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The Weather Research and Forecasting Model with Aerosol–Cloud Interactions (WRF-ACI): Development, Evaluation, and Initial Application
Citation:
Glotfelty, T., Kiran Alapaty, J. He, P. Hawbecker, X. Song, AND G. Zhang. The Weather Research and Forecasting Model with Aerosol–Cloud Interactions (WRF-ACI): Development, Evaluation, and Initial Application. Monthly Weather Review. American Meteorological Society, Boston, MA, 147(5):1491-1511, (2019). https://doi.org/10.1175/MWR-D-18-0267.1
Impact/Purpose:
Particulate matter, PM, (aerosol) pollution impacts clouds and weather at short and long timescales. In particular, PM impacts on warm period clouds such as thunderstorm clouds is currently missing in almost all models. New science has been developed to incorporate this missing science into a weather model used for air quality and hydrology research at EPA. We find that PM impacts warm period cloud processes resulting in an increase of shortwave cloud radiative forcing by about ~3 W/m2 a strong forcing modulating weather at small and large timescales.
Description:
The Weather Research and Forecasting Model with Aerosol Cloud Interactions (WRF-ACI) is developed for studying aerosol effects on grid-scale and subgrid-scale clouds using common aerosol activation and ice nucleation formulations and double moment cloud microphysics in a scale-aware subgrid-scale parameterization scheme. Comparisons of both the standard WRF and WRF-ACI models’ results for a summer season against satellite and reanalysis estimates show that the WRF-ACI system improves the simulation of cloud liquid and ice water paths. Correlation coefficients for nearly all evaluated parameters are improved, while other variables show slight degradation. Results indicate a strong cloud lifetime effect from current climatological aerosols increasing domain average cloud liquid water path and reducing domain average precipitation as compared to a simulation with aerosols reduced by 90%. Increased cloud top heights indicate a thermodynamic invigoration effect, but the impact of thermodynamic invigoration on precipitation is overwhelmed by the cloud life time effect. A combination of cloud lifetime and cloud albedo effects increases domain average shortwave cloud forcing by ~3.0 W m−2. Subgrid scale clouds experience a stronger response to aerosol levels, while grid scale clouds are subject to thermodynamic feedbacks because of the design of the WRF modeling framework. The magnitude of aerosol indirect effects is shown to be sensitive to the choice of autoconversion parameterization used in both the grid-scale and subgrid-scale cloud microphysics, but spatial patterns remain qualitatively similar. These results indicate that the WRF-ACI model provides the community with a computationally efficient tool for exploring aerosol cloud interactions.
URLs/Downloads:
DOI: The Weather Research and Forecasting Model with Aerosol–Cloud Interactions (WRF-ACI): Development, Evaluation, and Initial Application
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