Statistical characterization of the sea-breeze physical mechanisms through in-situ and satellite observations

Abstract

The physical mechanisms that take place under sea-breeze (SB) conditions in the Palma basin (Mallorca island, western Mediterranean sea) are analysed through the inspection of data from automatic weather stations (AWS) during the period 2009–2017. Satellite-derived land-surface and sea-surface temperatures (LST and SST, respectively) are used to compute the surface temperature difference (LST–SST) in the Palma basin. It is found that during daytime hourly averages for each month of this difference are always positive and maximal during summer time. A method is proposed to select the SB events using data from AWS. SB conditions are mainly reported during the warm months of the year (from April to September). Results from the statistical analysis of the selected SB events show that the morning reversal strongly depends on the speed and direction of the large-scale winds. Besides, weak wind conditions are reported during the morning reversal and once the SB starts the cold advection from the sea counteracts the radiative heating and the 2-m temperature levels off. The maximum surface temperature difference under SB conditions is larger than 5°C and it is often reported several hours after the morning reversal. About 2 hr later the maximum wind speed is formed, strongly influenced by the amount of soil moisture.