Distribution of water vapor in the stratosphere

The development of a relatively lightweight dew-point radiosonde was coupled with a flight program to measure the water vapor in the stratosphere. The technique of obtaining data on descent as well as on ascent provided a method for checking the internal consistency of single flight observations. Data from three flights which meet the criterion of such self consistency are presented. One flight gave data which showed an essentially constant mixing ratio of approximately 4×10−5 g/g through the stratosphere with some decrease above 72,000 feet. The other two flights show a low water-vapor content in a layer just above the tropopause with a mixing ratio 1/20 that of the first flight at an altitude of 55,000 feet. An increase in water vapor with altitude above this layer is observed, the increase being such as to give a mixing ratio for the three flights which is of the same order of magnitude at 100,000 feet.