Evidencia de ondas ecuatoriales en Salinas y Galápagos

Abstract

La importancia fundamental de estas ondas en las regiones tropicales (30°S-30°N) y especialmente en el sector ecuatorial (5°S-5°N), radica en que al propagarse más rápidamente que en regiones subtropicales, permiten un ajuste oceánico más rápido y eficaz ante cualquier alteración oceano-atmosférica. Sin embargo las ondas "interesantes" son las que transmiten cambios anormales, ya que en algunos casos lo hacen sin dispersión. Por ejemplo, las ondas Kelvin que son originadas en el Pacífico Ecuatorial Occidental, por la supresión o cambios de dirección de los vientos del este y coherentes con eventos ENOS, viajan a lo largo del Pacífico Ecuatorial hasta chocar con el continente sudamericano.

Time Series of daily averages of some oceanic-atmospheric variables from SAL (array formed by La Libertad and Salinas stations) and GAL (array formed by Santa Cruz-San Cristóbal-Baltra stations), had been analized using Empirical Orthogonal Functions (EOF) and Spectral Analysis. EOF analysis determined that in both stations, the first and second modes explained the great variability . In SAL they represented 39.7% and 23.8%, and in GAL 56.6% and 20.5% respectively of the total variation of the series. The presence of the annual cycle in the first mode, reveals the existence of this periodicity in all the serie, although in some of them, it was not evident in a first visual-graphic analysis. The second mode represented the relation between the sea level and winds, reflecting that some of these oscillations were forced atmospherically and surely related to changes of local or remote trades winds. Also, the Spectral Analyses of the time series and of the first and second modes of SAL an GAL, showed the presence of different oscillations with periods lesser than annuals. These were coincident with that of the equatorial waves (Kelvin and Rossby-gravity), some tide periodicities and some atmospheric oscillations. Finally the cross spectral analysis between atmospheric and oceanic variables suggested in some cases, a local atmospheric forcing.