Investigation of the consistency of atmospheric CO2 retrievals from different space-based sensors: Intercomparison and spatiotemporal analysis

Abstract

In recent years, global warming caused by emission of CO 2 has attracted considerable attention from the public. Although the measurements from AIRS, GOSAT, SCIAMACHY and IASI have been frequently used to derive atmospheric CO 2 concentration, comprehensive quantification of the differences among these CO 2 products is still not fully investigated yet. In this paper, a series of strategies have been proposed to allow the CO 2 products from different instruments to be physically inter-comparable. Based on this, these CO 2 products are inter-compared in terms of magnitude and their spatiotemporal distributions. The results reveal that the correlations among these CO 2 products are relatively weak, and some discrepancies are detected in terms of the CO 2 spatiotemporal characteristics, demonstrating more efforts should be made in the future to improve the retrievals of CO 2 . Their spatial coverage differences reflected in this study imply the great necessity to generate consistent products with improved spatial and temporal continuities by combining these CO 2 measurements.

Mapping Global Atmospheric CO2 Concentration at High Spatiotemporal Resolution

“…Although the data points from ACOS are slightly wider than those from BESD, both ACOS and BESD show poor global coverage. These results agree with those presented in the study conducted by Wang et al [11].…”

“…Bai et al [35] stated that significant seasonal variations of CO 2 in the Northern Hemisphere were closely related to human activities and green vegetation. Wang et al [11] also found that seasonal cycles exist in the retrieved XCO 2 concentrations from satellites in the Northern Hemisphere and that there are no significant seasonal variations in the Southern Hemisphere. From Figure 4, we can also see that there is no noticeable seasonal variation in the Southern Hemisphere, particularly for Australia and the southern part of South America.…”

“…In view of different spatial samplings, to account for retrieval uncertainties, the XCO 2 data with fine spatial scale are aggregated to a new value according to the uncertainty weight of individual XCO 2 retrievals to suit the relatively coarse scale during fusion [11]. The detailed "aggregated" method can be found in [13].…”

“…To date, the Orbiting Carbon Observatory-2 (OCO-2) [7], the Greenhouse gases Observing SATellite (GOSAT) [8], and the SCanning Imaging Absorption Spectrometer for Atmospheric CHartographY (SCIAMACHY) [9] are the only three satellite instruments that can retrieve XCO 2 with significant sensitivity in the boundary layer [10]. Although these satellites have been used to measure global XCO 2 concentrations, because of cloud contamination and limitations due to the instrument observation modes (e.g., GOSAT observes in lattice points), the available data points for retrieved XCO 2 from any single satellite are very limited [3,11].…”

Fusion of space-based CO<inf>2</inf> products and its comparison with other available CO<inf>2</inf> estimates

“…Due to different samplings method, for example, different satellites, different overpass, and different filtering strategies, etc., it is necessary to unify these differences into the same level before combining ACOS and BESD XCO 2 products into a fused data [12,14].…”