Precipitation Measurement Methods and Equipment's

What is Rain Gauge ?

The instrument which is used for measurement of rainfall or precipitation is called as Rain Gauge.

Pluviometer, Ombrometer, Hyetometer, Udometer are the different names of rain gauge. 

Types of Rain Gauge: 

1.Non Recording rain gauge

2.Recording rain gauge

Non Recording Rain Gauge:

These rain gauge are most widely adopted in India. They are known as “non recording type” because they do not record the rain but only collect the rain.

In India, mostly used id Symon’s non recording type rain gauge till the year 1969. But in 1969 Indian meteorological department has adopted another model called “Standard Gauge”.

Any cylinder with vertical sidewall can be used to measure the rainfall. Standard vessels must be used so that measurements are comparable and errors are of the same magnitude. This rain gauge do not give the variation of precipitation in time. They give only the total precipitation over a certain time interval.

Recording rain gauge :

This type of rain gauge can give us a permanent automatic rainfall record in the form of rain fallen vs time plot come on graph paper. 

Types of Recording rain gauge:

1.Tipping Bucket Type 

2.Weighing Bucket Type

3.Natural Syphon Type

Tipping Bucket Type:

The tipping bucket rain gauge consists of a funnel that collects and channels the precipitation into a small see-saw 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. Modern tipping rain gauges consist of a plastic collector balanced over a pivot. When it tips, it actuates a switch which is then electronically recorded or transmitted to a remote collection station.

Weighing Bucket Type:

A weighing-type rain 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.

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.

Natural Syphon Type:

In this rain gauge, the rainfall collected by a funnel shaped collector and lead into a float chamber due to this float which is rise. As a float rises, a pen attached to the float through a lever records the elevation of the float on a rotating drum.

A syphon arrangement empties the float chamber as the float has reached a pre-set maximum level and again the reading starts from initial point. 

Graph drawn by natural syphon rain gauge.