Interannual variability of seasonal rainfall in Cordoba, Argentina, evaluated from ENSO and ENSO Modoki signals and verified with MODIS NDVI data

Abstract

El Nino–Southern Oscillation (ENSO) is an atmospheric and oceanic signal closely linked with the short-term (interannual) climate variability and, as part of the global atmospheric circulation, influences for several months the weather in different regions of the world. As a proxy of ENSO, the Southern Oscillation Index (SOI) has shown a moderate ability to predict rainfall behavior on the territory of Cordoba province, Argentina. Several studies last years have postulated for the existence of the El Nino Modoki, “a similar but different” type of El Nino, with an increasing interest in determining the characteristics of its evolution and the impact of associated teleconnections over the weather around the world. Moreover, spectral indicators such as the normalized difference vegetation index (NDVI) have also been used to monitor the ENSO cycle. The influence in a predictive way of both ENSO and ENSO Modoki over seasonal rainfall indicators: amount (PP), frequency (DPP) and maximum daily precipitation (PPmax), was analyzed during the period from 1960 to 2017 in Cordoba Province, Argentina. Complementarily, the ENSO influence on vegetation behavior was also assessed during the rainfall season by using NDVI data from MODIS-TERRA for the period 2000–2017 to verify the predictive potential of the climate signal. Before the beginning of the rainy season, the August and September SOI average (SOIas) shows negative linear relationships with the rainfall attributes in almost all the territory of Cordoba that, although significant in statistical terms, are relatively weak. El Nino Modoki Index (EMI) used to represent the ENSO Modoki did not improve predictions on the rainfall behavior in Cordoba compared to SOI. Although the ENSO (SOIas) explains a little portion of interannual variability on subsequent seasonal rainfall, just between 14 and 22% for the entire region, when ENSO phases’ fluctuations upon NDVI data were analyzed, a very similar scheme was established. It is important to realize these responses show a strong local dependence associated with the environment resources and agricultural scheme own of each place. These results validate the use of the ENSO as a warning signal to anticipate the productive risk of the region, particularly when the Neutral years are discarded.