Biophysical Impacts of Aerosols on Terrestrial Climate

TC CHAKRABORTY, Xuhui Lee, Dave Lawrence, Pacific Northwest National Laboratory

     Abstract Number: 172
     Working Group: Aerosol-Ecosystem Interactions

Abstract
Studies on aerosol impacts on the climate have traditionally focused more on changes in the atmospheric radiation budget. However, aerosols have a disproportionately higher impact on the Earth’s surface, where humans reside. Here, we isolate the impacts of aerosols on the surface climate to better understand the mechanisms that modulate the overall climate response to aerosol loading by developing a surface energy budget perspective to aerosol-climate interactions. We first quantify the impact of aerosols on local temperature through both radiative and non-radiative pathways using a reanalysis dataset with assimilated aerosol observations from satellites. We find that the relative strengths of these pathways depend heavily on both aerosol and land surface properties. Then, to capture the impact of aerosols on surface climate through non-radiative pathways, a global land model was run with and without aerosols. In both cases (estimates from reanalysis and land model), a conceptual framework to attribute surface temperature anomalies to its determinants was used to examine the relative impact of each pathway on the local surface temperature. The associated impacts on terrestrial evapotranspiration and land carbon uptake through global dimming and diffuse radiation fertilization effect of aerosols were also quantified on a global scale using the land model runs. We demonstrate that aerosols can increase evaporative cooling over and land, with the strength of this pathway dependent on vegetation density. This work advances our understanding of the biophysical mechanisms through which aerosols can impact surface temperature, terrestrial evapotranspiration, and land carbon uptake. We will also provide an introductory perspective on the importance of the diffuse radiation fertilization effect and the current uncertainties in its representation in Earth System Models.