El Niño-Southern Oscillation impacts on grape yields in Santana do Livramento, Brazil: understanding and early warning of crop failure conditions

Abstract

El Niño-Southern Oscillation (ENSO) is an important source of year–to–year fluctuations in the whole global climate system and in the southern Brazilian climate. El Niño events affect this region, imposing unfavorable weather conditions (rainy/humid/overcast) during critical grapevine phenological stages, compromising yields in the current and following crop seasons. The analysis of 29 crop cycles revealed patterns about grape yield oscillations in Santana do Livramento, Campanha Gaúcha, RS, Brazil. Yield deviations showed correlations with the Oceanic Niño Index (ONI) 3 months running means centered in November. La Niña events correlate with yield oscillations close to or above the tendency line. El Niño events are linked to various results, including the lowest and the highest yields. The four largest crop failures happened in El Niño events, while the three most severe of them happened in cases of early El Niño consolidation. The seven lowest yields were linked to El Niño, or low or descending yields in the previous year (s), or all these factors combined. Simple criteria allowing early warning of crop failure conditions were defined: ONI (or the monthly Niño - 3.4 Index) ≥ +0.5 °C in July (or earlier); and low or descending yields in the previous year (s)