Field Observations and Modeling of Surfzone Sensible Heat Flux

Surfzone sensible heat flux (H-S,H-SZ) obtained through direct eddy-covariance estimates was measured at four different sandy beach sites along Monterey Bay, California. The H-S,H-SZ source region is estimated from a footprint probability distribution function (pdf) model and is only considered when at least 70% of the footprint pdf occupies the surfzone. The measured H-S,H-SZ is 2 times the modeled interfacial sensible heat (H-S,H-int) using COARE3.5. A formulation for estimating sensible heat flux from spray droplets (H-S,H-spray) generated during depth-limited wave breaking is developed. The sea-spray generation function for droplet radii ranging over 0.1 <= ro <= 1000 mm is based on self-similar spectra of spray droplets measured from the surfzone forced by the average depth-limited breaking wave dissipation across the surfzone. However, it is shown that the size of the spume droplets that contribute to H-S,H-spray is limited owing to the relatively short residence time in air as the droplets fall to the sea surface during wave breaking. The addition of the surfzone-modeled H-S,H- (spray) to the COARE3.5H(S,int) gives values similar to the observed surfzone H-S,H-SZ, highlighting the importance of depth-limited wave-breaking processes to sensible heat flux. Measured H-S,H-SZ values are an order of magnitude larger than simultaneous open ocean observations.