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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union

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https://doi.org/10.5194/amt-2017-111
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
26 Jun 2017
Review status
This discussion paper is a preprint. A revision of this manuscript was accepted for the journal Atmospheric Measurement Techniques (AMT) and is expected to appear here in due course.
Bias assessment of lower and middle tropospheric CO2 concentrations of GOSAT/TANSO-FTS TIR Version 1 product
Naoko Saitoh1, Shuhei Kimoto1,a, Ryo Sugimura1,b, Ryoichi Imasu2, Kei Shiomi3, Akihiko Kuze3, Yousuke Niwa4, Toshinobu Machida5, Yousuke Sawa4, and Hidekazu Matsueda4 1Center for Environmental Remote Sensing, Chiba University, Chiba, 263-8522, Japan
2Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, 277-8564, Japan
3Japan Aerospace Exploration Agency, Tsukuba, 305-8505, Japan
4Meteologotical Research Institute, Tsukuba, 305-0052, Japan
5National Institute for Environmental Studies, Tsukuba, 305-8506, Japan
anow at: the Japan Research Institute, Tokyo, 141-0022, Japan
bnow at: Fujitsu FIP Corporation, Tokyo, 105-8668, Japan
Abstract. CO2 observations in the free troposphere can be useful for constraining CO2 source and sink estimates at the surface due to their representativeness being away from local point sources of CO2. The thermal infrared (TIR) band of the Thermal and Near Infrared Sensor for Carbon Observation (TANSO)−Fourier Transform Spectrometer (FTS) on board the Greenhouse Gases Observing Satellite (GOSAT) has been observing global CO2 concentrations in the free troposphere for about 8 years, and thus could provide a dataset with which to evaluate the vertical transport of CO2 from the surface to the upper atmosphere. This study evaluated biases in the TIR version 1 (V1) CO2 product in the lower troposphere (LT) and the middle troposphere (MT) (736–287 hPa), on the basis of comparisons with CO2 profiles obtained over airports using Continuous CO2 Measuring Equipment (CME) in the Comprehensive Observation Network for Trace gases by AIrLiner (CONTRAIL) project. Bias-correction values are presented for TIR CO2 data for each pressure layer in the LT and MT regions during each season and in each latitude band: 40°S–20°S, 20° S–20° N, 20° N–40° N, and 40° N–60° N. TIR V1 CO2 data had consistent negative biases of 1–1.5 % compared with CME CO2 data in the LT and MT regions, with the largest negative biases at 541–398 hPa, partly due to the use of 10-μm CO2 absorption band in conjunction with 15-μm and 9-μm absorption bands in the V1 retrieval algorithm. Global comparisons between TIR CO2 data to which the bias-correction values were applied and CO2 data simulated by Nonhydrostatic ICosahedral Atmospheric Model (NICAM)-based transport model (TM) confirmed the validity of the bias-correction values evaluated over airports in limited areas. In low latitudes in the upper MT region (398–287 hPa), however, TIR CO2 data in northern summer were overcorrected by these bias-correction values; this is because the bias-correction values were determined using comparisons mainly over airports in East Asia where CO2 concentrations in the upper atmosphere display relatively large variations due to strong updrafts.

Citation: Saitoh, N., Kimoto, S., Sugimura, R., Imasu, R., Shiomi, K., Kuze, A., Niwa, Y., Machida, T., Sawa, Y., and Matsueda, H.: Bias assessment of lower and middle tropospheric CO2 concentrations of GOSAT/TANSO-FTS TIR Version 1 product, Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2017-111, in review, 2017.
Naoko Saitoh et al.
Naoko Saitoh et al.

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Short summary
This study evaluated biases in GOSAT/TANSO-FTS thermal infrared (TIR) V1 CO2 product on 736–287 hPa on the basis of comparisons with CONTRAIL CME CO2 data over airports. TIR V1 CO2 data had consistent negative biases of 1–1.5 %, with the largest negative biases at 541–398 hPa. Global comparisons between TIR CO2 data to which the bias-correction values were applied and CO2 data simulated by NICAM-TM confirmed the validity of the bias-correction values evaluated over airports in limited areas.
This study evaluated biases in GOSAT/TANSO-FTS thermal infrared (TIR) V1 CO2 product on...
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