G M B Dobson’s research while affiliated with University of Oxford and other places

To meet an urgent demand for a hygrometer capable of use at all heights in the atmosphere, the dew-point hygrometer, which is shown to have many advantages, has been developed primarily for use in aircraft to measure dew-points, or rather frost-points, down to -90° c. It is necessary that the instrument should operate at the lowest possible frost-points as it has been discovered that the air in the stratosphere is very dry Laboratory studies of the deposition of water and ice from the vapour at low temperature are described. Below -90° c. it is not possible to operate a frost-point hygrometer because the deposit is in the form of an invisible glassy layer, but the instrument gives correct results at temperatures close to this limit. Details are given of the construction of different forms of hand-operated hygrometers, and work is now going on to develop a fully automatic frost-point hygrometer.