An airborne amplitude-modulated 1.57 μm differential laser absorption spectrometer: simultaneous measurement of partial column-averaged dry air mixing ratio of CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; and target range

Sakaizawa, Daisuke; Kawakami, S.; Nakajima, M.; Tanaka, Tomoaki; Morino, Isamu; Uchino, Osamu

doi:10.5194/amt-6-387-2013

Cited by 16 publications

(7 citation statements)

References 29 publications

(33 reference statements)

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“…Instruments based on differential absorption LIDAR (DIAL) have been performing pioneering measurements of SO 2 at volcanoes over 20 years ago 43 44 , yet have not become a standard approach to measure volcanic gases. DIAL is increasingly used in global warming science to measure path averaged, ambient CO 2 concentrations 45 46 47 48 and has even been used to map a CO 2 plume at an industrial site 49 . Recently, a range-resolving DIAL has successfully measured 2-D volcanic CO 2 concentration profiles in the Campi Flegrei volcanic zone (Italy) from which CO 2 fluxes have been inferred 50 .…”

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A new frontier in CO2 flux measurements using a highly portable DIAL laser system

Queiβer

Granieri

Burton

2016

Sci Rep

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Volcanic CO2 emissions play a key role in the geological carbon cycle, and monitoring of volcanic CO2 fluxes helps to forecast eruptions. The quantification of CO2 fluxes is challenging due to rapid dilution of magmatic CO2 in CO2-rich ambient air and the diffuse nature of many emissions, leading to large uncertainties in the global magmatic CO2 flux inventory. Here, we report measurements using a new DIAL laser remote sensing system for volcanic CO2 (CO2DIAL). Two sites in the volcanic zone of Campi Flegrei (Italy) were scanned, yielding CO2 path-amount profiles used to compute fluxes. Our results reveal a relatively high CO2 flux from Campi Flegrei, consistent with an increasing trend. Unlike previous methods, the CO2DIAL is able to measure integrated CO2 path-amounts at distances up to 2000 m using virtually any solid surface as a reflector, whilst also being highly portable. This opens a new frontier in quantification of geological and anthropogenic CO2 fluxes.

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confidence: 99%

A new frontier in CO2 flux measurements using a highly portable DIAL laser system

Queiβer

Granieri

Burton

2016

Sci Rep

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“…The absorption spectra of atmospheric CO 2 has been studied by satellite 9,10 and ground-based passive spectrometers 11 , as a means to obtain the CO 2 distribution. IPDA measurements from aircraft have also been demonstrated [12][13][14][15] as part of efforts to develop spaceborne lidars. Converting absorption measurements to CO 2 concentrations requires precise spectroscopic knowledge, which is typically derived from controlled laboratory experiments [16][17][18][19] .…”

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Spectroscopic measurements of a CO2 absorption line in an open vertical path using an airborne lidar

Ramanathan

Mao

Allan

et al. 2013

Applied Physics Letters

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We used an airborne pulsed integrated path differential absorption (IPDA) lidar to make spectroscopic measurements of the pressure-induced line broadening and line center shift of atmospheric carbon dioxide (CO 2 ) at the 1572.335 nm absorption line. We scanned the lidar wavelength over 13 GHz (110 pm) and measured the absorption lineshape at 30 discrete wavelengths in the vertical column between the aircraft and ground. A comparison of our measured absorption lineshape to calculations based on HITRAN shows excellent agreement with the peak optical depth accurate to within 0.3%. Additionally, we measure changes in the line center position to within 5.2 MHz of calculations, and the absorption linewidth to within 0.6% of calculations. These measurements highlight the high precision of our technique, which can be applied to suitable absorption lines of any atmospheric gas.Optical remote sensing of trace gases in the atmosphere is widely used to understand terrestrial processes 1-4 . However, the accuracy of such remote sensing measurements can be limited by the accuracy of the spectroscopy of the absorption lines 5 . Lab-based precision laser spectroscopy measurements are difficult to validate in the open atmosphere with passive remote sensing instruments 4 owing to complications arising from clouds and aeorosols 6,7 and uncertainties in the air mass factor 8 . In this letter, we report laser absorption spectroscopy measurements of carbon dioxide (CO 2 ) made in an open vertical atmospheric path. Using an aircraftmounted pulsed lidar, we study the effect of pressure on the 1572.335 nm (6359.967 cm −1 ) line of the CO 2 vibrational-rotational band.The absorption spectra of atmospheric CO 2 has been studied by satellite 9,10 and ground-based passive spectrometers 11 , as a means to obtain the CO 2 distribution. IPDA measurements from aircraft have also been demonstrated 12-15 as part of efforts to develop spaceborne lidars. Converting absorption measurements to CO 2 concentrations requires precise spectroscopic knowledge, which is typically derived from controlled laboratory experiments [16][17][18][19] . Our present work extends spectroscopic investigations to conditions closer to those of atmospheric remote sensing.The lidar instrument, primarily designed for measuring the tropospheric CO 2 concentration in the column beneath the aircraft 15,20 , was flown aboard the NASA DC-8 during the ASCENDS 21 (Active Sensing of CO 2 Emissions over Nights, Days and Seasons) campaign in 2011, at altitudes ranging from 2 to 13 km above sea level. The 1572.335 nm absorption line was chosen based on its optimal line strength and temperature sensitivity 22 . A schematic of our lidar instrument is shown in FIG. 1(a) and the relevant system parameters tabulated (table I). Our lidar source was a distributed feedback diode laser amplified by an erbium-doped fiber amplifier (EDFA) operating in a master oscillator power amplifier configuration. The laser was gated with an acousto-optic modulator (AOM) to transmit a train of discrete puls...

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“…The ranging of the hard-target was possible by utilizing the phase difference between the monitored and the received signal. Because CW signals were used for this ranging, there was folding ambiguity [24]. A priori information on the range-i.e., if the information has the precision of c/(2f m ), where c is the speed of light and f m is the modulation frequency-solves this problem.…”

Section: Preliminary Configuration and Resultsmentioning

confidence: 99%

Calibration and Improved Speckle Statistics of IM-CW Lidar for Atmospheric CO2 Measurements

et al. 2020

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An intensity modulated, continuous-wave (IM-CW) integrated path differential absorption (IPDA) fiber-based lidar is developed herein for measuring atmospheric carbon dioxide (CO2). There are two main challenges in improving measurement accuracy, which have not been given enough attention in the previous research: one is that temperature sensitivity in optical components causes biases, due to the drift of component characteristic, and the other is that speckle noise deteriorates the signal-to-noise ratio. With the components thermally controlled, a target calibration accuracy of 0.003 dB is realized, corresponding to a CO2 concentration precision of better than 1 ppm for a 1 km path. A moving diffuser can reduce speckle noise by time averaging. In this paper, movement of the diffuser is substituted by the perturbation of the emitted laser beam by using a vibrating motor mounted on the optical antenna. Selecting on and off wavelengths with a small wavelength separation can improve the correlation between two laser speckle fields. These improvements result in the improved accuracy of the IPDA lidar system. Finally, the lidar performance was analyzed after the improvements described above were implemented. The diurnal variations of the atmospheric CO2 concentration using a topographic target were performed, and the results showed good agreement with the data measured by an in situ sensor. The root mean square (rms) of the deviation between the IPDA lidar and the in situ sensor was less than 1.4%.

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An airborne amplitude-modulated 1.57 μm differential laser absorption spectrometer: simultaneous measurement of partial column-averaged dry air mixing ratio of CO<sub>2</sub> and target range

Cited by 16 publications

References 29 publications

A new frontier in CO2 flux measurements using a highly portable DIAL laser system

A new frontier in CO2 flux measurements using a highly portable DIAL laser system

Spectroscopic measurements of a CO2 absorption line in an open vertical path using an airborne lidar

Calibration and Improved Speckle Statistics of IM-CW Lidar for Atmospheric CO2 Measurements

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