Question about wet deposition during snow

CMAQ
1

Hi all,

Could you help give some references on how wet deposition of gases and particles are calculated in the winter, when there is snow instead of rain. I am doing Hg simulation and found that Hg wet deposition in the winter months are underestimated. Want to explain that but need to figure out how Hg wet deposition is calculated in winter, when there is snow.

Thanks,
Lin

2

Hi, Lin-

Please checkout section 6.12 of the CMAQ users’ guide (CMAQ/DOCS/Users_Guide/CMAQ_UG_ch06_model_configuration_options.md at main · USEPA/CMAQ · GitHub) and Chapter 11 of the original CMAQ science document (CMAS: Community Modeling and Analysis System) for more information about how wet scavenging and deposition is calculated.

Below-cloud scavenging by snow is not explicitly calculated at this time. However, wet removal of gas and aerosol species occurs according to a parameterization that is based on precipitation rate, Henry’s law coefficient (for gases) and total water content (i.e., the sum of cloud water, rain water, graupel, ice, and snow).

Please let me know if you have any other questions.

Kathleen

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