High-resolution observations of inner core dynamics of Hurricane Alberto (2000) from MISR on NASA's Terra satellite

The Multiangle Imaging SpectroRadiometer (MISR) instrument on NASA's Terra satellite reveals detailed cyclonic rotation and dynamic structures inside the eyewall of Hurricane Alberto (2000). Using stereoscopic techniques and visible radiances from 9 consecutive viewing angles (+70.5º, +60.0º, +45.6º, +26.1º, nadir, -26.1º, -45.6º, -60.0º, -70.5º), the instrument can determine cyclone cloud structure and motions accurately within 7 min. Unlike thermal radiance techniques (e.g., CO2 peeling), the stereo technique does not require knowledge of atmospheric thermal structure and is less sensitive to radiometric calibration errors. In the Alberto (2000) case, MISR cross-track cloud winds are digitized at high (550 m horizontal and ~200 m vertical) resolutions to evaluate the cyclone's ratational velocity as a function of radial distance. The observed rational velocity shows two distinct rotational velocities 4.8 cyc/day and 18 cyc/day inside the eyewall. The faster velocity is located near the edge of eyewall and associated with two mesovortices as the cyclone underwent its second intensification during August 18-22, 2000. Since 2000 MISR has made many valuable tropical cyclone observations at such a high resolution, which can be used to better understand inner-core dynamics and intensification processes. A future WindCam concept for hurricane observation and forecasting will be discussed in this paper.