Initializing WRF-Chem with previous run (auxinput12)

[cwaigl]

I use WRF-Chem with biomass burning, using prep-chem-sources.exe and convert_emiss.exe to generate a wrffirechemi_d01 file. I'm using GOCART -- chem_opt = 300, and no other extra anthropogenic or biogenic emissions. My runs are typically 72 (or 48) hours, and I am trying to intialize any given run with the last hourly dataset of the previous run's output via chem_in_opt = 1. My wrfout files are 24 hourly frames per file, so the previous day's run produced three files with 24 frames and one file with 1 frame.

I've used the following two approaches, but in either case I am a) not sure the initialisation data is used at all; b) whenever it looks that it might have been used (that is, wildfire smoke related species are distributed in places outside the fire locations for the new run), the distribution at early hours in the new output differs noticeably from the distribution at the end of the previous run; c) in any event, the first frame of the new run does not contain any initialization data (though levels of the species I'm interested in are not 0 -- just very low levels): data only appears in the second frame (hour 1).

• Approach 1: I linked the last wrfout file of the previous run (containing a lone last hour) to wrf_chem_input_d01 and set the following in namelist.input:
  
  auxinput12_inname = 'wrf_chem_input_d<domain>',
  auxinput12_interval_m = 86400,
  io_form_auxinput12 = 2,
  frames_per_auxinput12 = 1

• Approach 2: I linked all previous wrfout files to wrf_chem_input_d01_yyyy-mm-dd_HH:MM:SS and set the following in namelist.input:
  
  auxinput12_inname = 'wrf_chem_input_d<domain>_<date>',
  auxinput12_interval_m = 86400,
  io_form_auxinput12 = 2,

I'm not sure what to set frames_per_auxinput12 to in the second case as I have three files with 24h and one file -- the one I presumed is being used -- with 1h. But on the other hand, maybe WRF is looking for the previous file?

Any input on how to correctly configure this initialization would be welcome, in particular how to start the initialized background at the first frame of the new output file (or what to do otherwise).