Comparison of Satellite-Observed XCO2 from GOSAT, OCO-2, and Ground-Based TCCON

Ge Han,Chengzhi Xiang,Wei Gong,Ailin Liang

doi:10.3390/rs9101033

Abstract

CO2 is one of the most important greenhouse gases. Its concentration and distribution in the atmosphere have always been important in studying the carbon cycle and the greenhouse effect. This study is the first to validate the XCO2 of satellite observations with total carbon column observing network (TCCON) data and to compare the global XCO2 distribution for the passive satellites Orbiting Carbon Observatory-2 (OCO-2) and Greenhouse Gases Observing Satellite (GOSAT), which are on-orbit greenhouse gas satellites. Results show that since GOSAT was launched in 2009, its mean measurement accuracy was −0.4107 ppm with an error standard deviation of 2.216 ppm since 2009, and has since decreased to −0.62 ppm with an error standard deviation of 2.3 ppm during the past two more years (2014–2016), while the mean measurement accuracy of the OCO-2 was 0.2671 ppm with an error standard deviation of 1.56 ppm from September 2014 to December 2016. GOSAT observations have recently decreased and lagged behind OCO-2 on the ability to monitor the global distribution and monthly detection of XCO2. Furthermore, the XCO2 values gathered by OCO-2 are higher by an average of 1.765 ppm than those by GOSAT. Comparison of the latitude gradient characteristics, seasonal fluctuation amplitude, and annual growth trend of the monthly mean XCO2 distribution also showed differences in values but similar line shapes between OCO-2 and GOSAT. When compared with the NOAA statistics, both satellites’ measurements reflect the growth trend of the global XCO2 at a low and smooth level, and reflect the seasonal fluctuation with an absolutely different line shape.

Highlights

Human activities have led to a dramatic increase in greenhouse gas (GHG) and pollutant concentrations in the atmosphere, and a significant increase in GHGs, especially CO2, has had a significant impact on global climate
The comparison was divided into two aspects. We compared their accuracy in measuring atmospheric carbon dioxide column concentration with total carbon column observing network (TCCON) XCO2 measurements at all of the sites around the world since their launch
We compared the global distribution of the XCO2 measurements of the two satellites

Summary

Introduction

Human activities have led to a dramatic increase in greenhouse gas (GHG) and pollutant concentrations in the atmosphere, and a significant increase in GHGs, especially CO2, has had a significant impact on global climate. Other scholars validated and compared the data retrieval accuracy of GOSAT with the total carbon column observing network (TCCON), Scanning Imaging Absorption spectrometer for Atmospheric Chartography (SCIAMACHY), and GEOS-Chem model calculations [10,11,12,13,14,15,16,17,18]. As compared with its precursors [13,19,20,21], OCO-2 exhibits evident improvements in spatial resolution and measurement accuracy, which enables it to supplement the data on XCO2, detect surface fluxes of CO2, and better understand the global carbon cycle [2,22,23,24].

Methods

Results

Conclusion