Definitions of Daily Statistics – Columns reading from left to right.
Readings are taken daily at 0800
Temperature (Max. & Min) – This is the highest and lowest temperature between 0800 on each successive day.
Wind – The wind varies continuously but the direction given is the dominant direction for the 24-hour period
Rainfall – The precipitation is measured to an accuracy of 0.1mm using a standard 5” copper gauge. The automatic gauge has a minimum of 0.2mm and loses accuracy in heavy rainfall. More details are given in the Guide to Setting up a Station section.
E.T. – this abbreviation stands for Evapotranspiration. This figure is the amount of equivalent water vapour returned to the atmosphere from wet surfaces and that through transpiration, the exhaling of moisture from plant life.
U.V. – this is the maximum daily index of ultra violet radiation using the U.S. National Service Weather
Table of 0 – 2 Minimal, 3 – 4 Low, 5 – 6 Moderate, 7 – 9 High and 10+ Very High.
Solar Radiation – this is technically known as Global Solar Radiation, a measure of the intensity of the
sun’s radiation reaching a horizontal surface.
Sunshine (Global) – this is a measure of sunshine as calculated from the weather station’s solar sensor and receives radiation direct from the sun and also reflected amounts from cloud and sky, the “all sky solar radiation incident on a horizontal surface”. Small amounts are received even when cloud is present and the sun is hidden. This value provides the best relationship between solar pv panel output on a daily basis than direct sunshine. This sensor has a threshold of 100W/m2.
Sunshine (Direct) – a dedicated sunshine instrument or Sun Duration Sensor is used for this data. Direct solar radiation is measured from a small area around the solar disc and perpendicular to the incoming beam using a pyrheliometer. The threshold is 120W/m2 as defined by the World Meteorological Office definition of sunshine.
Humidity – This is the amount of water vapour in the ambient air at 0800.
Temperature – This figure is the spot temperature at 0800.
Barometer – this is a reading of atmospheric pressure at 0800, which is adjusted to the equivalent sea-level pressure. Atmospheric pressure changes with the altitude of the barometer so this provides a standardised figure.
Temperature (Soil) – this specialised thermometer provides a reading of soil temperature at a depth of 5cm, again taken at 0800.