A surface acoustic wave frost-point hygrometer for measurements of stratospheric water vapour
Conventional frost-point hygrometers observe frost on their cold point by optical means [1,2,3], thereby requiring several micrometres of ice to form. We have developed a new hygrometer which uses surface acoustic wave (SAW) devices to determine when condensation has occurred. At the oscillation frequencies used (hundreds of MHz), the SAW device is capable of responding to a few monolayers of condensate, increasing sensitivity and reducing response time. The principle of the method has been demonstrated in the laboratory by calibration against a chilled mirror frost-point hygrometer, and the sensor has had a number of technical balloon flights. Here we describe the principle of the technique and present some preliminary results.
In: Harris, N.R.P., Guirlet, M., Amanatidis, G.T. (eds.). Stratospheric ozone 1999. Proceedings of the fifth European symposium, Saint Jean de Luz, France, 1999, Luxembourg, Office for Official Publications of the European Communities, 742-745.