Evaluation of Multiple Precipitation Sensor Designs for Precipitation Rate and Depth, Drop Size and Velocity Distribution, and Precipitation Type

Observations of the precipitation rate/depth, drop size distribution, drop velocity distribution, and precipitation type are compared from six in situ precipitation sensor designs over 12 months to assess their performance and provide a benchmark for future design and deployment. The designs considered are tipping bucket (TBR), drop counting (RAL), acoustic (JWD), optical (LPM), single-angle visiometer with capacitor (PWD21), and dual-angle visiometer (PWS100). Precipitation rates are compared for multiple time resolutions over the study period, while drop size and velocity distributions are compared with cases at stable precipitation rates. To examine precipitation type, a new index and a logic algorithm to amalgamate consecutive precipitation type observations consistently is introduced and applied. Overall, the choice of instrument for deployment depends on the usage. For fast response (less than 15 min), the PWD21 and TBR should not be used. As precipitation rate or the duration of a sample increases, the correlation of the TBR with the majority of other instruments increases. However, the PWD21 consistently underestimates precipitation. The RAL, PWS100, and JWD are within ±15% for precipitation depth over 12 months. All instruments are inconsistent in their ability to observe drop size and velocity distributions for differing precipitation rates. There is low agreement between the instruments for precipitation type estimation. The PWD21 and PWS100 rarely report some precipitation types, but the LPM reports more broadly. Meteorological stations should use several instrument designs for redundancy and to more accurately capture precipitation characteristics.