Comparison of rainfall characteristics of a small portable rainfall simulator and a portable wind and rainfall simulator

In this investigation two rainfall simulators have been compared, concerning drop size distribution, drop fall velocity, and spatial rainfall distribution. Additionally, the effect of wind onto rainfall characteristics is measured with the combined wind and rainfall simulator. The results indicate that the used nozzles in both simulators have very small water discharge fluctuations (< 2 %). Regarding drop size distribution a very dose relation of both simulators and natural rainfall (Marshall & Palmer Distribution) can be observed. Owing to low fall heights, measured drop fall velocities are too slow ranging from 3.4 to 5 m s(-1). The spatial rainfall distribution of the small rainfall simulator is very homogenous with a Chistiansen Coefficient (CU) of 91 %. In contrast, the combined wind and rainfall simulator has CU values of 60 %, which clearly improve with simultaneous simulation of wind (CU = 76 %). The collected variables of both simulators show extremely low fluctuations throughout all tests and are therefore reproducible in field investigations at any time.