July 2018 to present – We are collaborating with the National Oceanic and Atmospheric Administration (NOAA) to design and develop a GNSS-RO weather sensor on a balloon platform. High-level project goals include improving global weather predictions and advancing climate research. Some time soon, we hope our work will improve the forecasting of high-impact weather events such as hurricanes and tropical cyclones.
Global Navigation Satellite System Radio Occultation (GNSS-RO) is a remote sensing technique that detects changes in received GNSS radio signals as they pass through the Earth’s atmosphere. A GNSS radio occultation occurs when a GNSS satellite rises or sets across the Earth horizon with respect to a GNSS observer (see figure). The GNSS signal passing through the atmosphere is measurably bent, which provides atmospheric information such as temperature, pressure, humidity, and ionospheric electron count.
The use of GNSS receivers via the radio occultation technique has led to significant advances in weather and climate research by providing high-accuracy vertical resolution of refractivity, temperature, and water vapor information. While there are several operational space satellite missions with GNSS-RO payloads, there continues to be: 1) gaps in spatial data; 2) difficulty in remotely sensing the planetary boundary layer, and 3) limited funds for GNSS-RO missions. Our research aims to tackle these major issues and provide long-term and highly accurate atmospheric thermodynamic information that are complementary to state-of-the-art satellite observations.
In 2018, NCL successfully conducted two high-altitude balloon flights carrying two GNSS-RO payloads, reaching 33.2 km (109,041 ft) in altitude. The team successfully tracked five major GNSS constellations during these two flight campaigns. Additionally, NCL collected relevant GNSS-RO data by tracking GNSS satellites to negative elevation angles. These data were post-processed into excess phase delays, and input into post-processing software to retrieve bending angle vertical profiles. The post-processed results agreed well with the simulated profiles, providing a preliminary validation of NCL’s experiments.
Bryan Chan presented preliminary results at American Geophysical Union (AGU 2018) and American Meteorological Society (AMS 2019) conferences. We look forward to continuing this research and sharing these results with the scientific community.