Very high surface PM2.5 concentrations

[Krishna Kedia]

Hi everyone,

I am observing very high PM2.5 surface concentrations in my WRF-Chem simulations using FINN v2.5. I am running MOZART-MOSAIC 4 BIN (chem_opt = 202) option with biomass_burn_opt = 2 (BIOMASSB_MOZC) and namelists are attached.

Upon analysing the ebu_pm25 values, I see that the plumerise module allocates half of the total input emissions (i.e. ebu_in_pm25) to the surface and the remaining half to the rest of the model layers. Is my understanding correct? 
I am observing surface concentration values several times higher than the observations which points towards too high input emissions at the surface. So, is there a more suitable method to distribute the emissions vertically instead of splitting them halfway in smoldering and flaming phases?

I am using the standard mapping: 
 'oc->OC;aerosol', 'bc->BC;aerosol', 'pm25->PM25 + -1.*OC + -1.*BC;aerosol',
'pm10->PM10 + -1.*PM25;aerosol'

However, I also saw this mapping in one of the discussions.
'oc -> 0.24*PM25 + 0.3*PM10;aerosol', 'bc -> 0.01*PM25 + 0.08*PM10;aerosol',
'sulf -> -0.01*PM25 + 0.02*PM10;aerosol',
'pm25 -> 0.36*PM25;aerosol','pm10 -> -0.61*PM25 + 0.61*PM10;aerosol'

Is there a reason why only ~50% of original PM2.5 is being used in this mapping and none of the original OC, BC emissions are? I am just wondering if there's supporting literature that justifies using scaled down PM2.5 emissions as input to the model.

Any insights on potential causes of very high surface PM2.5 from fire emissions using FINNv2.5 would be greatly appreciated. 

Thanking you
Krishna

[Gabriele Pfister]

Hello  Krishna

the standard mapping you are using is fine and the one that should be used for the latest FINN versions. I am not sure what you mean by "very high" and high compared to what but keep in mind that fire emissions are in general very uncertain. Have you compared FINNv2.5 to FINNV1.5 or other inventories such as QFED? 

As for the plumerise code, the factor between smoldering and flaming and the plumerise depend on the  biome burned and  ambient environmental conditions, it is not a constant factor. You can look up these papers which describe the plumerise scheme that has been integrated in WRF-Chem:  

Freitas, S. R., Longo, K. M., Chatfield, R., Latham, D.,
Silva Dias, M. A. F., Andreae, M. O., Prins, E., Santos, J. C.,
Gielow, R., and Carvalho Jr., J. A.: Including the sub-grid
scale plume rise of vegetation fires in low resolution atmo-
spheric transport models, Atmos. Chem. Phys., 7, 3385–3398,
doi:10.5194/acp-7-3385-2007, 2007

Freitas, S. R., Longo, K. M., Trentmann, J., and Latham, D.: Tech-
nical Note: Sensitivity of 1-D smoke plume rise models to the
inclusion of environmental wind drag, Atmos. Chem. Phys., 10,
585–594, doi:10.5194/acp-10-585-2010, 2010

Gabi

--

================================
Gabriele Pfister

Atmospheric Chemistry Observations & Modeling (ACOM) Lab

NSF National Center for Atmospheric Research (NCAR)

Email: pfi...@ucar.edu

Work Phone: +1 303 497 2915

Web: https://staff.ucar.edu/users/pfister

[Krishna Kedia]

Hi Dr Pfister,

Thank you for your inputs. Based on your suggestion I am performing a simulation with FINNv1.5. However, I am unsure on how to incorporate gridded products like GFED, QFED or GFAS in WRF-Chem because fire_emiss utility isn't compatible for those. If you have any ideas on how fire EI sensitivity beyond FINN could be explored in WRF-Chem (or any studies that have done so) that would be quite valuable. I could only find Wu et al 2025 but details of how QFED was implemented in WRF-Chem is elusive in this paper.

I also have a follow up question regarding species mapping. FINNv2.5 has HONO emissions available, but there is no ebu_in_hono for any of the biomass_burn_opt options which means there is no way to incorporate the effect of wildfire HONO emissions in the model. Is that correct?
I am curious because I came across this paper on importance of HONO in defining the plume photochemistry in initial few hours of the fire (Peng et. al. 2020). So I was wondering if it is worth exploring HONO effects on O3 photochemistry in wildfire plumes using WRF-Chem.

Looking forward to hearing your thoughts on either of the questions.

Thank you
Krishna  

[Gabriele Pfister]

Hello Krishna

unfortunately we cannot help you in using other fire emission inventories in WRF-Chem but maybe someone else in the community has code to do so and is willing to share it?

As for adding HONO. You would have to modify the code for it, i.e. add the new emissions to the registry.chem and then also in the respective plumerise modules. It should not be too hard, you only have to duplicate what is currently done for other species. 

Best luck, 

Gabi