Olympic Mountains Experiment

The Cloud Radar System (CRS) is an airborne W-band (94 GHz) polarimetric Doppler radar designed for the NASA ER-2 aircraft. CRS provides radar observations of clouds and precipitation from the surface to the lower stratosphere. It has a horizontal resolution of 150 m and a horizontal sampling interval of 50 m. Its vertical resolution is 100 m with a vertical sampling interval of 37.5 m.

The Airborne Multiangle SpectroPolariMetric Imager (AirMSPI) is a passive remote sensing, airborne pushbroom camera developed by the Jet Propulsion Laboratory (JPL) along with engineers from the University of Arizona and the University of Texas. AirMSPI operates across eight spectral bands (355, 380, 445, 470, 555, 660, 865, 935 nm) to deliver multiangle radiance and linear polarization imagery, which can be used to determine aerosol and cloud microphysical properties. AirMSPI has a spatial resolution ranging from 10 to 25 meters, depending on the scan mode, and typically captures images at a rate of 23 Hz. It was designed to be mounted on the nose of NASA’s ER-2 aircraft and has been used in several aerosol and cloud research missions.

The ER-2 X-Band Doppler Radar (EXRAD) is a dual-beam, X-band radar mounted on NASA’s ER-2 aircraft. It was initially intended to be used on the Global Hawk but was instead developed for the ER-2 to replace the ER-2 Doppler Radar (EDOP). EXRAD measures backscatter to determine radar reflectivity, Doppler velocity, and linear depolarization ratio. These measurements help to analyze the phase, orientation, size, and other properties of precipitation particles. EXRAD operates at 9.6 GHz and has a range resolution between 37.5 and 300 meters. It has a swath width of 28 km at an altitude of 20 km during scanning mode, with a typical sampling frequency of 0.25 seconds.

The Advanced Microwave Precipitation Radiometer (AMPR) is an airborne passive microwave radiometer. AMPR provides calibrated brightness temperatures, which can be used to determine cloud and precipitation characteristics. It operates across four microwave channels: 10.7, 19.35, 37.1, and 85.5 GHz. These frequencies are sensitive to precipitation, making AMPR well-suited for studying rain events. It has a surface footprint size ranging from 640 m (85.5 GHz) to 2.8 km (10.7 GHz).

The High-Altitude Wind and Rain Airborne Profiler (HIWRAP) is an airborne Ka- and Ku-band, dual-beam Doppler radar system. It measures radar reflectivity and 3-D wind fields within clouds and precipitation, making it ideal for research missions into hurricanes and severe storms. It was designed to operate at higher altitudes (~ 20 km) than previous airborne wind profilers, allowing for a better vertical profile of the troposphere. HIWRAP has a range resolution of 150 m and operates at the following frequencies: 13.5 GHz, 13.9 GHz, 33.7 GHz, and 35.6 GHz.

The Cloud Physics Lidar (CPL) is an airborne lidar system designed specifically to provide multi-wavelength measurements of cirrus clouds, sub-visual cirrus clouds, and aerosols. It measures lidar backscatter at three wavelengths: 355 nm, 532 nm, and 1064 nm. These measurements can be used to determine cloud optical depth, particle size distribution, extinction profiles, aerosol layers, and other properties. CPL has a vertical resolution of 30 m and a typical horizontal resolution of 200 m. It has a measurement sampling rate of 1 Hz.

The Enhanced MODIS Airborne Simulator (eMAS) is an airborne cross-track scanning spectrometer operated by the Airborne Sensor Facility (ASF) at NASA Ames Research Center. eMAS captures high-resolution imagery of cloud and surface features, which can be used to develop and test algorithms for MODIS satellite observations. It operates across 38 spectral channels covering wavelengths from 0.445 to 14.1 µm and has a scan rate of 6.25 Hz. eMAS offers a spatial resolution of 50 meters and a swath width of 37.25 kilometers at an altitude of 20 kilometers.

The Cloud Particle Imager (CPI) is an airborne imager developed by SPEC Inc. CPI captures high-resolution (2.3 μm pixel size) images of cloud particles that pass through its sampling volume. It uses a charge-coupled device (CCD) camera operating at 810 nm to record images and can capture up to 74 frames per second with a refresh rate of 40 Hz. The images from CPI can be used to determine microphysical properties such as particle size and shape.

The Nezorov Probe is an in situ airborne hot-wire probe that measures clouds' liquid water content (LWC) and total water content (TWC). It determines LWC and TWC by detecting heat loss from its two sensors caused by evaporation of cloud water and convective heat losses. Operating at a constant temperature of 90 degrees Celsius, it can measure LWC and TWC in the range of 0.005-3 grams per cubic meter. The Nevzorov Probe provides measurements every second with an accuracy of 10%.

The King Probe is an in situ airborne cloud instrument developed by Warren King (Commonwealth Scientific and Industrial Research Organisation) and manufactured by Particle Measuring Systems (PMS) and Droplet Measurement Technologies (DMT). The King Probe measures cloud liquid water content (LWC) by detecting the heat released when water droplets vaporize. It operates at a constant temperature of approximately 100°C and has a data output rate of 1 to 10 Hz. The probe is commonly used in studies of cloud microphysics and aircraft icing.

The Cloud Spectrometer and Impactor (CSI) is an in situ airborne probe that measures total condensed water (TCW) content in clouds. It combines a counterflow virtual impactor (CVI) with a lightweight cloud droplet probe. It can measure cloud particles ranging from 2 to 50 μm in size and has a typical sampling frequency of 1 second.

The Cloud Droplet Probe (CDP) is an in situ cloud probe manufactured by Droplet Measurement Technologies. It measures the particle size distribution and concentration for cloud particles in the 2-50 μm size range. CDP detects pulses of light scattered from a laser (658 nm) to count and size individual cloud droplets. CDP has a typical measurement rate of 1 Hz and can detect concentrations of up to 2000 particles per cubic centimeter.

The High Volume Precipitation Spectrometer (HVPS) is an in situ airborne particle imager manufactured by SPEC Inc. It uses a 128-photodiode array to capture images of precipitation particles. These images can be used to determine the particles' shape, size, and concentration. HVPS-3 has a pixel resolution of 150 μm and a maximum field of view of 1.92 cm.

The 2D-Stereo Particle Probe (2D-S) is an in situ airborne optical imaging device developed by SPEC Inc. It uses two diode laser beams to create stereo images of cloud particles via linear array shadowing. These images allow for the determination of cloud particle size distribution, particle number concentration, and ice or liquid water content. 2D-S has a resolution of 10 µm and can measure hydrometeors ranging from 25 to 1280 µm.

The Rosemount Icing Detector (RICE) is an in-situ airborne probe developed by Rosemount Inc. It uses magnetostrictive oscillation to detect shifts in frequency caused by ice accumulation on the sensing cylinder. These frequency changes correlate with the rate of ice buildup, which helps determine liquid water content. RICE typically samples every second.

The 2D-C/P Hydrometeor Imaging Probe (2D-C/P) is an in situ, airborne instrument that captures images of hydrometeors. It records these images by detecting the illuminated or shadowed states of the photodiode array as the shadow of the hydrometeors passes over. 2D-C/P also offers measurements of particle size distribution, cloud droplet concentration, and hydrometeor shape. Typically, 2D-C/P probes have an image resolution of 25 micrometers and can image hydrometeors with diameters up to 1600 micrometers.

The Doppler on Wheels (DOW) is a network of mobile Doppler radars operated by the Center for Severe Weather Research (CSWR). DOW includes three dual-frequency, dual-polarization radars that operate in the X-band frequency range (9.35-9.55 GHz). They feature a narrow beam (0.8-0.9 degrees), rapid-scan capabilities, and a gate spacing of 15 to 600 meters. DOW radars are mounted on 7500 series International Workstar Trucks and can be easily deployed to various locations to gather radar measurements of meteorological phenomena such as tornadoes, hurricanes, and microbursts. Since its inception in the 1990s, the DOW has participated in numerous research and educational programs. It has been part of the National Science Foundation (NSF) Lower Atmospheric Observing Facilities (LAOF) program since 2008.

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 Next Generation Weather Radar (NEXRAD) is a network of high-resolution, S-band radars operated by the National Weather Service (NWS), the Federal Aviation Administration (FAA), and the United States Air Force. NEXRAD measures the magnitude of the returned energy to provide reflectivity, velocity, and spectrum width observations, which can be processed to create mosaic maps of precipitation. NEXRAD radars typically operate with a 0.9-degree beamwidth, 0.25 to 1 km spatial resolution, and a maximum range of 230 to 460 km. Currently, over 160 NEXRAD radars are operating across the United States and some overseas locations.

Riegl Airborne Laser Scanners are airborne lidar systems manufactured by Riegl Laser Measurement Systems. They are typically used for topographic mapping of glacial, agricultural, urban, and geological areas. They typically operate in the near-infrared wavelength range. They can operate at altitudes up to approximately 14,000 feet, have a field of view of about 60 to 75 degrees, and can reach measurement rates up to about 3 MHz, depending on the lidar system.

Spectrometers are instruments used to separate and analyze the spectral components of a substance. They usually measure the electromagnetic radiation that has been reflected, absorbed, or transmitted by the physical sample. Spectrometers can operate across the ultraviolet to infrared spectrum. The most common types include optical, nuclear magnetic resonance, and mass spectrometers. They can be used on aircraft, research vessels, vehicles, and other ground-based platforms.

The Airborne Snow Observatory (ASO) is an airborne system of remote sensing instruments used to measure snow properties such as snow albedo, snow depth, and snow water equivalent. ASO includes a CASI 1500 imaging spectrometer and a Riegl Q1560 scanning lidar. The CASI spectrometer operates across the 380-1050 nm range and is employed to retrieve spectral albedo. The Riegl Q1560 lidar functions at the 1064 nm wavelength and measures surface elevation to determine snow depths. Snow depth measurements are provided at spatial resolutions of 3m and 50m, while snow water equivalent measurements are available only at a 50m resolution.

Radiosondes are a balloon-borne instrument package used to collect profile measurements of pressure, temperature, humidity, and winds. These sensors are connected to a radio transmitter that sends the measurements to a ground receiver typically operating in the 400-406 MHz range. They typically provide measurements at 1-6 seconds, depending on the type and manufacturer of the radiosonde. Radiosondes are used for weather forecasting, ground truth satellite data, atmospheric research, and input for weather prediction models.

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.

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.

Pluvio is a ground-based weighing precipitation gauge manufactured by OTT HydroMet. It measures precipitation amount and rate by determining its weight using a high-capacity collection bucket. Pluvio can measure rain, snow, sleet, hail, and mixed precipitation types. It has a standard sampling interval of 1 minute and an accuracy of ± 0.05 to 0.1 mm.

The Precipitation and Imaging Probe (PIP) is an airborne optical spectrometer developed by Droplet Measurement Technologies. It measures the size and shape of particles ranging from 100 to 6200 μm. It provides two-dimensional images with a pixel resolution of 100 μm. PIP operates at a wavelength of 660 nm and typically samples every second. It has a sample area of 260 mm by 6.2 mm and can function at airspeeds of 10 to 200 meters per second.

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.

A snow measuring rod is a ground-based instrument used to measure snow depth. It is designed to be pushed into the snow until the underlying surface is reached to determine the snow depth. Snow measuring rods can be manual or automated, with the automated rod able to measure the depth and position simultaneously.

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.

X-band radars are ground-based radars that operate in the 8-12 GHz frequency range. They provide measurements of radar reflectivity, Doppler velocity, and other radar parameters to characterize precipitation and clouds. Due to operating on a smaller wavelength, the X-band radars are more sensitive and can detect smaller particles, making them useful for studying light precipitation and cloud development.

Generic-Atmospheric State (Gen-AtmsState) refers to non-specific instruments on a platform used for measurements of atmospheric state parameters. These are typically in situ sensors that measure temperature, pressure, humidity, and wind speed/direction. Types of atmospheric state instruments include thermometers, hygrometers, barometers, and anemometers.