The role of OCO-3 XCO2 retrievals in estimating global terrestrial net ecosystem exchanges

IF 5.2 1区 地球科学 Q1 ENVIRONMENTAL SCIENCES
Xingyu Wang, Fei Jiang, Hengmao Wang, Zhengqi Zhang, Mousong Wu, Jun Wang, Wei He, Weimin Ju, Jingming Chen
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Abstract

Abstract. Satellite-based column-averaged dry air CO2 mole fraction (XCO2) retrievals are frequently used to improve the estimates of terrestrial net carbon exchanges (NEE). The Orbiting Carbon Observatory 3 (OCO-3) satellite, launched in May 2019, was designed to address important questions about the distribution of carbon fluxes on Earth, but its role in estimating global terrestrial NEE remains unclear. Here, using the Global Carbon Assimilation System, version 2, we investigate the impact of OCO-3 XCO2 on the estimation of global NEE by assimilating the OCO-3 XCO2 retrievals alone and in combination with the OCO-2 XCO2 retrievals. The results show that when only the OCO-3 XCO2 is assimilated (Exp_OCO3), the estimated global land sink is significantly lower than that from the OCO-2 experiment (Exp_OCO2). The estimate from the joint assimilation of OCO-3 and OCO-2 (Exp_OCO3&2) is comparable on a global scale to that of Exp_OCO2. However, there are significant regional differences. Compared to the observed global annual CO2 growth rate, Exp_OCO3 has the largest bias, and Exp_OCO3&2 shows the best performance. Furthermore, validation with independent CO2 observations shows that the biases of the Exp_OCO3 are significantly larger than those of Exp_OCO2 and Exp_OCO3&2 at mid and high latitudes, probably due to the fact that OCO-3 only has observations from 52° S to 52° N. Our study indicates that assimilating OCO-3 XCO2 retrievals alone leads to an underestimation of land sinks at high latitudes, and that a joint assimilation of OCO-2 and OCO-3 XCO2 retrievals is required for a better estimation of global terrestrial NEE.
OCO-3 XCO2 数据检索在估算全球陆地净生态系统交换中的作用
摘要。基于卫星的柱平均干空气二氧化碳摩尔分数(XCO2)检索经常被用来改进对陆地净碳交换(NEE)的估算。2019年5月发射的轨道碳观测站3号(OCO-3)卫星旨在解决有关地球上碳通量分布的重要问题,但其在估算全球陆地净碳交换量方面的作用仍不清楚。在此,我们利用全球碳同化系统(第 2 版),通过单独同化 OCO-3 XCO2 检索数据以及结合 OCO-2 XCO2 检索数据,研究了 OCO-3 XCO2 对全球 NEE 估计的影响。结果表明,仅同化 OCO-3 XCO2(Exp_OCO3)时,估计的全球陆地吸收汇明显低于 OCO-2 试验(Exp_OCO2)。在全球范围内,OCO-3 和 OCO-2 联合同化(Exp_OCO3&2)的估计值与 Exp_OCO2 的估计值相当。不过,地区差异很大。与观测到的全球二氧化碳年增长率相比,Exp_OCO3 的偏差最大,而 Exp_OCO3&2 的性能最好。此外,用独立的二氧化碳观测数据进行验证表明,Exp_OCO3 在中高纬度的偏差明显大于 Exp_OCO2 和 Exp_OCO3&2,这可能是由于 OCO-3 仅有南纬 52 度到北纬 52 度的观测数据。我们的研究表明,仅同化 OCO-3 XCO2 数据会导致低估高纬度地区的陆地吸收汇,因此需要联合同化 OCO-2 和 OCO-3 XCO2 数据,以更好地估算全球陆地 NEE。
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来源期刊
Atmospheric Chemistry and Physics
Atmospheric Chemistry and Physics 地学-气象与大气科学
CiteScore
10.70
自引率
20.60%
发文量
702
审稿时长
6 months
期刊介绍: Atmospheric Chemistry and Physics (ACP) is a not-for-profit international scientific journal dedicated to the publication and public discussion of high-quality studies investigating the Earth''s atmosphere and the underlying chemical and physical processes. It covers the altitude range from the land and ocean surface up to the turbopause, including the troposphere, stratosphere, and mesosphere. The main subject areas comprise atmospheric modelling, field measurements, remote sensing, and laboratory studies of gases, aerosols, clouds and precipitation, isotopes, radiation, dynamics, biosphere interactions, and hydrosphere interactions. The journal scope is focused on studies with general implications for atmospheric science rather than investigations that are primarily of local or technical interest.
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