针对中国陆地碳汇反演的大气二氧化碳浓度观测网络最优化设计

Optimal design of surface CO_(2)observation network to constrain China's land carbon sink

精准估算陆地生态系统碳汇对中国制定碳减排措施、实现碳中和目标有重要科学支撑作用.大气反演方法基于大气二氧化碳浓度观测数据,可有效估算地面二氧化碳通量的时空分布.目前中国陆地生态系统碳汇的大气反演估算仍有巨大不确定性,其中一个重要瓶颈在于缺乏足够的二氧化碳观测站点.本文研发了针对中国区域的大气反演框架,提出了二氧化碳观测网络的站点布设方案以最大程度降低中国陆地碳汇反演估算的不确定性.研究表明,在现有站点基础上,亟需在生长季植被生产力较高的东南、东北、华北和青藏高原地区增设二氧化碳观测站点.若在中国建设30个大气二氧化碳观测站点可将碳汇估算不确定性从每年10亿吨碳降低至3亿吨碳;建设60个站点可将不确定性进一步降低至每年2亿吨碳.这些站点将是“天-空-地”综合碳观测系统的重要组成部分,服务于中国二氧化碳收支反演和精准核算.

Accurate estimate of the size of land carbon sink is essential for guiding climate mitigation actions to fulfill China's net-zero ambitions before 2060.The atmospheric inversion is an effective approach to provide spatially explicit estimate of surface CO_(2)fluxes that are optimally consistent with atmospheric CO_(2)measurements.But atmospheric inversion of China's land carbon sink has enormous uncertainties,with one major source arising from the poor coverage of CO_(2)observation stations.Here we use a regional atmospheric inversion framework to design an observation network that could minimize uncertainties in inverted estimate of China's land carbon sink.Compared with the large spread of inverted sink(~1 Pg C a~(-1))from state-of-the-art inversions using existing CO_(2)observations,the uncertainty is constrained within 0.3 Pg C a~(-1)when a total of 30 stations were deployed,and is further reduced to approximately 0.2 Pg C a~(-1)when 60 stations were deployed.The proposed stations are mostly distributed over areas with high biosphere productivity during the growing season,such as Southeast China,Northeast China,North China,and the Tibetan Plateau.Moreover,the proposed stations can cover areas where existing satellites have limited coverage due to cloud shadowing in the monsoon season or over complex topography.Such ground-based observation network will be a critical component in the future integrated observing system for monitoring China's land carbon fluxes.