Interaction Of The Cyclonic Winds With The Infrasonic Signal Generated By A Large Maritime Storm
Date of Award
Ph.D. in Physics
Physics and Astronomy
William W. Frazier
Joseph R. Gladden
The collision of counter propagating ocean surface waves of like periods is known to produce an infrasonic signal termed a microbarom. It has been suggested that microbaroms associated with large maritime storms are generated far from the storm center at a location in which the storm swell and background swell have equal period and are counter-propagating. It is shown in this work that the interaction of the atmospheric microbarom signal generated by a large maritime storm with the cyclonic winds of the storm results in a characteristic acoustic signal far from the storm which could potentially be used to estimate storm intensity from infrasonic measurements. Numerical propagation modeling has predicted that one particular characteristic, back azimuth, might be analyzed to estimate storm intensity. For a storm in the open Atlantic, microbaroms which have strongly interacted with the storm winds are predicted to have back azimuths oriented towards the storm center and are only expected to be observed in a localized region to the northwest of the storm. Microbaroms which have weakly interacted with the storm are predicted to have back azimuths oriented towards the source region and are expected to be observed most clearly from the south of the storm. The size of the region in which the strongly interacting signal is observed has been found to be strongly dependent on wind speeds in the storm center and therefore observation of this signal might allow estimation of storm intensity from infrasonic data. Acoustic data has been collected during the 2010 and 2011 Atlantic hurricane seasons using infrasound arrays deployed in Florida, North and South Carolina, New Jersey, New York, and Connecticut. Observations of microbaroms which have not interacted strongly with the storm are in agreement with the prediction that the location of the microbarom source region is far from the storm center. Additionally, observations of microbaroms with back azimuths such that interaction with the storm is likely are in strong agreement with predictions from propagation modeling.
Blom, Philip Stephen, "Interaction Of The Cyclonic Winds With The Infrasonic Signal Generated By A Large Maritime Storm" (2013). Electronic Theses and Dissertations. 770.