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| Author: | Gernot Hartmann |
| Institution: | Federal Institute for Geosciences and Natural Resources, Stilleweg 2, 30655 Hannover, GERMANY |
| Email: | hart@sdac.hannover.bgr.de |
| Authors: | Ceranna, Lars; Hartmann, Gernot |
Abstract Title:
"Installation and Operation of the Infrasound Station I27DE Neumayer, Antarctica" |
Abstract:
The I27DE infrasound array was installed at the German Neumayer research base in Antarctica during the austral summer of 2002/2003. The array consists of nine elements with an aperture of about 2 km. In a comparison of different nine-element array configurations, it was found that the distribution of the individual stations on a spiral, resulting in a configuration like a "pinwheel", provides an optimum array response function.
The array was designed taking into consideration the harsh weather conditions on the Ekstrom ice shelf, characterized by low environmental temperatures down to -40°C and frequent storms with wind speeds up to 45 m/s. Therefore, the most attention was paid to the wind-noise reducing pipe arrays. They consist of 16 arms of 15-m-long porous hoses, each encased in a perforated polyethylene pipe. These pipes were laid out in shallow trenches extending radially from each sensor in a foam-insulated aluminum container starting alternately 10 m and 20 m from the sensor. Thus, the overall diameter of the pipe array is 70 m. At two of the nine stations, larger pipe arrays with 32 arms 70 m diameter and 16 arms 90 m diameter were installed in order to compare their efficiency with respect to wind-noise reduction. As expected, the larger number of arms leads to a noise reduction above 0.5 Hz, which could be a significant improvement for wind speeds above 10 m/s. However, the increasing snow accumulation on top of the pipe arrays has not only reduced the wind noise for high wind speed but has also reduced the difference in the noise levels of the different pipe arrays.
The array has been reliably operated since the installation was completed in February 2003. The data availability is nearly 100 %. Data is continuously transmitted to the IDC via a permanent satellite link. After the successful test period in the Antarctic winter of 2003 and the first yearly routine maintenance in December 2003 and January 2004, it is planned to certify I27DE as IMS infrasound station in 2004. |
| Keywords: | Infrasound station, Antarctica, Array configuration, Pipe array |
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