Validation of Column-Averaged Dry-Air Mole Fraction of CO_2 Retrieved from OCO-2 Using Ground-Based FTS Measurements  

作　　者：Yanmeng BI Qian WANG Zhongdong YANG Jie CHEN Wenguang BAI 

机构地区：[1]National Satellite Meteorological Center,China Meteorological Administration

出　　处：《Journal of Meteorological Research》2018年第3期433-443,共11页气象学报（英文版）

基　　金：Supported by the TanSat Project(2011AA12A104)under a contract with the National Science and Technology Support Program of China

摘　　要：In order to correctly use the column-averaged atmospheric COdry-air mole fraction(XCO) data in the COflux studies, XCOmeasurements retrieved from the Orbiting Carbon Observatory-2(OCO-2) in 2015 were compared with those obtained from the global ground-based high-resolution Fourier Transform Spectrometer(FTS) participating in the Total Carbon Column Observing Network(TCCON). The XCOretrieved from three observing modes adopted by OCO-2, i.e., nadir, target, and glint, were separately validated by the FTS measurements at up to eight TCCON stations located in different areas. These comparisons show that OCO-2 glint mode yields the best qualitative estimations of COconcentration among the three operational approaches. The overall results regarding the glint mode show no obvious systematic biases. These facts may indicate that the glint concept is appropriate for not only oceans but also land regions. Negative systematic biases in nadir and target modes have been found at most TCCON sites. The standard deviations of XCOretrieved from target and nadir modes within the observation period are similar, and larger than those from glint mode. We also used the FTS site in Beijing, China, to assess the OCO-2 XCOin 2016. This site is located in a typical urban area, which has been absent in previous studies. Overall, OCO-2 XCOagrees well with that from FTS at this site. Such a study will benefit the validation of the newly launched TanSat products in China.In order to correctly use the column-averaged atmospheric CO_2 dry-air mole fraction(XCO_2) data in the CO_2 flux studies, XCO_2 measurements retrieved from the Orbiting Carbon Observatory-2(OCO-2) in 2015 were compared with those obtained from the global ground-based high-resolution Fourier Transform Spectrometer(FTS) participating in the Total Carbon Column Observing Network(TCCON). The XCO_2 retrieved from three observing modes adopted by OCO-2, i.e., nadir, target, and glint, were separately validated by the FTS measurements at up to eight TCCON stations located in different areas. These comparisons show that OCO-2 glint mode yields the best qualitative estimations of CO_2 concentration among the three operational approaches. The overall results regarding the glint mode show no obvious systematic biases. These facts may indicate that the glint concept is appropriate for not only oceans but also land regions. Negative systematic biases in nadir and target modes have been found at most TCCON sites. The standard deviations of XCO_2 retrieved from target and nadir modes within the observation period are similar, and larger than those from glint mode. We also used the FTS site in Beijing, China, to assess the OCO-2 XCO_2 in 2016. This site is located in a typical urban area, which has been absent in previous studies. Overall, OCO-2 XCO_2 agrees well with that from FTS at this site. Such a study will benefit the validation of the newly launched TanSat products in China.

关 键 词：Orbiting Carbon Observatory-2(OCO-2) Fourier Transform Spectrometer(FTS) carbon dioxide(CO2) VALIDATION 

分 类 号：X51[环境科学与工程—环境工程]