G2301-m

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G2301-f

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OSCAR lab

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OSCAR portable

TBD

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NOAA Picarro

The Picarro G2401m is a commerical instrument that measures CO2, CH4, CO, and H2O. The analyzer is based on Wavelength-Scanned Cavity Ring Down Spectroscopy (WS-CRDS), a time-based measurement utilizing a near-infrared laser to measure a spectral signature of the molecule. Gas is circulated in an optical measurement cavity with an effective path length of up to 20 kilometers. A patented, high-precision wavelength monitor makes certain that only the spectral feature of interest is being monitored, greatly reducing the analyzer’s sensitivity to interfering gas species, and enabling ultra-trace gas concentration measurements even if there are other gases present. As a result, the analyzer maintains high linearity, precision, and accuracy over changing environmental conditions with minimal calibration required.

The measurement software of the NOAA Picarro has been modified to have a shorter measurement interval (~1.2 seconds instead of ~2.4 seconds) by reducing the number of scans of the CO spectroscopic peak and therefore yielding a less-precise CO measurement (1σ on 1-2 second measurements is ~9 ppb instead of ~4 ppb). The instrument was also modified to have a lower cell pressure set point (80 torr instead of 140 torr) to allow it to operate across the full pressure altitude range of the DC8 without requiring upstream pressurization of the sample stream.

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In Situ Measurements of Aerosol Microphysical Properties

Five instruments, two nucleation-mode aerosol size spectrometers (NMASS; Williamson et al., 2018), two ultra-high sensitivity aerosol spectrometers (UHSAS; Kupc et al., 2018), and a laser aerosol spectrometer (LAS) comprise the AMP package. The AMP package provides particle size distributions with up to one-second time resolution for dry aerosol particles between 0.003 and 4.8 µm in diameter. Details of methods, uncertainties, and data products from the AMP package are in Brock et al. (2019). During ATom, the instruments were used to investigate how particles in the remote atmosphere influence climate by examining the origin of small particles in the remote atmosphere and their growth to sizes where they can affect clouds and the sources, characteristics, and distribution of soil dust and sea-spray particles, and 3) the importance long-range transport from human and natural sources on background aerosol properties.

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Harvard Tracer Suite

HTS is composed of two instruments based on absorption of near-infrared laser radiation in high finesse optical cavities. A Picarro G2401-m analyzer based on wavelength-scanned cavity ring-down spectroscopy (CRDS) measures CO2, CH4, and CO concentrations at 2-second intervals. A Los Gatos 913-0014 EP analyzer based on off-axis integrated cavity output spectroscopy (ICOS) measures N2O and CO concentrations at 1-second intervals. Extensive modifications have been applied to these commercial analyzers for flight and include vibration isolation, temperature control, additional flow control and pumping capacity for high-altitude sampling, sample drying, and in-flight calibrations using WMO-traceable compressed gas standards to verify stable and accurate performance throughout the full DC-8 flight envelope.

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Alpha Jet Ozone Instrument

Alpha Jet (O3) Ozone instrument details

Measurements of ozone (O3) mixing ratios are performed using a commercial O3 monitor (2B Technologies Inc., model 205 (http://www.twobtech.com/model_205.htm)) based on ultraviolet (UV) absorption techniques and modified for flight worthiness. The dual-beam instrument uses two detection cells to simultaneously measure UV light intensity differences between O3-scrubbed air and un-scrubbed air to give precise measurements of O3. The monitor has been modified by upgrading the pressure sensor and pump to allow measurements at high altitudes, including a lamp heater to improve the stability of the UV source, and the addition of heaters, temperature controllers and vibration isolators to control the monitor’s physical environment.

Ozone inlet

The air intake is through Teflon tubing (perfluroalkoxy-polymer, PFA) with a backward-facing inlet positioned on the underside of the instrument wing pod. Air is delivered through a 5 µm PTFE (polytetrafluroethylene) membrane filter to remove fine particles prior to analysis.

Ozone instrument calibrations:

The O3 monitor has undergone thorough instrument testing in the laboratory to determine the precision, linearity and overall accuracy. Eight-point calibration tests (ranging from 0 – 300 ppbv) are typically performed before and after each flight using an O3 calibration source (2B Technologies, model 306 referenced to the WMO scale). The calibration of all 2B Technologies Ozone Calibration Sources is traceable to NIST through an unbroken chain of comparisons and is sent back to the vendor annually for calibration. Calibrations in a pressure- and temperature-controlled environmental chamber have also been carried out using the O3 calibration source over the pressure range 200 - 800 mbar and temperature range -15 to +25 ⁰C; typical pressure and temperature ranges observed in the wing-mounted instrument pod during flight.

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Harvard University Picarro Cavity Ring Down Spectrometer

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In-Situ Measurements of Aerosol Optical Properties

Three instruments, a cavity ringdown (CRD) aerosol extinction spectrometer, a photoacoustic absorption spectrometer (PAS), and an ultra-high sensitivity aerosol size spectrometer (UHSAS) comprise the AOP package. The AOP package provides multi‐wavelength, multi-RH aerosol extinction and absorption measurements with fast response and excellent accuracy and stability on aircraft platforms. The instruments will also characterize the optics of black carbon (BC) mixing state, brown carbon, and water uptake of aerosol. Aerosol asymmetry parameter, needed for radiative transfer modeling, will be calculated from dry and humidified particle size distributions.

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