Background information on the rain gauge

Measuring the Rain

In this activity, students will construct a simple rain gauge. In this activity, students will build on their understandings about how scientists use tools to measure and collect data about the environment. This activity is part of a set of five activities designed to support students collecting data about the weather.

The other activities are:. Nature of science In this activity, students will build on their understandings about how scientists use tools to measure and collect data about the environment.


On other occasions, and mainly due to security concerns, gauges are placed on rooftops. This is the case for those networks focused on flood forecasting and monitoring, for which the measure of accuracy is not so relevant as for other meteorological purposes. Yagmur Derin, Emmanouil N. The study areas involve nine mountainous ground validation sites exhibiting dense gauge networks Fig.

Figure 7.

Geographic locations of the study regions. Every region has a different rain gauge network density and time period of data record. The conditional mean annual precipitation versus elevation of each rain gauge is provided in Fig. The extreme precipitation in this study is defined according to the 90th percentile threshold of the rainfall magnitude. To ensure consistency across different domains, ground validation datasets are limited to daily time resolution and in situ data records span a minimum of 6 years during —15 Table 7. Table 7. General information of the rain gauge datasets representing the ground validation of the different study regions.

Over the Taiwan study area most of the precipitation occurs during the eastern Asia rainy season in April and from typhoons from May to September, while the remaining months represent the dry period exhibiting low precipitation. The Swiss Alps receive the larger rain amount on the western foothills of the Alps due to westerly winds. Shadow effects result in drier inner alpine valleys, while southern circulation from the Mediterranean generates intense precipitation on the southern side of the Alps in autumn.

The Italian Alps region is characterized by steep topographic gradients. It should be noted that the Italian Alps and Swiss Alps are combined to one region and named as the Alps. By using rain gauges over the —15 period, kriging-based area interpolation maps of the region were created Delrieu et al. The region is mainly characterized by a Mediterranean climate.

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Extension of the mountains effects of the Black Sea determines the region climate types. For this reason, the inland zones observe a more continental climate Yucel and Onen, The Himalayan study area is located in the subtropical zone and is influenced by the monsoon system Salerno et al. Orographic effects on precipitation have been studied over this region Sing and Kumar, ; Ichiyanagi et al. This dataset is created by combining all information sources available at CPC and taking advantage of the optimal interpolation objective analysis technique at 0.

Hence, grid cells were extracted for analysis over the US Rocky Mountains reporting data for the period of — The region is characterized by a highland alpine climate.

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The orographic effect on precipitation can be seen from Fig. Precipitation patterns are controlled by the interaction of synoptic-scale atmospheric currents and the complex Andean topography Manz et al. Precipitation in this area is represented by a complex interaction of low-level jet stream with local topography and the Inter Tropical Convergence Zone ITCZ.

Rain Gauge Facts

Central Colombia experiences a bimodal annual cycle of precipitation with high rain seasons in April—May and September—November months resulting from the double passage of the ITCZ over the region Villa et al. For detailed information related to these regions, readers are recommended to Derin et al. Malcolm J. Don D. Precipitation is measured with a rain gauge, the majority of which are little more than standard cylindrical vessels so designed that rainfall is stored within them and does not evaporate before it can be measured WMO, In an effort to ensure that consistent measurements of the precipitation reaching the ground are obtained, observers are recommended to use standard instruments, which are set up in a uniform manner in representative locations.

Many national meteorological institutions provide pamphlets designed to ensure good standard observation practice and the World Meteorological Organization WMO plays an effective coordinating role. Precipitation that falls on the rain gauge orifice drains through a funnel into a removable container from which the rain may be poured into a graduated glass measuring cylinder. Monthly storage gauges are designed to measure the rainfall in remoter areas and are invaluable on the higher parts of reservoir catchments.

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Ideally, rainfall should be measured at ground level but this gives rise to problems due to rain splashing into the gauge. The higher the rim is placed, the more some rain will be blown away from the gauge orifice and goes unrecorded. If the inner container of a rain gauge overflows as the result of exceptional rainfall, or possibly because of irregular emptying, it is important that the surplus water held in the outer casing should also be recorded.

Corrections may need to be made to the measurements taken at any gauges visited later than the standard time during spells of wet weather. Problems occur in snow prone areas. Small quantities of sleet or snow which fall into a rain gauge will usually melt to yield their water equivalent, but if the snow remains in the collecting funnel it must be melted to combine with any liquid in the gauge. If there is deep fresh snow lying on the ground at the time of measurement, possibly burying the gauge, a core of the snow should be taken on level ground and melted to find the equivalent rainfall.

Countries with snow cover throughout the winter months require regular snow course surveys Hudleston, to measure precipitation.

Continuously recording rain gauges are invaluable for flood studies. A more recent development is the tilting bucket gauge linked to a logger, which runs for at least 1 month. A daily or monthly storage gauge is often installed on the same site as a recording gauge to serve as a check gauge and to avoid the possibility of loss of data due to instrument failure. Plate 2 d shows an automatic rain gauge with telemetry for remote monitoring. Particular care must be taken when siting a new rain gauge from which the resulting records are to be published.

Water Corporation of WA - Make a rain gauge

The gauge should be placed on level ground, ideally in a sheltered location with no ground falling away steeply on the windward side. Obstructions such as trees and buildings, which affect local wind flow, should be a distance away from the gauge of at least twice their height above it. In particularly exposed locations, such as moorlands, it used to be standard British practice to install a turf wall Hudleston, around the gauge but it has proved difficult to sustain the level of turf maintenance that is needed.

Rain gauges provide a spot sample of the rain falling over a catchment area. The number of gauges required to give a reliable estimate of catchment rainfall increases where rainfall gradients are marked. In hilly country, where orographic effects may lead to large and consistent rainfall variations in short distances, it may be necessary to adopt the high densities suggested in Table 3.

Thereafter high densities are only required where control accuracy necessitates it. Table 3. Rain gauges required in a hill area IWE, In large areas of the tropics, there is great variation in rainfall from place to place on any one day but only a relatively small variation in annual totals. In such areas the rain gauge densities of Table 3. There are several methods for computing catchment precipitation from rain gauge measurements. The more frequently used techniques include simple numerical procedures averaging or interpolation , interpolation from isohyetal maps or Thiessen polygons and trend surfaces.

The simplest objective method of calculating the average monthly or annual catchment rainfall is to sum the corresponding measurements at all gauges within or close to the catchment boundaries and to divide the total by the number of gauges. The arithmetic mean provides a reliable estimate provided the whole catchment is of similar topography and the rain gauge stations are fairly evenly distributed. If accurate values of area rainfall are obtained first from a large number of rainfall stations, by one or other of the more time-consuming methods described below, the mean of the corresponding measurements from a smaller number of stations may provide equally acceptable results.


The isohyetal method is generally considered to be the most accurate method of computing catchment rainfall although a good understanding of the rainfall of a region is needed to ensure its reliability. The monthly or annual rainfall total recorded by each gauge within or close to the catchment boundaries is plotted on a contour base map. Isohyetal lines lines joining points of equal rainfall are then drawn on the map taking into account the likely effects of topography on the rainfall distribution.

Rain Gauge

The total precipitation over the catchment for the period considered is obtained by measuring the areas between isohyets by GIS techniques or by planimeter. The mean catchment rainfall is calculated by summing the products of the areas between each pair of isohyets and the corresponding mean rainfall between them, and then dividing by the total catchment area.

The invention of the rain gauge in Korea came two hundred years before inventor Christopher Wren created a rain gauge tipping bucket rain gauge circa in Europe. Born in Fort Scott, Kansas, in , Hatfield claimed to have been "a student of meteorology" for 7 years, during which time he discovered that by sending a secret combination of chemicals into the air clouds could be produced in large enough quantities that rain was sure to follow.

Wallace E Howell as the city's official "rainmaker". Share Flipboard Email. Mary Bellis, known by some as CalmX, was an experimental artist, film director and producer, video game content creator, and freelance writer for some 18 years. She specialized in writing about inventors and inventions, in particular. Bellis died in March

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