Rain gauge

A rain gauge (also known as an udometer, pluviometer, or an ombrometer) is an instrument used by meteorologists and hydrologists to gather and measure the amount of liquid precipitation over an area in a predefined period of time.It employs the principle of feedback ... the incoming water pushes the buoy upwards, making the lower 'adjusting conic needle' to let pass the same amount of water that enters into the container, this way ... the needle records on the drum the amount of water flowing through it at every moment—in mm of rainfall per square meter. A rain gauge (also known as an udometer, pluviometer, or an ombrometer) is an instrument used by meteorologists and hydrologists to gather and measure the amount of liquid precipitation over an area in a predefined period of time. The first known rainfall records were kept by the Ancient Greeks, about 500 B.C. People living in India began to record rainfall in 400 B.C. The readings were correlated against expected growth. In the Arthashastra, used for example in Magadha, precise standards were set as to grain production. Each of the state storehouses were equipped with a rain gauge to classify land for taxation purposes. In 1247, the Song Chinese mathematician and inventor Qin Jiushao invented Tianchi basin rain and snow gauges to reference rain, snowfall measurements, as well as other forms of meteorological data. In 1441, the Cheugugi was invented during the reign of Sejong the Great of the Joseon Dynasty of Korea as the first standardized rain gauge. In 1662, Christopher Wren created the first tipping-bucket rain gauge in Britain in collaboration with Robert Hooke. Hooke also designed a manual gauge with a funnel that made measurements throughout 1695. It was Richard Towneley who was the first to make systematic rainfall measurements over a period of 15 years from 1677 to 1694, publishing his records in the Philosophical Transactions of the Royal Society. Towneley called for more measurements elsewhere in the country to compare the rainfall in different regions, although only William Derham appears to have taken up Towneley's challenge. They jointly published the rainfall measurements for Towneley Park and Upminster in Essex for the years 1697 to 1704. The naturalist Gilbert White took measurements to determine the mean rainfall from 1779 to 1786, although it was his brother-in-law, Thomas Barker, who made regular and meticulous measurements for 59 years, recording temperature, wind, barometric pressure, rainfall and clouds. His meteorological records are a valuable resource for knowledge of the 18th century British climate. He was able to demonstrate that the average rainfall varied greatly from year to year with little discernible pattern. The meteorologist George James Symons published the first annual volume of British Rainfall in 1860. This pioneering work contained rainfall records from 168 land stations in England and Wales. He was elected to the council of the British meteorological society in 1863 and made it his life's work to investigate rainfall within the British Isles. He set up a voluntary network of observers, who collected data which were returned to him for analysis. So successful was he in this endeavour that by 1866 he was able to show results that gave a fair representation of the distribution of rainfall, and the number of recorders gradually increased until the last volume of British Rainfall that which he lived to edit, for 1899, contained figures from 3,528 stations — 2,894 in England and Wales, 446 in Scotland, and 188 in Ireland. He also collected old rainfall records going back over a hundred years. In 1870 he produced an account of rainfall in the British Isles starting in 1725. Due to the ever-increasing numbers of observers, standardisation of the gauges became necessary. Symons began experimenting on new gauges in his own garden. He tried different models with variations in size, shape, and height. In 1863 he began collaboration with Colonel Michael Foster Ward from Calne, Wiltshire, who undertook more extensive investigations. By including Ward and various others around Britain, the investigations continued until 1890. The experiments were remarkable for their planning, execution, and drawing of conclusions. The results of these experiments led to the progressive adoption of the well-known standard gauge, still used by the UK Meteorological Office today, namely, one made of '... copper, with a five-inch funnel having its brass rim one foot above the ground ...' Most modern rain gauges generally measure the precipitation in millimetres in height collected on each square meter during a certain period, equivalent to litres per square metre. Previously rain was recorded as inches or points, where one point is equal to 0.254 mm or 0.01 of an inch.