RII Track-4:FAST: An investigation of tropical cyclone intensity using synthetic aperture radars and complementary satellite ocean observations

University Of Hawaii, Honolulu

Investigators

Abstract

Tropical cyclones (TC) are one of the most dangerous natural phenomena impacting the United States. Measurements of TC intensity such as wind speed are sparse and uncertain. In this project, we use an all-weather satellite technology called synthetic aperture radar (SAR) to collect high-resolution (10 m) information about the atmosphere, wave, and ocean environment within TC centers. The first objective is to improve the retrieval of wind speed and rainfall intensity within TCs. The second objective is to expand our understanding of air-sea exchanges through various satellite observations. Analysis of the novel SAR TCs database will ultimately lead to improved forecasts of TC intensity. This project will develop methods to extract the storm size, rainfall intensity and wind speeds which increases the confidence in SAR imagery for operations such as the National Hurricane Center. The project will foster new collaborations between the University of Hawai’i at Manoa (UHM) and the National Aeronautics and Space Administration (NASA) / Jet Propulsion Laboratory (JPL) in Pasadena, California, a premier, internationally renowned center for Earth-observing satellites. The project will assist in future research projects associated with satellite missions within the United States. We hypothesize that SAR-derived wind speeds, storm sizes, and radial structure within TCs will provide useful insights to air-sea exchanges and constrain forecast models under extreme forcing. C-band SARs are sensitive to rain. In contrast, L-band SARs, like NASA’s planned NiSAR, are less sensitive to rain. Therefore, the complementary analysis of these radars will reduce contamination of rainfall on wind speed retrievals. We will build the capacity of both C- and L-band co- and cross- polarized SARs to estimate moderate to high wind speeds especially under rainfall. Other satellite technologies measure sea surface temperature, sea surface height, and ocean salinity. These variables in conjunction with the SAR wind speeds and a theoretical model will provide a bottom-up view of TC ocean-atmosphere characteristics. We will evaluate the ocean response as it relates to the storm magnitude and size. We can directly evaluate the added benefit of the SAR-derived variables and the underlying theories. The convergence of multiple satellite technologies is expected to provide insights into the coupled ocean-atmosphere system under extreme conditions within TCs. Both improving SAR wind speed retrievals and assessing satellite observations will help NASA plan for future missions especially those involving the retrieval of environmental information within TCs. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.