Concerning outcomes of GOSAT-2 information evaluation and the beginning of their public launch

Regarding results of GOSAT-2 data analysis and the start of their public release

Column-averaged dry air mole fractions of carbon dioxide, methane, and carbon monoxide obtained from satellite data


Announcement of the science business


Greenhouse gases for satellite observation "IBUKI-2" (GOSAT-2) is a joint project funded by the Japanese Ministry of the Environment (MOE), the Japan Aerospace Exploration Agency (JAXA) and the National Institute for Environmental Studies (NIES) ) (hereinafter collectively the “three parties”) as the successor to the greenhouse gas observing satellite “IBUKI” (GOSAT), which was introduced in 2009 and is still in operation.

GOSAT-2 was launched from JAXA Tanegashima Space Center on October 29, 2018 with the H-IIA launch vehicle No. 40 (H-IIA F40). GOSAT-2 later collected the first light data with the on-board instruments: first on November 5th and 6th, 2018 images with the thermal and near infrared sensor for carbon observation – Cloud and Aerosol Imager-2 (CAI-2) and further on November 12-14. December 2018, data from the Thermal and Near Infrared Sensor for Carbon Observation – Fourier Transform Spectrometer-2 (FTS-2) confirming that the onboard instruments are functioning normally. In addition, on February 1, 2019, GOSAT-2 switched its operating mode to nominal and started global observations of CAI-2 and FTS-2. Note that the spectral radiation data observed by CAI-2 and FTS-2 has been distributed to the public as GOSAT-2 Level 1B product since August 5, 2019 from the following website:

GOSAT-2 Product Archives, National Institute for Environmental Studies

Subsequently, on July 5, 2019, NIES published the first retrieval results for methane (CH4) and carbon monoxide (CO) using a proxy method (see e.html) .

This press release provides an overview of the polling results for Carbon Dioxide (CO2), CH4 and CO using a complete physical method. This is the first report from the GOSAT-2 observation. The full physics method is used to calculate the propagation of light in the atmosphere based on a physical model and is used for GOSAT-2 to simultaneously retrieve column-averaged dry air mole fractions of CO2, CH4 and CO. This includes the monitoring of greenhouse gases Currently in operation satellites. GOSAT-2 is the only satellite that can simultaneously estimate the column-averaged concentrations of these three gas species.

Figure 1 shows the global distributions of the column-averaged dry air mole fractions of CO2, CH4, and CO (labeled XCO2, XCH4, and XCO, respectively) obtained in May 2019 from GOSAT-2 FTS-2 data using the full physical method.

As can be seen from the monthly mean CO2 concentration in the entire atmosphere, based on the GOSAT observation in May 2019, which at that time reached the record high of 409.4 ppm (see http: //www.gosat.nies.go. jp / en / recent-global) -co2.html) the photosynthesis of medium and high latitude forests in the northern hemisphere is not fully activated as of May 2019 and CO2 concentrations in Russia and Canada remain high. In terms of CH4 concentration, it appears to be high in Southeast China, Northern India, Northern Europe / Africa and Eastern North America, while the concentration of CO, a newly added gas species for GOSAT-2 observation, is high in the region from India appears to be through North Southeast Asia to China, Central Africa and Mexico and its leeward side. The high CO concentrations observed are believed to be due to the use of fossil fuels and biofuels (including charcoal) in the region from India to China, as well as forest fires in Central Africa and Mexico.

Figure 2 shows the global distributions of the column-averaged dry air mole fractions of CO2 and CH4 obtained from GOSAT FTS data using the full physics method in May 2019. As can be seen from the figures, the areas where GOSAT-2 data is available have increased significantly compared to areas with GOSAT data, including oceans and tropical regions with high levels of cloud cover. The number of observed data from which CO2 and other gas species are successfully retrieved is 11,000 for GOSAT and 25,000 for GOSAT-2, which is 2.3 times the number of GOSAT. This increase is mainly due to the two technical improvements: the intelligent pointing mechanism – a new feature introduced in the FTS-2 that detects cloudy areas in real time using the camera installed in the FTS-2 and automatically changes the observation point to a cloud-free area; and the expanded range of possible pointing angle in the direction of flight (along the trail) for sunshine observations over the ocean.

The retrieval results of CO2 and other gases based on GOSAT-2 FTS-2 data using the full physics method have been validated with the ground-based observation data from the Total Carbon Column Observing Network (TCCON). When comparing the FTS-2 (land area) data from March to May 2019 with ground-based data collected at 23 TCCON sites (Figure 3), a difference between these two data of 4.1 ± 3.8 ppm ( 1.0 ± 0.9%). for CO2 5.5 ± 17.4 ppb (0.3 ± 0.9%) for CH4 and 21.2 ± 9.0 ppb (22.7 ± 9.7%) for CO. (All these data from GOSAT-2 are higher than the TCCON data.) Although these values ​​are better than GOSAT data two years after their introduction, they have not reached the quality level of the latest data products from GOSAT FTS (V2.90, -0.35 ± 2.19 ppm (-0.1 ± 0.6%) for CO2, 2.2 ± 13.4 ppb (0.1 ± 0.7%) for CH4). Further improvements to GOSAT-2's data products are required.

This result of the full physics method specified in this press release, together with the result of the proxy method, was made available as a GOSAT-2 Level 2 product to researchers whose research proposals were incorporated into the research announcements of the GOSAT series (1st and 2nd RA) ) and research institutions that have signed cooperation agreements with MOE, JAXA and / or NIES. As soon as the associated documents including the validation results are available, all these data products from the GOSAT-2 product archive will be released for the general public.

We will work to further improve the accuracy of the retrieval and to increase the amount of data retrieved. In addition, we plan to proceed with the inversion analysis of the net flows, the generation of level 4 products and the estimation of anthropogenic emissions, and gradually achieve the results of GOSAT.


From EurekAlert!

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