Mid-latitude Airborne Cirrus Properties Experiment

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

The Chemical Ionization Mass Spectrometer was developed by NOAA. This instrument can take high-precision measurements of gases such as nitric acid, water vapor, and hydrochloric acid. This instrument was designed to take measurements accurately in the boundary layer. The detection limit for CIMS is in the parts-per-trillion range, and the temporal resolution is 50s.

The Single Particle Soot Photometer (SP2) is laser-induced photometer manufactured by Droplet Measurement Technologies. SP2 provides measurements of black carbon (BC) mass content of individual aerosol particles as well as the optical and physical properties of the particles containing BC. SP2 can be utilized on airborne or ground-based platforms and can be deployed with a paired Humidified-Dual SP2 (HD-SP2). It can detect aerosol particles with a diameter size of 200-400 nm and can measure 25,000 particles/second.

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The High Volume Particle Sampler, also known as the High Volume Precipitation Spectrometer (HVPS), measures particle size distributions and obtains particle images in the size range of about 0.1 cm to 6 cm. It is an open-path instrument located on the outside of the aircraft, typically below the wing. A laser sheet throws a shadowgraph image of the hydrometeor (cloud droplets or ice crystals) in the sample volume on a photodiode array. As the hydrometeor moves through the sample volume, this optical array records the moving shape and a two-dimensional picture can be recorded. At an air speed of 100 m/s, the sample volume is 310 l/s. The recorded images can be analyzed for size distributions, number concentrations, and further cloud properties detailed below. Hydrometeors in the range of 0.3−19.2 mm can be fully recorded at a 150 μm resolution; larger particles can only be sized along the direction of flight. In order to keep the pixel resolution along the flight path constant, the system clock frequency is adjusted according to the detected True Air Speed (TAS) by the data system itself. The maximum clock frequency for the HVPS is 240 kHz. The HVPS data recorded during this project has 400 m m resolution along the flight path.

The Closed-path Laser Hygrometer (CLH) is a tunable diode laser hygrometer that was developed by the University of Colorado along with the Jet Propulsion Laboratory (JPL). The CLH measures water vapor via second-harmonic absorption spectroscopy. It provides measurements approximately every 1.5 seconds and is typically flown on commercial aircraft, making it an ideal instrument to collect tropospheric water vapor measurements.

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 the 254 nm wavelength allowing it to calculate the ozone number density due to the accurate ozone absorption cross section at that wavelength. It has a sampling rate of 2 Hz and a horizontal resolution of 100 to 200 meters at typical research flight speeds.

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 consists of 5 parallel condensation nucleus counters (CNCs) that are used to sample particles within the 3 to 60 nm diameter range. It can be equipped on multiple types of aircraft and is ideal for sampling cirrus clouds in the upper atmosphere. NMASS provides fast time response measurements at a temporal resolution of 10 Hz.

The Cloud Particle Imager (CPI) is an airborne imager manufactured by SPEC Inc. CPI collects high resolution (2.3 μm pixel size) images of cloud particles that pass through its sample volume. It uses a charge-coupled device (CCD) camera that operates at 810 nm to record images and can take up to 74 frames per second with a refresh rate of 40 Hz. The imagery from CPI can be used to derive microphysical properties such as particle size and habit.

The Focused Cavity Aerosol Spectrometer (FCAS) is an in situ airborne optical particle counter designed by Particle Measuring Systems, Inc. FCAS measures the light scattered by the individual aerosol particles to determine the particle size distribution. It can detect aerosol particles in the size range of 0.06 to 2 μm and can operate at altitudes up to 20 km. Typically, FCAS provides measurements at a sampling rate of 10 seconds.

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 measure water vapor in the atmosphere. DLH operates in the near-infrared region at around 1.4 μm and has a measurement frequency of 100 Hz. It has the capability to provide accurate measurements of water vapor even while flying through clouds.

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 consists of two instruments with distinctly 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 is able to identify and limit systematic errors while in flight. It provides measurements of water vapor mixing ratio from 1 to 1000 ppmv at a frequency of 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 that operates at 1.37 μm to measure atmospheric water vapor in the upper troposphere and lower stratosphere. JLH has a minimum spatial resolution of 25 m and has a detection range of 1 to 500 ppmv. It has a typical sampling rate of 1 Hz and can provide measurements at a precision of 0.05 ppmv.

The Aircraft Laser Infrared Absorption Spectrometer (ALIAS) is a high-resolution spectrometer developed by the Jet Propulsion Laboratory (JPL) to fly aboard the NASA ER-2. ALIAS takes real-time measurements of various nitrogen, carbon, and hydrogen compounds, including NO2, CH4, and HCl. Its ability to be flown at high altitudes paired with its fast sample rate makes the ALIAS an ideal instrument to study atmospheric chemistry processes within polar stratospheric clouds (PSC’s).

The Meteorological Measurement System (MMS) is an in situ airborne instrument used for measuring atmospheric state parameters. MMS provides high resolution and accurate measurements of atmospheric pressure, temperature, and wind direction and speed immediately around the plane. Additional parameters can be derived such as 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. FCDP measures the concentration and size of cloud droplets by detecting the amount of light scattered by the particles. It measures particles within the diameter size range of 1.5-50 microns and has a typical measurement frequency of 1 Hz.

The 2D-Stereo Particle Probe (2D-S) is an in situ airborne optical imaging probe developed by SPEC Inc. The 2D-S uses two diode laser beams to produce stereo cloud particle images through linear array shadowing. Through the imagery, cloud particle size distribution, particle number concentration, and ice/liquid water content can be determined. It has a resolution of 10 µm and can measure hydrometeors in the 25-1280 µm range.