Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys

The Cryogenic Frost Point Hygrometer (CFH) is a balloon-borne hygrometer developed by the University of Colorado. CFH uses the chilled-mirror principle to measure water vapor from the Earth's surface up to the mid-stratosphere. It is more sensitive to water vapor than standard radiosondes, enabling it to measure dew point temperatures with an accuracy of 0.2 K. During the balloon’s flight, CFH collects measurements approximately every 2 seconds and has a vertical resolution of about 50 meters in the troposphere and 100 meters in the stratosphere.

Ozonesondes are in situ balloon-borne instruments used to measure ozone concentration profiles. An ozonesonde consists of an electrochemical ozone sensor connected with a meteorological radiosonde to collect ozone, temperature, pressure, and humidity measurements as it ascends through the atmosphere. It provides ozone profile measurements at a resolution of 100 to 150 m. Ozonesondes have a typical measurement rate of 0.1 Hz and can collect profiles up to around 35 km.

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 Aircraft-Integrated Meteorological Measurement System (AIMMS) is an in situ airborne sensor developed by Aventech Research, Inc. It measures the aircraft's position, altitude, temperature, relative humidity, static pressure, and three-dimensional wind vector. The system includes an Inertial Measurement Unit (IMU), Global Positioning System (GPS), Air Data Probe (ADP), and a central processing module (CPM) for processing the GPS data. AIMMS provides data at a rate of up to 20 Hz and can operate in temperatures ranging from -20 to 50 degrees Celsius.

The Atmospheric Vertical Observations of CO2 in the Earth’s Troposphere (AVOCET) is an airborne in situ spectrometer built by NASA’s Langley Research Center (LaRC). AVOCET uses a differential, non-dispersive infrared spectrometer to provide high-resolution measurements of carbon dioxide (CO2). It operates at the 4.26 μm CO2 absorption band and has a measurement frequency of 5 Hz. Since the early 1990s, AVOCET has been used in multiple field studies and has taken part in over 450 science flights.

Video cameras capture video recordings of various phenomena for research purposes. They are used on aircraft to provide continuous views of weather and terrain below the flight path. Video cameras are also employed to verify the aircraft's flight track. Additionally, they are deployed at field sites to monitor changes in vegetation, land cover, clouds, air quality, glaciers, and other Earth science phenomena.

The Polarized Imaging Nephelometer (PI-Neph) is an in situ airborne nephelometer developed at the Laboratory of Aerosols, Clouds, and Optics (LACO) at the University of Maryland Baltimore County (UMBC). PI-Neph measures the ambient scattering coefficient and phase matrix of aerosols to validate satellite aerosol observations. It simultaneously measures at 473 nm, 532 nm, and 671 nm wavelengths, with a scattering angle range of 2 to 178 degrees. PI-Neph typically records measurements every 12 or 36 seconds.

The Differential Aerosol Sizing and Hygroscopicity Spectrometer Probe (DASH-SP) is an in situ airborne spectrometer developed by Brechtel Manufacturing, Inc. It uses differential mobility analysis (DMA) combined with multiple humidification and sizing modules to measure aerosol optical size and hygroscopic growth factors. The probe can deliver faster measurement resolution compared to other hygroscopicity techniques. DASH-SP measures aerosol particles in the size range of 0.1–1.0 μm and operates at a wavelength of 532 nm. Its typical sampling rate is 1 Hz.

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 Laser Aerosol Spectrometer (LAS) is an in situ airborne spectrometer manufactured by TSI, Inc. LAS measures particle size by analyzing how particles scatter light. It operates at a 633 nm wavelength and detects particles ranging from 0.09 to 7.5 μm. LAS can deliver complete particle size distributions at a rate of 10 Hz. It is commonly used as part of aerosol instrument suites, such as NASA’s Langley Aerosol Research Group Experiment (LARGE) and NOAA’s Aerosol Microphysical Properties (AMP).

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.

Gas Chromatography/Mass Spectrometry (GC-MS) is an in situ measurement technique used to analyze volatile organic compounds (VOCs) in the atmosphere. It employs gas chromatography to separate components of an air sample, and mass spectrometry to ionize, identify, and quantify gas species. GC-MS is utilized to detect VOCs, halocarbons, hydrocarbons, and various other pollutants. It can be used for ground-based or airborne operations.

The Proton Transfer Mass Spectrometer (PTR-MS) is an in situ spectrometer used both on aircraft and ground, developed by the University of Innsbruck in Austria. It detects volatile organic compounds (VOCs) without the need for sample preparation at very low concentrations. PTR-MS employs chemical ionization mass spectrometry, enabling quick and highly sensitive VOC detection. It has a signal integration time ranging from 0.5 to 1 second.

The Georgia Institute of Technology Chemical Ionization Mass Spectrometer (GT-CIMS) is an in situ airborne spectrometer. It employs a lower-pressure flow tube reactor to detect reactive nitrogen species such as nitric acid and peroxyacetyl nitrate (PAN) in the lower atmosphere. GT-CIMS typically has a temporal resolution of 1 second and a detection limit of 10 pptv.

The Thermal-Dissociation Laser Induced Fluorescence (TD-LIF) is an in situ airborne sensor developed at UC Berkeley. It combines the TD and LIF techniques to measure nitrogen dioxide (NO2), peroxynitrates, nitric acid (HNO3), and other stable organic nitrates in the atmosphere. TD-LIF operates at a wavelength of 585 nm and typically measures at a frequency of 1 Hz.

The Scanning Mobility Particle Sizer (SMPS) is an in situ aerosol sensor that can be operated on airborne or ground-based platforms, manufactured by TSI Incorporated. SMPS uses a differential mobility analyzer (DMA) to measure the electrical mobility diameter of aerosol particles, which helps determine the size distribution. It also counts the number of aerosol particles using a condensation particle counter (CPC). It detects particles in the size range of 10-1000 nm and typically takes about 10 seconds to complete each scan.

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 Soluble Acidic Gases and Aerosols (SAGA) is an in-situ airborne sampler owned and operated by the University of New Hampshire. It uses a mist chamber and ion chromatography to collect and analyze specific aerosol species. It can provide samples of nitric acid, chloride, sulfates, nitrates, sodium, potassium, ammonium, and calcium. SAGA has a typical sampling interval of 5 to 15 minutes and a detection limit of 1 to 25 pptv, depending on the sampled species.

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 Spectrometers for Sky-Scanning, Sun-Tracking Atmospheric Research (4-STAR) is an airborne sun-sky spectrometer that measures direct solar irradiance and sky radiance. These measurements can be used to retrieve column-integrated information on aerosols, clouds, and trace gases such as aerosol optical depth, extinction, and single scattering albedo. 4-STAR operates in the 350-1650 nm wavelength range and has a typical horizontal resolution of about 100 m.

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 Single Particle Soot Photometer (SP2) is an in situ laser-induced photometer developed by Droplet Measurement Technologies. SP2 measures the black carbon (BC) mass in individual aerosol particles, along with their optical and physical properties that contain BC. The device detects aerosol particles with diameters of 200-400 nm and can analyze up to 25,000 particles per second. It operates at a sampling rate of 1 Hz and uses a wavelength of 1.06 μm. It can be used on airborne or ground-based platforms and paired with a Humidified-Dual SP2 (HD-SP2).

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 Differential Absorption Lidar (DIAL) - High Spectral Resolution Lidar (HSRL) is an airborne lidar that combines both DIAL and HSRL techniques to measure ozone and aerosols at the same time. DIAL typically operates at wavelengths of 289 nm and 300 nm to profile ozone. The HSRL modification adds a three-wavelength (355 nm, 532 nm, 1064 nm) narrowband laser to the DIAL system, enabling measurements of aerosol backscatter, extinction, depolarization, and other aerosol properties. For ozone measurements, DIAL-HSRL generally has a vertical resolution of 330 m and a temporal resolution of 90 seconds. For aerosol measurements, it features a vertical resolution of 30 m and a temporal resolution of 10 seconds.

The Whole Air Sampler (WAS) is an airborne in-situ instrument that collects air samples for analyzing trace gases, such as nonmethane hydrocarbons (NMHCs), halocarbons, alkyl nitrates, and various sulfur compounds found in the troposphere. Air samples collected by the WAS are then analyzed using gas chromatography and mass spectrometry to identify the gases present. The WAS collects samples every minute, allowing scientists to get a clear picture of the environment's chemical composition as research aircraft pass through.

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 Compact Atmospheric Multispecies Spectrometer (CAMS) is an in situ airborne spectrometer developed by the University of Colorado. CAMS uses mid-IR (3.53 μm) absorption spectroscopy to measure formaldehyde and ethane in the atmosphere. It employs difference-frequency generation (DFG) to produce mid-IR light by mixing two near-IR (1562 and 1083 nm) laser sources. CAMS provides high-precision measurements at a sampling rate of 1 Hz.

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 In Situ Airborne Formaldehyde (ISAF) is an airborne optical sensor developed by NASA's Goddard Space Flight Center (GSFC). ISAF uses laser-induced fluorescence (LIF) to measure formaldehyde throughout the troposphere and lower stratosphere. It operates at a wavelength of 353 nm and has a sampling frequency of 1 Hz. ISAF can detect formaldehyde concentrations from 10 pptv to hundreds of ppbv with an accuracy of 10%.

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 High Resolution Aerosol Mass Spectrometer (HR-AMS) is an in situ airborne mass spectrometer designed to detect aerosol composition and chemistry. It is a modified version of the Aerodyne Aerosol Mass Spectrometer developed by the University of Colorado. It measures the mass concentrations of aerosol particles ranging from 50 nm to 1 μm. HR-AMS detects aerosol composition through impaction at 600 °C, followed by electron ionization and mass spectral analysis. It has a measurement sampling rate of 1 Hz.

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 Fast Cloud Droplet Probe (FCDP) is an in situ airborne cloud probe manufactured by SPEC Inc. The FCDP measures the concentration and size of cloud droplets by detecting light scattered by particles. It detects particles with diameters ranging from 1.5 to 50 microns and typically records measurements at 1 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.

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 Aerosol Optical Properties (AOP) is an in situ airborne suite consisting of a Cavity Ringdown Spectrometer (CRDS), a Photoacoustic Absorption Spectrometer (PAS), and an Ultra-High Sensitivity Aerosol Size Spectrometer (UHSAS). It provides multi-wavelength measurements of aerosol extinction, absorption, and other properties. CRDS measures aerosol extinction at 405, 532, and 662 nm wavelengths and has an accuracy of less than 2%. PAS measures absorption at 405, 532, and 660 nm wavelengths and has a sampling rate of 1 Hz. UHSAS measures the size distribution of aerosol particles within the size range of 0.008 to 1 μm. The measurements from the combined AOP instrument package allow for the calculation of radiative forcing and atmospheric heating rates.

The Charged-couple device (CCD) Actinic Flux Spectroradiometer (CAFS) is an in situ airborne spectroradiometer developed by the Atmospheric Radiation Investigations and Measurements (ARIM) laboratory at NCAR. CAFS measures spectrally resolved ultraviolet and visible actinic flux between 280-650 nm. These measurements can be used to derive the photolysis frequencies for several chemical compounds such as ozone, nitrogen dioxide, formaldehyde, and nitrate. CAFS has a temporal resolution of 1 Hz and a wavelength resolution of about 1.8 nm at 297 nm.

The CalTech Chemical Ionization Mass Spectrometer (CIT-CIMS) is an in situ airborne single-mass spectrometer. CIT-CIMS uses CF3O-ion chemistry and compact time-of-flight and triple quadrupole spectrometers to measure specific atmospheric trace gases such as nitric acid, hydrogen peroxide, and sulfur dioxide. It was designed with rapid scan capabilities, enabling it to operate at a high temporal resolution (10 Hz) and detect a wide range of masses. CIT-CIMS is typically used for airborne observations but can also be employed for ground-based measurements.

The Differential Absorption Carbon monOxide Measurements (DACOM) is an airborne in situ spectrometer system. It uses the differential absorption technique and an infrared tunable diode laser (TDL) to collect measurements of nitrous oxide (N2O), carbon dioxide (CO2), carbon monoxide (CO), and methane (CH4) in the atmosphere. DACOM operates across the 4.7, 4.5, and 3.3 μm wavelengths to access the absorption lines for CO, N2O, and CH4. It has a measurement frequency of 5 Hz and a precision of about 1 ppbv.

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 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 Fast Cloud Droplet Probe (FCDP) is an in situ airborne cloud probe manufactured by SPEC Inc. The FCDP measures the concentration and size of cloud droplets by detecting light scattered by particles. It detects particles with diameters ranging from 1.5 to 50 microns and typically records measurements at 1 Hz.

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

The 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 Whole Air Sampler (WAS) is an airborne in-situ instrument that collects air samples for analyzing trace gases, such as nonmethane hydrocarbons (NMHCs), halocarbons, alkyl nitrates, and various sulfur compounds found in the troposphere. Air samples collected by the WAS are then analyzed using gas chromatography and mass spectrometry to identify the gases present. The WAS collects samples every minute, allowing scientists to get a clear picture of the environment's chemical composition as research aircraft pass through.

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.

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 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.

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

The 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 Picarro gas concentration analyzer is an in situ airborne or ground-based sensor manufactured by Picarro, Inc. It uses Wavelength-Scanned Cavity Ring Spectroscopy (WS-CRDS) to measure trace gases such as carbon dioxide, carbon monoxide, methane, and water vapor. For carbon dioxide measurements, the laser within Picarro operates at 1603 nm wavelength, while 1651 nm wavelength is used for methane and water vapor measurements. Picarro has a typical sampling time of 2.5 seconds. Depending on the model, Picarro can also provide measurements of carbon isotopes for gas concentrations.

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 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 Fast Cloud Droplet Probe (FCDP) is an in situ airborne cloud probe manufactured by SPEC Inc. The FCDP measures the concentration and size of cloud droplets by detecting light scattered by particles. It detects particles with diameters ranging from 1.5 to 50 microns and typically records measurements at 1 Hz.

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 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 Aircraft-Integrated Meteorological Measurement System (AIMMS) is an in situ airborne sensor developed by Aventech Research, Inc. It measures the aircraft's position, altitude, temperature, relative humidity, static pressure, and three-dimensional wind vector. The system includes an Inertial Measurement Unit (IMU), Global Positioning System (GPS), Air Data Probe (ADP), and a central processing module (CPM) for processing the GPS data. AIMMS provides data at a rate of up to 20 Hz and can operate in temperatures ranging from -20 to 50 degrees Celsius.

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

The 2D-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 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.

Rosemount Temperature Probes are in situ airborne temperature sensors manufactured by Rosemount, Inc. They provide atmospheric temperature measurements and are typically used to collect flight-level meteorological observations. Rosemount Temperature Probes consist of temperature transmitters, thermocouple sensors, resistance temperature detectors, and other temperature sensors.

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.