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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Consistency in XCO2 Retrievals from Sciamachy, Gosat and OCO-2 for Spatio-Temporal Characteristics at a Global Scale
摘要： Long-term XCO2 retrievals, which are obtained by the three measurements including SCIAMACHY, GOSAT and OCO-2, are publicly available from 2003 to date. These XCO2 data can help us better understanding the underlying processes of uptake and release of CO2 in biosphere and anthropogenic emissions at global scales via probing into the characteristics of the spatio-temporal variations of XCO2. We investigated the inconsistency of the spatio-temporal variations of XCO2 in these three measurements by combining with NDVI data. We apply a global land mapping XCO2 datasets generated by data-driven spatio-temporal geostatistics method to the correlation analysis with NDVI. As a result, XCO2 demonstrate smooth variations in time without jumping in the time node between the three measurements. They demonstrate similar patterns of correlation coefficients with NDVI which could indicate the process of CO2 interchange in biosphere-atmosphere.
关键词： XCO2,spatio-temporal variations,correlation,inconsistency
更新于2025-09-23 15:22:29
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Modelling of XCO2 Surfaces Based on Flight Tests of TanSat Instruments
摘要： The TanSat carbon satellite is to be launched at the end of 2016. In order to verify the performance of its instruments, a ?ight test of TanSat instruments was conducted in Jilin Province in September, 2015. The ?ight test area covered a total area of about 11,000 km2 and the underlying surface cover included several lakes, forest land, grassland, wetland, farmland, a thermal power plant and numerous cities and villages. We modeled the column-average dry-air mole fraction of atmospheric carbon dioxide (XCO2) surface based on ?ight test data which measured the near- and short-wave infrared (NIR) re?ected solar radiation in the absorption bands at around 760 and 1610 nm. However, it is dif?cult to directly analyze the spatial distribution of XCO2 in the ?ight area using the limited ?ight test data and the approximate surface of XCO2, which was obtained by regression modeling, which is not very accurate either. We therefore used the high accuracy surface modeling (HASM) platform to ?ll the gaps where there is no information on XCO2 in the ?ight test area, which takes the approximate surface of XCO2 as its driving ?eld and the XCO2 observations retrieved from the ?ight test as its optimum control constraints. High accuracy surfaces of XCO2 were constructed with HASM based on the ?ight’s observations. The results showed that the mean XCO2 in the ?ight test area is about 400 ppm and that XCO2 over urban areas is much higher than in other places. Compared with OCO-2’s XCO2, the mean difference is 0.7 ppm and the standard deviation is 0.95 ppm. Therefore, the modelling of the XCO2 surface based on the ?ight test of the TanSat instruments fell within an expected and acceptable range.
关键词： XCO2 simulation,TanSat,XCO2 retrieval,HASM,?ight test
更新于2025-09-04 15:30:14
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Accurate mobile remote sensing of XCO<sub>2</sub> and XCH<sub>4</sub> latitudinal transects from aboard a research vessel
摘要： A portable Fourier transform spectrometer (FTS), model EM27/SUN, was deployed onboard the research vessel Polarstern to measure the column-average dry air mole fractions of carbon dioxide (XCO2) and methane (XCH4) by means of direct sunlight absorption spectrometry. We report on technical developments as well as data calibration and reduction measures required to achieve the targeted accuracy of fractions of a percent in retrieved XCO2 and XCH4 while operating the instrument under field conditions onboard the moving platform during a 6-week cruise on the Atlantic from Cape Town (South Africa, 34? S, 18? E; 5 March 2014) to Bremerhaven (Germany, 54? N, 19? E; 14 April 2014). We demonstrate that our solar tracker typically achieved a tracking precision of better than 0.05? toward the center of the sun throughout the ship cruise which facilitates accurate XCO2 and XCH4 retrievals even under harsh ambient wind conditions. We define several quality filters that screen spectra, e.g., when the field of view was partially obstructed by ship structures or when the lines-of-sight crossed the ship exhaust plume. The measurements in clean oceanic air, can be used to characterize a spurious air-mass dependency. After the campaign, deployment of the spectrometer alongside the TCCON (Total Carbon Column Observing Network) instrument at Karlsruhe, Germany, allowed for determining a calibration factor that makes the entire campaign record traceable to World Meteorological Organization (WMO) standards. Comparisons to observations of the GOSAT satellite and concentration fields modeled by the European Centre for Medium-Range Weather Forecasts (ECMWF) Copernicus Atmosphere Monitoring Service (CAMS) demonstrate that the observational setup is well suited to provide validation opportunities above the ocean and along interhemispheric transects.
关键词： solar tracker,EM27/SUN,atmospheric greenhouse gases,XCO2,XCH4,Fourier transform spectrometer,shipborne measurements
更新于2025-09-04 15:30:14
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Calibration and instrumental line shape characterization of a set of portable FTIR spectrometers for detecting greenhouse gas emissions
摘要： A comprehensive calibration procedure for mobile, low-resolution, solar-absorption FTIR spectrometers, used for greenhouse gases observations, is developed. These instruments commend themselves for campaign use and deployment at remote sites. The instrumental line shape (ILS) of each spectrometer has been thoroughly characterized by analyzing the shape of H2O signatures in open path spectra. A setup for the external source is suggested and the invariance of derived ILS parameters with regard to chosen path length is demonstrated. The instrumental line shape characteristics of all spectrometers were found to be close to nominal. Side-by-side solar observations before and after a campaign, which involved shipping of all spectrometers to a selected target site and back, are applied for verifying the temporal invariability of instrumental characteristics and for deriving intercalibration factors for XCO2 and XCH4, which take into account residual differences of instrumental characteristics. An excellent level of agreement and stability was found between the different spectrometers: the uncorrected biases in XCO2 and XCH4 are smaller than 0.01 and 0.15 %, respectively, and the drifts are smaller than 0.005 and 0.035 %. As an additional sensitive demonstration of the instrumental performance we show the excellent agreement of ground pressure values obtained from the total column measurements of O2 and barometric records. We find a calibration factor of 0.9700 for the spectroscopic measurements in comparison to the barometric records and a very small scatter between the individual spectrometers (0.02 %). As a final calibration step, using a co-located TCCON (Total Carbon Column Observation Network) spectrometer as a reference, a common scaling factor has been derived for the XCO2 and XCH4 products, which ensures that the records are traceable to the WMO in situ scale.
关键词： calibration,XCO2,XCH4,FTIR spectrometers,instrumental line shape,greenhouse gas emissions
更新于2025-09-04 15:30:14