Hurricanes and typhoons could be monitored from hundreds of miles away with relatively inexpensive instruments like barometers and anemometers, much like earthquakes are monitored by seismometers, a new study has found.
The red curve shows the leading edge of a packet of gravity waves radiating outward at the top of Typhoon Meranti on September 12, 2016. Credit: Visible image the Himawari satellite, maintained by the Japan Meteorological Agency, and processed by Brian McNoldy, University of Miami.
In the study, the scientists presented direct observations of the waves, obtained by NOAA aircraft flying in hurricanes and by a research buoy located in the Pacific Ocean. The waves, known as atmospheric gravity waves, are produced by strong thunderstorms near the eye and radiate outward in expanding spirals, the release explained.
“These very subtle waves can sometimes be seen in satellite images,” said David Nolan, a professor in the university’s Department of Atmospheric Sciences and lead author of the study. “We were able to measure them in aircraft data and surface instruments.”
Of course, hurricanes are very well observed by satellites, Nolan continued. “But these waves can reveal processes occurring in the eyewall of a hurricane that are obscured from the view of satellites by thick clouds,” he said. “Any additional measurements, even if they provide similar information as satellites, can lead to better forecasts.”
Computer simulations performed at the University of Miami’s Center for Computational Science can also reproduce the waves, showing that the wave strengths can be related to the maximum wind speed in the core of the storm. This suggests hurricanes and typhoons can be monitored from hundreds of miles away with instruments such as barometers and anemometers.
“The simulations suggest a correlation between wave amplitude and cyclone intensity, which could be used to make remote estimates of peak wind speeds,” the study’s abstract said.
For the study, researchers analyzed data obtained from 25 different penetrations by NOAA P3 aircraft into five hurricanes in 2003 and 2004, as well as data from the Extreme Air-Sea Interaction buoy deployed in the Pacific Ocean by Rosenstiel School scientists in 2010.
“The waves cause very weak upward and downward motions, which are recorded by the NOAA P3 as it flies through the storm,” explained Jun Zhang of NOAA’s Hurricane Research Division, a veteran of many hurricane flights. “But we were surprised at how clearly the waves could be detected at the surface.”