Constraining regional fluxes of CO2 and CH4 over Canada by merging atmospheric and ground observations

对大气中二氧化碳和甲烷等温室气体浓度增加的担忧，使人们更加了解这些气体在陆地表面和大气之间交换的位置、原因和速率至关重要。关键的差距是我们无法将大气层和地面上的观测结果合并起来，以不同的时空尺度为特征，并具有过程级的生物学知识。本研究的主要目标如下：（1）建立一个能够同时接收大气和地基观测数据的多时空尺度陆气耦合模式系统。(2)确定加拿大上空两种主要温室气体CO2和CH 4通量的位置、强度和原因。重点是解决区域尺度（10~1000公里）的通量在大陆，知识一直受到阻碍的模拟系统，不能解释高度变化的大气观测在大陆。最新的大气模型将与生物圈模型相结合，后者针对CO2/CH 4通量直接观测和森林清单分析等数据流进行了优化，而这些数据流以前是在没有大气观测的情况下使用的。因此，拟议的建模系统同化大气和地面的测量，从而产生“最佳猜测”通量，最佳的大气和生物圈的知识是一致的。拟议的研究计划将在气候科学方面取得进展：对当前温室气体源/汇的更详细了解将增强预测未来气候的能力。此外，拟议的研究方案将为量化和监测温室气体排放奠定基础，从而为加拿大履行《京都议定书》规定的义务作出贡献。

Concerns over increases in atmospheric concentrations of greenhouse gases such as CO2 (carbon dioxide) and CH4 (methane) make it critically important to improve understanding of where, why, and at what rates these gases are exchanged between the land surface and the atmosphere. The key gap is our inability to merge observations in the atmosphere and on the ground, characterizing diverse spatio-temporal scales, with process-level biological knowledge. The objectives of this study are as follows: (1) Develop a land-atmosphere modeling system that can ingest both atmospheric and ground-based observations at multiple spatial and temporal scales. (2) Determine the locations, strengths, and reasons for fluxes of CO2 and CH4, the two major greenhouse gases, over Canada. The focus is on resolving regional scale (10~1000 km) fluxes over the continent, knowledge of which have been hampered by modeling systems that cannot interpret the highly varying atmospheric observations over the continent. State-of-the-art atmospheric models will be combined with biospheric models that are optimized against such datastreams as direct CO2/CH4 flux observations and forest inventory analyses, previously used in absence of the atmospheric observations. Thus the proposed modeling system assimilates both atmospheric and ground-based measurements, thereby yielding "best-guess" fluxes that are optimally consistent with both atmospheric and biospheric knowledge. The proposed research program will make steps forward in climate science: a more detailed knowledge of sources/sinks of current greenhouse gases leads to enhanced capability to project future climate. Furthermore, the proposed research program will contribute towards Canada's obligations under the Kyoto Protocol by building the foundation for quantifying and monitoring emissions of greenhouse gases.