Strong Local Evaporative Cooling Over Land Due to Atmospheric Aerosols
Strong Local Evaporative Cooling Over Land Due to Atmospheric Aerosols
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DOI：
10.1029/2021ms002491
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发表时间：
2021-05-01
影响因子：
6.8
通讯作者：
Lawrence, David M.
中科院分区：
文献类型：
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作者：
Chakraborty, T. C.;Lee, Xuhui;Lawrence, David M.
气溶胶可以通过增加植物冠层的阴影部分对太阳辐射的吸收来提高陆地生产力-漫射辐射施肥效应。虽然这一过程原则上可以改变地表蒸发，因为植物失水和碳吸收之间的耦合，并有可能改变地表温度，但传统上一直根据大气中的辐射效应来看待气溶胶与气候的相互作用。在这里，我们开发了一个建模框架，结合全球大气和陆地模型模拟的概念诊断工具，从表面能量预算的角度来研究这些相互作用。全球范围内，气溶胶使陆地蒸发分数（即蒸发消耗的净输入能量部分）增加了4%以上，区域范围内则接近40%。其主要机制是由于全球变暗（减少全球短波辐射）和扩散辐射施肥略有增加，从显热到潜热的能量分配增加。在植被中等密集的地区（叶面积指数>2），局部地表对气溶胶的冷却反应主要是通过蒸发途径，而不是入射辐射的减少。单独的漫射辐射施肥对总初级生产力（+2.18 Pg C y（-1）或+1.8%）的影响比对土地蒸发（+0.18 W m（-2）或+0.48%）和表面温度（-0.01 K）的影响更大。我们的研究结果表明，这是重要的陆面模式区分辐射强迫的数量（总幅度的变化）和质量（扩散分数的变化），以正确地模拟地面气候。
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 similar to 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.