Rain Gauges Versus Radar

Both rain gauges and radar-based tools have proven to be effective for measuring rainfall. Like all measurement systems, each type has its strengths and limitations. In a comprehensive study by Pollack, Dutton, Quinn, O’Connell, Mateo, et al (Newcastle University, UK, University of Genoa,  Italy) of radar-based versus rain gauge-based systems, there was less than an 8% variance between the two methods.

The primary use of rain data with level or flow data seeks to establish a recognizable relational pattern. Through ongoing collection of data and measurements over longer time frames, the 8% differential between radar and rain gauges is less significant. Either method will demonstrate good repeat-ability and will therefore support the relational study of rainfall versus level or flow.

Presented herein are factors, both pro and con, for radar and rain gauges. It is important to realize that radar provides a volumetric measure of rainfall for an area while a rain gauge provides data from a very specific point.

Radar Pros

  • Rapid deployment (one hour)
  • Good aggregate (volumetric) measure of rainfall
  • No set-up costs or field installation
  • No ongoing maintenance
  • Not effected by weather (freezing)
  • No costs or issues from vandalism or damage
  • Low ongoing costs
  • Can provide current and historical data
  • Can be utilized for the exact period of time required

Radar Cons

  • Ongoing cost for service
  • Not as “local” as a rain gauge
  • Terrain caused errors in some locations
  • Can be affected by weather shadowing

Rain Gauge Pros

  • Simple low-cost instrument
  • Provides localized data better suited to catchment areas
  • Accepted as the “ground truth”
  • Many users own them already and they might be deployed

Rain Gauge Cons

  • Prone to error from splashing and for wind turbulence
  • Thunderstorm with high wind turbulence error is up to 40%
  • Labor intensive for installation
  • Labor intensive for maintenance
  • Freezing in winter months
  • Time needed for install and deployment