Coupling between Sea and Air 



PIERRE WELANDER 



Institute of Meteorology, University of Stockholm, Stockholm, Sweden 



PRACTICALLY all the physical, chemical and biological processes 

 that take place in the sea are critically dependent on the fact that 

 the sea has a free surface communicating with the atmosphere. 

 The air-sea boundary phenomena and their relation to the interior 

 processes in the sea have accordingly been subjected to an ever 

 increasing interest by the oceanographer. In particular, a great 

 deal of both theoretical and field work has been done on the 

 mechanical-thermodynamic transfer processes at the sea surface. 

 The importance of these processes in determining the physical 

 state and the dynamics of the oceans is obvious. In fact, one can 

 show, by the use of the basic laws of mechanics and thermo- 

 dynamics, that for an ocean of given dimensions and of a given 

 chemical composition the distribution of temperature and salinity 

 as well as the motion of the water in the entire ocean is determined 

 by a knowledge of the following boundary quantities: {a) the 

 pressure and wind stress acting on the surface, {b) the net heat 

 flux through the surface layer, (c) the net water flux through the 

 surface layer (due to evaporation, precipitation, freezing, melting, 

 and river supply). 



In this case, we do not consider short-term fluctuations such as 

 the astronomic tides, which require a determination of the body 

 forces within the ocean, nor variations in the geologic time scale, 

 which bring in different bottom processes, weathering effects, etc. 



The fact that we can be satisfied in knowing the heat flux 

 through the surface layer and do not need a determination of the 

 interior heating function, is an essential simplification for com- 

 parisons with the atmosphere. This simplification, of course, 

 results from the small amount of transparency in the sea which 



401 



