APU

Disdrometers provide a measure of the precipitation size distribution at the surface. These observations offer an important constraint on the retrieval of precipitation properties from remote sensors and help to gain insights into variability in precipitation observations. The network will be established to resolve/measure variations in rain rate type, intensity, and size distributions (e.g., D0) on scales 1–5 km (order of the GPM footprint) within an area of ~25 km2.

Sixteen or more  parsivels will be configured to operate autonomously if required.  The  Parsivel network will provide measures of rain drop size distribution (DSD), particle phase, and fall-velocity.  Particle sizes detected will range from 0.3 mm to 20 cm, with a geometrically increasing bin size from 0.125 mm at 0.3 mm to 1 mm at 6 mm drop diameters.  The Autonomous Parsivel  Unit (APU) is an optical disdrometer based on single particle extinction that measures particle size and fall velocity. This APU consists of the Parsivel, which was developed by OTT in Germany, and its support systems, which were designed and built by the University of Alabama in Huntsville.