Large value of LNO

[Xin Zhang]

Dear Mary,

I got two kinds of simulated LNO and LNO2 at 2015/08/31 19:00:00.

Both of them is calculated by taking the difference of vertical profiles between simulations with and without lightning.

The simulated duration is 1 day (check_single.pdf, 2015/08/31 00:00:00 - 2015/09/01 00:00:00) and 5 months with nudging (check_month.pdf, 2015/04/01 00:00:00 - 2015/09/01 00:00:00) respectively.

(a) and (b) in attachments are two selected places in US.

As you can see, profiles of 1 day simulation looks normal. But profiles of 5 months is strange, LNO is very large when compared with LNO2. Is this related with the removal of LNO or other elements?

The chemical mechanism is RACM2_Berkeley2. Here's my setting related to lightning:

&physics
 lightning_option                   = 11,    
 iccg_method                        = 2,    
 cldtop_adjustment                  = 0,    
 lightning_dt                       = 72,    
 lightning_start_seconds            = 648,    
 flashrate_factor                   = 2.0,    
&chem
 lnox_opt                           = 1,
 n_ic                               = 500,
 n_cg                               = 500,

Best regards,

Xin

[Mary Barth]

Xin,

I agree that LNO looks to have a high mixing ratio. I suspect the 5-month simulation has higher mixing ratios because trace gases have accumulated in the upper troposphere, especially if the location is within the anticyclone associated with the North American Monsoon.

Have you evaluated these results yet? Both the lightning flash rate and the NO2 should be compared with observations. Lightning flash rate data can be obtained from ground networks (some local LMAs, the NLDN, ENTLN) or satellite, noting that the parameterization predicts total flash rate and partitions it into CG and IC flashes. And, as you know, aircraft and satellite data (OMI) can help with NO2.

My opinion is that n_ic and n_cg equal to 500 is too high. I would suggest 200 moles NO/flash based on Pollack et al. (2016). See the attached figure for LNOx production estimates from various publications. 

-- Mary

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[Xin Zhang]

Hi Mary,

Thank you for your explanation and suggestions!

How about the lifetime of NO in the upper troposphere (UT) in WRF-Chem? As mentioned in Nault et al. (2016), the UT NOx day time lifetime is ~3 h near thunderstorms and ~0.5–1.5 days away from thunderstorms. If the lifetime isn't 2-8 days assumed in Schumann & Huntrieser (2007), then how did LNO accumulate in the UT in WRF-Chem?

I've compared 2015/08/31 results (the one of 5 months' simulation, 500 mol/flash) with ENTLN total flashes and OMI tropospheric NO2 column. The 'BEHR_ColumnAmountNO2Trop' in the figure is calculated by combining WRF-Chem NO2 profile, OMI slant column density of NO2, and cloud information. It looks like BEHR_ColumnAmountNO2Trop is much larger than OMI_ColumnAmountNO2Trop.

By the way, I attached the time series of NO, NO2 and O3 of the level 24 (~300 hPa). NO is always very large in most areas and O3 increases as NO2 decreases after 10:00 UTC. It's related to the oxidization of NO by an organic peroxide and the production of O3 by photolyzation. But, the large value of NO throughout the time seems strange.

 month.zip

Best regards,

Xin

[Xin Zhang]

Hi Mary,

After changing n_ic and n_cg to 200 and flashrate_factor to 1.0, I got the similar large LNO.

Attachments:

1. MJJA total flashes (ENTLN and WRF)

2. 20140612 total flashes (16:00 - 17:30)

3. mp4 files: LNO and LNO2 profile at different places (2014/06/12 17:30 )

[Xin Zhang]

Finally, I find that the mozbc didn't set the initial and boundary condition successfully.

It caused the little value of O3 which result in large NO and small NO2.

After wrfinput and wrfbdy files are generated correctly, it works now.

Regards,
Xin