SCAMP: A SYSTEM FOR CHARACTERIZING AND MEASURING PRECIPITATION

SCAMP was conceived in 2014 in response to a request for proposals by the UI Office of the Vice Chancellor for Research. It is designed to quantitatively characterize the vertical profile of precipitation particles falling from clouds and storms, including the particle size distributions and surface precipitation, and document the scavenging of air particulates by the falling precipitation. Thus, this suite of instruments records the evolution of precipitation below the altitudes of typical operational scanning weather radars, and is complementary to those as well as any other instrumentation (e.g. aircraft) sampling the precipitation overhead. The instrumentation is designed to document light rainfall and light/heavy snowfall.

The cornerstone of the system is a Metek Micro Rain Radar (MRR), a vertically pointing K-band (24 GHz/1.24 cm wavelength) Doppler radar. It has 30 adjustable range gates yielding a maximum range of 300 to 3000 m, and records equivalent radar reflectivity factor, vertical velocity (Nyquist +/- 6 m s-1), and spectral width.

The OTT Parsivel2 Optical Disdrometer is a laser-based (780 nm wavelength) disdrometer working on the “extinction principle” where particles falling through the laser “sheet” (180 nm x 30 mm x 1mm) cause attenuation of the signal (size), and duration in the beam provides fall speed. It records both size (one dimension– 0.2 to 25 mm with 32 classes) and particle fall speeds (0.2 – 20 m/s), and has options for estimating precipitation type, amount, intensity, visibility, and equivalent radar reflectivity.

The Droplet Measurement Technology MPS Particle Spectrometer provides 2D images of particles passing through the laser emitted across the arms of the probe, and thus records particle shapes, sizes and fall velocities. These data will be particularly helpful for snowfall, when crystal/aggregate dimensions are needed, but also provides additional size information for rainfall sensed by the Parsivel2.

The Geonor T-200B Precipitation Gauge is a weighing–bucket (vibrating wire) precipitation gauge with 600 mm capacity that provides accumulated precipitation (rain or snow) at 1 minute intervals.  It is surrounded by a Geonor-designed wind screen to improve reliability of the measurements in windy conditions.

A TSI Optical Particle Sizer 3330 measures number concentrations of aerosol particles of size 0.3 to 10 mm that are pulled into its inlet, and can be used in tandem with the precipitation instrumentation to study aerosol scavenging by precipitation.

For documenting weather conditions during data collection, a Lufft Ultrasonic Weather Station in included within SCAMP. Measurements 8 meters above ground of temperature, humidity, pressure, wind direction, and wind speed are collected at 1 minute intervals.

All instruments are mounted on a grounded flatbed trailer, and transported by a van outfitted with computers for real-time data scrutiny and analysis. A portable generator supplies power to the instruments, data loggers, and computers.

SCAMP is a unique facility that faculty can request for use in government-sponsored large field campaigns, as well as for local data collection efforts. SCAMP is also providing DAS students the exciting opportunity to collect and analyze data with state-of-the-art equipment in both undergraduate and graduate courses.