MRI-R2: Acquisition of a Semi-Continental Scale Atmospheric Acoustic Transportable Array

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Intellectual MeritThis Major Research Instrumentation-Recovery and Reinvestment project will create a real-time infrasound array whose sensing elements are co-located with the 400 seismic stations in the USArray Transportable Array component of the NSF EarthScope program. This continuously sampled array, of an unprecedented scale, will provide opportunities for groundbreaking and interdisciplinary research in atmospheric acoustics, atmospheric science, and seismology. The array will sample mean values and fluctuations of the surface air pressure with nominal 70 kilometer station spacing, with a dynamic range of about 7 orders of magnitude, and with a sampling frequency of up to 40 Hz. This dense network of infrasound sensors will permit study of the nature of long-range infrasound propagation from regional to continental distances, and study of the sources of infrasound signals, using actual acoustic data, free of concerns about seismic-to-acoustic coupling. The array will not only record signals from a range of sources, it will permit study of propagation from these sources under widely varying atmospheric conditions. These data will be used to test atmospheric models and improve understanding of regional to long range infrasound propagation physics. Continuous monitoring of signals from repeating distant sources provides opportunities to probe high altitude winds, yielding valuable information to validate, tune, and improve global whole-atmosphere numerical weather and climate models. Recording actual pressure variations will aid studies of thermospheric attenuation, assess the utility of algorithms for correcting recorded signal amplitudes for wind effects and provide more data for full-waveform analyses. Atmospheric phenomena that can be studied with unprecedented spatio-temporal coverage include solar and lunar atmospheric tides, upper-level and lower-level jet streams, weather fronts, boundary-layer convection, tornadoes, nocturnal drainage flows, and gravity waves. Simultaneous and continuous observations of atmospheric and seismic noise will facilitate adaptive seismometry, a process analogous to adaptive optics in which the effects of atmospheric loading at the Earth's surface are accounted for in seismic channels to reduce noise at long periods. There also will be serendipitous avenues for research that will not be discovered until the data begin to flow. Real time data delivery capabilities will be utilized to allow open and free data distribution.Broader ImpactThis observatory will provide data for research in atmospheric acoustics, seismology and atmospheric science. As papers result from this dataset, it will be easier for institutions to attract researchers and students interested in conducting research in these areas. This network, and the data it will provide, will broaden the participation in science. It will provide many opportunities for training in data analysis, as well as validating models used in atmospheric science and atmospheric acoustics. It will provide opportunities for increasing the quality of very long-period seismic data for studies of the solid earth, and possibly reducing horizontal noise on seismic records by applying corrections derived from long period barometric data. The managing laboratory has a commitment to supporting the integration of research and education at every academic level. The data from the infrasound array will be made freely available in near real time, without restriction, through an on-line data management system, to everyone inside and outside the scientific community. Science teachers will be able to access data they are interested in and incorporate it into their science curricula. Project scientists will work with "Perspectives on Ocean Science," which is an earth and ocean science speaker series hosted by Birch Aquarium at Scripps Institution of Oceanography, to provide the public with direct access to up-to-date science in a presentation that is specifically designed for a lay audience. "Perspectives on Ocean Science" reaches an audience of almost 15 million viewers.