Development of the MethaneSAT Cloud Filter
Abstract
The MethaneSAT satellite mission aims at quantifying anthropogenic methane emissions by measuring reflected solar radiation in two spectral windows in the short wave infrared range. In the 1,249 nm - 1,305 nm spectral range the sensor will measure the oxygen (O2) singlet Delta band with a full width at half maximum (FWHM) of 0.17 nm. Additionally, the instrument will observe most of the 2v3 absorption band of methane (CH4) and a 3v1+v3 carbon dioxide (CO2) band in the spectral range 1,598 nm - 1,676 nm at a spectral resolution of 0.23 nm at FWHM. Clouds and aerosols can introduce biases into the inversion of trace gas column concentrations from solar backscatter measurements. We therefore develop a framework to detect contaminated scenes based on information from several indicators for flagging cloudy soundings.One such processor makes use of surface pressure retrievals to infer the presence of scattering particles in the field of view of the sensor. These retrievals specifically consider O2 airglow emission (see Sun et al. 2022). A complementary algorithm takes advantage of differences in the atmospheric light path between the two spectral windows of MethaneSAT in the presence of aerosols and clouds. Here, we retrieve water vapor column concentrations from the 1.3 µm and 1.6 µm windows under the assumption of the geometric lightpath. Additional cloud filtering metrics are presented, and we explore supervised learning techniques trained on a comprehensive dataset of synthetic MethaneSAT spectra at realistic noise levels to produce a synthesis cloud filter. Our screening approach is applied to measurements of the MethaneAIR instrument (Staebell et al. 2021) to demonstrate its capacity in screening for clear scenes. Finally, we present our strategy for filtering out cloud shadows.ReferencesSun et al.: An optimal estimation-based retrieval of upper atmospheric oxygen airglow and temperature from SCIAMACHY limb observations, AMT 2022, https://doi.org/10.5194/amt-15-3721-2022.Staebell et al.: Spectral calibration of the MethaneAIR instrument, AMT, 2021, https://doi.org/10.5194/amt-14-3737-2021.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFM.A53C..03W