Numerical Study of the Aerosol-Cloud-Interactions in Different Weather Regimes over the Eastern North Atlantic

The presence of warm boundary layer stratiform clouds over the Eastern North Atlantic (ENA) region is commonly influenced by the Azores High. During the summer season, the Bermuda-Azores High tends to strengthen and expand, leading to more persistent high-pressure conditions and often warmer, drier weather in its vicinity. To investigate aerosol-cloud interactions more realistically, this study employs the Weather Research and Forecast model coupled with a chemistry component (WRF-Chem), incorporating aerosol chemistry components that activate to cloud condensation nuclei (CCN) and accounting for aerosol spatiotemporal variation. This study focuses on aerosol indirect effects (AIE), particularly long-range transport aerosols, in the ENA region under three different weather regimes: ridge with surface high-pressure system, post-trough with surface high-pressure system, and weak trough. This presentation details the setup of the WRF-Chem simulation to approximate the scale of Large-Eddy Simulation (LES) using realistic aerosol variations from reanalysis data. It evaluates the model’s performance in capturing the liquid water path (LWP) and cloud fraction under three different weather regimes. Additionally, we conducted a perturbed experiment to increase aerosol amounts by up to five times. Our findings reveal that in the perturbed experiments, the introduction of more aerosols to precipitating and non-precipitating clouds produces different responses, highlighting the differences in LWP susceptibility to changes in CCN concentration.

This work is supported by the DOE Office of Science Early Career Research Program and the ASR Program. This work was performed under the auspices of the U.S. DOE by LLNL under contract DE-AC52-07NA27344. LLNL-ABS- 867184.