Storia degli strumenti per la misura della pioggia: dall'orinale di Benedetto Castelli ai radar e ai sistemi satellitari

Rain is one of the most "early" measured meteorological quantities in the world. Information on the measurement of rainfall can be found in India (4th cen-tury BC), Palestine (2nd century BC) and China (13th century). In Korea, in the middle of the 15th century, the first "standardized" rain gauge was carried out, the use of which was probably linked to the cultivation of rice; in the same period a network of rainwater stations was implemented which remained active until 1907. These instruments were unknown to Father B. Castelli, the first in Europe to begin the scientific study of rains with a more engineering interest; in 1639 he designed a simple device (jokingly called in italian orinale, urinal), for measuring rain. In 1663 important changes were introduced by C. Wren who designed rain gauge in which the water collected by a funnel passed into a "tipping bucket". At the end of the 18th century many mechanical instruments were developed to measure both the amount of rain and the duration of the rainy event (Landri-ani's chronohyograph, 1782), and the amount of water precipitated in the unit of time (Landriani's hyometrograph, 1782 and Hermann's hyetometrograph 1789). Over the centuries, many types of rain gauges have been developed with dif-ferent technological "characteristics" (weighing, siphon, tipping bucket etc.). At 19th century's end, rain gauges, like other meteorological measuring instruments and systems, began to be made according to internationally established standards. In the 20th century there were further developments of assembly techniques using microprocessors and new concept sensors. The application of these tech-nologies allowed the design of instruments to refine the measurements of the rainfall event and its characteristics such as: the microprocessor-based pluvio-intensimeter, the impactometer, an instrument for measuring the energy of rain, used in studies of erosive phenomena. In the second half of the 20th century, the measurement of rain entered the group of quantities measurable with remote sensing thanks to the birth of the Radar, LIDAR, and the launch of meteorologi-cal satellites.