Modeling lightning-NO<sub><i>x</i></sub> chemistry on a sub-grid scale in a global chemical transport model
For the first time, a plume-in-grid approach is implemented in a chemical transport model (CTM) to parameterize the effects of the nonlinear reactions occurring within high concentrated NO<sub><i>x</i></sub> plumes from lightning NO<sub><i>x</i></sub>...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-05-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/16/5867/2016/acp-16-5867-2016.pdf |
| Summary: | For the first time, a plume-in-grid approach is implemented in a chemical
transport model (CTM) to parameterize the effects of the nonlinear reactions
occurring within high concentrated NO<sub><i>x</i></sub> plumes from lightning NO<sub><i>x</i></sub>
emissions (LNO<sub><i>x</i></sub>) in the upper troposphere. It is characterized by a set
of parameters including the plume lifetime, the effective reaction rate
constant related to NO<sub><i>x</i></sub>–O<sub>3</sub> chemical interactions, and the
fractions of NO<sub><i>x</i></sub> conversion into HNO<sub>3</sub> within the plume. Parameter
estimates were made using the Dynamical Simple Model of Atmospheric Chemical
Complexity (DSMACC) box model, simple plume dispersion simulations, and the
3-D Meso-NH (non-hydrostatic mesoscale atmospheric model). In order to
assess the impact of the LNO<sub><i>x</i></sub> plume approach on the NO<sub><i>x</i></sub> and O<sub>3</sub>
distributions on a large scale, simulations for the year 2006 were
performed using the GEOS-Chem global model with a horizontal resolution of
2° × 2.5°. The implementation of the LNO<sub><i>x</i></sub>
parameterization implies an NO<sub><i>x</i></sub> and O<sub>3</sub> decrease on a large scale
over the region characterized by a strong lightning activity (up to 25 and
8 %, respectively, over central Africa in July) and a relative increase
downwind of LNO<sub><i>x</i></sub> emissions (up to 18 and 2 % for NO<sub><i>x</i></sub> and
O<sub>3</sub>, respectively, in July). The calculated variability in NO<sub><i>x</i></sub> and
O<sub>3</sub> mixing ratios around the mean value according to the known
uncertainties in the parameter estimates is at a maximum over continental
tropical regions with ΔNO<sub><i>x</i></sub> [−33.1, +29.7] ppt and
ΔO<sub>3</sub> [−1.56, +2.16] ppb, in January, and ΔNO<sub><i>x</i></sub> [−14.3, +21] ppt and ΔO<sub>3</sub> [−1.18,
+1.93] ppb, in July, mainly depending on the determination of the
diffusion properties of the atmosphere and the initial NO mixing ratio
injected by lightning. This approach allows us (i) to reproduce a more
realistic lightning NO<sub><i>x</i></sub> chemistry leading to better NO<sub><i>x</i></sub> and O<sub>3</sub>
distributions on the large scale and (ii) to focus on other improvements to
reduce remaining uncertainties from processes related to NO<sub><i>x</i></sub> chemistry
in CTM. |
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| ISSN: | 1680-7316 1680-7324 |