Coupling spectral‐bin cloud microphysics with the MOSAIC aerosol model in WRF‐Chem: Methodology and results for marine stratocumulus clouds

Abstract

Aerosol‐cloud interaction processes can be represented more physically with bin cloud microphysics relative to bulk microphysical parameterizations. However, due to computational power limitations in the past, bin cloud microphysics was often run with very simple aerosol treatments. The purpose of this study is to represent better aerosol‐cloud interaction processes in the Chemistry version of Weather Research and Forecast model (WRF‐Chem) at convection‐permitting scales by coupling spectral‐bin cloud microphysics (SBM) with the MOSAIC sectional aerosol model. A flexible interface is built that exchanges cloud and aerosol information between them. The interface contains a new bin aerosol activation approach, which replaces the treatments in the original SBM. It also includes the modified aerosol resuspension and in‐cloud wet removal processes with the droplet loss tendencies and precipitation fluxes from SBM. The newly coupled system is evaluated for two marine stratocumulus cases over the Southeast Pacific Ocean with either a simplified aerosol setup or full‐chemistry. We compare the aerosol activation process in the newly coupled SBM‐MOSAIC against the SBM simulation without chemistry using a simplified aerosol setup, and the results show consistent activation rates. A longer time simulation reinforces that aerosol resuspension through cloud drop evaporation plays an important role in replenishing aerosols and impacts cloud and precipitation in marine stratocumulus clouds. Evaluation of the coupled SBM‐MOSAIC with full‐chemistry using aircraft measurements suggests that the new model works realistically for the marine stratocumulus clouds, and improves the simulation of cloud microphysical properties compared to a simulation using MOSAIC coupled with the Morrison two‐moment microphysics.

Urbanization-induced land and aerosol impacts on sea breeze circulation and convective precipitation

“…The WRF-Chem-SBM model used in this study is based on Gao et al (2016), with updates in both WRF-Chem (Grell et al, 2005;Skamarock et al, 2008) and the SBM (Khain et al, 2004;Fan et al, 2012). The SBM version coupled with WRF-Chem is a fast version with https://doi.org/10.5194/acp-2020-411 Preprint.…”

“…Compared with the original WRF-Chem model which uses two-moment bulk microphysics schemes, besides the advancements in cloud microphysical process calculations in SBM, the aerosol-cloud interaction processes which impact both cloud and aerosol properties are physically improved. These processes are aerosol activation, resuspension, and in-cloud wetremoval (Gao et al, 2016). Theoretically both aerosol and cloud processes can be more realistically simulated compared with the original WRF-Chem, particularly under the conditions of complicated aerosol compositions and aerosol spatial heterogeneity.…”

“…This would result in improved simulations of both ACI and aerosol-radiation interactions (ARI). Following on Gao et al (2016) where the model was applied to a warm stratocumulus cloud case, we apply the model to the deep convective storm case in this study.…”

“…In this study, we aim at understanding how the changes in Houston land cover and anthropogenic aerosols as a result of urbanization modify the sea-breeze induced convective storm and precipitation jointly and respectively. To answer the science question, we employ the Chemistry version of Weather Research and Forecast (WRF) model coupled with the spectralbin microphysics (WRF-Chem-SBM) scheme, a model we previously developed and applied to warm stratocumulus clouds (Gao et al, 2016), to simulate a deep convective storm case that occurred over the Houston region and produced heavy precipitation. Sensitivity tests are performed to look into the joint and respective effects of urban land and anthropogenic aerosol on storm development and precipitation.…”

Global aerosol modeling with MADE3 (v3.0) in EMAC (based on v2.53): model description and evaluation

“…Resuspension of aerosol particles from evaporating/sublimating cloud particles or precipitating hydrometeors is an important process to be represented, which has recently been confirmed by Gao et al (2016). For MADE3 we completely revised the routines describing the redistribution of the resuspended aerosol.…”