China’s first global carbon flux dataset produced through CO2 monitoring satellite

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By Wan Yu, People’s Daily

Chinese scientists recently created the country’s first global carbon flux dataset based on data collected by the country’s first carbon dioxide (CO2) monitoring satellite TanSat. The achievement means that China is capable of conducting the quantitative spatial monitoring of the global carbon budget and helping take an inventory of the carbon budgets around the world.

More importantly, the capability bears great significance for the country’s goal to peak carbon dioxide emissions before 2030 and achieve carbon neutrality before 2060.

Relevant findings about the breakthrough have been published by a research group led by Liu Yi, a researcher from the Institute of Atmospheric Physics, Chinese Academy of Sciences, in the science journal Advances in Atmospheric Sciences in collaboration with many scientists from China and the U.K.

While ground observation enables researchers to obtain accurate and comprehensive information, the method of calculating carbon emissions and absorption based on measurement of the concentrations of atmospheric carbon dioxide offers a broad and clear view of the situations, which can effectively complement ground observation, noted Liu.

Researchers used an advanced data assimilation system to simulate the transmitting process of CO2 in the atmosphere and the amounts of CO2 in the atmosphere at every moment in every place in consistent with the observation data gathered from TanSat, and finally got the closest approximation of the true value of carbon flux, Liu said.

China’s first CO2 monitoring satellite TanSat was launched on Dec. 22, 2016, which is the world’s third carbon-sniffing satellite, following Japan’s Greenhouse Gases Observing Satellite (GOSAT) launched in 2009 and the Orbiting Carbon Observatory-2 (OCO-2) sent into space by the U.S. in 2014. On Dec. 22, 2015, NASA released the first global CO2 map, which indicated that the atmospheric CO2 levels in some of the middle and low latitudes surpassed 400 ppm.

China developed and launched the satellite TanSat to conduct dynamic monitoring of the atmospheric CO2 concentration and provide global carbon distribution data, which not only represents the country’s active efforts to cope with global climate change, but also shows the country’s sense of responsibility as a major country, said Li Jiahong, chief engineer of China’s National Remote Sensing Center.

The monitoring of greenhouse gases through satellite is based on the atmospheric absorption pool theory. Gases like CO2 and oxygen absorb relatively more light waves whose lengths are between the near-infrared band and shortwave-infrared band and form characteristic atmospheric absorption spectra.

While taking account of auxiliary information including atmospheric pressure and temperature and eliminating interference factors like atmospheric particulate matter, researchers can get the atmospheric CO2 column concentrations in the observation paths of CO2 monitoring satellite through inverse algorithm based on strict quantitative measurement of the intensity of the absorption spectra.

Changes in global CO2 flux (the amount of CO2 that passes a unit area per unit time), the core data base of research into carbon cycle, can be deduced with the help of sequential analysis of global atmospheric CO2 column concentrations and a series of models in the data assimilation system.

The acquisition of highly accurate atmospheric absorption spectra is relied on the main payload of the TanSat CO2 monitoring satellite, CO2 detector, which can detect atmospheric absorption spectrum channels with the wavelengths of 2.06µm, 1.6µm, and 0.76µm. The resolving power of the detector can reach 0.04 nm.

Cloud and aerosol polarization imaging detector (CAPI), another important payload of China’s TanSat CO2 monitoring satellite, can gather auxiliary information on cloud and aerosol and help eliminate interference factors for accurate calculation of CO2 concentrations.

In addition, CAPI can collect aerosol data on a global scale, which can not only help meteorologists improve the accuracy of weather forecast, but offer important data for research into PM2.5 and other causes of air pollution.

Chlorophyll fluorescence remote sensing represents an important application of the TanSat. The ultra high spectral resolution data collected by TanSat helps not only conduct dynamic monitoring of global atmospheric CO2 concentration, but also calculate chlorophyll fluorescence in vegetation through reverse algorithm.

Satellite chlorophyll fluorescence measurements can help researchers accurately estimate global vegetation photosynthetic productivity, which, in combination with the global CO2 concentration data calculated synchronously, is expected to significantly improve the capability to observe global sources and sinks of carbon.

Some scientists even think the detection of chlorophyll fluorescence, rather than greenhouse gases, is the most innovative and revolutionary observation task of greenhouse gas observing satellites like GOSAT, OCO-2, and TanSat.

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