Importance of the Vertical Grid Choice for Passive Infrared Sounding from Space-based and Ground-based Platforms

The vertical grid choice can impact the information content of thermodynamic soundings retrieved from passive spectrometers. This study explores the effects of different grid spacings on thermodynamic soundings from ground-based (Atmospheric Emitted Radiance Interferometer, AERI) and space-based (Cross-track Infrared Sounder, CrIS) infrared (IR) spectrometers. Information content from CrIS is not significantly impacted by the grid resolution, except in the situation where a vertical grid is very coarse (greater than 700 m in spacing). Contrastingly, ground-based temperature sounding is very sensitive to the vertical grid choice, with maximum information content being attained in a grid that has very fine vertical spacing near the surface. As a result, the synergy of ground- and space-based sensors together is also sensitive to the grid choice, with the vertical grids that maximize the ground-based information content proving to maximize the information in the instrument synergy as well. The vertical resolution of the retrievals from ground-based sensors is very sensitive to the vertical grid choice in the lowest 1000 m above ground level, while space-based sensor vertical resolution is less sensitive to the choice of vertical grid. When developing a synergy of ground- and space-based sensors, a vertical grid that maximizes the performance of the ground-based sensor is critical to maximizing the performance of the instrument synergy.