The PI wishes to devise an accurate means for measuring relative humidity in clouds, because this parameter is essential in the evolution of cloud microphysics. This proposal is to develop a new RH sensor capable of meeting this need. The sensor 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% is anticipated, with RH values > 100% also being measured. A prototype sensor for field use will be devised, designed, and fabricated using recent advances in laser diode technology. Research will be conducted to make possible the sensor's survivability under atmospheric conditions with high wind speed and large hydrometeors. Tests of the sensor will be conducted in atmospheric clouds under supersaturated conditions. The goal of this work is to develop and test a RH sensor for incloud use. If this work leads to a practical prototype, it is anticipated that a commercial version would find significant use in the cloud research community.
