A synoptic climatology of the near-surface wind along the west coast of South America

Abstract

Prevailing wind along the west coast of South America is equatorward, driven by the southeast Pacific anticyclone. The wind induces strong coastal upwelling that supports one of the most important fisheries in the world. This region lacks a dense network of in situ observations, so the high resolution (0.313°) NCEP Climate Forecast System Reanalysis is used here to present a synoptic climatology of the coastal wind along the Chile/Peru coast. Covariability between the alongshore pressure gradient and alongshore wind, which was previously identified for synoptic time scales near central Chile, is generalized for the whole coast and over annual time scales. Particular attention is paid to three prominent upwelling regions: Pisco (14.8°S), Punta Lengua de Vaca (30.0°S), and Punta Lavapie (36.4°S). Previous work has identified local maxima at these points but these are embedded in a broader low-level jet that exhibits a marked seasonal cycle of strong wind days due to the migration of the anticyclone and is associated with a shift of both the mean wind and a more frequent recurrence of strong wind events. Alongshore wind near Pisco is normally distributed year-round with a seasonal shift in the mean. Larger variability in the mean and distribution is found at Lavapie, associated with the seasonal change in storm tracks. The synoptic evolution that drives high-wind events at each location is characterized. A midlevel trough and surface cyclone precede wind maxima at each location and are followed by strong midlevel ridging and a strengthened surface anticyclone. © 2013 Royal Meteorological Society