JAXA EORC GOSAT retrieval

1. Introduction

TANSO-FTS simultaneously observes both reflected shortwave-infrared (SWIR) solar light and thermal infrared (TIR) emissions with a single FTS-mechanism. We use an entire TIR band to add only one piece of information in the troposphere. Assuming the CO2 and CH4 partial column-averaged dry air mole fractions of the two individual layers of LT and UT are constant, we retrieve the difference between the partial column-averaged dry mole fractions of the lower troposphere (LT) and upper troposphere (UT) by combining TIR and SWIR spectra data simultaneously, constraining accurate total column density. The pressure-height ranges of LT and UT are taken as 1 -0.6 and 0.6 -0.2 of the retrieved surface pressure, respectively.

The GHG long term trend viewer presents quick view and pick up data set of the target observation sites, where users are interested. Most of the target observations requested by the RA researchers are not included in the list.

2. Data description

L1B version

FTS L1B V220.220

About data category

• Airport (CONTRAIL)
  
  The CONTRAIL (Comprehensive Observation Network for TRace gases by AIrLiner) project is being jointly conducted by NIES (National Institute for Environmental Studies), the MRI (Meteorological Research Institute), JAL (Japan Airlines), JAMCO (JAMCO Corporation) and JAL-F (JAL Foundation). The CONTRAIL Database contains all the CO2 data measured by CME, as well as the information from the aircraft data system (aircraft position, temperature, wind direction and wind speed). These data have been used for GOSAT validation. GOSAT has targeted airports in serve.
• Possible Emission Source
  
  Possible large emission source site
• Megacity
  
  Highly populated cities urban area
• Calibration
  
  Vicarious calibration site
• TCCON (Total Carbon Column Observing Network)
  
  The Total Carbon Column Observing Network (TCCON) is a network of ground-based Fourier Transform Spectrometers that record spectra of the sun in the near-infrared. From these spectra, accurate and precise column-averaged abundances of atmospheric constituents including CO2, CH4, N2O, HF, CO, H2O, and HDO, are retrieved.
• Island and Others
  
  Targeting coasts and islands, while avoiding bays and channels in order to increase the yield rate of spectra.

About parameter

• yyyy/mm/dd and hh:mm:ss :
  
  Observation time defined as the start time of the exposure.
  
• XCO2_apr:
  
  A priori of the column averaged dry air mole fraction of CO2 calculated from CarbonTracker.
  units = ppmv
• XCO2_tot:
  
  Aerosol optical thickness at 0.72um is calculated from the retrieval state
  units = ppmv
• XCO2_low:
  
  Retrieved dry air mole fraction of CO2 in the lower troposphere defined as the partial layer from Psrf_ret up to 0.6 Psrf_ret.
  units = ppmv
• XCO2_upp:
  
  Retrieved dry air mole fraction of CO2 in the upper troposphere defined as the partial layer from 0.6 Psrf_ret up to 0.2 Psrf_ret.
  units = ppmv
• XCH4_apr
  A priori of the column averaged dry air mole fraction of CH4 calculated from CarbonTracker-CH4.
  units = ppmv
• XCH4_tot
  Retrieved column averaged dry air mole fraction of CH4.
  units = ppmv
• XCH4_low
  Retrieved dry air mole fraction of CH4 in the lower troposphere defined as the partial layer from Psrf_ret up to 0.6 Psrf_ret.
  units = ppmv
• XCH4_upp
  Retrieved dry air mole fraction of CH4 in the upper troposphere defined as the partial layer from 0.6 Psrf_ret up to 0.2 Psrf_ret.
  units = ppmv
• Psrf_apr
  A priori of the surface pressure calculated from NCEP Reanalysis 2. units = hPa
• Psrf_ret
  Retrieved surface pressure. units = ppmv
• AOT_076
  Retrieved aerosol optical thickness at 0.76 µm.
• AOT_160
  Retrieved aerosol optical thickness at 1.6 µm.
• AOT_206
  Retrieved aerosol optical thickness at 2.06 µm.
• SIF
  Retrieved solar-induces fluorescence which is assumed to be constant in the O2 A band.
  units = 10^-9 W/cm²/sr/cm^-1
• CLFLG
  Cloud flag visually judged from onboard camera images.
  0 = clear
  1 = cloudy
  -1 = not available
• latitude and longitude
  Observation location.
  units = degree

About data extraction

In order to use long term trend data of the point of interest, the viewer pick up data within the circle of 10km radius.

But the following adjacent site, the viewer pick up within the circle of 1km or 2km radius.

The primary pointing system, which had been used between launch and Dec. 2014, larger pointing offset of about 5km.

Therefore, some cases include nearby target points.

3. Citation

Algorithm:

• Kikuchi, N., Kuze, A., Kataoka, F., Shiomi, K., Hashimoto, M., Suto, H., et al. (2017), Three-dimensional distribution of greenhouse gas concentrations over megacities observed by GOSAT, AGU fall meeting.
• The SWIR part of the algorithm is described by Kikuchi et al. (2016): Kikuchi, N., Y. Yoshida, O. Uchino, J. Morino, and T. Yokota: An advanced retrieval algorithm for greenhouse gases using polarization information measured by GOSAT TANSO-FTS SWIR I: Simulation study, J. Geophys. Res., 121, 21, 13129-13157, doi:10.1002/2015JD024720, 2016

Ancillary data

• NCEP_Reanalysis 2 data provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA, from their Web site at https://www.esrl.noaa.gov/psd/
• CarbonTracker results provided by NOAA ESRL, Boulder, Colorado, USA from the website at http://carbontracker.noaa.gov.
• CarbonTracker-CH4 results provided by NOAA ESRL, Boulder, Colorado, USA from the website at http://www.esrl.noaa.gov/gmd/ccgg/carbontracker-ch4/.

4. Links

• CONTRAIL
  http://www.cger.nies.go.jp/contrail/
• TCCON
  https://tccon-wiki.caltech.edu/

5. Acknowledgments

GHG Long term trend viewer was developed by JAXA/EORC. We would like to thank NIES GOSAT project members, and JAXA GOSAT project members.