This paper presents a method for predicting cloud height and amounts from the radiosonde soundings. The method can be applied to both operational and climatological analyses. The method, which uses only dew point depression, is based on at least two unpublished studies conducted in the 1950's with U.S. radiosondes using lithium chloride hygristors. Predicting clouds from radiosonde soundings was a topic of interest in the Former Soviet Union. In these studies, the vertical temperature gradient and the dew point or its vertical gradient were used.
Different nations use different relative humidity sensors.
There are no international standards for the transformation of relative humidity observations to dew point depression. Canada and the USA both use the same VIZ radiosonde, but apply different data reduction procedures. The implication of these facts is that the historical upper air humidity data records are inhomogeneous in most countries and regions. Errors in the gradients of temperature and humidity are frequently smaller than the errors in temperature and humidity since systematic errors are removed or reduced in calculating the difference R or T. 3. A method has been developed which determines cloud boundaries and cloud amounts from vertical profiles of temperature, relative humidity, and dew-point depression.