Robustness of modeling climatic impacts of aerosol over East Asia using regional model: balance between boundary forcing and regional feedback

Abstract:

Aerosol has significant impacts on regional weather and climate over East Asia. Due to the complexity of aerosol impact, numerical model is often used to help understand the role of aerosol in the weather and climate systems over East Asia, which is still uncertain. Regional model, such as WRF-Chem, is widely used to investigate the aerosol impacts on cloud, precipitation, and circulation in recent years, due to its better performance in terms of capturing regional features of weather and climate systems at relatively high resolution with reasonable computational cost compared to global high resolution model. In this study, numerical experiments are conducted with different regional domain sizes during the summer over East Asia using WRF-Chem to examine the robustness of regional modeling results about aerosol climatic impacts over East Asia focusing on the balance between boundary forcing and regional feedback, which has not been paid enough attention on before. As previous studies, the simulated meteorological fields change with the domain size such as that over southern China the westerly winds strengthen while the southerly winds weaken with the increasing domain size, which leads to the southeastward shift of rainfall. Under different background meteorological fields, the aerosol impacts on latent heat and cloud cover have distinct spatial distributions. In result, in the lower atmosphere, aerosol induced anomalies of surface temperature and wind fields are different among the experiments with different domain sizes. In addition, the distributions of resulted meridional circulation anomalies are also significant different. This study cautions the robustness of modeling climatic impacts of aerosol over East Asia using regional model in terms of selecting appropriate simulation domain size.