10 years of height-resolved cloud-track winds from the Multi-angle Imaging SpectroRadiometer (MISR) instrument on the Terra satellite
While geostationary satellites provide excellent coverage at low latitudes and polar orbiting instruments such as MODIS yield wind information near the poles, until recently, no single instrument routinely produces near-global, model independent, cloud-track winds. However, by utilizing multiple visible channel views and fast image matching algorithms to identify common features and determine the image disparities, the MISR instrument on NASA's Terra satellite has now collected 10 years of height-resolved, cloud-track winds using a single, consistent algorithm. The MISR cloud-track winds are reported on mesoscale domains of 70.4 km × 70.4 km and referenced to stereoscopically derived heights above the earth ellipsoid, which have a nominal vertical resolution of approximately 500 m. Importantly, the stereo height assignment and wind retrieval are largely insensitive to instrument calibration changes because the pattern matcher relies only on relative brightness values, rather than the absolute magnitude of the brightness.
Comparisons with other wind datasets suggest that the MISR cloud-track vector winds are of comparable quality to the geostationary cloud drift winds and scatterometer winds routinely assimilated into global forecast models, but the MISR winds extend from nearly pole-to-pole and provide height resolution not available from these other sensors. Because the global winds are driven primarily by the global (im)balance of heating, monitoring variations in the winds over 10 years promises to yield important insights into the processes related to the hydrologic cycle and transport of heat and water vapor. We will describe the MISR cloud-track wind product and 10-year dataset and show the influence of large-scale phenomena such as the Madden-Julian Oscillation (MJO) and the El Niņo Southern Oscillation (ENSO) on the winds observed by MISR.