Summary:

The authors implement a cloud-height based flash rate scheme into the regional model CHIMERE and then evaluate the impact of lightning-NOx production on ambient ozone and NO2 concentrations, ozone profiles, the tropospheric OH burden, and the methane lifetime.

The magnitude of the lightning-NOx source is biased high, which has implications for the LNOx increment, OH burden, and CH4 lifetime. Thus, I think the authors need to re-run the simulation with a lower LNOx source, and then spend more time evaluating the lightning parameterization.  As the LNOx scheme is not new, it would help if they modify it to better simulate the seasonal cycle. Thus, I would suggest rejecting the manuscript – at least for now.

Main Comments:

The evaluation of the flash rate scheme needs to be enhanced.

L8 & L202: 8.82 Tg N yr-1 is too high of a production rate for just the Northern Hemisphere. It is consistent with ~15 Tg N yr-1 for the globe, a value that is well outside of the typically cited 2-8 Tg N yr-1 range.  You need to justify why you chose that value or choose a lower value.

L119: I don’t understand why the flash rate you obtain is so high given that you’ve scaled it to match a satellite product. What satellite data are you comparing to?  What is the estimated flash rate of the satellite-based observation? What is the Northern Hemisphere flash rate after applying the scaling factor? 

L210: You note that the model does not capture the seasonality of flash rates.  Could you compare the monthly model flashes for 0 to 35 N with OTD/LIS climatology.  It would also be interesting to compare the flash rates with the diel OTD/LIS climatology.  Is this a problem with the model’s cloud top heights or with the scheme itself?

L125: Typically, the “land-based” parameterization is used for grid boxes near land as well, i.e. continental convection extends a few grid boxes downwind of land.

L132: Could you give values of Hf for 0, 30, and 60 N.

L135: What is the ratio of CG to IC flashes that you obtain over the NH with this parameterization?

L140: Include a plot showing the percent of CG and IC LNOx emissions input into each 1-km layer for land and water over the tropics and midlatitudes.

L187: By what metric is the flash rate in agreement with the ISS-LIS data set?  How was the ISS-LIS May-August “climatology” obtained? What years were used? Was there a correction for viewing time? Was there a correction for detection efficiency?  How many total flashes are there during May-August (and the year) for ISS-LIS and the model.  How do the flash totals compare to the OTD/LIS climatology for this period.

L189: Yes, putting too many flashes in the tropics is a fairly well known bias of cloud-height based schemes.  Do you have any suggestions as to how this bias could be reduced while still retaining the cloud-height scheme?

You need to add comparisons with OMI/TROPOMI and SHADOZ.

 L214: The impact of lightning-NOx on atmospheric composition is larger in the mid- and upper-troposphere than it is at the surface, yet you begin with a surface comparison.  I would suggest saving that comparison for last.

You compare with surface concentrations and profiles.  You should also compare model NO2 with satellite-retrieved columns from OMI (January-December 2018)  or TROPOMI (April – December 2018).

The SHADOZ ozonesondes are a wonderful source of profile information and should be compared to.  Despite the acronym, there are a number of Northern Hemisphere sites.

It should be more revealing to calculate biases as a function of season as opposed to annually.

You need to improve the model simulation. This will add value to the comparison with observations.

L315-320: CH4 lifetime of 4.89 years is considerably less than range of 7-14.   Obviously, your large LNOx source is contributing to this low bias in lifetime.

You need to be careful with generalized statements.

There are numerous reasons why a model may have a high-or-low bias in ozone at the surface.  The magnitude of the LNOx source plays only a small role here.

Stratosphere-troposphere exchange is poorly resolved in this model due to its low model top.  This may make comparison with mid- and high-latitude ozone profiles problematic.

Minor Comments:

 L24: The range you cite here (8 to 4000 moles NO / flash) is for individual flashes.  Estimates of the mean production per flash are usually between 125 and 500 moles per flash.

L73: Is 998 hPa the mean surface pressure?

L74: A 200 hPa top layer is when evaluating O3 profiles.  What is the pressure of the model top?  Clearly, this model was designed for tropospheric chemistry. 

L160 and L201: Is this a climatological flash data set from ISS-LIS?  If so, what years does it cover?

L192: Are you saying that the modeled tropopause height is too high in the tropics?  If yes, please show.

L200: Why are you comparing May-August flash rates with the annual mean?

L207: You need to be clear here.  8.8 Tg N yr-1 for the NH is consistent with ~15 Tg N yr-1 for the globe, a value that is well outside of the 2-8 range but below 25.

L214: Why do you think emissions are underestimated?

L265: Do any of these studies give the NH burden? Or do they just list the total burden?

L269: Are you comparing to climatological ozone sondes or ozone sondes from 2018?  You should consider comparing to individual SHADOZ sondes as several of the sites are located in NH.

L279: Stratosphere-troposphere exchange is one cause for the very low biases you are seeing in the extratropics and at high latitudes. 

Grammatical Comments:

L19: such as lightning --- such as lightning and soil-NOx emissions

L24: 4000 mol NO per flash --- 4000 mol NO per individual flash

L25: suggest a value of 250 --- suggest a mean value of 250

L42: most frequently used CTH scheme --- the frequently used CTH scheme

L75: for chemical mechanisms --- for the chemical mechanism

L91: deep convection fluxes --- deep convective fluxes

L160: … but ISS-LIS only sees a small subset of total flashes …

L197: inconsistancies --- inconsistencies.

L223: represents a spatial variation --- varies spatially

L225: rest part of NH --- rest of the NH

L233: 10-25 ppbv enhancement of annual mean surface ozone due to lightning –

Figure 3d: 500-200 hPa or 500-300 hPa.  Caption is not consistent with figure.

I share the concerns of the reviewer who posted a comment on Nov. 19th, so I will not repeat them here.

One additional major concern: The scientific content of the paper is very low; it is not clear to me what new insights were found as a result of this analysis relative to what is already in the scientific literature. Therefore, I recommend that the authors consider publishing their manuscript in Geoscientific Model Development (https://www.geoscientific-model-development.net/) instead of ACP. GMD is meant for description papers of significant model development.