are used: spatially distributed Standardized Precipitation Index (SPI) -1, 3, 6 and 12 months-, and a modified Palmer Drought Severity Index (PDSI), derived from a calibrated water balance model.This system allows early drought detection, assessing SST 1 + 2 (lag −7), 3 (lag −9) and 3.4 (lag −9) anomalies and drought indices, in December for a season drought and May for an annual drought. These analyses demonstrates that, drought may forecasting up to 7–9 months before their occurrence, through SST regions observations, based on strong relationship between ENSO and droughts occurrence.