Global monitoring of tropical cyclones with a dual-frequency scatterometer

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Tuesday, 19 January 2010
Michael J. Brennan, NOAA/NWS/NHC, Miami, FL; and R. D. Knabb

Tropical cyclones (TCs) play a prominent role in the global climate. Consistently monitoring TCs worldwide is not only critical for making and improving forecasts and warnings for the protection of life and property, but is also required to reliably determine the existence and magnitude of long-term global or regional changes in TC frequency and intensity. Unfortunately, the tools available for global TC monitoring have always been, and continue to be, inadequate to detect many climatological changes in TC activity.

TC genesis, track, and intensity are monitored by a relatively limited collection of observational technologies with varying accuracy and spatial and temporal sampling. The availability of various technologies has dramatically changed during the past century, and to this day certain observational capabilities, in particular those flown on reconnaissance aircraft, are only available in a portion of a few of the world's TC basins. The most consistent observations of TCs during the past four decades have come from geostationary satellites. The high temporal and spatial coverage they provide make it unlikely for any bona fide TC to go undetected, and they have made it possible to apply the Dvorak Technique globally, providing a consistent method for TC intensity estimation for more than 30 years. The Dvorak Technique has limitations, however, that have been clearly revealed in cyclones extensively sampled by aircraft reconnaissance. However, while in situ wind measurements provided by aircraft represent the most accurate method for determining TC genesis and intensity, they are unavailable in a majority of the world's TCs, and even when available, they have severe sampling limitations.

A desirable enhancement to global TC monitoring would be a tool that combines the broad coverage offered by a satellite with the capability to actually measure the surface winds within a cyclone. Fortunately, satellite mission concepts for a next-generation scatterometer, the Dual Frequency Scatterometer (DFS), have been developed. DFS has the potential to measure ocean surface vector winds in nearly all weather conditions, including the cores of most hurricanes, which is not currently possible with QuikSCAT. This presentation will examine the strengths and weaknesses of the DFS mission for global TC monitoring, with a focus on how such a mission, especially one involving multiple satellites over many years, could improve the climate record of TCs and the understanding of the relationship between TCs and various climate forcing mechanisms.