"reactivity relative to HNO3" in ASX_DATA_MOD.F

CMAQ
1

What does the parameter “ar” represent in the ASX_DATA_MOD.F file, and how is it calculated? Is it used to calculate dry deposition of gas? How do I get this parameter when adding a new species?

2

The document on “How to Cite CMAQ” includes a reference for the M3DRY “Surface Exchange Processes”
https://www.epa.gov/cmaq/how-cite-cmaq

Surface Exchange Processes

M3DRY

Pleim, J. E., Ran, L., Appel, W., Shephard, M. W., & Cady‐Pereira, K. (2019). New bidirectional ammonia flux model in an air quality model coupled with an agricultural model. Journal of Advances in Modeling Earth Systems , 11(9): 2934-2957. doi: 10.1029/2019MS001728

There are two routines for ASX_DATA_MOD.F, the one that has ar is under the M3DRY option.

  Real            :: ar       ( ltotg )        ! reactivity relative to HNO3
  Real            :: dif0     ( ltotg )        ! molecular diffusivity [cm2/s]
  Real            :: lebas    ( ltotg )        ! Le Bas molar volume [cm3/mol ]
  Real            :: meso     ( ltotg )        ! Exception for species that 
                                                   ! react with cell walls. fo in 
                                                   ! Wesely 1989 eq 6.

I looked up one of the papers referenced in the code and found
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2015GL065839

It looks like ar is defined for each chemical species, and some of the species include notations of the literature source.

DATA subname( 68), dif0( 68), ar( 68), meso( 68), lebas( 68) / 'SVALK1 ',0.0514, 4572.8, 0.0, 280.5 / ! Pye et al. doi:10.5194/acp-17-343-2017; rel. reactivity per J. Bash

https://acp.copernicus.org/articles/17/343/2017/

4

Thank you for your help !