Multispecies Assessment of Factors Influencing Regional CO₂ and CH₄ Enhancements During the Winter 2017 ACT‐America Campaign

Abstract

Diagnosing carbon dioxide ( CO2) and methane ( CH4) fluxes at subcontinental scales is complicated by sparse observations, limited knowledge of prior fluxes and their uncertainties, and background and transport errors. Multispecies measurements in flasks sampled during the wintertime ACT‐America campaign were used for background characterization and source apportionment of regional anthropogenic CO2 and CH4 fluxes when ecosystem CO2 exchange is likely to be least active. Continental background trace gas mole fractions for regional enhancements are defined using samples from the upper troposphere and assessed using model products. Trace gas enhancements taken from flask samples in the lower troposphere with background levels subtracted out are then interpreted to inform CO2 and CH4 enhancement variability in the eastern United States. Strong correlations between CO2 and CH4 enhancements in the Midwestern and Mid‐Atlantic United States indicated colocated anthropogenic sources. Oil and natural gas influence was also broadly observed throughout the entire observational domain. In the Midwestern United States, agricultural influence on CO2 and CH4 enhancement variability was evident during above‐average wintertime temperatures. Weaker correlations between CO2 and anthropogenic tracer enhancements in the Southeastern United States indicated potentially nonnegligible wintertime ecosystem CO2 exchange, with biogenic tracers indicating more active surface processing than other regions. These whole‐air flask samples illuminated significant regional CO2 and CH4 sources or sinks during Atmospheric Carbon and Transport‐America (ACT‐America) and can provide additional information for informing regional inverse modeling efforts.

Autonomous Airborne Mid-IR Spectrometer for High Precision Measurements of Ethane during the NASA ACT-America Studies

“…As with our dynamic LOD estimates, these dynamic TMU estimates truly reveal the instrument performance range over the full range of aircraft maneuvers. The comparisons of the CAMS ethane measurements with the flask package (PFP) measurements acquired by NOAA on the same aircraft (Baier et al, 2019), discussed in Section 3.3, further supports the lower range of our TMU estimates. In 2 of the 3 field deployment phases the median TMU as a % of ambient values falls in the 4 to 5.2% range, which as will be seen in Section 3.3 yields nearly identical CAMS ethane values as the PFP values to within 4.5 ± https://doi.org/10.5194/amt-2020-210 Preprint.…”

“…When sampling plumes, by contrast, one would need to know the exact temporal filling profile of the PFP system in order to modify the CAMS averaging kernel. This is further discussed by Baier et al (2019). In plumes without taking this into account, one can thus obtain fast averages that are both too high, too low, and in agreement with the https://doi.org/10.5194/amt-2020-210 Preprint.…”

“…Both the C-130 and B200 were deployed with similar payloads and coordinated flight paths to study the transport of greenhouse gases by mid latitude weather systems e.g. Pal et al, (2020), quantification of regional, season fluxes of CO2 (Feng et al, 2019;and Zhou et al, 2020) and CH4 Barkley et al, (2019a,b), and evaluation of the Orbiting Carbon Observatory-2 (OCO-2) satellite Bell et al, (in press).…”

Autonomous airborne mid-infrared spectrometer for high-precision measurements of ethane during the NASA ACT-America studies

“…Collectively, all the ethane standard comparisons resulted in agreement between our direct absorption values and the assigned cylinder values in the range between −1.2 % and + 4.8 %. It is important to note that the NOAA standards were used by Baier et al (2019) in their programmable flask package (PFP) ethane measurements. Figure 9a shows an orthogonal distance linear regression (ODR) plot of our direct absorption results (with the daily corrections applied) integrated over the PFP time base as a function of the PFP ethane results for the entire spring 2018 fourth deployment.…”

“…As with our dynamic precision estimates, these dynamic TMU estimates truly reveal the instrument performance over the full range of aircraft maneuvers. The comparisons of the CAMS ethane measurements with the flask package (PFP) measurements acquired by NOAA on the same aircraft (Baier et al, 2019), discussed in Sect. 3.3, further support the lower range of our TMU estimates.…”