An accurate means is required for measuring relative humidity in clouds because this parameter is essential in the evolution of cloud microphysi@cs. The development of a new RH sensor capable of meeting this need is based on the optical measurement of haze droplets as they respond in size to changes in ambient RH; an accuracy of the RH measurement of + /- 0.02 percent is anticipated, with RH values > 100 percent also being measured. A prototype sensor for field use is devised, designed, and fabricated utilizing recent advances in laser diode technology. Research investigates the sensor's survivability under atmospheric conditions with high wind speed and large hydrometers. The sensor is tested in atmospheric clouds under supersaturated conditions.The potential commercial applivation as described by the awardee: The research addresses the development of a sensor for precise measurement of relative humidity near RH = 100 percent. This sensor has application for incloud measurements, as a calibration-facility sensor, and for other applications where water vapor supersaturations and subsaturations near RH 100 percent need to be measured.
