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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Volume 10, issue 10 | Copyright
Atmos. Meas. Tech., 10, 3877-3892, 2017
https://doi.org/10.5194/amt-10-3877-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 24 Oct 2017

Research article | 24 Oct 2017

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, Yosuke Niwa4, Toshinobu Machida5, Yousuke Sawa4, and Hidekazu Matsueda4 Naoko Saitoh et al.
  • 1Center for Environmental Remote Sensing, Chiba University, Chiba, 263-8522, Japan
  • 2Atmosphere and Ocean Research Institute, University of Tokyo, Kashiwa, 277-8564, Japan
  • 3Japan Aerospace Exploration Agency, Tsukuba, 305-8505, Japan
  • 4Meteorological 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 since they represent CO2 concentrations away from point source emissions. 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) (736–287hPa), 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: 40–20°S, 20°S–20°N, 20–40°N, and 40–60°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 541–398hPa, partly due to the use of 10µm CO2 absorption band in conjunction with 15 and 9µm 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 a transport model based on the Nonhydrostatic ICosahedral Atmospheric Model (NICAM-TM) confirmed the validity of the bias-correction values evaluated over airports in limited areas. In low latitudes in the upper MT region (398–287hPa), 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 Southeast Asia, where CO2 concentrations in the upper atmosphere display relatively large variations due to strong updrafts.

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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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