SGER: Modeling River Nitrogen Export to Coastal Zones in the Community Climate System Model (CCSM)

向沿海地区输送的氮(N)增加是人类对氮循环的干扰的主要后果之一，并对沿海生产力和微量气体排放产生重要影响。基于这一观察结果，本研究首次尝试在社区气候系统模型（CCSM）中模拟河流养分运输。DAYCENT模型作为土壤农业生物地球化学模型的基础，最终将在CCSM土地模型（CLM）中发展，该模型的淋溶氮通量将与CLM河流运输模型（RTM）耦合。（DAYCENT是世纪模型的日时间步长版本，世纪模型是一种土壤有机质模型，模拟日微量气体通量和土壤水动力学）。模拟的河流氮通量将与观测数据库和根据统计相关性得出的氮输出的简单经验估计进行比较。模拟的向沿海地区的N输出通量将通过与模拟和测量的大气N输入以及估计的沿海自然硝化速率进行比较，用于评估沿海N预算。该研究的更广泛影响包括建立CCSM中河流溶质运移模拟框架，这将有助于更完整地表示CCSM中全球N循环，并将为CLM与区域沿海模式的耦合提供重要的边界条件。

Increased nitrogen (N) delivery to coastal areas is one of the major consequences of human perturbation to the nitrogen cycle, and has important impacts on coastal productivity and trace gas emissions. Motivated by this observation, this research is a first effort to model river nutrient transport in the Community Climate System Model (CCSM). Leached N fluxes from the DAYCENT model, which serves as the basis for the soil agricultural biogeochemistry model that eventually will be developed within the CCSM Land Model (CLM), will be coupled to the CLM River Transport Model (RTM). (DAYCENT is the daily time step version of the Century Model, a soil organic matter model that simulates daily trace gas fluxes and soil water dynamics). Modeled river N fluxes will be compared to observational databases and to simple empirical estimates of N export derived from statistical correlations. Modeled N export fluxes to coastal areas will be used to evaluate coastal N budgets, through comparison to modeled and measured atmospheric N inputs and to estimated natural coastal nitrification rates. The broader impacts of the proposed study include the development of a framework for the simulation of river solute transport in the CCSM, which will contribute to the more complete representation of the global N cycle in the CCSM and will provide important boundary conditions for the coupling of the CLM with regional coastal models.