Ground-based measurements of XCO2 using grating spectrometers for validating GOSAT target observations over the Greater Tokyo Area

Ryoichi Imasu,  Atmosphere and Ocean Research Institute, The University of Tokyo,  imasu@aori.u-tokyo.ac.jp (Presenter)
Yutaka Matsumi,  Institute for Space-Earth Environmental Research, Nagoya University,  matsumi@nagoya-u.jp
Isamu Morino,  National Institute for Environmental Studies,  morino@nies.go.jp
Masafumi Ohashi,  Graduate School of Science and Engineering, Kagoshima University,  mohashi@ibe.kagoshima-u.ac.jp
Masahiro Kawasaki,  Research Institute for Humanity and Nature,  masahiro.kawasaki.26u@st.kyoto-u.ac.jp
Asaka Hasegawa,  tmosphere and Ocean Research Institute, The University of Tokyo,  asaka_h@aori.u-tokyo.ac.jp

The Greenhouse Gases Observing Satellite (GOSAT) science team has conducted mapping observations of the column-averaged dry-air mole fractions of CO2 (XCO2) over greater Tokyo area (Kanto Plain) since 2010. To validate the observation results, new type grating spectrometers, " Compact Array Spectrometer Targeting Local Emissions of CO2 (CASTLE-CO2)" developed at Nagoya University were deployed at four sites (Tokyo, Saitama, Chiba, and Ibaraki) in the area and have been operated from 2020. One additional spectrometer was deployed in a remote island, Minamitorishima, 1800km away from Tokyo for monitoring the background level of the gas concentration. On this island, another type of spectrometer, Fiber-Etalon Solar Measurement for Carbon Dioxide Sensor (FES-C), has been also operated from 2018 as a joint research of Japanese universities. One of CASTLE-CO2 was placed at a Total Carbon Column Observing Network (TCCON) site in Tsukuba city (Ibaraki) for its calibration. The original values measured by the CASTLE-CO2 have positive bias of about 7 ppm against TCCON data, and they can be reduced to about 1 ppm after applying a scaling factor. The characteristics of seasonal variations in XCO2 observed by the four CASTLE-CO2 installed in the greater Tokyo area differ from site to site. The three sites in Tokyo, Saitama, and Chiba show higher values than the TCCON site in Tsukuba, but the peaks appeared in the early winter season tend to be weaker than those of in situ measurements at ground observations as reported by Imasu and Tanabe (2018). Observations by FES-C on Minamitorishima have continued for more than two years, and they show a clear annual trend. Unlike the data observed at other sites on land, the data on the island were low from February to March just before the annual maximum. During this period, about 10 collocated measurements were performed with GOSAT (Sun glint observation) observations, showing almost consistent results. Long-term observations are ongoing at all observation sites, and the data will be compared with those from GOSAT-2 and the Orbiting Carbon Observatory (OCO)-2/-3.

Poster: Poster_Imasu__129_25.pdf 

Presentation Type: Poster

Session: 1.5b Results from current missions

Session Date: Monday (6/14) 12:00 PM