Tropical cyclone dynamics revealed by MISR high-resolution, height-resolved, cloud-track winds and cloud top heights

For over 10 years the Multi-angle Imaging SpectroRadiometer (MISR) instrument has been making global observations from NASA's polar orbiting Terra satellite. With nine cameras that acquire imagery in visible and near-infrared channels at up to 275 m spatial resolution over a period of seven minutes, MISR provides temporal and spatial detail unavailable from any other satellite instrument.

A stereophotogrammetric technique is employed to simultaneously retrieve the height and cross-track (east-west) motion of clouds at a spatial resolution of 1.1 km. Features at the cloud top are automatically tracked between different camera views to determine their displacement over time allowing motion orthogonal to the (north to south) motion of the satellite to be determined with high accuracy. The assignment of cloud top height is purely geometric, with a nominal vertical resolution of approximately 500 m, and does not depend on knowledge of the thermal structure of the atmosphere. These characteristics make MISR observations particularly useful in tropical cyclone environments, which are complex and dynamically evolving in both the horizontal and vertical.

We will describe MISR observations of tropical cyclones, focusing on cloud motion at different vertical levels and observations of rapidly evolving cloud tops. We will also discuss techniques for estimating divergence at the top of fully mature tropical cyclones and methods for inferring the associated vertical velocities. The MISR data suggest that many cloud top features are related to vortical hot towers and changes in system intensity. The MISR high-resolution, height resolved cloud track winds and cloud top height products are a new and potentially rich source of information on tropical cyclone dynamics.