# Meteorological instruments -- Temperature

## Measurement of Air Temperature

### The following instruments and devices are used for measuring temperature:

Liquid-in-glass Thermometer

Electrical Resistance Thermometer

Stevenson Screen

Thermometer Shed

### Definition of temperature

Temperature is the condition which determines the direction of the net flow of heat between two bodies.  The body which overall loses heat to the other is said to be at the higher temperature.

A thermometer is an instrument for measuring temperature by utilizing the variation of the physical properties of substances according to their thermal states.

### Meteorological requirements

Temperature measurements are required, for weather analysis and prediction, hydrological and agricultural application, and for climate studies.

For general meteorological work, the observed temperature should be representative of the free air conditions surrounding the station over as large an area as possible,  at a height of between 1.25 and 2 m above ground level.  In order to ensure that a thermometer is at true air temperature, it is necessary to protect it from solar radiation by a screen or shed which also serves to support the thermometer.  This screen also shelters it from precipitation while allowing the free circulation of air around it, and prevents accidental damage.

### Units of measurement

Kelvin (K)
degree Celsius (oC)
degree Fahrenheit (oF)

Equations for the conversion of temperature readings among K, oC and oF are:

c = k - 273.16
c = (f - 32) x 5/9
f  = c x 9/5 + 32
where k is temperature reading in K
c is temperature reading in oC
f is temperature reading in oF