Accurate Characterization of 3D Winds Using Stereographic Observations from the Hurricane Hunter Satellites

Wind is one of the fundamental variables in weather and its characterization is among the more important pieces of information contributing to the accuracy of global numerical weather prediction (NWP) models. While twice-daily deployments of radiosondes as well as near-continuous data from ground stations and aircraft deliver the vital in situ measurements of wind at various altitudes needed to provide initial conditions for NWPs, their data are geographically scattered and sparse. Satellite-based wind measurements, such as the GOES Derived Motion Winds (DMW) data product, can provide global wind data on horizontal winds to help fill in coverage gaps improving the accuracy of NWPs. However, the spatial resolution of the DMW data products is comparatively coarse and the sounding-based measurement of altitude is crude, especially in comparison to the shrinking grid size of ever-improving NWPs. Higher spatial resolution wind measurements with much more accurate altitude determinations are required to improve NWP results further.

In order to address this issue, the Boston-based Tropical Weather Analytics, Inc. (TWA), in partnership with the Montreal-based Canada Weather Analytics, Inc. (CWA), are developing the Orbital Weather Warning System (OWWS) which will consist of a constellation of microsatellite-pairs to provide high-resolution, wide-area stereographic observations of cloud cover from orbit in order to measure cloud altitudes and 3D winds including unique measurements of the vertical component of winds. This capability to perform precision cloud stereography from orbit has been developed over the last three decades by TWA’s predecessor, Visidyne, Inc., with funding from DoD and NASA. TWA’s most recent space-based investigation into orbital cloud stereography was the CyMISS (Tropical Cyclone intensity Measurements from the ISS) project which ran from 2014 to 2019 on the International Space Station (ISS). Funded by a series of grants from CASIS (Center for the Advancement of Science in Space), which manages the ISS US National Laboratory for NASA, CyMISS was executed by the TWA science team for NASA’s Tropical Cyclone Experiment as part of NASA’s CEO (Crew Earth Observations) activities on the ISS and provided important data to further develop the technology.

The first elements of the OWWS are the Hurricane Hunter Satellites (HHSats) being developed by TWA. The initial constellation of five satellite-pairs will use CubeSats in high-inclination, low Earth orbits fitted with an array of visible cameras to provide wide-area, daytime stereographic imagery with a pixel scale of about 100 meters. In addition to generating 2D cloud imagery with a resolution superior to that from JPSS and GOES, HHSat will provide unique 3D cloud imagery to aid weather analysts. The first pair of HHSats is currently being built by Phantom Space Corporation which will launch the satellites in 2025 and operate them during a planned five-year lifetime.

Proprietary stereo image processing techniques developed by TWA will also allow the altitudes of cloud features to be measured to an accuracy as good as ±100 meters. Tracking of the changing positions of those features during the course of an observation session will allow wind velocities to be measured to an accuracy approaching 1 meter/second with sub-kilometer spatial resolution using a technique analogous to that employed in the DMW algorithm. But unlike DMW, which supplies data only on the horizontal components of wind, HHSat 3D data will provide unique information which includes the vertical component of wind – a critical parameter in characterizing the increasing number of extreme weather events. With the initial HHSat constellation, as many as five observations can be acquired of selected targets each day. Current plans call for regular observations of selected regions of the globe (e.g. North American and the neighboring waters of the Atlantic and Pacific) as well as daily monitoring of the tropics for nascent tropical cyclone activity during the summer and the polar vortex during the winter to provide vital new data to initialize NWPs. This capability may assist in better understanding of jet streams and the polar vortex, as well as developing hyper-local wind information that lends itself to new predictive methods based on AI.