Toward High Precision XCO₂ Retrievals From TanSat Observations: Retrieval Improvement and Validation Against TCCON...

Area of Science:

• Earth Observation
• Atmospheric Science
• Remote Sensing

Background:

• TanSat is China's first CO2 measurement satellite, launched in 2016.
• Accurate CO2 retrievals are crucial for climate monitoring and carbon cycle studies.

Purpose of the Study:

• To improve the accuracy and precision of XCO2 retrievals from TanSat nadir mode data.
• To implement and validate an enhanced retrieval algorithm incorporating spectrum correction and combined O2 A and CO2 weak band analysis.

Main Methods:

• Implemented the University of Leicester Full Physics (UoL-FP) algorithm for TanSat.
• Developed a spectrum correction method using an 8th order Fourier series and analyzed solar calibration data.
• Extended retrieval to combined O2 A and CO2 weak bands and applied a Genetic Algorithm for quality control.
• Validated the improved retrieval against 20 Total Column Carbon Observing Network (TCCON) sites.

Main Results:

• The spectrum correction significantly improved O2 A band retrieval.
• 18.3% of retrieved data was identified as high quality after applying GA-based filters.
• The new approach achieved an average bias of -0.08 ppm and RMSE of 1.47 ppm when compared to TCCON.
• Demonstrated significant improvements in XCO2 retrieval accuracy and precision.

Conclusions:

• The developed methods enhance XCO2 retrieval from TanSat data.
• The improved retrieval accuracy and precision will benefit Level-2 data production.
• The methods are planned for application in TanSat's operational XCO2 processing.