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.

Condensation Particle Counters (CPCs) are in situ sensors that measure aerosol particle concentrations. CPCs determine aerosol levels by condensing fluid onto particles, causing them to grow to sizes detectable by optical scattering. Typically, CPCs can detect particles ranging from 7 nm to 3 μm, measure concentrations up to 100,000 particles per cubic centimeter, and provide readings every second. CPCs are manufactured by TSI Incorporated and can be used on airborne, shipborne, and ground-based platforms.

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 (OPC) is an optical device used to measure aerosol particle size and concentration. It determines particle size and concentration by detecting the intensity of scattered light. Most OPCs operate within the visible to near-infrared wavelengths (500-1100 nm) and have a time resolution of 1 second. They are typically used to measure particles larger than 0.5 μm in diameter. OPCs can be used for both airborne and ground-based applications.

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 Airborne Second Generation Precipitation Radar (APR-2) is a dual-frequency, cross-track scanning radar used for measuring precipitation from aircraft. 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 an altitude of 11,000 feet, it offers a horizontal resolution of 730 meters at 13.4 GHz and 920 meters at 35.6 GHz. The radar has a vertical resolution of 60 meters and a ground swath width of 10 km.

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 an in situ optical sensor produced by Droplet Measurement Technologies. It detects cloud condensation nuclei (CCN) by supersaturating the sampled air, allowing CCN particles to become detectable. The particles are then measured with an optical particle counter (OPC). CNC can detect particles from 0.75 to 10 μm in diameter and operates at a sampling rate of 1 Hz. It is suitable for both airborne and ground-based operations.

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 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.

LI-COR Gas Analyzer is an in situ gas analyzer manufactured by LI-COR. They can be deployed on aircraft, research vessels, vehicles, balloons, and ground-based platforms. They provide measurements of various trace gases such as carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and water vapor (H2O). Most models use Optical Feedback-Cavity Enhanced Absorption Spectroscopy (OF-CEAS) to collect measurements. LI-COR gas analyzers have a typical measurement rate of 1 Hz and an operating temperature range of -25 to 45 degrees Celsius.

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.

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.

A pyranometer is a ground-based or airborne radiation sensor that measures solar irradiance across a hemispherical field of view. It detects the amount of solar energy reaching the surface, capturing both direct and diffuse sunlight. Pyranometers operate within a spectral range of 280-3000 nm. They are most commonly used for solar monitoring, climate research, weather forecasting, agriculture, and energy management.

A pyrgeometer is a ground-based or airborne passive radiation sensor. It measures downward and upward longwave radiation in the 4-50 μm spectral range. Pyrgeometers measure changes in resistance/voltage using a thermopile sensor to determine longwave radiation. These measurements can be used to calculate the infrared radiation flux. Pyrgeometers are typically used for climatological, meteorological, and agricultural applications.

A pyrgeometer is a ground-based or airborne passive radiation sensor. It measures downward and upward longwave radiation in the 4-50 μm spectral range. Pyrgeometers measure changes in resistance/voltage using a thermopile sensor to determine longwave radiation. These measurements can be used to calculate the infrared radiation flux. Pyrgeometers are typically used for climatological, meteorological, and agricultural applications.

A pyranometer is a ground-based or airborne radiation sensor that measures solar irradiance across a hemispherical field of view. It detects the amount of solar energy reaching the surface, capturing both direct and diffuse sunlight. Pyranometers operate within a spectral range of 280-3000 nm. They are most commonly used for solar monitoring, climate research, weather forecasting, agriculture, and energy management.

The Particle Soot Absorption Photometer (PSAP) is an in situ airborne photometer manufactured by Radiance Research. It applies Beer's Law to measure the change in light transmission of aerosol particles. These measurements help determine aerosol absorption and extinction. PSAP operates across three wavelengths (467, 530, and 660 nm) and has a 1-second time resolution. It is usually deployed on aircraft, but it can also be used on ships and vehicles.

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 microwave radiometers (MWRs) are ground-based radiometers manufactured by Radiometrics Corporation and operated by the Atmospheric Radiation Measurement (ARM) Research Facility. MWR measures brightness temperature at 23.8 and 31.4 GHz to determine the column amounts of water vapor and liquid water in the atmosphere. MWR has a field of view (FOV) ranging from about 5.9 to 4.5 degrees depending on the channel and typically has a time resolution of 20 seconds for sky-view observations.

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 Aethalometer is an in situ aerosol measuring device made by Magee Scientific. It can be used on both airborne and ground-based platforms. It collects aerosols through a filter tape and gauges the attenuation of transmitted light to assess black carbon particle levels. The Aethalometer works across seven optical wavelengths (370, 470, 520, 590, 660, 880, and 950 nm) and delivers data at a rate of 1 Hz. It has a measurement range of 0-500 μg per cubic meter and a resolution of 0.1 μg per cubic meter.

The Atmospheric Emitted Radiance Interferometer (AERI) is a ground-based passive interferometer developed by the University of Wisconsin Space Science and Engineering Center (UW-SSEC) for the Department of Energy (DoE) Atmospheric Radiation Measurement (ARM) Program. It uses Fourier transform spectroscopy to measure downwelling thermal infrared emissions from the atmosphere. These measurements can be used to provide profile measurements of atmospheric temperature and water vapor and detect trace gases. AERI operates across the 3.3-19 μm spectral range and up to 25 μm for the extended range version of the instrument. It has an optimal vertical resolution of 100 meters and completes a full sky scan about every 20 seconds.

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 Total Sky Imager (TSI) is a ground-based, optical instrument developed by Yankee Environmental Systems (YES), Inc. TSI provides full-color, hemispheric images of the sky during the day using a charge-coupled device (CCD) imager. It also measures fractional sky cover and sun obscuration caused by clouds. TSI can be mounted on mobile platforms such as trailers and research vehicles, enabling it to collect cloud cover data in different locations during field studies.

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.

The Micropulse Lidar (MPL) is a ground-based lidar system used for cloud detection. It measures lidar backscatter at 532 nm to retrieve cloud properties such as cloud top and base height. It can also be used for the detection of aerosols. MPL has a vertical resolution of 15 m and a maximum range of 18 km. MPL can operate autonomously and typically provides 10-second averaged data.

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.

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.

Thermo Scientific Gas Analyzers are in situ gas analyzers manufactured by ThermoFisher Scientific. They provide precise measurements of various trace gases such as ozone, carbon dioxide, carbon monoxide, and sulfur dioxide. Thermo Scientific Gas Analyzers can be deployed on aircraft, research vessels, and ground-based platforms.

The Multifilter Rotating Shadowband Radiometer (MFRSR) is a ground-based passive radiometer used to measure the global and diffuse components of solar irradiance. It measures solar irradiance across six narrowband channels and one broadband channel. The nominal wavelengths of the narrowband channels are 415, 500, 615, 673, 870, and 940 nm. MFRSR has a typical sampling interval of 20 seconds and takes measurements at four different shadowband positions: nadir, first side-band, sun-blocked, and second side-band. MFRSR is deployed across several of the Department of Energy’s Atmospheric Radiation Measurement (ARM) User Facility sites.

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 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.