APPLICABILITY OF A COMPACT DOPPLER SENSOR FOR VEHICLE PRECIPITATION MEASUREMENTS

Abstract

 A compact low-cost Doppler rainfall sensor towards vehicle precipitation measurements is presented in this study. The applicability of the Doppler sensor for mobile measurements was examined in the vehicle observation conducted in Chiba on 25^th June 2020. Two Doppler rainfall sensors was prepared and mounted on the roof carrier of a car, but one was fixed to face upwards and another did horizontally, to see the sensitivity of sensors installed in the different direction. To compare the signals from the Doppler sensors with rainfall intensity, a reliable laser drop-sizing gauge was also placed on the roof carrier, together with a cup anemometer, a wind vane and GPS to get the traveling speed of the car. The signals seemingly responded to rainfall intensity but were apparently influenced by the relative wind speed measured by the wind anemometer, which can represent the relative motion of raindrops against the sensors on the moving car. Thus, a wind correction was applied to the signals in a simple way that the values were divided by the relative wind speed. As results, the corrected signals showed a clear linear relation to the rainfall intensity measured by the laser drop-sizing gauge, particularly true for the vertically-facing Doppler sensor. These results show that, by applying a linear regression model (R² = 0.84) to the corrected signals from the Doppler rainfall sensor, rainfall intensity can be estimated.