In:
Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 21, No. 14 ( 2021-07-22), p. 11113-11132
Kurzfassung:
Abstract. We measured the global distribution of tropospheric N2O
mixing ratios during the NASA airborne Atmospheric Tomography (ATom)
mission. ATom measured concentrations of ∼ 300 gas species and
aerosol properties in 647 vertical profiles spanning the Pacific, Atlantic,
Arctic, and much of the Southern Ocean basins, nearly from pole to pole,
over four seasons (2016–2018). We measured N2O concentrations at 1 Hz
using a quantum cascade laser spectrometer (QCLS). We introduced a new spectral
retrieval method to account for the pressure and temperature sensitivity of
the instrument when deployed on aircraft. This retrieval strategy improved
the precision of our ATom QCLS N2O measurements by a factor of three (based
on the standard deviation of calibration measurements). Our measurements show that most
of the variance of N2O mixing ratios in the troposphere is driven by
the influence of N2O-depleted stratospheric air, especially at mid- and
high latitudes. We observe the downward propagation of lower N2O mixing
ratios (compared to surface stations) that tracks the influence of
stratosphere–troposphere exchange through the tropospheric column down to
the surface. The highest N2O mixing ratios occur close to the Equator,
extending through the boundary layer and free troposphere. We observed
influences from a complex and diverse mixture of N2O sources, with
emission source types identified using the rich suite of chemical species
measured on ATom and the geographical origin calculated using an
atmospheric transport model. Although ATom flights were mostly over the
oceans, the most prominent N2O enhancements were associated with
anthropogenic emissions, including from industry (e.g., oil and gas), urban sources, and biomass
burning, especially in the tropical Atlantic outflow from Africa. Enhanced
N2O mixing ratios are mostly associated with pollution-related tracers
arriving from the coastal area of Nigeria. Peaks of N2O are often
associated with indicators of photochemical processing, suggesting possible
unexpected source processes. In most cases, the results show how
difficult it is to separate the mixture of different sources in the atmosphere,
which may contribute to uncertainties in the N2O global budget. The
extensive data set from ATom will help improve the understanding of N2O
emission processes and their representation in global models.
Materialart:
Online-Ressource
ISSN:
1680-7324
DOI:
10.5194/acp-21-11113-2021
DOI:
10.5194/acp-21-11113-2021-supplement
Sprache:
Englisch
Verlag:
Copernicus GmbH
Publikationsdatum:
2021
ZDB Id:
2092549-9
ZDB Id:
2069847-1
