Cirrus Regional Study of Tropical Anvils and Cirrus Layers Florida Area Cirrus 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.

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 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.

The JPL Laser Hygrometer (JLH) is an in situ airborne hygrometer developed at the Jet Propulsion Laboratory (JPL). It uses a tunable diode laser operating at 1.37 μm to measure atmospheric water vapor in the upper troposphere and lower stratosphere. JLH has a minimum spatial resolution of 25 meters and a detection range of 1 to 500 ppmv. It typically samples at 1 Hz and can provide measurements with a precision of 0.05 ppmv.

The MODIS Airborne Simulator (MAS) is an airborne multispectral spectrometer designed to simulate the satellite instrument Moderate-Resolution Imaging Spectrometer (MODIS). MAS operates over 50 spectral channels in the 0.55 to 14.2 μm range, providing high-resolution images of clouds and surface features. It has a horizontal spatial resolution of 50 meters and a swath width of about 36 kilometers at an altitude of 20 km at nadir. Its scan rate is 6.25 Hz, with each scan line containing 716 pixels.

The Microwave Temperature Profiler (MTP) is an airborne microwave radiometer developed by the Jet Propulsion Laboratory and later modified by NCAR. It measures brightness temperature from oxygen molecules at 56.363 GHz, 57.612 GHz, and 58.363 GHz. These measurements are converted into air temperature through a statistical retrieval process. It samples across 10 viewing angles and has a vertical resolution of 150 m near the aircraft. MTP provides profiles every 17 seconds with about 4 km of horizontal spacing.

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 Solar Spectral Flux Radiometer (SSFR) is an airborne radiometer developed by the Ames Atmospheric Radiation Group. It measures solar spectral irradiance in the troposphere. SSFR works within the 300-2150 nm wavelength range and offers a spectral resolution of 8-12 nm. It typically collects data at 1 Hz and has a radiometric accuracy of 3%.

The ER-2 Doppler Radar (EDOP) is an airborne X-band radar designed to operate on the nose of the ER-2 aircraft. It measures radar reflectivity, Doppler velocity, and spectrum width to characterize precipitation systems. EDOP operates at a 9.6 GHz frequency and provides data at a rate of 2 Hz. It has a typical gate spacing of 75 m and a beamwidth of 2.9 degrees. EDOP has been replaced by the EXRAD radar.

The Configurable Scanning Submillimeter-wave Instrument/Radiometer (CoSSIR) is an airborne imaging radiometer designed to measure ice clouds. It measures brightness temperature across 16 channels in the 183-874 GHz range. These measurements can determine ice cloud properties, water vapor profiles, and snowfall rates. CoSSIR has a surface footprint of 1.5 km at nadir at an altitude of 20 km. It has a scan cycle of 4.6 seconds.

The Radiation Measurement System (RAMS) is an airborne passive radiometer that measures broadband solar irradiance. RAMS includes two radiometers: the Total Solar Broadband Radiometer (TSBR) and the Fractional Solar Broadband Radiometer (FSBR). The TSBR operates in the 0.224 to 3.91 μm range, while the FSBR operates between 0.68 and 3.3 μm. It has a response time of approximately 60 milliseconds and can provide measurements every 5 meters for aircraft speeds around 75 m/s. RAMS is primarily used for airborne operations but can also be used to collect ground-based measurements.

The Multi-sample Aerosol Collection System (MACS) is an in situ airborne aerosol sampling system. It consists of a two-stage impact collector, which allows for the collection of aerosol particles on electron microscope grids for further analysis. MACS can collect particles as small as 0.02 μm for altitudes up to 60,000 feet. MACS can collect around 24 samples per flight.

The Aerosol Mass Spectrometer (AMS) is an in situ spectrometer developed by Aerodyne Research. It employs quadrupole mass spectrometry to measure aerosol chemical composition and properties. It can detect particles ranging from 40 nm to 1 micron in size and has a time resolution of up to 10 Hz. It can be installed on aircraft, research vessels, mobile laboratories, or other ground-based platforms.

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.

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 Linear Etalon Imaging Spectral Array (LEISA) is an airborne infrared (IR) hyperspectral imager. It is the airborne of the LEISA satellite instrument and is used for calibration and validation. It operates across the 1 to 2.5 microns spectral range to collect IR imagery. It has a spatial resolution of 2 meters at a 1 km altitude and of 20 meters at a 10 km altitude. LEISA has a swath width of approximately 29 degrees.

The Passive-Cavity Aerosol Spectrometer Probe (PCASP) is an in situ airborne optical spectrometer manufactured by Droplet Measurement Technologies. It detects light scattered by particles to determine aerosol size distribution and concentration within the 0.1 to 3.0 μm range. PCASP operates at a wavelength of 632 nm and typically samples at 10 Hz.

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.

The Microorifice Uniform Deposit Impactor (MOUDI) is an in situ airborne or ground-based sampler developed by the MSP Corporation. It is an eight-stage impactor used for high-accuracy aerosol sampling for gravimetric or chemical analysis. MOUDI has a sample flow rate of 30 liters per minute and can sample particles in the size range of 0.056-18 µm. It is used for applications such as air pollution research, engine emission testing, and aerosol analysis.

Broadband Radiometers (BBR) are modified versions of the Kipp & Zonen CM-22 pyranometers and CG-4 pyrgeometers. They have been adapted for use on airborne platforms through different instrument housing and signal amplification. BBR measures solar irradiance in the 0.2-3.6 μm wavelength range and infrared (IR) irradiance in the 4.5-42 μm range. These measurements can be used to derive net irradiance, radiative forcing, absorption, and albedo. It has a typical sampling rate of 1 Hz and a hemispheric field of view.

The Solar Spectral Flux Radiometer (SSFR) is an airborne radiometer developed by the Ames Atmospheric Radiation Group. It measures solar spectral irradiance in the troposphere. SSFR works within the 300-2150 nm wavelength range and offers a spectral resolution of 8-12 nm. It typically collects data at 1 Hz and has a radiometric accuracy of 3%.

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 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 Tandem Differential Mobility Analyzer (TDMA) is an in situ airborne and ground-based analyzer that measures the physical properties of aerosol particles, such as size distribution and concentration. It can measure particles in the size range of 0.013 to 0.75 mm with a size resolution of 0.013 mm at 0.2 mm. The TDMA is often combined with an Aerodynamic Particle Sizer (APS) to enable measurements of particles in the submicron range. A typical measurement sequence of TDMA takes approximately 45 minutes to complete.

TSI Particle Probes are in situ particle counters and detectors manufactured by TSI Incorporated. They are used to detect aerosol particles and determine concentration and particle counts. TSI Particle Probes are typically combined with particle sizers, which can measure size distribution. TSI Particle Probes can be deployed on aircraft, research vessels, and ground-based platforms.

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.

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.

Broadband Radiometers (BBR) are modified versions of the Kipp & Zonen CM-22 pyranometers and CG-4 pyrgeometers. They have been adapted for use on airborne platforms through different instrument housing and signal amplification. BBR measures solar irradiance in the 0.2-3.6 μm wavelength range and infrared (IR) irradiance in the 4.5-42 μm range. These measurements can be used to derive net irradiance, radiative forcing, absorption, and albedo. It has a typical sampling rate of 1 Hz and a hemispheric field of view.

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 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 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 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.

This data will be added in future versions

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.

The Scanning ARM Cloud Radar (SACR) is a ground-based Doppler radar system operated by the Department of Energy (DoE) Atmospheric Radiation Measurement (ARM) User Facility. It is a polarimetric Doppler radar consisting of three radar designs at different operating frequencies: X-SACR (9.71 GHz), Ka-SACR (35.3 GHz), and W-SACR (94 GHz). For each deployment location, two SACR radars are deployed with operating frequencies determined by atmospheric attenuation at the site. SACR provides measurements of radar reflectivity, Doppler velocity, spectrum width, and other polarimetric parameters at a gate spacing of 25 meters.

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 NOAA Portable Cloud Observatory (NPCO) is a ground-based system that profiles clouds using active and remote sensors. It features a millimeter-wave cloud profiling radar (MMCR), a three-channel (21 GHz, 31 GHz, 90 GHz) microwave radiometer, an infrared thermometer, and surface meteorological sensors. The MMCR operates at 35 GHz and collects radar observations at a 45-meter resolution to derive cloud properties. The radiometer measures brightness temperature to determine cloud liquid water content and water vapor. NPCO is housed in a standard 20-foot sea container and can be deployed on land or on research vessels for water-based operations.

The Millimeter-Wavelength Cloud Radar (MMCR) is a ground-based radar developed by the NOAA Environmental Technology Laboratory (ETL) for the Department of Energy (DoE) Atmospheric Radiation Measurement (ARM) sites. MMCR provides long-term observations of radar reflectivity, Doppler velocity, spectrum width, and other radar parameters for precipitating and nonprecipitating clouds up to 20 km above ground level (AGL). It is a vertically pointing, single-polarization radar system that operates at around 35 GHz. MMCR has a beamwidth of 0.2 degrees and typical vertical resolutions of 45 and 90 meters.

This data will be added in future versions.

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 ELectra DOppler RAdar (ELDORA) is an airborne radar system developed by the National Center for Atmospheric Research (NCAR) and France's Centre de Recherches en Physique de L'Environnement Terrestre et Planetaire (CRPE). It was designed to operate on the NCAR Electra aircraft, but it also operates on the Naval Research Lab (NRL) P-3 aircraft. It is an X-band (9.3-9.8 GHz) radar that measures radar reflectivity, Doppler velocity, and other radar parameters to characterize convective systems and clouds. ELDORA has a beamwidth of 1.8 degrees and a range resolution of 37.5 to 1200 meters, depending on radar configuration.

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 NPOESS Aircraft Sounder Testbed - Microwave (NAST-M) is an airborne microwave radiometer operated by the Massachusetts Institute of Technology (MIT). It measures brightness temperature, which can be used to retrieve water vapor profiles in the atmosphere. It consists of two radiometers: one operating across eight channels between 50-57 GHz and the other across nine at 118 GHz. In 2003, NAST-M was upgraded with two additional radiometers at 183 and 425 GHz to enhance water vapor retrievals and detect small hydrometeors. NAST-M has a spatial resolution of 2.6 km and a cross-track swath width of 100 km at a flight altitude of 20 km. Its typical integration time is 100 ms.

The Research Scanning Polarimeter (RSP) is an airborne, passive polarimeter developed by SpecTIR Corporation. It measures total radiance and linear polarization across nine spectral bands in the visible and infrared wavelengths (410-2250 nm). These measurements can be used to determine aerosol and cloud properties. RSP has a time resolution of 0.8 seconds, a field of view of 14 mrad, and a horizontal resolution of approximately 100 meters at an altitude of 5 km.

The NPOESS Aircraft Sounder Testbed - Interferometer (NAST-I) is an airborne infrared interferometer operated and maintained by NASA Langley Research Center (LaRC). It uses Fourier transform spectroscopy to measure brightness temperature and radiance. NAST-I operates within the spectral range of 3.7-16.1 µm and has a spectral resolution of 0.25 cm-1. It features a spatial resolution of 2.6 km and a cross-track swath width of 46 km at a flight altitude of 20 km. A complete scan cycle for NAST-I takes approximately 12.2 seconds.

The Far Infrared Sensor for Cirrus (FIRSC) is a remote passive airborne infrared spectrometer that uses Fourier transform spectroscopy (FTS) to measure the infrared radiance of cirrus clouds. FIRSC operates across two channels with a wavenumber range of 10-35 per centimeter and 80-135 per centimeter. It has a field of view of 0.03 radians, a footprint of less than one kilometer, and a scan time of 4 seconds.

The POLarization and Directionality of the Earth’s Reflectances (POLDER) is a spaceborne passive radiometer onboard the Japan Aerospace Exploration Agency’s Advanced Earth Observing Satellite. POLDER has also been used in several airborne investigations to calibrate instruments and measure surface reflectance and solar radiation. POLDER has a ground spatial resolution of 7 km by 6 km at nadir and operates across eight discrete spectral bands (443 nm - 910 nm).

The Multi-sample Aerosol Collection System (MACS) is an in situ airborne aerosol sampling system. It consists of a two-stage impact collector, which allows for the collection of aerosol particles on electron microscope grids for further analysis. MACS can collect particles as small as 0.02 μm for altitudes up to 60,000 feet. MACS can collect around 24 samples per flight.

The Microwave Temperature Profiler (MTP) is an airborne microwave radiometer developed by the Jet Propulsion Laboratory and later modified by NCAR. It measures brightness temperature from oxygen molecules at 56.363 GHz, 57.612 GHz, and 58.363 GHz. These measurements are converted into air temperature through a statistical retrieval process. It samples across 10 viewing angles and has a vertical resolution of 150 m near the aircraft. MTP provides profiles every 17 seconds with about 4 km of horizontal spacing.

The NOAA Chemical Ionization Mass Spectrometer (NOAA-CIMS) is an in situ airborne spectrometer developed by NOAA. It was designed to provide high-precision measurements of reactive nitrogen and halogen species such as nitric acid, nitric oxide, and bromine chloride in the upper atmosphere. It can also provide measurements of ozone and water vapor concentrations. NOAA-CIMS has a detection limit of 30 pptv and a temporal resolution of 1 second.

The NOAA Pressure and Temperature (NOAA PT) is an in situ airborne probe that measures atmospheric pressure and temperature. It comprises a digital pressure temperature transducer and slow and fast responding temperature probes. NOAA PT provides measurements of both static and ram pressure and upper air temperature every second. It has an accuracy of 0.5 degrees for temperature and 0.5 mbars for pressure.

The Video Ice Particle Sampler (VIPS) is an in situ airborne electro-optical instrument. It continuously collects and images cloud particles as small as 3 μm. Cloud particle samples are collected on a looped belt where they are exposed to a high-resolution video camera. Particle imagery is recorded at 30 Hz and has an image resolution of 1.12 μm per pixel. VIPS also provides particle size distribution and concentration.

The NOAA CH4 is an in situ airborne near-infrared tunable diode laser (TDL) absorption spectrometer. The laser is tuned to the methane (CH4) absorption line at 1.653 μm and measures the intensity of the transmitted radiation. The CH4 concentration is then determined using the Beer-Lambert law. NOAA CH4 scans continuously over the CH4 absorption at a rate of 0.25 to 0.5 kHz and has a typical integration time of 2 seconds.

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 Multiple-Angle Aerosol Spectrometer Probe (MASP) is an in situ airborne spectrometer. It measures the light intensity of scatter aerosol particles at 780 nm wavelength across multiple angles to determine particle size and concentration. It can detect particles within the 0.3 to 20 micron size range. MASP typically has a time resolution of 10 seconds.

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.

The Focused Cavity Aerosol Spectrometer (FCAS) is an in situ airborne optical particle counter developed by Particle Measuring Systems, Inc. FCAS detects light scattered by individual aerosol particles to determine their size distribution. It can detect aerosol particles ranging from 0.06 to 2 μm in size and operate at altitudes up to 20 km. Typically, FCAS provides measurements every 10 seconds.

The Particle Analysis by Laser Mass Spectrometry (PALMS) is a laser ionization mass spectrometer operated by NOAA. PALMS provides in situ measurements of aerosol particles and their chemical composition by using a UV laser pulse (193 nm) to generate ions. These ions are then analyzed with a time-of-flight mass spectrometer to produce the mass spectrum of each particle, which can be used to classify individual aerosol particles. PALMS has an aerosol size range of 0.2 to 3 microns and typically collects data at about 1 to 10 Hz. It can be used for either airborne or laboratory aerosol measurements.

The Solar Spectral Flux Radiometer (SSFR) is an airborne radiometer developed by the Ames Atmospheric Radiation Group. It measures solar spectral irradiance in the troposphere. SSFR works within the 300-2150 nm wavelength range and offers a spectral resolution of 8-12 nm. It typically collects data at 1 Hz and has a radiometric accuracy of 3%.

The High-Sensitivity Fast-Response CO2 Analyzer (Harvard CO2) is an in situ airborne spectrometer operated by Harvard University. It measures carbon dioxide (CO2) concentrations using a modified nondispersive infrared CO2 analyzer. CO2 mixing ratios are determined by measuring absorption at 4.26 μm. Harvard CO2 has a measurement sampling rate of 0.5 Hz and a precision of 0.05 ppm. Harvard is typically deployed on high-altitude aircraft like the ER-2, but it has been used for balloon-borne measurements.

The Closed-path Laser Hygrometer (CLH) is an in situ airborne tunable diode laser hygrometer developed by the University of Colorado and the Jet Propulsion Laboratory (JPL). It uses second-harmonic absorption spectroscopy to measure atmospheric water vapor. It operates at the 1.37 μm wavelength and has a measurement frequency of 0.8 Hz.

The NOAA Dual-Beam UV-Absorption Ozone Photometer (NOAA-O3) is an in situ optical balloon-borne and airborne instrument that measures ozone concentrations in the troposphere and lower stratosphere. It operates at a wavelength of 254 nm, enabling it to calculate ozone number density due to the precise ozone absorption cross section at that wavelength. It has a sampling rate of 2 Hz and a horizontal resolution of 100 to 200 meters during typical research flights.

The Airborne Laser Infrared Absorption Spectrometer (ALIAS) is an in situ airborne spectrometer developed by the Jet Propulsion Laboratory. It can also be deployed on balloons. It uses mid-infrared (3.4–8 μm) absorption spectroscopy to measure atmospheric gases such as nitrous oxide (N2O), nitrogen dioxide (NO2), nitric acid (HNO3), hydrochloric acid (HCl), carbon monoxide (CO), and methane (CH4). ALIAS has a vertical resolution of 15 m and a time resolution of 3 seconds or less.

The Nucleation-mode Aerosol Size Spectrometer (NMASS) is an airborne, in situ spectrometer used to measure particle size distribution and cloud condensation nuclei (CCN). NMASS includes five parallel condensation nucleus counters (CNCs) that sample particles within the 3 to 60 nm diameter range. It can be mounted on various types of aircraft and is ideal for sampling cirrus clouds in the upper atmosphere. NMASS delivers rapid measurements with a temporal resolution of 10 Hz.

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.

Harvard Water Vapor (HWV) is an in situ airborne hygrometer developed at Harvard University that measures water vapor mixing ratios in the upper troposphere and lower stratosphere. HWV includes two instruments with different methods for detecting water vapor: the Lyman-α photo-fragment fluorescence instrument (LyA) and a tunable diode laser direct absorption instrument (HHH -Harvard Herriott Hygrometer). By combining both instruments, HWV can identify and reduce systematic errors during flight. It provides measurements of water vapor mixing ratio from 1 to 1000 ppmv at 1 Hz and with an accuracy of 5%.

The JPL Laser Hygrometer (JLH) is an in situ airborne hygrometer developed at the Jet Propulsion Laboratory (JPL). It uses a tunable diode laser operating at 1.37 μm to measure atmospheric water vapor in the upper troposphere and lower stratosphere. JLH has a minimum spatial resolution of 25 meters and a detection range of 1 to 500 ppmv. It typically samples at 1 Hz and can provide measurements with a precision of 0.05 ppmv.

NOx/NOxy is an in situ chemiluminescence instrument that measures nitrogen oxides and ozone in the atmosphere. It offers a spatial resolution better than 100 meters at typical DC-8 research flight speeds. NOx/NOxy can be used on ground-based, airborne, and shipborne platforms, enabling it to support various atmospheric chemistry and air quality studies.

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.

The Cloud Integrating Nephelometer (CIN) is an in situ airborne nephelometer developed by Gerber Scientific. It measures the asymmetry parameter, optical extinction coefficient, and extinction-to-backscatter ratio of clouds. It operates at the 635 nm wavelength and can measure cloud particles within the 4-2500 μm size range. CIN has a typical measurement rate of 1 Hz and a measurement accuracy of 2% and 10% for the asymmetry parameter and optical extinction coefficient, respectively.

Argus is a two-channel, tunable diode laser instrument developed at NASA Ames Research Center. It collects in situ measurements of carbon monoxide (CO), nitrous oxide (N2O), and methane (CH4) in the atmosphere using second harmonic spectroscopy. Argus operates in the mid-infrared range (3.3 and 4.7 micrometers) and has an accuracy of about 3% for data rates between 0.1 and 0.5 Hz. Its lightweight and compact design makes it ideal for small payload platforms such as balloons and uncrewed aerial vehicles (UAVs).

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 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 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.

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 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 Continuous Flow Diffusion Chamber (CFDC) is an in situ airborne optical particle counter (OPC). It uses vertical flow through two chambers with different wall temperatures to grow ice particles inside the OPC at the bottom of the instrument, which helps determine particle size distribution. The CFDC can also measure flow rate, temperature, and humidity if conditions are stable. It measures the size distribution of aerosol particles ranging from 0.4 to 20 mm. The device counts particles every 0.2 seconds and records particle spectra every 10 seconds.

The Cloud Integrating Nephelometer (CIN) is an in situ airborne nephelometer developed by Gerber Scientific. It measures the asymmetry parameter, optical extinction coefficient, and extinction-to-backscatter ratio of clouds. It operates at the 635 nm wavelength and can measure cloud particles within the 4-2500 μm size range. CIN has a typical measurement rate of 1 Hz and a measurement accuracy of 2% and 10% for the asymmetry parameter and optical extinction coefficient, respectively.

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.