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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Volume 11, issue 1 | Copyright
Atmos. Meas. Tech., 11, 127-140, 2018
https://doi.org/10.5194/amt-11-127-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 10 Jan 2018

Research article | 10 Jan 2018

Measurement of atmospheric CO2 column concentrations to cloud tops with a pulsed multi-wavelength airborne lidar

Jianping Mao1, Anand Ramanathan1, James B. Abshire2, Stephan R. Kawa2, Haris Riris2, Graham R. Allan3, Michael Rodriguez3, William E. Hasselbrack3, Xiaoli Sun2, Kenji Numata2, Jeff Chen2, Yonghoon Choi4, and Mei Ying Melissa Yang4 Jianping Mao et al.
  • 1Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD 20740, USA
  • 2NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USA
  • 3Sigma Space Inc., Lanham, MD 20706, USA
  • 4NASA Langley Research Center, Hampton, VA 23681, USA

Abstract. We have measured the column-averaged atmospheric CO2 mixing ratio to a variety of cloud tops by using an airborne pulsed multi-wavelength integrated-path differential absorption (IPDA) lidar. Airborne measurements were made at altitudes up to 13km during the 2011, 2013 and 2014 NASA Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) science campaigns flown in the United States West and Midwest and were compared to those from an in situ sensor. Analysis of the lidar backscatter profiles shows the average cloud top reflectance was ∼ 5% for the CO2 measurement at 1572.335nm except to cirrus clouds, which had lower reflectance. The energies for 1µs wide laser pulses reflected from cloud tops were sufficient to allow clear identification of CO2 absorption line shape and then to allow retrievals of atmospheric column CO2 from the aircraft to cloud tops more than 90% of the time. Retrievals from the CO2 measurements to cloud tops had minimal bias but larger standard deviations when compared to those made to the ground, depending on cloud top roughness and reflectance. The measurements show this new capability helps resolve CO2 horizontal and vertical gradients in the atmosphere. When used with nearby full-column measurements to ground, the CO2 measurements to cloud tops can be used to estimate the partial-column CO2 concentration below clouds, which should lead to better estimates of surface carbon sources and sinks. This additional capability of the range-resolved CO2 IPDA lidar technique provides a new benefit for studying the carbon cycle in future airborne and space-based CO2 missions.

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Precise global measurement of CO2 in the Earth’s atmosphere is needed to understand carbon–climate feedbacks. Ideally we would measure from space 24/7 over all land and sea surfaces, in all-sky conditions, clouds, haze or dust and achieve near 100 % usable data. NASA-GSFC has developed a laser instrument to measure CO2 from an aircraft flying at over 40 000 feet as a satellite precursor. Here we demonstrate this measurement capability, highlighting data in the presence of a variety of clouds.
Precise global measurement of CO2 in the Earth’s atmosphere is needed to understand...
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