Continuity of precipitation amount observations with automation

Atmospheric Environment Service (AES) uses Automated Weather Observing System (AWOS) to automate principal weather stations. One-year long (1995/1996) data set of simultaneous man and AWOS hourly observations is used to detect the presence of systematic instrumental and siting biases between the two kinds of observations of certain climatological elements, such as temperature, precipitation amount, wind.

This study examines the effect of automation on measurement of precipitation amounts for the purpose of adjusting long-term climatological time series. AWOS uses modified AES Fisher and Porter Weighing Gauge for precipitation totals, while observers read rainfall amounts from the manual AES Standard Type B Rain Gauge and snowfall amounts from the Nipher Snow Gauge, which sometimes are combined with ruler measurements of snow depth. In most cases AWOS is located in open areas close to the runways, which is usually a few hundred meters away from the old manned site.