Effect of disdrometer sampling area and time on the precision of precipitation rate measurement

Abstract. Due to the discretized nature of rain, the measurement of a continuous precipitation rate by disdrometers is subject to statistical sampling errors. Here, Monte Carlo simulations are employed to obtain the precision of rain detection and rate as a function of disdrometer collection area and compared with World Meteorological Organization guidelines for a one-minute sample interval and 95 \% probability. To meet these requirements, simulations suggest that measurements of light rain with rain rates R ≤ 0.50 mm h⁻¹ require a collection area of at least 6 cm × 6 cm, and for R > 1 mm h⁻¹, the minimum collection area is 10 cm × 10 cm. For R = 0.01 mm h⁻¹, a collection area of 2 cm × 2 cm is sufficient to detect a single drop. Simulations are compared with field measurements using a new hotplate device, the Differential Emissivity Imaging Disdrometer. The field results suggest an even larger plate may be required to meet the stated accuracy, although for reasons that remain to be determined.