Publikationsdatum:
2018-07-24
Beschreibung:
Recent satellite measurements of a layer of enhanced nitrous oxide (N 2 O) in the mesosphere-lower thermosphere (MLT) from the Atmospheric Chemistry Experiment-Fourier Transform Spectrometer have suggested an unexpected, minor high-altitude production source. Here we report the development of a mechanism and the first model simulations, which can explain the formation of this MLT N 2 O layer. N 2 O production occurs primarily via a reaction route involving the excitation of N 2 from secondary electrons. Simulations using the Whole Atmosphere Community Climate Model, with external forcing from the Global Airglow model, quantitatively reproduce the observed vertical, latitudinal, and seasonal N 2 O variations. Sensitivity results indicate that photoelectrons are far more important than previously predicted, causing approximately two thirds of global N 2 O production in the MLT. Energetic electron precipitation over high latitudes provides the remaining contribution. Solar cycle analysis reveals N 2 O enhancements of up to ×2 at solar maximum compared to solar minimum. ©2018. The Authors.
Print ISSN:
0094-8276
Digitale ISSN:
1944-8007
Thema:
Geologie und Paläontologie
,
Physik
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