El Nio Southern Oscillation and Drought

Recent research investigation about the effects of El Niño on the rainfall distribution in northern Mexico shows that this climatic phenomenon has an influence on rainfall patterns. During El Niño years, rainfall was below normal during summers and above normal during winters (Magaña et al.,

Figure 10.3 Monthly mean rainfall values in the study area and for Mexico showing the main rainfall season from June through September. Coahuila is the state with the smallest value and Durango with the largest one. [Based on 60 years of data (1941-2000) collected from the National Meteorological Service]

Figure 10.3 Monthly mean rainfall values in the study area and for Mexico showing the main rainfall season from June through September. Coahuila is the state with the smallest value and Durango with the largest one. [Based on 60 years of data (1941-2000) collected from the National Meteorological Service]

2003; Tiscareño et al., 2003). Magaña et al. (2003) also established that during La Niña years, rainfall was normal or little bit above normal during summers, but rainfall showed a declining pattern during winters.

Tiscareño et al. (2003) used variables related to the El Niño/Southern Oscillation (ENSO; sea-surface temperatures and pressure differences in the Pacific Ocean; chapter 3) and correlated them to rainfall data. This allowed the identification of wet and dry periods that coincided with hot and cold periods of the Pacific Ocean waters. Based on this analysis, Tiscareño et al. arrived at the conclusion that the drought of 1982-83, which affected almost the entire country, was a result of the ENSO.

Agricultural production is also affected by the ENSO. This phenomenon has caused a decrease in national grain production since the 1960s (Tiscareño-López, 1999). Tiscareño et al. (2003) also showed considerable interannual yield variations as a result of climate anomalies in Mexico.

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