A New Method for Accurate Remote Measurement of Tropical Cyclone Intensities

Abstract:

In terms of loss of life and property, tropical cyclones (TCs) are the most destructive natural phenomenon on earth. Real-time in situ measurements of TC intensities are available only in the Atlantic basin and eastern Pacific.

CyMISS (Cyclone Measurements from the International Space Station) is a project that has been approved by CASIS* to be flown on the International Space Station (ISS). Its purpose is to demonstrate a new technique for the accurate real-time measurement of the intensities of strong (category 3-5) TCs via passive instrumentation from low earth orbit. Our method, which is based on the widely accepted Emanuel model for the thermodynamics of TCs, requires the measurement of only two quantities: the temperature, T, of the cirriform deck comprising most of the eyewall cloud tops, and the height, h, of these cloud tops above sea level. Measurement of T to an accuracy of ±1 K and h to an accuracy of ±100 m, combined with readily available information on ambient sea surface temperatures and the ambient sea-level pressure near the periphery of the TC, determines the central sea-level pressure, P_c, of the storm to an accuracy of ±5 hPa. This is an improvement by a factor of ~2-3 over the accuracy attainable via the modified Dvorak method and provides a real-time estimate of peak sustained winds within a strong TC to an accuracy of ±10 knots. Our method can thus yield accurate and nearly real-time information on TC intensities prior to landfall. More accurate real-time knowledge of P_c will also provide improved initialization of NWP models, thereby improving the accuracy and reliability of TC forecasts.

We will measure h by the use of a pseudo-stereoscopic technique applied to visible and infrared imagery taken from the ISS. To determine T, we will initially utilize near-simultaneous measurements by GOES-R and other advanced MetSats. CyMISS will be complementary to NASA's upcoming CYGNSS mission, in that we will be able to measure TC intensities even at the highest peak sustained winds found in these storms. In a future operational system, our method can be deployed via a constellation of 4-5 nanosatellites that would provide the first worldwide, real-time, accurate measurements of TC intensities.

*CASIS (Center for the Advancement of Science in Space) manages the U.S. National Laboratory on the ISS.