Acoustical Monitoring and Analysis of Lightning

In the continuing effort to understand the behavior of lightning, arrays of radio receivers currently in use enable us to see the progression of negative leaders. Positive leaders, however, remain largely invisible outside clouds because they do not emit sufficiently strong radio pulses. To remedy this deficiency, this project will revive and improve the use of acoustic methods for locating positive (and negative) lightning leaders and apply these methods at Langmuir Laboratory in central New Mexico, where a Lightning Mapping Array and other instruments and facilities are already in place to provide the necessary complementary information.

One major goal of the study is to characterize positive leaders and positive cloud-to-ground lightning. A second major goal is to determine which of the acoustic lightning emissions come from the gas dynamic expansion of portions of the rapidly heated lightning channel and which from electrostatic field changes. A third major goal is to test the hypothesis that infrasonic signals are associated with and precede lightning initiation, and a fourth major goal is to image positive leaders and other events during triggered lightning experiments.

A networked array of acoustic transducers will be installed in the Magdalena Mountains of Central New Mexico, where Langmuir Laboratory already has a wide range of instruments to monitor thunderstorms and lightning. A recent pilot study in this area has shown co-incident infrasound acoustic sources and electromagnetic radiation sources. The present work will expand the pilot acoustic network so that more varied and extensive sources can be imaged in three dimensions plus time.

Intellectual Merit: Lightning has been investigated with different techniques, but an integrated approach involving simultaneous use of multiple techniques will yield new insights and better results. New technology has enabled distributed deployments of GPS-based acoustic networks that will provide complementary information to the already existing instrumentation systems from Langmuir Laboratory.

Broader Impacts: This project has immediate impact on scientific problems directly related to lightning hazards, as well as basic science of lightning dynamics. Undergraduate and graduate students will be involved in the scientific and applied aspects of the project. The work will enable integration and cross-disciplinary interaction between engineers, atmospheric, and earth scientists.