Dry-bulb temperature: The external air temperature measured in a standard meteorological screen.
Wet-bulb temperature: The temperature measured by a wet-bulb thermometer in a standard meteorological screen.
External dew-point temperature: The dew-point temperature of the external air (the temperature at which the air would become saturated if cooled)
Wind direction: The direction from which the wind is blowing, measured clockwise from true north.
Wind Speed: The wind speed measured at a height of 10m above the ground.
Direct radiation: The intensity (irradiance) of the solar beam emanating from the sun's disc and the region of sky immediately around it, measured perpendicular to the beam.
Diffuse radiation: The intensity (irradiance) of solar radiation emanating from the sky, excluding that portion immediately around the sun, measured on the horizontal plane.
Global radiation: The intensity (irradiance) of solar radiation falling on the horizontal plane.
Solar altitude: The angular elevation of the centre of the sun's disc above the horizontal plane.
Solar azimuth: The horizontal angle between the vertical plane containing the centre of the sun's disc and the vertical plane running in a true north-south direction, measured clockwise from true north.
Cloud cover: The proportion of the sky covered by cloud.
Atmospheric pressure: The pressure exerted by the atmosphere.
External relative humidity: The relative humidity of the external air (water vapour pressure expressed as a percentage of saturated vapour pressure)
External moisture content: The moisture content of the external air (mass of water vapour expressed as a fraction of mass of dry air)
