Characteristics of the Atmosphere and Surface in New Channels planned for the GeoXO Imager

The GeoXO Imager (GXI) is the planned replacement for the Advanced Baseline Imager (ABI) that is present on the current series of NOAA geostationary satellites. Scheduled for launch in 2032, GXI will contain two channels that are new to NOAA's geostationary program. The first is a near-infrared channel centered in a water vapor absorption band near 0.91 µm. This daytime-only channel will contain information about the total water vapor in the atmospheric column. The other is an infrared channel centered near 5.15 µm. This channel will be more sensitive to boundary layer water vapor than any of the existing ABI channels. Together, both of these channels are expected to offer significant benefits in identification of mesoscale water vapor features in the boundary layer.

This work will highlight some of the expected characteristics and benefits of these new channels, using a combination of observations from existing instruments, like the Flexible Combined Imager (FCI), and simulations from both the Community Radiative Transfer Model (CRTM) and the Moderate Resolution Atmospheric Transmission model (MODTRAN). To best exploit the atmospheric and cloud properties contained in these new channels, we must also understand the characteristics of the Earth's surface at these wavelengths. The properties of the surface at 0.91 µm will be explored in this presentation, including differences in surface albedo between the 0.91 µm channel and the window channel at 0.86 µm. Characterizing these differences will be critical to interpreting imagery, retrieving column water vapor, and quantifying the resulting uncertainties. At 5.15 µm, factors confounding the retrieval of low level water vapor will include quantification of surface emissivities, as well as understanding the role of diurnal heating and cooling in influencing brightness temperatures observed in this channel.