On the Determination of Moisture Gradients from Radiosonde Records 1, 2

Abstract

The humidity indicated by the rapidly rising radiosonde lags behind the true humidity of the air, making moisture gradient determinations uncertain by a factor of 4. Application of isothermal laboratory determinations of the lag to the readings may be misleading because the radiosonde, in rising through the atmosphere, usually passes from warm air to cooler air. The lag of the strip may be quite different under these circumstances. By comparison of radiosonde reports with airplane humidity soundings, it is found that in the case of the radiosonde moving from warm, dry air (about − 5°C) to cooler, moister air (about − 18°C) the lag may increase to 165 seconds. When it passes to cooler, drier air, the lag decreases to 10 to 20 seconds. Using these lags and assuming an exponential approach to the final value, more nearly correct values of the humidity at particular heights can be computed from the radiosonde records.