Revised Parameterisations of Air-Sea Interactions

It is important for the user of this atlas to realize that determination of the exchanges of energy, mass and momentum between air and sea from ship synoptic observations is done by so-called parameterisations. The word “parameterisation” hides the fact that a complex process is subsumed under simple formulations depending on local variables observed at the sea surface, which may not be sufficient to describe conditions of the atmosphere or the processes involved. On the other hand, the use of parameterisations is the only way to calculate climatological air-sea interaction fields from the few meteorological quantities measured or observed on V.O.F. ships. The coefficients of parameterisations are most often empirically determined, and are subject to experimental and systematic errors. Additionally, ship observations are primarily made for the purpose of synoptic meteorology, and are not necessarily optimal for determinations of air-sea interactions. A number of considerations led us to select parameterisations for the air-sea exchange which deviate in several details from the ones Bunker used. In the following we discuss the parameterisations we have adopted, and reasons and considerations for our choice.