The climatology of sea breezes on sardinia

摘要

Hourly wind speed and direction data from 12 coastline stations on Sardinia, Italy, are analysed in order to characterize sea breezes in the region. A set of criteria based on the diurnal reversal of wind direction, and the thermal gradient necessary to drive the circulation, is used to identify sea breeze days. Statistics are presented that describe the occurrence, duration, and strength of the sea breezes. On a stationwide basis, sea breezes are most frequent in the summer months (May-August), when they appear on more than one-third of the days. Sea breeze occurrence and duration are the greatest for the stations on the east coast of the island. The all-station average sea breeze duration reaches a maximum of about 9 h in June. The strength of the sea breezes is roughly 3 m s~(-1) during summer months on average over all stations in the sample. An analysis of mean daily hodographs for the stations in the sample shows clearly the onshore-offshore nature of the sea breeze circulation, and the response of the sea breezes to the local coastline. Sea breezes are shown to develop simultaneously on all coasts of the island under appropriate synoptic conditions.