Biological and Environmental Research - Earth and Environmental System Sciences
Earth and Environmental System Modeling
22 January 2021

Disproportionate Control on Aerosol Burden by Light Rain

Aerosol in light rain.
Science

Atmospheric aerosols are of great climatic and environmental importance due to their effects on the Earth’s radiative energy balance and air quality. Aerosol concentrations are strongly influenced by rainfall via wet removal. However, global climate models commonly suffer from a well-known problem of ‘too much light rain and too little heavy rain’. The impact of simulated rainfall intensities on aerosol burden at the global scale is still unclear. Here we show that rainfall intensity has profound impacts on aerosol burden, and light rain has a disproportionate control on it.

Impact

The implication of the findings in this study is that understanding the nature of aerosol scavenging by rainfall is critical to aerosol–climate interaction and its impact on climate.

Summary

By Implementing the stochastic deep-convection scheme into the Zang-McFarlan (ZM) deterministic deep-convection scheme, we improve the representation of convection in the National Center for Atmospheric Research Community Atmosphere Model version 5 (NCAR CAM5) and the US Department of Energy (DOE) Energy Exascale Earth System Model (E3SM) Atmosphere Model version 1 (EAMv1). The light-rain (1–20 mm d−1) frequency in these two models is reduced markedly. As a result, the aerosol wet removal is reduced; the aerosol burden is increased globally, especially over the tropics and subtropics, by as much as 0.3 in aerosol optical depth in tropical rain belts. It is attributed to the dominant contribution of light rain to the accumulated wet removal by its frequent occurrence despite its weak intensity.

Contact
Guang Zhang
Scripps Institution of Oceanography
Publications
Wang, Y, W Xia, X Liu, S Xie, W Lin, Q Tang, H Ma, Y Jiang, B Wang, and GJ Zhang.  2021.  "Disproportionate Control on Aerosol Burden by Light Rain."  Nature Geoscience.  https://doi.org/10.1038/s41561-020-00675-z.