ENSO events and daily rainfall in Ecuador

Previous analysis of the relationship between ENSO and annual rainfall in Ecuador shows that the coastal regions of southern Ecuador are strongly influenced by the ENSO phenomenon. Abundant rainfall is generally associated with heating in eastern tropical Pacific and weakened south Pacific trade winds that permit a migration of the inter-tropical convergence zone far to the south and bring warm moist air. The purpose of this analysis is to determine the characteristics of the daily rainfall at the origin of the yearly anomalies. The ENSO influence is characterize by an increase of the number of day with heavy rainfall (> 10 mm) from March to May. This is associated with a decrease of the number of dry days, as the number of days with low rainfall (0 to 10 mm) does not vary. The yearly maximum daily rainfall is generally greater during the ENSO years, but the stronger daily rainfalls have been observed during normal years. The number and length of sequences with two or more consecutive days with heavy rainfall are also generally greater during ENSO years, but the three longer sequences have been observed during normal years. As conclusion, we can say that the increase in yearly rainfall is due to an extension of the rainy season with an increase of days with heavy rainfall but not to exceptional intense or lengthy sequences.