Lightning NO fixes upper-air ozone in CMAQ
Adding lightning nitric oxide to CMAQv5.2 raises underestimated mid/upper-tropospheric ozone and nitrate rain, especially when flashes are timed with observations.
Source
Simulating lightning NO production in CMAQv5.2: performance evaluations
Study at a glance
- Design
- Computational / modelling — CMAQv5.2 April–September 2011 runs with and without lightning-NO schemes
- N
- Base plus three LNO schemes on a 12 km CONUS domain; not an observational sample N
- Population
- US atmospheric chemistry (ozone, NOx, nitrate wet deposition) in CMAQv5.2
- Outcome
- Improved mid/upper-tropospheric ozone and nitrate deposition when lightning NO is included
Structured fields used in claim comparison tables when every cited study has a complete layer.
Inspect source passages
Lightning NO fixes upper-air ozone in CMAQ
These passages occur verbatim in the stored paper text. They support the points listed below; they do not verify every statement in the explanation.
The domain is 299 by 459 cells at 12 km grid spacing.
The model domain consists of 299 north–south grid cells by 459 east–west grid cells utilizing 12 km × 12 km horizontal grid spacing, 35 vertical layers with varying thickness extending from the surface to 50 hPa and an approximately 10 m midpoint for the lowest (surface) model layer.
Simulations cover April to September 2011.
The simulation time period covers the months from April to September 2011 with a 10 d spin-up period in March.
What they did
Authors ran CMAQv5.2 (CB6, 12 km, April–September 2011) with Base (no LNO) and three lightning-NO schemes (mNLDN, hNLDN, pNLDN), then compared DM8HR ozone, NOx, DISCOVER-AQ P-3B profiles, sondes, and NADP nitrate wet deposition.
What they found
Without LNO, mid/upper tropospheric ozone and domain-wide nitrate wet deposition (except the Pacific Coast) are too low. Hourly lightning timing (hNLDN) often best matches surface ozone in the Northeast. Where the Base already overpredicts surface ozone, adding LNO can worsen bias while still raising correlation—other NOx sources remain wrong.
The limits
What it doesn't show
Schemes inherit WRF convection errors. pNLDN is for forecasts without observed flashes, not a substitute for process truth. One US summer 2011 cannot generalize globally, and vertical LNO placement remains uncertain.
Key terms
- LNO
- Nitric oxide immediately produced by lightning flashes (later NOx).
- NLDN
- National Lightning Detection Network providing flash observations.
- hNLDN / mNLDN / pNLDN
- CMAQ lightning schemes using hourly observed, monthly, or precipitation-based flashes.
- DM8HR ozone
- Daily maximum 8-hour ozone mixing ratio.
- NADP
- National Atmospheric Deposition Program wet-deposition network.
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Quiz yourself
Without LNO, CMAQ ozone aloft was often:
Common questions
Why add lightning NO?
It is a growing share of NOx as anthropogenic emissions fall, and it makes ozone aloft.
Does it always help surface ozone?
No; if the Base is already high, LNO can increase bias.
What about nitrate rain?
All LNO schemes raise underestimated wet NO3− deposition.
Which scheme for forecasting?
pNLDN, which uses convective precipitation instead of observed flashes.
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