NASA African Monsoon Multidisciplinary Analyses

Dropsondes, also known as dropwindsondes, are in situ instruments designed to be released from aircraft. They are equipped with Global Positioning System (GPS) receivers and sensors to collect profile measurements of pressure, temperature, humidity, wind speed, and wind direction. Dropsondes are important during field investigations because they enable researchers to collect vertical profiles in remote locations and during severe weather conditions. Typically, dropsondes have a vertical resolution of 5 meters and provide wind speed and direction measurements every 0.25 seconds, while temperature, pressure, and humidity are recorded every 0.5 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 Lidar Atmospheric Sensing Experiment (LASE) is an airborne lidar system developed at NASA's Langley Research Center (LaRC). LASE uses the differential absorption lidar technique to provide profile measurements of water vapor and aerosols in the atmosphere. LASE operates at the 815 nm wavelength and has a measurement frequency of 5 Hz. For aerosol scattering profiles, LASE has a horizontal resolution of 200 m and a vertical resolution of 30 m. It has a horizontal resolution of 5 km and a vertical resolution of 0.2 km for water vapor measurements.

The Counterflow Virtual Impactor (CVI) is an in situ airborne instrument that samples cloud droplets. It samples cloud droplets by removing them from the surrounding air through inertial impaction. CVI is typically deployed with additional sensors to provide measurements of cloud particle concentration, cloud liquid water, and water vapor of the sample droplets. CVI can detect cloud droplets as small as 7 microns in diameter and has a typical time response of 1 second.

The Carbon monOxide by Attenuated Laser Transmission (COBALT) is an in situ airborne spectrometer made by Los Gatos Research. It uses off-axis integrated cavity output spectroscopy (OA-ICOS) to measure carbon monoxide in the troposphere and tropopause. COBALT operates at a wavelength of 4.60 μm and has a typical sampling rate of 1 Hz. COBALT delivers measurements with a precision of 0.2 ppbv and does not need regular calibration.

Generic-Chemistry Related Sensors (Gen-Chemistry) refers to non-specific instruments on a platform used for atmospheric chemistry measurements. These are typically in situ analyzers that measure various chemical compounds such as trace gases, halocarbons, volatile organic compounds, nitrates, aerosols, and other chemical species. Measurements can include mixing ratio, composition, particle size, optical properties, and particle size distribution.

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 Optical Particle Counter is an instrument based on the principle of light scattering from particles. It is a real time instrument that is typically used to measure particles above 0.05 μm in diameter.

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 Cloud Aerosol and Precipitation Spectrometer (CAPS) is an in situ airborne spectrometer manufactured by Droplet Measurement Technologies. It combines the Cloud Imaging Probe (CIP), the Cloud and Aerosol Spectrometer (CAS), and the Hotwire Liquid Water Content (LWC) Sensor into a single instrument. CAPS measures the size distribution of aerosol, cloud, and liquid droplets for particles between 50-1600 μm in size, with a time resolution of 1 Hz. It can also capture images of cloud particles and provide measurements of temperature, pressure, and LWC.

A Tunable Diode Laser Absorption Spectrometer (TDLAS) is an in situ optical spectrometer used either on aircraft or on the ground. TDLAS detects the wavelength-dependent absorption of light to measure the concentrations of various trace gases. It can also identify the gas species' temperature, pressure, velocity, and mass flux when applicable. TDLAS typically has a time resolution of 1 second.

The Ultra-High Sensitivity Aerosol Spectrometer (UHSAS) is an in situ spectrometer developed by Droplet Measurement Technologies. It can be used on both airborne and ground-based platforms to measure aerosol size distribution and concentration. UHSAS determines particle size by detecting the peak light signals from aerosol particles illuminated by a 1054 nm laser. It can sample particles in the 60–1000 nm size range and operates at a sampling frequency of 10 Hz.

The Aerodynamic Particle Sizer (APS) is an in situ spectrometer manufactured by TSI Instruments. APS measures aerodynamic particles in the 0.5-20 μm size range. It also measures the light-scattering intensity of the particles in the 0.37-20 μm optical size range. APS provides particle size distributions for 52 channels at a typical sampling time of 1 second. It uses a laser diode operating at 655 nm and has a size resolution of 0.02 μm at 1 μm. APS can be deployed on aircraft, ships, or ground-based platforms.

The Condensation Nuclei Counter (CNC) is optical method for counting atmospheric aerosol particles.

The Diode Laser Hygrometer (DLH) is an in situ airborne hygrometer developed by NASA’s Langley Research Center (LaRC). It uses tunable diode laser absorption to detect water vapor in the atmosphere. DLH operates in the near-infrared range at about 1.4 μm and has a measurement frequency of 100 Hz. It can deliver precise measurements of water vapor even when flying through clouds.

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 Meteorological Measurement System (MMS) is an in situ airborne instrument used to measure atmospheric state parameters. MMS provides high-resolution, accurate measurements of atmospheric pressure, temperature, and wind direction and speed immediately around the plane. Additional parameters that can be derived include potential temperature, true airspeed, turbulence dissipation rate, and Reynolds number. Measurements of all parameters are typically collected at a rate of 20 Hz.

Nephelometers are in situ optical sensors that can be airborne or ground-based. They measure the total scattering and backscattering of aerosol particles in the atmosphere. Nephelometers operate at three wavelengths: 450 nm, 550 nm, and 700 nm, with a typical time resolution of 1 Hz.

Dropsondes, also known as dropwindsondes, are in situ instruments designed to be released from aircraft. They are equipped with Global Positioning System (GPS) receivers and sensors to collect profile measurements of pressure, temperature, humidity, wind speed, and wind direction. Dropsondes are important during field investigations because they enable researchers to collect vertical profiles in remote locations and during severe weather conditions. Typically, dropsondes have a vertical resolution of 5 meters and provide wind speed and direction measurements every 0.25 seconds, while temperature, pressure, and humidity are recorded every 0.5 seconds.

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 High Altitude Monolithic Microwave integrated Circuit (MMIC) Sounding Radiometer (HAMSR) is an airborne microwave sounder developed by the Jet Propulsion Laboratory through the NASA Instrument Incubator Program. HAMSR measures brightness temperature, which can be used to derive three-dimensional profiles of temperature, water vapor, and cloud liquid water in the atmosphere. It operates across 25 spectral channels in three microwave bands (50-60 GHz, 118 GHz, 183 GHz) and has a sampling frequency of 5 seconds. HAMSR has a horizontal spatial resolution of 2 km at nadir and a field of view of approximately 40 km at an altitude of 20 km.

The Langley Aerosol Research Group Experiment (LARGE) is an in situ airborne instrument suite that measures aerosol and cloud microphysical and optical properties, such as size distribution, number concentration, and scattering and absorption coefficients. LARGE includes several instruments, such as the Ultra-High Sensitivity Aerosol Spectrometer (UHSAS), Particle-Into-Liquid Sampler (PILS), Particle Soot Absorption Photometer (PSAP), Cloud and Aerosol Spectrometer (CAS), Cloud Imaging Probe (CIP), and additional cloud and aerosol sensors. The LARGE instruments operate over the 450-700 nm wavelength range, detect particles ranging from 0.003 to 20 μm, and measure at a frequency of 1 Hz. It is primarily used for airborne measurements but can also be deployed on ground-based platforms like vehicles.

The Arrival Time Difference Network (ATDnet) is a ground-based lightning detection network operated by the United Kingdom Meteorological Office. It consists of several sensors across Europe that detect lightning in Europe, northern Africa, and the northern Atlantic Ocean. It uses very-low-frequency (VLF) sensors to detect the electromagnetic waves or sferics generated by lightning strikes to determine the number and location of lightning strikes. These sensors operate at a central frequency of 13.733 kHz and have a time resolution of 1 ns. ATDnet has a location accuracy of 1-3 km.

The ZEUS Long-Range Lightning Detection Network is a ground-based network of ZEUS lightning detection systems across Europe, Africa, and Brazil. ZEUS detects the sferics emitted by a cloud-to-ground lightning strike in the very low frequency (VLF) spectrum (7-15 kHz). The lightning location and time are determined by using the arrival time difference (ATD) technique. ZEUS can measure 70 sferics per second and has a spatial accuracy of 10-20 km within the network periphery.

FLUXNET is a global network of eddy covariance flux towers. Each tower is equipped with gas sensors to continuously measure the fluxes of trace gases such as carbon dioxide, methane, and water vapor between the land surface and the atmosphere. These towers are also equipped with various meteorological sensors to measure air temperature, precipitation, winds, radiation, and soil temperature. Currently, FLUXNET has over 250 flux tower sites across the globe in various vegetation types such as tundra, tropical, forest, and grasslands.

The Surface-sensing Measurements for Atmospheric Radiative Transfer (SMART) is a ground-based remote instrument suite operated by NASA Goddard Space Flight Center (GSFC). It consists of several remote sensing instruments, such as a micro-pulse lidar, sun photometer, and broadband radiometers housed in a twenty-foot trailer. SMART provides measurements of solar spectral radiance, surface spectral bi-directional reflectance, albedo, and shortwave and longwave irradiance at a spectral resolution of 1 nm. It operates across the ultraviolet to microwave spectral range. SMART is part of the SMARTLabs mobile facilities.

The Chemical, Optical, and Microphysical Measurements of In-situ Troposphere (COMMIT) is a ground-based instrument suite operated by NASA Goddard Space Flight Center (GSFC). It consists of several gas, aerosol, and meteorological sensors housed in a twenty-foot trailer. COMMIT measures trace gas concentrations for sulfur dioxide, carbon monoxide, carbon dioxide, ozone, and nitrogen oxides. It provides measurements of aerosol mass concentrations and size distribution for the 5 nm to 20 μm size range. It also provides observations of aerosol extinction, scattering, and absorption in the 370 to 950 nm wavelength range. COMMIT is part of the SMARTLabs mobile facilities.

The Sferics Timing and Ranging Network (STARNET) is a long-range lightning detection system spanning South America and the Atlantic Ocean. It uses Very Low Frequency (VLF) receivers to detect sferics from lightning strikes. It operates at 7-15 kHz and measures 130 sferics per second. STARNET has a location accuracy of 2 to 10 km in South America and about 20 km in the Atlantic Ocean.

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.

The Tropical Ocean/Global Atmosphere (TOGA) C-band Radar is a ground-based radar that was developed for the TOGA COARE campaign. It is a C-band (5600-5650 MHz) Doppler radar that measures reflectivity, Doppler velocity, spectrum width, and other radar parameters to characterize precipitation. It is currently located at Wallops Flight Facility (WFF) and can be deployed for land or sea-based operations. The TOGA radar has a beam width of 1.55 degrees and a typical bin spacing of 150 meters.