Calibration Techniques and Testing of Hygrometers for Horizontal Soundings of the Troposphere and Lower Stratosphere

Abstract

The measurement of the water vapor content of the atmosphere from a constant level balloon imposes new requirements, involving very long term stability for several months of flight, and light weight. In the first plan, a precise relative humidity calibration chamber was developed to measure the long-period drift of state-of-the-art sensors, particularly aluminium oxide elements. All were found to have a significant drift over a one month period, including a specially built sensor made of a vibrating quartz microbalance with an adsorbing coating.