Joint retrieval of atmospheric temperature and water vapor from AIRS thermal infrared and OCO-2 near-infrared measurements

Abstract. Combining thermal-infrared emission measurement with near-infrared absorption measurement can be a pathway to improved remote sensing of temperature and water vapor profiles from the surface to the upper troposphere. The addition of near-infrared radiance data to the thermal can significantly enhance the information content close to the surface in the planetary boundary layer, and is effective in clear or near-clear daytime conditions over land and ocean glint. A proof-of-concept study is presented using thermal-infrared Atmospheric Infrared Sounder (AIRS) radiances combined with near-coincident, near-infrared radiances from the Orbiting Carbon Observatory-2 (OCO-2) in a joint optimal estimation retrieval. Results indicate a significant increase in information content and reduced retrieval error for both temperature and water vapor between the surface and ~800 mb. Comparisons of retrieved profiles to coincident radiosondes show limited-to-no reduction in biases of temperature and water vapor over the forecast-derived a priori near the surface, indicating that improvements in the forward-modelling and/or retrieval algorithm are needed.