Sampling Adjustment Factors for Rainfall Recorded at Fixed Time Intervals

Abstract

Precipitation data collected at fixed time intervals will most likely miss true maximum accumulations for durations equal or close to the sampling interval. This becomes a problem when fixed-interval rainfall data are used for frequency analysis. Sampling adjustment factors (SAF) are often used to correct for this mismatch between true and observed maxima. An SAF is the average ratio of the true maximum accumulation to the maximum given by a fixed-interval gauge record. This paper uses high temporal-resolution data from ALERT-type rain gauges in the Kansas City area to derive an empirical relationship for SAF versus the sampling ratio, which is the ratio of the duration of interest to the sampling interval. This relationship is consistent across durations ranging from 1 to 24 h, and is in good agreement with other studies.