The thompson-eidhammer (TE) microphysics scheme has been selected for use in the NOAA next generation 3-KM storm-scale rapid refresh forecast system (RRFS)

The TE microphysics uses water-friendly (WFA) and ICE-friendly (IFA) aerosol number concentrations from the gocart monthly climatologies and overly simplified empirical emissions (based on the climatologies) to activate cloud and ICE number concentrations. This method constrains the model such that IT can only be used to study the effects of aerosols on clouds and precipitation in terms of the background aerosol climatology. In addition, there is an aerosol inconsistency between microphysics and radiation processes in RRFS: while the microphysics uses the gocart aerosol climatology, the radiation uses climatology (2003-2013) based on the MERRA2 aerosol reanalysis product. We recently developed a simple and yet more realistic aerosol emission approach, which includes sea-salt, dust, and biomass burning emission modules as well as anthropogenic aerosol emissions, to provide realistic aerosol emissions for WFA and IFA. This approach was applied in a global configuration of the unified forecast system (UFS) weather model, and was shown to improve forecasts of precipitation over polluted regions such as europe and north america (LI ET AL. 2023). We also recently developed the RRFS-smoke and dust (RRFS-SD) aerosol model, which is slated to be part of the operational RRFS V1 implementation. We updated the aerosol direct feedback to use the SUM of the prognostic smoke and dust tracers with the MERRA2 aerosol climatology, and significantly improved the forecast of radiation fluxes, near-surface temperature and wind speed during wildfire events (LI ET AL. 2022). This smoke and dust direct feedback methodology has been accepted for the operational RRFS V1 operational implementation. In this proposal, we will use the prognostic wildfire smoke, dust, sea salt and anthropogenic aerosol emission from RRFS-SD together with MERRA2 climatology to represent the WFA and IFA for the TE microphysics indirect feedback. Thus, the aerosol representation will be consistent between microphysics and radiation processes. The prognostic aerosol emissions will be used to more realistically constrain droplet and ICE activation in microphysics, and the microphysics will be tuned accordingly. Since the main source of IFA is dust, which is already advected in RRFS, we may simply convert dust into IFA, and set IFA as a diagnostic variable instead of a prognostic tracer to save computing time. Subsequent tuning of cloud fraction, turbulence, and convection parameterization will be performed in order to achieve an optimal numerical weather prediction in RRFS, since they are undoubtedly tuned to compensate for the currently deficient aerosol climatologies. A complete team of physics suite developers at NOAA/GSL is willing to support this work, which will benefit both air quality and short-range weather forecasts. IT is expected to implement the proposed aerosol representation for microphysics in the RRFS V2 operational configuration. This proposal is being submitted to the fire weather competition, FW-2. The total funding requested by this proposal is $447,875 for the two years.