CO2, CH4, CO and H2O WS-CRD Spectrometer 


Picarro G2401-mc WS-CRDS

QCL Carbon Monoxide (CO) and Nitrous Oxide (N₂O)


Aerodyne CS-108

O3 Chemiluminescence


1-Channel Fast Response Chemiluminescence Ozone

Vacuum UV Resonance Fluorescence CO


Aero-Laser VURF CO Instrument

Picarro WS-CRDS CO2, Methane, CO, and H2O Instrument

The Picarro G2401-mc utilizes wavelength scanned cavity ring down spectroscopy, a technique wherein the exponential decay of optical extinction within a resonant cavity is modified by molecular absorption. This decay time is called a ring-down time. Over a specific wavelength range, ring-down times are proportional to the concentration of the absorbing species. 

Model G2401-mc provides time series of the dry mole fraction of carbon dioxide (CO2), methane (CH4) and carbon monoxide, and mole fraction of water vapor (H2O). Sampling rates typically range from 0.25 - 0.77 Hz.

Acquired in 2017, the instrument was modified in collaboration with Picarro in 2018 to add several lower cell pressure modes of operation. This added functionality allows optimization of the trade off between high altitude operation (~15km) and resolution (both temporal and mole fraction). The table below shows the expected performance specifications for each mode.


G2401-m performance metrics for 3 operational modes

The G2401-mc is certified for operation on both the NCAR/NSF Gulfstream V and the NCAR/NSF C-130. More information can also be found here.


QCL Carbon Monoxide (CO) and Nitrous Oxide (N₂O)

This Aerodyne QCL Carbon Monoxide (CO), Nitrous Oxide (N2O) and water vapor instrument was acquired in 2017. The quantum cascade laser (QCL) sensor operates on the principle of direct absorbance of infrared radiation near 4.6 µm. The optical spectrometer consists of a thermoelectrically cooled QCL laser source, alignment and wavelength calibration optics, photodetector, and an approximately 0.5 L Herriott cell that provides a 76-m path length. The optical bench is housed in an unsealed, vibrationally isolated aluminum box.

To improve accuracy of airborne observations, the Core Atmospheric Tracers group implemented a continuous purge of the optical housing using dry air scrubbed in order to remove residual CO and thereby eliminate the contribution of ambient pressure CO and N2O absorbance to the background spectral fit.

Upon implementing this configuration change and optimization of spectral fit parameters for improved CO quantification, the instrument underwent environmental chamber and null test flight characterization to confirm adequate performance in airborne applications. This instrument was first deployed during the 2018 WE-CAN field campaign. In 2019 it was certified for GV operation in order to undergo high altitude GV flight tests in preparation for the 2022 ACCLIP experiment. In laboratory and airborne operation, a 1-s precision of 0.3 ppbv is observed for each measurand. During airborne operations the instrument typically performs with a ± 1 ppbv overall uncertainty in N2O and CO determinations.

During airborne operations the instrument typically performs with a ± 1 ppbv overall uncertainty in N2O and CO determinations.


Frank Flocke helping set up the Aerodyne QCL instrument for characterization in the EOL Environmental Chamber.

Calibration Methods: 

Hourly in-flight calibrations of 2-4 minute duration are typically conducted with 1-2 working standards and in coordination with other sensors. Working standard concentrations are traceable to WMO network by laboratory calibration against NOAA GMD primary standard suite maintained by RAF.


Single Channel Fast Response Chemiluminescence O3 

The HAIS single channel NCAR chemiluminescence instrument provides state of the art precision and time response (1-5 Hz) for a broad range of atmospheric science research campaigns. Observational experiments focusing on dynamical processes take advantage of the 1-channel ozone instrument. Example applications include investigation of trade-wind cloud system development during the CSET campaign, investigations of dynamical processes requiring tracers of stratospheric air composition (e.g., PREDICT, CONTRAST, ACCLIP, T-REX, and CGWaveS), and employed as a conserved micrometeorological cloud entrainment tracer (e.g., RICO, DYCOMS-II). When an airborne experiment includes a full atmospheric chemical payload, the HAIS 1-channel ozone instrument is incorporated into the 2-channel NOx or NOy instrument and supported by the NOx and Ozone Measurement Group


Teresa Campos conducts pre-flight preparations of fast ozone instrument


Aero-Laser Vacuum-UV Resonance Fluorescence CO

Slated for eventual retirement from the suite of NSF LAOF supported measurements, the Aero-Laser fluorescence CO instrument has served the NSF community for over 18 years, with a precision of 2 ppbv. The QCL instrument provides a better precision and time response, but at the cost of a larger footprint. Where possible, the QCL has replaced the VURF sensor for most NSF LAO community measurement requests.


Aero-Laser VURF CO Instrument





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Core Atmospheric Tracers