Influence of ENSO on Droughts and Vegetation in a High Mountain Equatorial Climate Basin

Several studies have assessed droughts and vegetation considering climatic factors, particularly El Nino-Southern Oscillation (ENSO) at different latitudes. However, there are knowledge gaps in the tropical Andes, a region with high spatiotemporal climatic variability. This research analyzed the relationships between droughts, vegetation, and ENSO from 2001-2015. Meteorological drought was analyzed using the Standardized Precipitation Evapotranspiration Index (SPEI) for 1, 3 and 6 months. Normalized Difference Vegetation Index (NDVI) was used to evaluate vegetation, and ENSO indexes were used as climate drivers. The Wavelet coherence method was used to establish time-frequency relationships. This approach was applied in the Machangara river sub-basin in the Southern Ecuadorian Andes. The results showed significant negative correlations during 2009-2013 between the SPEI and NDVI, with the SPEI6 lagging by nine months and a return period of 1.5 years. ENSO-SPEI presented the highest negative correlations during 2009-2014 and a return period of three years, with ENSO leading the relationship for around fourteen months. ENSO-NDVI showed the highest positive correlations during 2004-2008 and a return period of one year, with the ENSO indexes continually delayed by approximately one month. These results could be a benchmark for developing advanced studies for climate hazards.

Automated summary

This study analyzed the relationships between droughts, vegetation, and El Nino-Southern Oscillation (ENSO) in a sub-basin of the tropical Andes. The results showed significant negative correlations between meteorological drought and vegetation, with ENSO playing a major role in this relationship.