Abstract
Sea surface temperature (SST) is directly affected by the diurnal cycle of the sun's radiation. Over 200 cases of diurnal cycles of SST are analysed in conjunction with their associated meteorological fields to investigate the phase of the diurnal SST cycle and understand the sensitivity of the diurnal warm layer to meteorological variability during the day. A classification is presented which categorises diurnal warming shapes into four separate groups based on different wind and insolation fluctuations. Differences between the shape of the diurnal signal at the surface and depth are investigated in order to interpret the diurnal variations detected by satellite and in situ measurement techniques. The results highlight the variability in the shape of the diurnal SST cycle and draw attention to the large differences in temperature that can occur between the surface and 1 m under low wind and strong heating conditions. This is important for air–sea heat and gas exchange as the diurnal temperature variations at the surface, under low winds, can be much larger than that which has been presented in the past with in situ observations.
Acknowledgements
A.S.-M. was supported for this work by a SOC studentship at Southampton Oceanography Centre. The work contributes to the EU Framework 6 MERSEA Integrated Project. The IMET buoy data sets were obtained from the Upper Ocean Group at Woods Hole Oceanographic Institution and the R/V Franklin skin data was obtained from the SEAFLUX website (http://curry.eas.gatech.edu/SEAFLUX/valdata-cg.html). We are grateful to Gary Wick, Mark Pritchard and Simon Josey for their helpful discussions.