by: Prof Emeritus Paul Joss, MIT/Visidyne Senior Vice President for Research, Dr. A.T. Stair, President, Visidyne, Inc., Andrew Le Page, Senior Scientist, Visidyne, Inc.
Hurricanes are by far nature’s most destructive natural phenomenon, with average worldwide annual losses of around 19,000 lives and $26 billion in property damage. The terms hurricane and typhoon are used in different parts of the world to refer to the same phenomenon, which scientists call a tropical cyclone. If scientists could more accurately measure the intensities of these severe storms and better predict their paths as they approach land, it would allow coastal residents and emergency responders to better prepare – potentially saving countless lives and significantly reducing property damage. To address this issue, the ISS National Lab and NASA are supporting a project by Visidyne, Inc. to significantly improve intensity measurements and, subsequently, path predictions of strong tropical cyclones using a measurement technique from the low Earth orbit vantage point of the ISS.
MIT researcher Paul Joss is the Principal Investigator of the Visidyne project, Tropical Cyclone Intensity Measurements from the ISS (CyMISS). The CyMISS measurement approach is based on original work by MIT researcher Kerry Emanuel, and involves simultaneous and very accurate determination of the altitudes and temperatures at the tops of a storm’s eyewall clouds. The eyewall is the ring of extreme weather conditions surrounding the eye of the storm, where the highest winds and most torrential rainfall are located. By combining the eyewall cloud-top altitude and temperature data with information about sea-level surface temperatures, scientists can retrieve the storm’s central sea-level air pressure, which leads to more accurate prediction of the intensities (peak wind speeds) and paths of the storms before they hit land.
As a first step in measuring the altitude of eyewall clouds using passive sensors, the CyMISS team created an anaglyph 3D view of Super Typhoon Atsani in the Pacific Ocean during August 2015. This view was produced using the parallax information contained in a sequence of more than 200 digitally processed images of the storm taken from the ISS. Astronaut Kimiya Yui mounted a standard Nikon digital camera in a window within the Cupola of the space station and pointed it in a fixed direction that Visidyne had selected. The timer was set to take photographs automatically once every second for about four minutes, beginning shortly before and continuing after Super Typhoon Atsani passed through the camera’s field-of-view. At the time the images were taken, the ISS was orbiting about 400 kilometers (250 miles) above the western Pacific Ocean, with a minimum slant range of about 800 kilometers (500 miles) from the ISS to the eye of the storm.
The images used to create the anaglyph 3D view were remapped to a common projection, approximating an overhead view covering about 225 kilometers by 150 kilometers (140 miles by 93 miles). This processing was required to remove the effects resulting from the ever- changing range and viewing angle from the ISS as it moved past the storm. In addition, the contrast of the 3D view has been increased to improve the visibility of features as small as 100 meters (300 feet) across. This allows scientists to view features about a factor of ten smaller than what is possible with conventional visible-band imagery from the GOES weather satellites.
This remarkable and unique 3D view clearly reveals variations in the cloud-top altitudes, as well as the height difference between the high clouds above the eyewall of the storm and the low clouds inside the eye. The successful creation of the anaglyph 3D view is an important milestone because it demonstrates use of the parallax technique to measure the altitudes of a tropical cyclone’s eyewall clouds from space.
The original photographs are courtesy of the NASA-JSC Earth Science and Remote Sensing Unit, and the image processing and preparation of the stereo view was done by Andrew LePage of Visidyne, Inc.