GPM Cold Season Precipitation Experiment

The Conical Scanning Millimeter-wave Imaging Radiometer (CoSMIR) is an airborne imaging radiometer designed to validate the Special Sensor Microwave Imager/Sounder (SSMIS) instrument. CoSMIR operates across nine spectral channels in the 50-183 GHz range to measure microwave brightness temperature. It has a surface footprint resolution of 1.4 km by 1.4 km at an altitude of 20 km at nadir. CoSMIR can perform both conical and cross-tracking scanning.

The Airborne Second Generation Precipitation Radar (APR-2) is a dual-frequency, cross-track scanning airborne radar used for measuring precipitation. It detects radar backscatter from rain to determine reflectivity, Doppler velocity, and linear depolarization ratio (LDR). APR-2 operates at 13.4 GHz and 35.6 GHz and has a pulse repetition frequency (PRF) of 5000 Hz. At a flight altitude of 11,000 feet, it has a horizontal resolution of 730 meters at 13.4 GHz and 920 meters at 35.6 GHz. APR-2 has a vertical resolution of 60 meters and a ground swath width of 10 km.

The Precision Radiation Thermometer (PRT-5) is an in situ infrared temperature sensor. It makes non-contact infrared (8-14 μm) temperature measurements between -50 to 150 degrees Celsius with an accuracy of 0.5 degrees Celsius. It has a typical field of view of 2 degrees and a response time of either 0.3 Hz, 3 Hz, or 30 Hz. PRT-5 can be deployed on aircraft, vehicles, research vessels, and other ground-based platforms. It can be used for sea surface, ocean water, cloud, and air temperature measurements.

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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.

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.

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 National Research Council of Canada (NRC) Airborne W- and X-band Radar (NAWX) is an airborne polarimetric Doppler radar developed by NRC and ProSensing Inc. It provides measurements of clouds and precipitation. NAWX operates at 9.41 GHz and 94.05 GHz. NAWX has a resolution of 150 m for the X-band radar and 60 m for the W-band radar.

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 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 Cloud Combination Probe (CCP) is an in situ cloud probe manufactured by Droplet Measurement Technologies. It consists of a Cloud Droplet Probe (CDP), Cloud Imaging Probe (CIP), and Liquid Water Content (LWC) Probe. Both the CIP and CDP measure particle size distribution for the 12.5 μm- 1.55 mm and 2-50 μm size range, respectively. They both operate at the 658 nm wavelength and have a sampling frequency ranging from 0.05 to 25 Hz. CIP also provides 2D imagery to determine the size and shape of the particles. LWC Probe uses a hotwire sensor to measure LWC in the 0 to 3 grams per cubic meter.

The Forward Scattering Spectrometer Probe (FSSP) is an in situ airborne optical particle counter initially developed by Particle Measuring Systems, Inc. It determines particle size distribution by measuring the light intensity scattered by individual particles within the cloud. FSSP can detect particles ranging from 0.5 to 47 μm in diameter. It functions at a wavelength of 633 nm and typically samples at a rate of 1 Hz.

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 Cloud Particle Spectrometer with Polarized Detection (CPSPD) is an in situ airborne spectrometer manufactured by Droplet Measurement Technologies. It measures forward and backward scattered light of cloud and aerosol particles at 658 nm. These measurements can be used to derive particle properties such as particle size distribution, number concentration, effective diameter, and liquid water content. CPSPD measures particles in the 0.65 to 30 μm size range and measures 20,000 particles per second. It has a selectable sampling frequency of 0.04 to 20 seconds.

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 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.

The Raman Lidar (RL) is a ground-based lidar system operated by the Department of Energy’s (DoE) Atmospheric Radiation Measurement (ARM) User Facility. It detects Raman backscatter in the ultraviolet range (355 nm) to provide profiles of water vapor, temperature, and aerosol and cloud optical properties. It also detects Raman backscatter from water vapor at 408 nm and molecular nitrogen at 387 nm to help derive aerosol optical properties and water vapor mixing ratios. It has a range resolution of 7.5 m, a time resolution of 10 seconds, and a pulse repetition frequency of 30 Hz. RL can deliver profile measurements from approximately 200 m up to 10 km above ground level.

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The Ultra-High Frequency (UHF) Wind Profiler is a ground-based Doppler radar. It measures electromagnetic signals to detect wind speed and direction. UHF Wind Profilers operate at the 300-1000 MHz frequency range. Due to operating at a high frequency, they allow for high-resolution wind measurements within the boundary layer.

This data will be added in future versions.

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.

Generic-Radiometers refer to non-specific radiometers on a platform. These are typically passive microwave radiometers that measure brightness temperature. Radiometers can be used to retrieve temperature and water vapor profiles, soil moisture content, ocean salinity, precipitation and cloud properties, and vegetation.

Digital cameras are used to provide imagery for research applications. Cameras are used on aircraft to collect aerial imagery for mapping and surveying, environmental monitoring, cloud observations, agriculture, geological studies, and other Earth science applications. They are also used at field sites to capture visual observations to monitor changes in land cover, vegetation, clouds, air quality, glaciers, and other phenomena.

The Snowflake Video Imager (SVI) is a ground-based imaging system developed at Wallops Flight Facility (WFF). It records greyscale imagery of snowflakes to determine snowflake size and orientation distribution. It can operate autonomously in harsh winter conditions with winds up to 50 knots and temperatures as low as -40 degrees Celsius. SVI has a high frame rate of 60 Hz and a nominal pixel size of 0.05 mm by 0.1 mm.

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The Vertically Pointing X-band Radar (VertiX) is a ground-based radar operated by the McGill University Radar Observatory. It is an X-band (9.41 GHz) Doppler radar that measures the reflectivity and Doppler velocity of targets directly above to provide time-height radar imagery. It can detect all precipitation target types as well as some ice clouds. VertiX has a range resolution of 45 meters and typically provides data every 1.5 seconds.

W-band radars are highly sensitive radars used for atmospheric research. They operate around the 94-95 GHz frequency band, allowing for the detection of small water droplets. W-band radars are used for cloud and precipitation studies since they can provide more detailed observations than typical weather radars. They can be deployed on research vessels, aircraft, and mobile ground-based platforms.

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.

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.

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.

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.

The Dual Polarization Radiometer (DPR) is a ground-based radiometer manufactured by Radiometer Physics. It measures brightness temperature at 90 GHz and 150 GHz. These measurements can be used for rain observations, soil moisture measurements, total liquid water content, and cloud microphysics. DPR has a temporal resolution of 1 second and a spatial resolution of 6 degrees half power beam width (HPBW).

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 ADvanced MIcrowave RAdiometer for Rain Identification (ADMIRARI) is an airborne passive microwave radiometer. ADMIRARI measures brightness temperatures at 10.7, 21.0, and 36.5 GHz frequencies along two polarized planes. It is also equipped with a Micro Rain Radar (MRR) to observe rain structure and a cloud lidar to estimate cloud base. ADMIRARI's measurements can be used to determine rain/cloud liquid water path (LWP) and integrated water vapor (IWV). It has a temporal resolution of 1 second and a spatial resolution of 5 degrees.

Ceilometers are ground-based remote sensing sensors that measure cloud ceilings and vertical visibility. They utilize a laser or another light source to detect backscatter from clouds, precipitation, and aerosols. Ceilometers provide detailed and precise measurements under all weather conditions and are cost-effective to operate. They are commonly used in boundary layer and cloud research.

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.