Iowa Flood Studies

The Two-Dimensional Video Disdrometer (2DVD) is a stationary, ground-based optical disdrometer. It features two line-scan cameras that continuously measure various precipitation properties such as droplet shape, fall velocity, and size distribution. The 2DVD accurately measures all precipitation particles with a diameter greater than 0.2 mm, making it ideal for different precipitation studies.

The Autonomous Parsivel Unit (APU) is an in situ ground-based optical disdrometer. APU measures the size and fall velocity of hydrometeors with a range of 0-25 mm in size and 0-20 m/s in fall speed. Using these measurements, the drop size distribution, type, intensity, and amount of precipitation can be determined. APU operates in the 650-780 nm wavelength range and typically samples every 10 seconds.

Soil moisture probes are in situ ground-based sensors that measure soil water content. The most common type of soil moisture probes used for scientific research use dielectric permittivity techniques, such as capacitance or time-domain reflectometry sensors. These types of probes measure the charge-storage capacity of the soil to determine the soil moisture content. They typically operate at frequencies around 50 MHz and above to reduce sensitivity to salinity. Soil moisture probes provide continuous measurements and are relatively easy to deploy.

Rain gauges are ground-based instruments that measure liquid precipitation amounts directly over a specified period. Different rain gauges, such as tipping buckets and weighing gauges, collect and record data in various ways. Because of their small size and easy setup, rain gauges can be placed in different locations and are often used alongside other precipitation instruments like disdrometers to gather more details, such as precipitation rate and size distribution.

Stream gauges are ground-based sensors that measure the water level or stage of rivers and streams at specific locations. The flow or discharge of a river can then be calculated from these stage measurements. These gauges can provide continuous data, making them useful for monitoring flood risk and water supply. The United States Geological Survey (USGS) operates a network of over 10,000 stream gauges across the United States to assist with flood prediction and water resource management.

The Dual-frequency Dual-polarized Doppler Radar (D3R) is a mobile Ku-/Ka-band radar that was developed for NASA’s Global Precipitation Measurement (GPM) mission Ground The Dual-frequency Dual-polarized Doppler Radar (D3R) is a mobile Ku-/Ka-band radar developed for NASA’s Global Precipitation Measurement (GPM) mission Ground Validation (GV) program. D3R measures radar backscatter to provide reflectivity, Doppler velocity, differential reflectivity, correlation coefficient, and other radar observations. These measurements help derive droplet size distribution and identify hydrometer types. D3R has a beam width of approximately 0.9 degrees, a maximum range of 30 km, and a gate spacing of 150 m. It operates at wavelengths similar to the Dual-frequency Precipitation Radar (DPR) on the GPM Core satellite and can be used to validate DPR observations.

The X-Band Polarimetric Doppler Weather Radar (XPOL) is a ground-based, transportable polarimetric radar manufactured by ProSensing. XPOL measures reflectivity, Doppler velocity, and polarimetric radar parameters to characterize precipitation and clouds. XPOL operates at a 9.41 GHz frequency and has a typical beam width of 1.4 degrees. It has a selectable range resolution of 15-150 meters.

The Micro Rain Radar (MRR) is a ground-based, vertically oriented, continuous wave K-band (24.23 GHz) radar that measures various parameters of precipitation, such as liquid water content and rain rate, from near ground level to the lower troposphere. The backscatter captured by the MRR’s antenna can determine precipitation size distributions ranging from 0.25 mm to 4.53 mm and can also calculate the frequency shift of falling precipitation to determine its velocity. Additional uses of the MRR include identifying bright bands, nowcasting precipitation, and tracking chemical transport during precipitation events. It has a range resolution of 10 to 200 meters and a sampling time of 10 seconds.

The NASA S-band Dual Polarimetric Radar (NPOL) is a portable, ground-based scanning dual-polarimetric Doppler radar. As an active remote sensor, NPOL detects reflected electromagnetic waves to determine radar reflectivity, Doppler velocity, rainfall rate, particle size distribution, water content, and precipitation type. Normally, NPOL has a beamwidth of 0.95°, a gate spacing of 0.15 km, and a maximum range of 150 km. It is operationally comparable to Doppler radars used by the U.S. National Weather Service’s Next Generation Weather Radar (NEXRAD) network, but NPOL has the benefit of being fully deployable.