Editing Rain gauge (section)

==Types==
[[File: Automatic Rain gauge(Interior).JPG|thumb|A self-recording rain gauge (interior)]]
Types of rain gauges include [[graduated cylinder]]s, weighing gauges, tipping bucket gauges, and simply buried pit collectors. Each type has its advantages and disadvantages while collecting rain data.

===U.S. standard rain gauge===
The standard United States [[National Weather Service]] rain gauge, developed at the start of the 20th century, consists of an {{cvt|8|in}} funnel emptying into a metal graduated cylinder,<ref>{{cite web |year=2009 |title=8 Inch Non-Recording Standard Rain Gauge |url=http://www.crh.noaa.gov/iwx/program_areas/coop/8inch.php |publisher=[[National Weather Service]] Office, Northern Indiana |url-status=live |archive-url=https://web.archive.org/web/20081225234123/http://www.crh.noaa.gov/iwx/program_areas/coop/8inch.php |archive-date=25 December 2008 |access-date=2 January 2009}}</ref> {{Cvt|2.525|in}} in diameter, which fits inside a larger container that is {{cvt|8|in}} in diameter and {{cvt|20|in}} tall. If the rainwater overflows the graduated inner cylinder, then the larger outer container will catch it. When measurements are taken, then the height of the water in the small graduated cylinder is measured, and the excess overflow in the large container is carefully poured into another graduated cylinder and measured to give the total rainfall.<ref name=":02">{{cite web |author=Chris Lehmann |year=2009 |title=10/00 |url=http://nadp.sws.uiuc.edu/CAL/2000_reminders-4thQ.htm |archive-url=https://web.archive.org/web/20100615115408/http://nadp.sws.uiuc.edu/cal/2000_reminders-4thQ.htm |archive-date=15 June 2010 |access-date=2 January 2009 |publisher=Central Analytical Laboratory}}</ref> A cone meter is sometimes used to prevent [[leak]]age that can result in alteration of the data. In locations using the metric system, the cylinder is usually marked in mm and will measure up to {{cvt|250|mm|1}} of rainfall.

Each horizontal line on the cylinder is {{cvt|0.5|mm|2}}. In designs made for areas using Imperial units, each horizontal line represents {{cvt|0.01|in}} inches.

===Pluviometer of intensities===
[[File:Pluviograf Jardi.jpg|thumb|Pluviometer of intensities (1921)]]
The '''pluviometer of intensities''' (or Jardi's pluviometer) is a tool that measures the average intensity of rainfall in a certain interval of time. It was initially designed to record the rainfall regime in Catalonia but eventually spread throughout the world.<ref name="East1967">{{cite book|title=Water Resources Series|url=https://books.google.com/books?id=l24qAAAAMAAJ&q=Royal+observatory+HongKong+jardi|access-date=23 October 2011|year=1967|publisher=United Nations}}</ref>
{{Blockquote | style=font-size:100% | ''It employs the principle of [[feedback]]&nbsp;... 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&nbsp;... the needle records on the drum the amount of water flowing through it at every moment—in mm of rainfall per square meter. ''}}
It consists of a rotating drum that rotates at constant [[speed]], this drum drags a graduated sheet of cardboard, which has the [[time]] at the [[Abscissa and ordinate|abscissa]] while the y-axis indicates the [[height]] of rainfall in [[rain|mm of rain]]. This height is recorded with a pen that moves vertically, driven by a buoy, marking on the paper the [[rain]]fall over time. Each cardboard sheet is usually used for one day.

As the rain falls, the water collected by the funnel falls into the container and raises the buoy that makes the pen arm rise in the vertical axis, marking the cardboard accordingly. If the rainfall does not vary, the water level in the container remains constant, and while the drum rotates, the pen's mark is more or less a horizontal line, proportional to the amount of water that has fallen. When the pen reaches the top edge of the recording paper, it means that the buoy is "up high in the tank" leaving the tip of the conical needle in a way that uncovers the regulating hole, ''i.e.'', the maximum flow that the apparatus is able to record. If the rain suddenly decreases, making the container (as it empties) quickly lower the buoy, that movement corresponds to a steep slope line that can reach the bottom of the recorded cardboard if it stops raining.

The rain gauge of intensities allowed precipitation to be recorded over many years, particularly in Barcelona (95 years), apart from many other places around the world, such as Hong Kong.<ref name = "East1967" /><ref name="KongOffice1974">{{cite book |author=T. Y. Chen |title=Comparison of Jardi and Workman Rate-of-Rainfall Gauges |url=http://www.hko.gov.hk/publica/tnl/tnl018.pdf |access-date=23 October 2011 |year=1974 |publisher=Royal Observatory, Hong Kong |url-status=live |archive-url=https://web.archive.org/web/20150924045406/http://www.hko.gov.hk/publica/tnl/tnl018.pdf |archive-date=24 September 2015 }}</ref>

===Weighing precipitation gauge===
A weighing-type precipitation gauge consists of a storage bin, which is weighed to record the mass.  Certain models measure the mass using a pen on a rotating drum, or by using a [[vibrating wire]] attached to a [[data logger]].<ref name=":0" /> The advantages of this type of gauge over tipping buckets are that it does not underestimate intense rain, and it can measure other forms of precipitation, including rain, hail, and snow. These gauges are, however, more expensive and require more maintenance than tipping bucket gauges.

The weighing-type recording gauge may also contain a device to measure the number of chemicals contained in the location's atmosphere. This is extremely helpful for scientists studying the effects of greenhouse gases released into the atmosphere and their effects on the levels of the [[acid rain]]. Some [[Automated airport weather station|Automated Surface Observing System]] (ASOS) units use an automated weighing gauge called the AWPAG (All Weather Precipitation Accumulation Gauge).

===Tipping bucket rain gauge===
[[File: Exterior tipping bucket.JPG|thumb|The exterior of a tipping bucket rain gauge]]
[[File: Interior tipping bucket.JPG|thumb|The interior of a tipping bucket rain gauge]]

The tipping bucket rain gauge consists of a funnel that collects and channels the precipitation into a small [[seesaw]]-like container. After a pre-set amount of precipitation falls, the lever tips, dumping the collected water and sending an electrical signal. An old-style recording device may consist of a pen mounted on an arm attached to a geared wheel that moves once with each signal sent from the collector. In this design, as the wheel turns the pen arm moves either up or down leaving a trace on the graph and at the same time making a loud "click".

The tipping bucket rain gauge is not as accurate as the standard rain gauge, because the rainfall may stop before the lever has tipped. When the next period of rain begins it may take no more than one or two drops to tip the lever. This would then indicate that a pre-set amount has fallen when only a fraction of that amount has actually fallen. Tipping buckets also tend to underestimate the amount of rainfall, particularly in snowfall and heavy rainfall events.<ref>Groisman, P.Y. (1994): "[http://ams.allenpress.com/perlserv/?request=get-abstract&doi=10.1175%2F1520-0477(1994)075%3C0215:TAOUSP%3E2.0.CO%3B2 The Accuracy of United States Precipitation Data]" [[Bulletin of the American Meteorological Society]] '''75'''(2): 215–227.</ref><ref>{{cite web|url=http://www.usbr.gov/pn/agrimet/precip.html|title=AgriMet Pacific Northwest Region - Bureau of Reclamation|first=Bureau of|last=Reclamation|website=www.usbr.gov|url-status=live|archive-url=https://web.archive.org/web/20081025193858/http://www.usbr.gov/pn/agreement/precip.html|archive-date=2008-10-25}}</ref> The advantage of the tipping bucket rain gauge is that the character of the rain (light, medium, or heavy) may be easily obtained. Rainfall character is decided by the total amount of rain that has fallen in a set period (usually 1 hour) by counting the number of pulses during that period. Algorithms may be applied to the data as a method of correcting the data for high-intensity rainfall.

[[File: Tipping Bucket Recorder.JPG|thumb|left|Tipping bucket rain gauge recorder]]
[[File: Close up chart.JPG|thumb|left|Closeup of a tipping bucket rain gauge recorder chart]]

Modern tipping rain gauges consist of a plastic collector balanced over a pivot. When it tips, it actuates a switch (such as a [[reed switch]]) which is then electronically recorded or transmitted to a remote collection station.

Tipping gauges can also incorporate elements of weighing gauges whereby a [[strain gauge]] is fixed to the collection bucket so that the exact rainfall can be read at any moment. Each time the collector tips, the strain gauge (weight sensor) is re-zeroed to null out any drift.

To measure the ''water equivalent'' of frozen precipitation, a tipping bucket may be heated to melt any ice and snow that is caught in its funnel. Without a heating mechanism, the funnel often becomes clogged during a frozen precipitation event, and thus no precipitation can be measured. Many [[Automated airport weather station#Automated Surface Observing System (ASOS)|Automated Surface Observing System (ASOS)]] units use heated tipping buckets to measure precipitation.<ref>"[http://www.nws.noaa.gov/asos/tipbuck.htm The Tipping Bucket Rain Gauge] {{webarchive|url=https://web.archive.org/web/20110629133314/http://www.nws.noaa.gov/asos/tipbuck.htm |date=2011-06-29 }}." [[National Weather Service]].</ref>

===Optical rain gauge===
This type of gauge has a row of collection funnels. In an enclosed space below each is a [[laser diode]] and a [[Photodiode|photo transistor detector]]. When enough water is collected to make a single drop, it drops from the bottom, falling into the laser beam path. The sensor is set at right angles to the laser so that enough light is scattered to be detected as a sudden flash of lights. The flashes from these photodetectors are then read and transmitted or recorded. Different type of optical range gauges have been used throughout the decades. The technology has also improved.

===Acoustic rain gauge===
Acoustic [[disdrometer]]s, also referred to as hydrophones, are able to sense the sound signatures for each drop size as rain strikes a water surface within the gauge. Since each sound signature is unique, it is possible to invert the underwater sound field to estimate the [[Raindrop size distribution|drop-size distribution]] within the rain. Selected moments of the drop-size distribution yield rainfall rate, rainfall accumulation, and other rainfall properties.<ref>{{cite web|url=http://glossary.ametsoc.org/wiki/Acoustic_rain_gauge|title=Acoustic rain gauge - AMS Glossary|website=glossary.ametsoc.org|url-status=live|archive-url=https://web.archive.org/web/20140416181049/http://glossary.ametsoc.org/wiki/Acoustic_rain_gauge|archive-date=2014-04-16}}</ref>