Seasonality and anomalies of sea surface temperature off the coast of Nayarit, Mexico Emilio Palacios-Hernández & Laura E. Carrillo & Anatoliy Filonov & Luis Brito-Castillo & Carlos E. Cabrera-Ramos Received: 19 March 2009 / Accepted: 5 November 2009 # Springer-Verlag 2009 Abstract Sea surface temperature (SST) harmonic and empirical orthogonal function (EOF) analyses covering 18 years were performed for the area located from 114° to 105° W and from 18° to 25° N. The results indicate that the influence of the annual signal predominates over the semi- annual signal, and the closer to the coast, the stronger the annual harmonic. Several interannual anomalies arose that are connected with the main global indexes, especially the Oceanic Niño Index. Pearson correlations between the first temporal mode of the SST and regional rainfalls in Nayarit indicate that maximum correlations (r >0.7) are observed when there is a +1-month lag between the series. However, this result indicates that SST is delayed with 1 month after rainfall occurrence, which shows that the dominant influence in this relationship is not the SST forcing. Keywords Nayarit . Rainfall . SST 1 Introduction Sea surface temperature (SST) data obtained by satellite infrared images are often used for the calculation of latent and sensible heat flows (Curry and Webster 1999), as a passive tracer of currents (Palacios-Hernandez et al. 1996), climatic studies (Meza 2006; Lavín et al. 2003), and prognoses of the ocean–atmosphere interaction (Enfield 1996; Enfield and Mayer 1997; Hernández 2002; Meza 2006). These data are of great importance in most environmental studies as a dominant indicator of climate change. Using data of SST anomalies allows the identifi- cation of different weather and oceanographic phenomena. El Niño-Southern Oscillation (ENSO) is one of the most significant patterns of interannual variability worldwide, and SST is one of the main tracers that distinguish this pattern through positive anomalies (Wang and Fiedler 2006). In Mexico, the effects of El Niño appear in the rise of water temperature, sea level, and the interannual variations of weather conditions of practically the entire western Mexican coast (Martínez 2006). Other causes of SST variations exist, such as “La Niña” and the oscillations of the South Pacific and the North Pacific high-pressure centers. For a few decades, high-resolution SST data are available from satellites. Researchers have used SST data from the Eastern Tropical Pacific to analyze ENSO events (Wang and Fiedler 2006), climatic changes, inter-decadal variability (Mestas-Nuñez and Miller 2006), atmospheric Responsible Editor: Franciscus Colijn E. Palacios-Hernández : A. Filonov : L. Brito-Castillo Universidad de Guadalajara, Revolución 1500, Col. Olímpica, Guadalajara, Jalisco 44840, Mexico L. E. Carrillo El Colegio de la frontera Sur, Av. Centenario, Km. 5.5. Cd. Chetumal, Quintana Roo 77014, Mexico L. Brito-Castillo (*) Centro de Investigaciones Biológicas del Noroeste (CIBNOR), Unidad Sonora, Campus Guaymas, Estero de Bacochibampo, Guaymas, Sonora 85454, Mexico e-mail: lbrito04@cibnor.mx C. E. Cabrera-Ramos Centro de Investigación Científica y de Educación Superior de Ensenada, Km. 107 Carretera Tijuana-Ensenada, Ensenada, Baja California 22860, Mexico Ocean Dynamics DOI 10.1007/s10236-009-0244-z