This work builds on the research conducted by this group under a previous National Science Foundation (NSF) grant. There are three principal tasks:
1. Develop the Active Temperature Ozone Moisture Microwave Spectrometer (ATOMMS) satellite-to-satellite radio occultation retrieval system, including characterization of turbulence effects. 2. Continue development of an algorithm to mitigate problems associated with the non-uniqueness of the inversion solution at the top of the marine boundary layer (MBL) in warm environments (super-refraction). 3. Develop a global, high-resolution water vapor climatology spanning tropospheric regions warmer than -25 degrees Celsius.
The first objective is aimed to further develop ideas for an active radio occultation (RO) system to realize a number of key advantages relative to passive observations suggested from their Global Positioning System (GPS) RO research, such as ~200 m vertical resolution, high precision and insensitivity to clouds. The latter two foci are to achieve anticipated but thus far unrealized middle and lower tropospheric applications of GPS RO. The MBL is fundamentally important to weather and climate as the region of exchange between the surface and free troposphere but is poorly modeled and observationally limited to a few regional field campaigns. The combination of the GPS RO MBL retrieval method with new open loop GPS measurements will overcome an apparently intractable problem to make GPS RO the first orbiting system to routinely profile the MBL, and thus provide improved climatological knowledge of the MBL.
ATOMMS represents the logical next step of a satellite-to-satellite occultation spectrometer actively probing microwave water and ozone absorption lines. Such a system appears capable of revolutionary advances such as ~200 m vertical resolution profiles of water vapor, temperature and pressure with ~1% water precisions, ~0.4 Kelvin temperature and ~10 m geopotential heights extending from near the surface to the mesopause. With additional frequencies, other trace constituents such as water isotopes, can be determined in the upper troposphere and above with similar performance.
The broader impacts of this work derive from the potential of the active radio occultation technique to provide Global Climate Observing System benchmark observations at high vertical resolution (but low horizontal, temporal resolution) of water vapor and other trace gases such as ozone, from the surface to the mesopause. Such observations can be used to study climate processes and constrain models.
