[Errors Analysis and Correction in Atmospheric Methane Retrieval Based on Greenhouse Gases Observing Satellite Data]

Area of Science:

• Atmospheric Science
• Remote Sensing
• Spectroscopy

Context:

• Accurate atmospheric methane (CH4) retrieval is vital for climate monitoring.
• Uncertainties in surface properties and atmospheric profiles (temperature, humidity, pressure) significantly impact CH4 measurement precision.
• Surface reflectance variability and atmospheric profile errors introduce substantial retrieval errors, including systematic ones difficult to resolve with CH4 bands alone.

Purpose:

• To introduce and validate novel correction methods for enhancing atmospheric CH4 retrieval accuracy.
• To mitigate errors stemming from surface reflectance and atmospheric condition uncertainties.
• To improve the precision of CH4 column-averaged mixing ratio measurements.

Summary:

• This study proposes a ratio spectrometry method to minimize surface reflectance effects and a CO2 band correction method to address atmospheric profile uncertainties.
• By converting absolute radiance spectrometry to ratio spectrometry and utilizing the CO2 1.61 μm band, these methods correct for systematic errors.
• The combined approach significantly reduces retrieval errors caused by ground properties and atmospheric conditions, validated using Greenhouse gases Observing Satellite (GOSAT) data.

Impact:

• The developed methods successfully reduce CH4 retrieval errors caused by ground and atmospheric uncertainties.
• Validated results show retrieved CH4 column-averaged mixing ratios closely align with GOSAT Level2 products.
• Achieved retrieval precision of up to -0.24% demonstrates a significant improvement in atmospheric CH4 monitoring capabilities.