Characterization and validation of CH4 profiles derived from the GOSAT thermal infrared band

Abstract:

Methane (CH₄) is one of most effective greenhouse gases which is responsible for global warming since pre-industrial time. CH₄ emitted from anthropogenic and natural sources can be identified but poorly quantified in the local scale. Vertical profiles of CH₄ are retrieved from the Greenhouse gases Observing SATellite (GOSAT) Thermal InfraRed (TIR) band, and the evaluation of the GOSAT TIR CH₄ profile is being conducted. Here we show the results of the comparison of GOSAT TIR and the aircraft CH₄ in-situ profiles measured by the National Oceanic and Atmospheric Administration (NOAA) and the Alpha Jet Atmospheric eXperiment (AJAX). We compare the TIR CH₄ with the aircraft profiles from 15 NOAA sites and Railroad valley measured by AJAX. GOSAT TIR CH₄ profiles are collected under conditions within 200 km and ±12 hours from the aircraft measurements at each observation site. The TIR CH₄ profiles agree well with aircraft profiles and average differences have slightly negative biases (-3 to -6 ppb) in both the boundary layer and the free troposphere.Satellite based CH₄ measurements can provide the large spatial and temporal that improve the understanding of CH₄ transport, surface emissions and chemical loss.