JULES-CN: a coupled terrestrial Carbon-Nitrogen Scheme (JULES vn5.1)
JULES-CN: a coupled terrestrial Carbon-Nitrogen Scheme (JULES vn5.1)
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DOI：
10.5194/gmd-2020-205
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发表时间：
2020-07
期刊：
影响因子：
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通讯作者：
A. Wiltshire;E. Burke;S. Chadburn;C. Jones;P. Cox;T. Davies-Barnard;P. Friedlingstein;A. Harper
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文献类型：
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作者：
A. Wiltshire;E. Burke;S. Chadburn;C. Jones;P. Cox;T. Davies-Barnard;P. Friedlingstein;A. Harper
抽象的。了解陆地碳循环的未来变化对于可靠地预测气候变化及其对生态系统的影响十分重要。众所周知，氮可以限制植物对增加的大气二氧化碳的反应，因此在地球系统模型中包括氮是很重要的。在这里，我们提出了在JULES陆面模式（JULES-CN）的陆地氮循环的实施。两个版本进行了讨论-在英国地球系统模型（UKESM 1），它有一个散装土壤地球化学模型和一个开发版本，解决了土壤地球化学与深度的一个实施。氮循环是基于模型中现有的碳循环。它以一种有效的方式代表了所有关键的陆地氮过程。生物固定和氮沉积是外部输入，通过沥滤和大量气体损失参数化发生损失。养分限制降低了碳利用效率（CUE -净初级生产力与毛初级生产力的比率），并可减缓土壤分解。我们表明，生态系统水平的限制氮净初级生产力是一致的观测估计和模拟的碳和氮库和通量是有限的可用的观测。氮限制的影响在北方中纬度地区最为明显。氮循环的引入提高了全球净生态系统交换的年际变化的代表性，这在JULES的碳循环版本（JULES-C）中过于明显。它还降低了CUE并改变了其在20世纪的响应，并限制了CO2施肥效应，因此模拟的当前陆地碳汇减少了约0.5 Pg C yr−1。包括一个预测土地氮计划标志着一个进步的功能和现实的JULES和UKESM模式。
Abstract. Understanding future changes in the terrestrial carbon cycle is important for reliable projections of climate change and impacts on ecosystems. It is known that nitrogen could limit plants' response to increased atmospheric carbon dioxide and is therefore important to include in Earth System Models. Here we present the implementation of the terrestrial nitrogen cycle in the JULES land surface model (JULES-CN). Two versions are discussed – the one implemented within the UK Earth System Model (UKESM1) which has a bulk soil biogeochemical model and a development version which resolves the soil biogeochemistry with depth. The nitrogen cycle is based on the existing carbon cycle in the model. It represents all the key terrestrial nitrogen processes in an efficient way. Biological fixation and nitrogen deposition are external inputs, and loss occurs via leaching and a bulk gas loss parameterisation. Nutrient limitation reduces carbon-use efficiency (CUE – ratio of net to gross primary productivity) and can slow soil decomposition. We show that ecosystem level limitation of net primary productivity by nitrogen is consistent with observational estimates and that simulated carbon and nitrogen pools and fluxes are comparable to the limited available observations. The impact of N limitation is most pronounced in northern mid-latitudes. The introduction of a nitrogen cycle improves the representation of interannual variability of global net ecosystem exchange which was much too pronounced in the carbon cycle only versions of JULES (JULES-C). It also reduces the CUE and alters its response over the twentieth century and limits the CO2-fertilisation effect, such that the simulated current day land carbon sink is reduced by about 0.5 Pg C yr−1. The inclusion of a prognostic land nitrogen scheme marks a step forward in functionality and realism for the JULES and UKESM models.