Sources of Error in Methods of Measuring Precipitation

Sources of Errors in Non-Recording Gauge

• Some water is used to wet the surface of instrument.
• The rain recorded may be less than the actual rainfall due to the direction of the rainfall as affected by wind.
• Dents in the collector and tube may also cause error.
• Some water is absorbed by the measuring stick.
• Losses due to evaporation can also take place.
• The volume of stick replaces some water which causes some error.

Sources of Error in Tipping Bucket Type Rain Gauge

• Dents in the collector.
• Moistening of inside-surface of the funnel and the tube.
• Rain drops splashing from the collector.
• For very intense rain some water is still pouring into the already filled bucket.
• Inclination of the gauge may result in catching less or more rain than the actual amount.
• Error in measurement due to wind.
• Remedial measures for Error in Precipitation measurement
• Removal of error due to dents obviously needs repair of the instrument. For rain recorded with dents a correction should be applied.
• Errors such as moistening of the inside surfaces of the gauge, splashing of rainwater from the collector and pouring of water into the already filled bucket during an intense rain can only be corrected by some correction factor.
• Inclined instrument needs to be reinstalled. The correction factor however can be calculated from the angle of inclination.
• For wind protection certain wind shields are designed and used which are called Splash Guards. Proper setting of gauge above ground level is necessary.