Spatial influence and oceanic thermal response to Santa Ana events along the Baja California Peninsula

Abstract

Meteorological data were recorded at eight stations located along the coast of the Pacific Ocean and three along the coast of the Gulf of California, aimed to assess the spatial influence of Santa Ana weather conditions in the Baja California Peninsula. February 2002 featured two Santa Ana events: one from the 9 to the 12 and another from the 21 to the 22. The first Santa Ana event had the strongest winds, however relative humidity and temperature behaved similarly on both events at some stations. Data from the Pacific Ocean showed typical Santa Ana condition patterns: wind speed and temperature increase opposed to decreased relative humidity values. Data from the Gulf of California did not show the typical temperature rise of a Santa Ana condition, but there was a decrease on the amplitude of the diurnal variability of air temperature and relative humidity as well as a marked increase on wind strength. Wind direction during the Santa Ana events on the Pacific side was NE and NW on the Gulf of California. NE winds are associated to the shift on the position of the North Pacific High Pressure Center, which moves towards the continent. Data suggest that relative humidity may be the best parameter to monitor both occurrence and length of Santa Ana conditions on the Pacific side. Normal weather conditions show a negative air-sea temperature difference, but during both Santa Ana events this difference was positive and higher than 10 ºC. Latent and sensible heat fluxes drastically increased during both events, reaching values more than three times higher than those for normal conditions, which is due to the presence of strong winds combined with a drier and hotter air mass over the ocean.