The Electronic Rothamsted Archive
The Electronic Rothamsted ArchiveGo to the next chapter.
This document provides information about the meteorological records as preserved in the Electronic Rothamsted Archive.
You are also able to request data. As well as browsing through the information provided here, you may mark the variables you are interested in extracting, and request that data.
Rothamsted has one of the longest continuous sets of weather recordings in the world. The observations are taken daily at 0900GMT. The records are still kept in the hand-written form as they have from the beginning but modern technology is also used. Both the Rothamsted mainframe and personal computers are used to store and distribute the data. This data is primarily for the use of Rothamsted staff in connection with their field experiments and the Meteorological Office at Bracknell who maintain a comprehensive database of weather recordings from the whole country.
Records of day to day weather were originally in the form of diaries kept by the large farms and estates, may of which still exist. Although these do not contain any actual data they are a valuable source of information regarding our weather of years gone by. Rothamsted's daily meteorological instrument records as we know them, began in February 1853.
At an early stage in Sir John Lawes agricultural research work, he realised how important the weather was in the growth of crops, particularly rainfall, and the effect this had on the leaching of nutrients from the soil.
He tried many ways of measuring rainfall before finally settling for a gauge of one thousandth of an acre. The original gauge was built in 1852, constructed mainly of timber with a lead funnel, and positioned slightly north of the present one. The rainwater was collected in carboys and weighed daily to find the amount of rain. This gauge became weak and in 1873 a new one was constructed on the present site. At the same time the technique of weighing was replaced by galvanized iron calibrated cylinders which made the job of rain measurement much easier. The gauge itself has seen little change in its long history other than routine repairs and new collecting tanks as the older ones rusted away. The current tanks are about four years old and are made of modern plastics following on from glass, iron and steel ones previously used. The funnel was completely restored in 1992 to its original hardwood and lead construction.
At various times other smaller raingauges were used, both 5 and 8 inch funnel diameter. In 1948, the present 5 inch diameter gauge was installed which is now the Meteorological Office standard. In our case the gauge is surrounded by a turf wall retained by brick; this reduced wind eddies in our exposed position.
At Rothamsted we have had a recording raingauge since 1921 which has always been of the natural syphon type. Rain is collected in a float chamber and recorded on a daily chart on the clock drum. This has the capability to record 10mm of rain before syphoning begins and the recording will then restart at the bottom of the chart. From this we can derive both rate and time of rainfall. (Go to section Rainfall data to select variables for extraction).
Although Lawes had built the 1/1000th acre raingauge, he still had the problem of where the excess water was going and what nutrients were being lost (leached) by drainage. In 1870 the three percolation gauges (or drain gauges as they are sometimes known) were brought into use. They consist of undisturbed blocks of soil of 20 inches (51cm), 40 inches (102cm) and 60 inches (152cm) in depth and of area equal to the raingauge at 1/1000th of an acre.
The gauges were constructed by digging round and under the block of soil, placing perforated steel plates underneath at the required depth and bricking up the sides. The soil inside the gauges remained undisturbed throughout the construction process. He now had the ability to not only measure the rainfall, but also to find out how much of the rain was draining through the soil and, by analysis, how much nutrient was being lost. The drainage water was also originally measured by weighing the carboys of collected water, but these too were converted to calibrated cylinders. All three gauges remain very much as built and are still in use for their original purpose. The soil has never been deep cultivated, only the top is kept clear by hand weeding, and they have never been cropped. (Go to section Drainage data to select variables for extraction).
Lawes and Sir Henry Gilbert began to look at the whole of plant growth. Many other climatic conditions affect plant growth other than the rain they had measured until now. Temperature and sunshine give the plant energy to use the nutrients released by rain and in 1878 they started to measure the air temperature with thermometers very similar to those we still use today. Readings were taken of current dry and wet bulb temperatures to calculate humidity etc, and maximum and minimum temperature of the day and night. (Go to section Air temperature data to select variables for extraction).
Later, in the 1920s, it became possible to record soil temperature using specially adapted thermometers. These were originally set at depths of 4, 8, 12, 24 and 48 inches under grass cover, and 4, 8 and 12 inches under bare soil. Although we still use the same type of thermometers today we have "gone metric" and record at depths of 10, 20, 30, 50 and 100cm. All temperatures are now in degrees centigrade, the change from Fahrenheit taking place in 1970. (Go to section Soil temperature data to select variables for extraction).
Sunshine readings, or more correctly hours of bright sunshine, were first recorded in 1892 using a Campbell-Stokes sunshine recorder, similar to the instrument in use today. The instrument works by focussing the sun's rays and burning a mark on a card which is then measured. The cards are specially treated to prevent them catching fire and are of varying lengths applicable to the time of year; winter, equinox (used twice a year) and summer. (Go to section Sunshine hours, cloud cover and solar radiation to select this variable for extraction).
Solar radiation has been recorded at Rothamsted since 1921 using various instruments. Presently a Kipp and Zonen pyranometer is used, which is the world meteorological standard; the signal is recorded on an integrator and chart recorder. (Go to section Sunshine hours, cloud cover and solar radiation to select this variable for extraction).
Although wind estimations using the Beaufort scale have always been used at Rothamsted, it was not until 1944 that an anemometer was installed. This gives the run of wind per day, for many years measured in miles per day, but now as kilometers per day at 2m above the ground. We also have the Dines anemograph to continually measure wind speed and direction. This was installed in 1978 and replaced an older pressure tube anemograph dating from 1954. The wind vane is at 42 feet above ground level. (Go to section Wind data to select variables for extraction).
Many other observations are taken including measuring evaporation from an open water tank, amount of cloud, state of the ground surface, visibility, current weather and barometric pressure. A comprehensive diary is also kept using the Beaufort letter shorthand.