Temperature and humidity
The weather station uses standard instrumentation, recognised by the UK Met Office. The white, louvered Stevenson Screen houses the mercury thermometers, which measure daily maximum and minimum temperatures, as well as humidity - calculated by the wet and dry-bulb thermometers. It is painted white to reflect the heat of the sun, whilst at the same time allowing free flowing air through its louvers. All temperature and humidity readings are backed up with an electronic sensor, which sends data to the computer via a wireless data logger.
Inside the Stevenson Screen
The picture shows the four thermometers housed inside the screen: one to measure the daily maximum temperature, one for the daily minimum temperature, and the two vertical wet and dry-bulb thermometers used to calculate humidity. The thermograph (right) and hygrograph (left) measure continuous temperatures and humidity.
Rainfall and soil temperatures
Two raingauges are used: a standard 5-inch Snowdon gauge, which is used to measure rainfall every 24hrs. There is also an electronic gauge, which sends data every 5 minutes to the computer via a data logger.
Soil and grass temperatures are also measured, to a depth of 100cm. These readings are particularly useful to growers and farmers who rely on the soil being a certain temperature before seeds and plants will grow. The grass minimum thermometer measures the lowest temperature on the grass surface at night: the temperatures at this level drops faster than the air temperature, especially on clear, calm nights. This will, therefore, measure ground frosts - when the grass temperature falls below 0C.
Wind speed and sunshine
The wind speed is measured by a cup anemometer, situated on the roof of the house. It measures the wind speed every 5 minutes, and will record the highest gust of the day in mph. At the same point, there is an electronic sunshine recorder, measuring the hours of sunshine from dawn till dusk daily.
Anemometer and sunshine recorder
Both situated on the roof for maximum exposure.
Air Pressure
I use a precision barometer to ascertain the air pressure each morning. This gives readings at this station's altitude to the nearest tenth of a millibar. This reading is then converted to a sea-level equivalent.