Winds between San Diego and San Clemente Island


  • Clive E. Dorman


Dense ship observations off San Diego were used to capture the diurnal and seasonal wind trends. The land breeze regime extends to 40 km off San Diego in the winter, but goes to less than 10 km when averaged for the winter. Significant diurnal variations in wind speed occur in all seasons from the coast to beyond 140 km. Ship observations were averaged over 0.2° of latitude and longitude. These have significant structure that is obscured in other studies based upon 1° averages. Wind speeds decrease by a factor of 2 or more from 140 km offshore to the coast in both the northerly and westerly component. The mean flow has a weak summer southerly component. This is in opposition to earlier studies which indicated northerly mean monthly flow all year. Ship observations were compared to San Diego Airport and San Clemente Island measurements in order to check the accuracy of allowing land measurements to substitute for over water measurements. San Diego winds were found to be very representative of the nearest 10 km of ocean in wind speed and direction on the diurnal and seasonal scales. San Diego would be a good proxy station from which to infer the long-term near shore meteorlogical conditions. San Clemente Island wind speeds are systematically less than the ship observed wind speeds in the easterly component. But the correspondence between the northerly component at San Clemente and ships is irregular in the diurnal and monthly means. This station could not be used to infer the northerly component without an uncertain and elaborate correction.