You are here:
Precipitation Partitioning Across Grey Zone Scales using Scale-Aware Cloud Formulations: Impacts of Aerosols
Citation:
Glotfelty, T., K. Alapaty, J. He, P. Hawbecker, X. song, AND G. Zhang. Precipitation Partitioning Across Grey Zone Scales using Scale-Aware Cloud Formulations: Impacts of Aerosols. 2019 Meteorology and Climate - Modeling for Air Quality Conference, Davis/Sacramento, CA, September 11 - 13, 2019.
Impact/Purpose:
The next generation modeling system for environmental modeling (air quality, water and soil pollution) uses global scales with mesh refinements and lacks epa-centric cloud science. A state of the art cloud scheme was developed in-house to meet the needs of the next generation modeling system. An existing modeling system was used to validate the science and also study how particulate matter and weather interacts.
Description:
The Weather Research & Forecasting model with Aerosol Cloud Interactions has been developed to investigate the scale dependency of aerosol-cloud interactions (ACI) across the “grey zone” scales for grid scale clouds (Morrison Scheme) and subgrid scale clouds (Multi-Scale Kain-Fritsch scheme) that include cloud microphysical processes. The impacts of ACI are examined across regions in the eastern and western U. S. at 36, 12, 4, and 1 km grid spacing for short-term periods during the summer of 2006. ACI impacts are determined by comparing simulations with current climatological aerosol levels to simulations where aerosol levels have been reduced by 90%. The aerosol cloud lifetime effect is found to be the dominant ACI process leading to suppressed precipitation in regions of the eastern U.S., while regions in the western U. S. experience offsetting impacts on precipitation from the cloud lifetime and thermodynamic invigoration effects of aerosols. Generally, the cloud lifetime effect weakens with decreasing grid spacing due to a decrease in the relative importance of autoconversion compared to accretion. Subgrid scale ACI are dominant at 36 km while grid scale ACI are dominant at 4 and 1 km, however, grid scale and subgrid scale ACI are comparable at 12 km. The equivalent impacts of grid scale and subgrid scale processes at 12 km lead to peculiar behavior of ACI, indicating competition for available moisture by the grid-scale and subgrid-scale cloud formulations. The work implies including subgrid scale convective cloud microphysics and ice/mixed phase cloud ACI processes may be necessary in weather and climate models to study ACI.