In:
Atmospheric Measurement Techniques, Copernicus GmbH, Vol. 13, No. 10 ( 2020-09-30), p. 5149-5163
Abstract:
Abstract. Column-averaged dry-air mole fractions of carbon dioxide (XCO2) and
methane (XCH4) measured by a solar viewing portable Fourier transform
spectrometer (FTS, EM27/SUN) have been characterized and validated by
comparison using in situ profile measurements made during the transfer
flights of two aircraft campaigns: Korea-United States Air Quality Study
(KORUS-AQ) and Effect of Megacities on the Transport and Transformation of Pollutants at Regional and Global Scales (EMeRGe). The aircraft flew over
two Total Carbon Column Observing Network (TCCON) sites: Rikubetsu, Japan
(43.46∘ N, 143.77∘ E), for the KORUS-AQ campaign and
Burgos, Philippines (18.53∘ N, 120.65∘ E), for the EMeRGe
campaign. The EM27/SUN was deployed at the corresponding TCCON sites during
the overflights. The mole fraction profiles obtained by the aircraft over
Rikubetsu differed between the ascending and the descending flights above
approximately 8 km for both CO2 and CH4. Because the spatial
pattern of tropopause heights based on potential vorticity values from the
ERA5 reanalysis shows that the tropopause height over the Rikubetsu site was
consistent with the descending profile, we used only the descending profile
to compare with the EM27/SUN data. Both the XCO2 and XCH4 derived
from the descending profiles over Burgos were lower than those from the
ascending profiles. Output from the Weather Research and Forecasting Model
indicates that higher CO2 for the ascending profile originated in
central Luzon, an industrialized and densely populated region about 400 km
south of the Burgos TCCON site. Air masses observed with the EM27/SUN
overlap better with those from the descending aircraft profiles than those
from the ascending aircraft profiles with respect to their properties such
as origin and atmospheric residence times. Consequently, the descending
aircraft profiles were used for the comparison with the EM27/SUN data. The
EM27/SUN XCO2 and XCH4 data were derived by using the GGG2014
software without applying air-mass-independent correction factors (AICFs).
The comparison of the EM27/SUN observations with the aircraft data revealed
that, on average, the EM27/SUN XCO2 data were biased low by 1.22 %
and the EM27/SUN XCH4 data were biased low by 1.71 %. The resulting
AICFs of 0.9878 for XCO2 and 0.9829 for XCH4 were obtained for
the EM27/SUN. Applying AICFs being utilized for the TCCON data (0.9898 for
XCO2 and 0.9765 for XCH4) to the EM27/SUN data induces an
underestimate for XCO2 and an overestimate for XCH4.
Type of Medium:
Online Resource
ISSN:
1867-8548
DOI:
10.5194/amt-13-5149-2020
DOI:
10.5194/amt-13-5149-2020-supplement
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2020
detail.hit.zdb_id:
2505596-3
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