期刊名称：Journal of Advances in Modeling Earth Systems
电子版ISSN：1942-2466
出版年度：2021
卷号：13
期号：5
页码：e2021MS002491
DOI：10.1029/2021MS002491
出版社：John Wiley & Sons, Ltd.
摘要：Aerosols can enhance terrestrial productivity through increased absorption of solar radiation by the shaded portion of the plant canopy—the diffuse radiation fertilization effect. Although this process can, in principle, alter surface evaporation due to the coupling between plant water loss and carbon uptake, with the potential to change the surface temperature, aerosol-climate interactions have been traditionally viewed in light of the radiative effects within the atmosphere. Here, we develop a modeling framework that combines global atmosphere and land model simulations with a conceptual diagnostic tool to investigate these interactions from a surface energy budget perspective. Aerosols increase the terrestrial evaporative fraction, or the portion of net incoming energy consumed by evaporation, by over 4% globally and as much as ∼40% regionally. The main mechanism for this is the increase in energy allocation from sensible to latent heat due to global dimming (reduction in global shortwave radiation) and slightly augmented by diffuse radiation fertilization. In regions with moderately dense vegetation (leaf area index >2), the local surface cooling response to aerosols is dominated by this evaporative pathway, not the reduction in incident radiation. Diffuse radiation fertilization alone has a stronger impact on gross primary productivity ( 2.18 Pg C y −1 or 1.8%) than on land evaporation ( 0.18 W m −2 or 0.48%) and surface temperature (−0.01 K). Our results suggest that it is important for land surface models to distinguish between quantity (change in total magnitude) and quality (change in diffuse fraction) of radiative forcing for properly simulating surface climate. Plain Language Abstract Atmospheric particles or aerosols are known to enhance plant growth by increasing photosynthesis in leaves that are normally shaded from direct sunlight, a phenomenon known as the diffuse radiation fertilization effect. Since photosynthesis and water vapor released from plants are linked, this would imply that there is more evaporative cooling at the surface under polluted skies, a mechanism of aerosol-induced cooling that has not been explicitly considered in past studies. In the present study, we test this hypothesis on a global scale by combining a modeling framework with an offline energy balance method. We show that the surface cooling due to the evaporative pathway is stronger than due to the radiative effect of aerosols for moderately dense vegetation. Traditionally, aerosol-climate interactions are viewed in light of their radiation impacts on the atmospheric energy budget. Our study provides a new, surface energy budget perspective on these interactions and highlight the importance of differentiating between the quantity and quality of radiative forcing at the Earth's surface when examining the impact of aerosols on the surface climate.
关键词：aerosols;atmosphere-biosphere interactions;diffuse radiation fertilization effect;earth system modeling;evapotranspiration;global land model;gross primary productivity;surface energy budget;surface temperature
