Intercomparison and evaluation of satellite peroxyacetyl nitrate observations in the upper troposphere–lower stratosphere
Peroxyacetyl nitrate (PAN) is an important chemical species in the troposphere as it aids the long-range transport of NO<sub><i>x</i></sub> and subsequent formation of O<sub>3</sub> in relatively clean remote regions. Over the past few decades observations from...
| Main Authors: | , , , , , , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-11-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/16/13541/2016/acp-16-13541-2016.pdf |
| Summary: | Peroxyacetyl nitrate (PAN) is an important chemical species in the
troposphere as it aids the long-range transport of NO<sub><i>x</i></sub> and subsequent
formation of O<sub>3</sub> in relatively clean remote regions. Over the past few
decades observations from aircraft campaigns and surface sites have been used
to better understand the regional distribution of PAN. However, recent
measurements made by satellites allow for a global assessment of PAN in the
upper troposphere–lower stratosphere (UTLS). In this study, we investigate
global PAN distributions from two independent retrieval methodologies, based
on measurements from the Michelson Interferometer for Passive Atmospheric
Sounding (MIPAS) instrument, on board Envisat from the Institute of
Meteorology and Climate Research (IMK), Karlsruhe Institute of Technology, and
the Department of Physics and Astronomy, University of Leicester (UoL).
Retrieving PAN from MIPAS is challenging due to the weak signal in the
measurements and contamination from other species. Therefore, we compare the
two MIPAS datasets with observations from the Atmospheric Chemistry
Experiment Fourier transform spectrometer (ACE-FTS), in situ aircraft data
and the 3-D chemical transport model TOMCAT. MIPAS shows peak UTLS PAN
concentrations over the biomass burning regions (e.g. ranging from 150 to
> 200 pptv at 150 hPa) and during the summertime Asian monsoon as
enhanced convection aids the vertical transport of PAN from the lower
atmosphere. At 150 hPa, we find significant differences between the two
MIPAS datasets in the tropics, where IMK PAN concentrations are larger by
50–100 pptv. Comparisons between MIPAS and ACE-FTS show better agreement
with the UoL MIPAS PAN concentrations at 200 hPa, but with mixed results
above this altitude. TOMCAT generally captures the magnitude and structure of
climatological aircraft PAN profiles within the observational variability
allowing it to be used to investigate the MIPAS PAN differences. TOMCAT–MIPAS
comparisons show that the model is both positively (UoL) and negatively (IMK)
biased against the satellite products. These results indicate that satellite
PAN observations are able to detect realistic spatial variations in PAN in
the UTLS, but further work is needed to resolve differences in existing
retrievals to allow quantitative use of the products. |
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| ISSN: | 1680-7316 1680-7324 |