The NASA Global Hydrology Resource Center (GHRC) DAAC published the Autonomous Parsivel Unit (APU) instrument Micro Article. APU is a laser-based optical disdrometer that measures the size and fall velocity of precipitation particles. APU consists of the Parsivel2 laser disdrometer and its data reporting system. It uses single particle extinction to measure the size and velocity of precipitation particles. The APU transmitter creates a 54 cm2 horizontal measurement area using a 650 nm laser beam. When a particle passes through the measurement area, it reduces the intensity of the laser signal reaching the instrument’s receiver. The magnitude of signal reduction is used to determine the size of the precipitation particle while the duration of the reduction is used to determine the particle’s fall velocity. APU uses these measurements to determine, for example, the drop size distribution and amount of precipitation. APU precipitation data are used for a variety of applications including flood warning systems and atmospheric modeling. The micro article provides an overview of the APU instrument and its applications to support GHRC’s current and future APU datasets. The micro article is available here: https://ghrc.nsstc.nasa.gov/home/micro-articles/instrument-autonomous-parsivel-unit-apu
