Artificial reduction of inj in GFAS within HEMCO and potential solutions

[jinlx]

Name and Institution (Required)

Name: Lixu Jin
Institution: University of Montana

Description of your issue or question

In the process of integrating GFAS fire emissions into models using HEMCO, fire injection heights are artificially reduced. This reduction occurs when the 0.1x0.1 degree GFAS fire emission heights are averaged down to fit the model's coarser resolution. Pixels without fires are assigned emission heights of 0, which skews the average injection height downwards when these zeros are included in the averaging process.

This issue leads to inaccurately low plume injection heights in model simulations using GFAS, potentially affecting the modeled distribution and transport of fire emissions and their impacts on air quality and climate.

A temporary workaround involves performing a weighted averaging of the injection heights by flux amount, derived from Dr. Jeff Pierce's insights. This method corrects the artificial reduction of injection heights by accounting for the actual emission strengths of fire pixels, as demonstrated in Jin et al. (2023). The corresponding scripts are provided in ipynb/py format.

A better way is to write a HEMCO extension to do so from the discussion with Drs. Jeff Pierce, Dylan Millet, and Lu Hu. This solution would ensure that the averaging process accurately reflects the spatial distribution and intensity of fire emissions across different resolutions. We are thinking about if it is easy to correct the issue and make it in the GEOS-Chem standard version.

Thanks,
Lixu

Scripts to work around the issue:
GFAS_injs_ipynb.txt
GFAS_injs_py.txt

Reference:
Jin, L., Permar, W., Selimovic, V., Ketcherside, D., Yokelson, R. J., Hornbrook, R. S., Apel, E. C., Ku, I.-T., Collett Jr., J. L., Sullivan, A. P., Jaffe, D. A., Pierce, J. R., Fried, A., Coggon, M. M., Gkatzelis, G. I., Warneke, C., Fischer, E. V., and Hu, L.: Constraining emissions of volatile organic compounds from western US wildfires with WE-CAN and FIREX-AQ airborne observations, Atmos. Chem. Phys., 23, 5969–5991, https://doi.org/10.5194/acp-23-5969-2023, 2023

[yantosca]

Thanks for the issue @jinlx. We will await your PR.

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