Abstract
Atmospheric motion vectors (AMVs), derived by tracking patterns, represent the winds in a layer characteristic of the pattern. AMV height (or pressure), important for applications in atmospheric research and operational meteorology, is usually assigned using observed IR brightness temperatures with a modeled atmosphere and can be inaccurate. Stereoscopic tracking provides a direct geometric height measurement of the pattern that an AMV represents. We extend our previous work with multi-angle imaging spectro–radiometer (MISR) and GOES to moderate resolution imaging spectroradiometer (MODIS) and the GOES-R series advanced baseline imager (ABI). MISR is a unique satellite instrument for stereoscopy with nine angular views along track, but its images have a narrow (380 km) swath and no thermal IR channels. MODIS provides a much wider (2330 km) swath and eight thermal IR channels that pair well with all but two ABI channels, offering a rich set of potential applications. Given the similarities between MODIS and VIIRS, our methods should also yield similar performance with VIIRS. Our methods, as enabled by advanced sensors like MODIS and ABI, require high-accuracy geographic registration in both systems but no synchronization of observations. AMVs are retrieved jointly with their heights from the disparities between triplets of ABI scenes and the paired MODIS granule. We validate our retrievals against MISR-GOES retrievals, operational GOES wind products, and by tracking clear-sky terrain. We demonstrate that the 3D-wind algorithm can produce high-quality AMV and height measurements for applications from the planetary boundary layer (PBL) to the upper troposphere, including cold-air outbreaks, wildfire smoke plumes, and hurricanes.
Highlights
Height assignment using infrared (IR) methods is arguably the largest source of uncertainty in atmospheric motion vectors (AMVs) derived by tracking cloud and water vapor features in satellite imagery
The former is possible only for moderate resolution imaging spectroradiometer (MODIS) on Terra, since multi-angle imaging spectro–radiometer (MISR) does not fly on Aqua, and only for the reflective channels because MISR lacks thermal IR capabilities
Because the templates in the MODIS-GOES case are taken from the GOES advanced baseline imager (ABI) fixed-grid projection, and in the MISR-GOES case, templates are taken from the MISR swath mapped into a Space Oblique Mercator projection, there cannot be a perfect comparison with identical pattern content in the respective templates
Summary
Height assignment using infrared (IR) methods is arguably the largest source of uncertainty in atmospheric motion vectors (AMVs) derived by tracking cloud and water vapor features in satellite imagery. To infer the height of a feature pattern, a conventional AMV height assignment relies on collocated thermal IR radiances in the same images and requires knowledge of an a priori atmospheric thermodynamic profile (e.g., temperature lapse rate) [1]. Such IR-based height assignment methods have at least three fundamental limitations. The height that characterizes an AMV feature is not necessarily that of the brightest or coldest pixel Rather, it is determined by a collection of dark and bright (cold and warm) pixels, and the contrast of these pixels relative to the background. These limitations have led to several modifications in IR-based algorithms in which one works better than another depending on the type of cloud scene [5]
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