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首页> 外文期刊>Atmospheric chemistry and physics >Representing sub-grid scale variations in nitrogen deposition associated with land use in a global Earth system model: implications for present and future nitrogen deposition fluxes over North America
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Representing sub-grid scale variations in nitrogen deposition associated with land use in a global Earth system model: implications for present and future nitrogen deposition fluxes over North America

机译：代表与全球地球系统模型中的土地使用相关的氮沉积的子网格规模变化：对北美的目前和未来的氮沉积势态的影响

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Reactive nitrogen (N) emissions have increased over the last 150 years as a result of greater fossil fuel combustion and food production. The resulting increase in N deposition can alter the function of ecosystems, but characterizing its ecological impacts remains challenging, in part because of uncertainties in model-based estimates of N dry deposition. Here, we use the Geophysical Fluid Dynamics Laboratory (GFDL) atmospheric chemistry-climate model (AM3) coupled with the GFDL land model (LM3) to estimate dry deposition velocities. We leverage the tiled structure of LM3 to represent the impact of physical, hydrological, and ecological heterogeneities on the surface removal of chemical tracers. We show that this framework can be used to estimate N deposition at more ecologically relevant scales (e.g., natural vegetation, water bodies) than from the coarse-resolution global model AM3. Focusing on North America, we show that the faster removal of N over forested ecosystems relative to cropland and pasture implies that coarse-resolution estimates of N deposition from global models systematically underestimate N deposition to natural vegetation by 10% to 30% in the central and eastern US. Neglecting the sub-grid scale heterogeneity of dry deposition velocities also results in an underestimate (overestimate) of the amount of reduced (oxidized) nitrogen deposited to water bodies. Overall, changes in land cover associated with human activities are found to slow down the removal of N from the atmosphere, causing a reduction in the dry oxidized, dry reduced, and total (wet+dry) N deposition over the contiguous US of 8 %, 26 %, and 6 %, respectively. We also find that the reduction in the overall rate of removal of N associated with land-use change tends to increase N deposition on the remaining natural vegetation and facilitate N export to Canada. We show that sub-grid scale differences in the surface removal of oxidized and reduced nitrogen imply that projected near-term (2
机译：由于大石化石燃料燃烧和食品生产，反应性氮（N）排放量在过去150年内增加。由此产生的N沉积增加可以改变生态系统的功能，但表征其生态影响仍然挑战，部分原因是基于模型的N干沉积估计的不确定性。在这里，我们使用地球物理流体动力学实验室（GFDL）大气化学 - 气候模型（AM3）与GFDL陆地模型（LM3）耦合，以估计干沉积速度。我们利用LM3的瓷砖结构来代表物理，水文和生态异质性对化学示踪剂的表面去除的影响。我们表明该框架可用于在更生态上相关的尺度（例如，天然植被，水体）中估算N沉积，而不是来自粗辨率的全球模型AM3。专注于北美，我们表明，相对于农田和牧场的森林生态系统的速度更快地删除了N型植物和牧场的粗辨率估计从全球模型的N沉积系统地低估N沉积到中央和中央植被的10％至30％。美国东部。忽略干沉积速度的子网格规模的异质性也导致沉积在水体中的还原（氧化）氮的量的低估（估量）。总体而言，发现与人类活动相关的陆地覆盖的变化减缓从大气中去除n，导致干燥氧化，干燥的降低，并且总（湿+干）n沉积在连续8％的情况下分别为26％和6％。我们还发现，与土地利用变化相关的N的总体速率的减少往往会增加剩余的自然植被和促进加拿大的N沉积。我们表明，亚网格尺度差异在表面去除氧化和降低的氮气意味着预测的近期（2

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