A rain gauge is an essential instrument used by meteorologists and hydrologists to measure the amount of liquid precipitation over a specific area during a defined period. Let’s explore different types of rain gauges and their functionalities:

1. Non-Recording Type Rain Gauge (Symons Rain Gauge):

   • This is the most common type used by meteorological departments.
   • It consists of a cylindrical vessel with a diameter of 127 mm (5 inches) and an enlarged base (210 mm diameter).
   • The funnel at the top has a circular brass rim that fits precisely into the vessel.
   • A receiving bottle, thinner than the cylinder, collects rainfall from the funnel.
   • During heavy rainfall, the amount often exceeds the bottle’s capacity, so readings should be taken 3 to 4 times a day.
   • The water in the receiving bottle is measured using a graduated glass with an accuracy of up to 0.1 mm.
   • Rainfall is measured daily at 8:30 AM IST and recorded as the day’s total.
   • Proper care and maintenance are crucial to keep the gauge accurate, especially during dry weather.

2. Recording Type Rain Gauges:

   • These gauges automatically record rainfall data over time.
   • There are three main types:
     • Weighing Bucket Type Rain Gauge:
       • Self-recording rain gauge.
       • A receiver bucket is supported by a spring or lever balance.
       • The bucket’s movement due to increasing weight is transmitted to a pen, which traces a record on a clock-driven chart.
       • The resulting curve is called the mass curve.
     • Tipping Bucket Type Rain Gauge:
       • Circular rain gauge with a 30 cm diameter.
       • Sharp-edged receiver with a funnel.
       • Two buckets pivot under the funnel.
       • When one bucket receives 0.25 mm of precipitation, it tips, discharging its rainfall into a container, while the other bucket moves under the funnel.
       • An electric circuit completes, marking the movement on a clock-driven receiving drum.
     • Floating or Natural Syphon Type Rain Gauge:
       • Less common but used in specific applications.
       • Utilizes a floating syphon mechanism to measure rainfall.