Integrating constraints on biosphere-atmosphere exchange: from ecosystem scales to the global atmosphere

要可靠地预测污染对气候系统的影响，就需要更好地了解生物圈与大气层之间的相互作用。拟议的研究计划的重点是整合越来越多的基于空间和地面的大气成分观测，以更好地了解控制二氧化碳（CO2）和臭氧这两种重要温室气体的大气丰度的过程。社区面临的一个主要挑战是如何利用大气CO2的测量，以量化CO2的源和汇的区域，政策相关的规模。对流层上部的臭氧是一种强烈的温室气体，而在地表附近，它是一种有害的污染物，对植物和动物产生不利影响。实际上，要准确预测大气中的二氧化碳水平，就必须正确地考虑臭氧丰度增加对植被的不利影响，以及生物圈对大气中二氧化碳的吸收。然而，再现臭氧的分布是一项挑战，因为臭氧的分布变化很大，反映了空间异质的光化学源和汇与大气迁移之间的平衡。拟议工作的具体目标是： 1)确定温室气体观测卫星和轨道碳观测站进行的空基CO2观测在何种条件下能够对区域尺度上的CO2通量提供限制，并确定如何将卫星测量的信息与生态系统尺度联系起来; 2)综合对臭氧和氮氧化物、甲醛和一氧化碳（这些都是重要的臭氧前体）的卫星观测，以更好地量化地表臭氧丰度，特别侧重于更好地量化与干沉降相关的臭氧汇，这主要反映了植被对臭氧的吸收; 3)确定气候引起的对流层上层和平流层下层大规模环流的变化将如何影响对流层上层臭氧的分布。 该计划将使用先进的数据同化技术，将地基和天基观测提供的信息在从生态系统尺度到全球大气的一系列尺度上联系起来。为了弥合这些尺度，这项工作将采用WRF区域模型、GEOS-Chem全球化学传输模型和CESM化学气候模型。拟议的研究计划将是跨学科的，并将为学生提供独特的培训经验。人们日益认识到，需要采取更加综合和跨学科的办法来应对我们作为一个社会所面临的许多环境挑战。该研究计划将有助于确保加拿大下一代气候科学家拥有应对这些挑战所需的知识多样性。

Reliable projections of the impact of pollution on the climate system require an improved understanding of the coupling between the biosphere and the atmosphere. The proposed research program is focused on integrating the growing suite of space-based and ground-based observations of atmospheric composition to obtain a better understanding of the processes controlling the atmospheric abundances of carbon dioxide (CO2) and ozone, two important greenhouse gases. A major challenge facing the community is how to exploit the measurements of atmospheric CO2 to quantify CO2 sources and sinks on regional, policy-relevant scales. Ozone in the upper troposphere acts as a strong greenhouse gas, whereas near the surface it is a harmful pollutant that adversely impacts plants and animals. Indeed, accurate projections of atmospheric CO2 levels will require correctly accounting for the adverse impacts of increased ozone abundances on vegetation, and consequently the uptake of atmospheric CO2 by the biosphere. Reproducing the distribution of ozone is challenging, however, because it is highly variable, reflecting a balance between photochemical sources and sinks, which are spatially heterogeneous, and atmospheric transport. The specific objectives of the proposed work are to: 1) determine the conditions under which space-based CO2 observations from the Greenhouse gases Observing Satellite (GOSAT) and the Orbiting Carbon Observatory (OCO-2) can provide constraints on CO2 fluxes on regional scales, and to determine how to link the information from the satellite measurements down to ecosystem scales; 2) integrate satellite observations of ozone and NOx, HCHO, and CO, which are important ozone precursors, to better quantify surface ozone abundances, with a specific focus on better quantifying the sink of ozone associated with dry deposition, which primarily reflects the uptake of ozone by vegetation; 3) determine how climate-induced changes in the large-scale circulation of the upper troposphere and lower stratosphere will impact the distribution of upper tropospheric ozone. The program will use advanced data assimilation techniques to link the information provided by ground-based and space-based observations across a range of scales, from ecosystem scales to the global atmosphere. To bridge these scales, the work will employ the WRF regional model, the GEOS-Chem global chemical transport model, and the CESM chemistry-climate model. The proposed research program will be interdisciplinary and will provide students a unique training experience. There is increasing recognition that a more integrated and interdisciplinary approach is needed to address many of the environmental challenges that we face as a society. The research program will help ensure that the next generation of climate scientists in Canada possesses the diversity of knowledge required to address these challenges.