Meteorological instruments -- Humidity

Measurement of Humidity

Humidity is generally measured by a psychrometer:
Mercury-in-glass type Psychrometer		Platinum Resistance type Psychrometer
Definition of relative humidity Relative humidity is defined as the ratio, in per cent, of the observed vapour pressure to the saturation vapour pressure with respect to water at the same temperature and pressure. A hygrometer is an instrument for measuring the humidity of the atmosphere. A psychrometer is a type of hygrometer that is most widely used.
Meteorological requirements Humidity measurements are required for weather analysis and prediction, hydrological and agricultural application, and for climate studies. They are particularly important for their relevance to the changes of state of water in the atmosphere. A hygrometer should be placed in a screen or shed to protect it from direct solar radiation, atmospheric contaminants, rain and wind.
Unit of measurement
per cent (%)