Program     Ocean-atmosphere interactions and multi-scale climate variability in a changing climate       Poster Observed precipitation changes in Ecuadorian coast influenced by Interdecadal and Interannual Variability during the Period 1975-2014 Freddy Hernández* , INOCAR Leonor Vera, INOCAR Susy Marín, INOCAR Presenter Email: freddy.hernandez@inocar.mil.ec Continental Ecuador, with a relatively short coast (750 Km), is subject to a coastal climate defined by two seasons: a rainy period between January and March, with a unimmodal distribution with maximum peaks in March and April, and a dry season between June and December. This seasonality is influenced by several factors, including global and regional atmospheric circulation, local air masses determined by the topography, oceanic currents (the equatorial front, the Humboldt current system, among others) and the Andean mountains. Nevertheless, the normal development of this seasonality is from time to time altered by the interannual variability of El Nino (La Nina), which is characterized by an anomalous warming (cooling) of the Central-Eastern Pacific Ocean. These alterations impact the ecosystem, modify the circulation patterns and bring social-economic consequences to the country with different levels of impact. As an example, Guayaquil, a city in low lands, registered a monthly precipitation increase about 1400%, in May71983, during the 1982-1983 El Nino and, several coastal locations, showed a decrease up to 100%, in February/1999, at the beginning of a La Nina period. Eleven ENSO events occurred between 1975 and 2014 were analyzed, indifferently to its origin (canonical, Modoki or central). The length of each one is variable; while El Nino had a durations between 5 and 19 months, La Nina last between 5 and 33 months. Additionally, two El Nino events categorized as extraordinary, occurred in 1982-1983 and 1997-1998. In the late 1990s a shift in global scale was detected in ocean-atmospheric conditions. Nowadays studies relate this shift to a change of phase in the Interdecadal Pacific Oscillation (IPO). In this context, the period concerning this work covers both phases of the IPO, a positive phase from 1975 to1999, in which 7 El Nino (including two El Nino extreme episodes) and 5 La Nina events were found; and a negative phase from 2000 to 2014, with 4 El Nino and 5 La Nina events. In the ongoing negative IPO period, more frequent events but with a shorter duration have occurred. El Nino, La Nina, and normal conditions scenarios were discriminated in both IPO phases, using a non-parametric test to determine differences between the precipitation ranges. The results suggest that precipitation at three locations in the Ecuadorian coast (Esmeraldas, Libertad and Guayaquil) is not influenced by the Interannual and Interdecadal variability. The implications of the differences and relations found are discussed in this work.

f7f7f7">