GPS meteorology

GPS meteorology refers to the use of the effect of the atmosphere on the propagation of the Global Positioning System's (GPS) radio signals to derive information on the state of the (lower, neutral) atmosphere. There are currently two main operational techniques in use in GPS meteorology: GPS limb sounding from orbit, and GPS water vapour monitoring.

Water vapour is a very important gas for meteorological and climatological studies, because of the latent heat it carries in transport. Additionally it is a powerful greenhouse gas. The GPS technique is especially valuable because it measures absolute water vapour content or partial pressure rather than relative humidity, which corresponds to water vapour contents that are strongly dependent on the often not precisely known temperature.