Favre and Coantio 



radiation, measurement of refractive index, use of the ionic probe. 

 These techniques which depend on the thermodynamic properties of 

 mioist air present advantages from the point of view of miniaturi- 

 zation, whereas those based on electromagnetic properties are 

 advantageous from the point of view of bandwidth. Psychrometry 

 and Lyman alpha absorption seem to be the most promising ones, 

 the latter appearing to have the best chance for adaptation to parti- 

 cularly difficult measuring conditions (Coantic and Leducq [ 1969] ). 



For practical reasons, psychrometry has been chosen for a 

 first deeper investigation. A small calibrating tunnel has been built 

 and various types of miniaturized small time constant psychrometers 

 have been manufactured and tested. A prototype psychrometer is 

 used with wet and dry balsa fibers, of which surface temperature is 

 measured by platinum resistors (5 microns in diameter), the result- 

 ing electrical signals being fed into a small analogue computer, 

 whose output is directly proportional to specific humidity fluctuations, 

 The physical size of the sensing head is a few miUinneters and the 

 bandwidth several cycles per second (Leducq [ 1970]). These results 

 are only preliminary, and further studies are now being undertaken. 



3. Data Processing 



Considering on one hand the volume of measurements to be 

 taken, and on the other hand the necessity, mentioned in II. 2, to 

 separate any variable in its "mean," "phase average" and "turbu- 

 lent" parts, the use of digital data acquisition and processing methods 

 seem unavoidable. 



Preliminary studies have been done of a small data acquisition 

 system for continuous digitizing and numerical tape recording of 

 turbulent variables. The recorded data could be later, pre-pro- 

 cessed on the system itself and eventually transferred to a large 

 computer for a comprehensive treatment. This data acquisition 

 system could also be useful for control process of the tunnel and of 

 the measuring equipments, thereby largely increasing the efficiency 

 of the facility. 



VII. CONCLUSIONS AND PROSPECTS 



The research program which has just been introduced is 

 obviously a long-term one. It is therefore too soon to state any 

 definitive conclusion, and we can only try to survey some preliminary 

 results, and to think about the probable prospects of the research 

 we have undertaken. 



The main result of the work performed till now is the detailed 

 definition of a scientific experiment which, although done in the 

 laboratory, seems capable to give results applicable to the natural 

 processes occurring near the ocean-atmosphere interface. The 



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