Measured vertical profiles of temperature and wind are used to model infrasound propagation over a representative high savanna habitat typically occupied by the African elephant, Loxodonta africana, to predict calling distance and area as a function of the meteorological variables. The profiles were measured up to 300 m above the surface by tethered balloon-borne instruments in Etosha National Park, Namibia, during the late dry season. Continuous local surface layer measurements of wind and temperature at 5 and 10 m provide the context for interpreting the boundary layer profiles. The fast field program (FFP) was used to predict the directionally dependent attenuation of a 15-Hz signal under these measured atmospheric conditions. The attenuation curves are used to estimate elephant infrasonic calling range and calling area. Directionality and calling range are shown to be controlled by the diurnal cycle in wind (shear) and temperature. Low-level nocturnal radiative temperature inversions and low surface wind speeds make the early evening the optimum time for the transmission of low-frequency sound at Etosha, with range at a maximum and directionality at a minimum. As the night progresses, a nocturnal low-level wind maximum (jet) forms, reducing upwind range and calling area. The estimated calling area drops rapidly after sunrise with the destruction of the inversion. Daytime calling areas are usually less than 50 km2, while early evening calling areas frequently exceed 200 km2 and are much less directional. This marked diurnal cycle will be present in any dry savanna climate, with variations due to local topography and climate. Calling range and low-frequency sound propagation cannot be effectively understood without knowledge of meteorological controls.
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March 1997
March 01 1997
Meteorology and elephant infrasound at Etosha National Park, Namibia
David Larom;
David Larom
Department of Environmental Sciences, University of Virginia, Charlottesville, Virginia 22903
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Michael Garstang;
Michael Garstang
Department of Environmental Sciences, University of Virginia, Charlottesville, Virginia 22903
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Malan Lindeque;
Malan Lindeque
Ministry of Environment and Tourism, Directorate of Resource Management, Private Bag 13306, Windhoek, Namibia
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Richard Raspet;
Richard Raspet
National Center for Physical Acoustics, University of Mississippi, University, Mississippi 38677
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Mark Zunckel;
Mark Zunckel
Atmospheric Impacts Management, CSIR, Ematek, P.O. Box 395, Pretoria 0001, Republic of South Africa
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Yvonne Hong;
Yvonne Hong
Atmospheric Impacts Management, CSIR, Ematek, P.O. Box 395, Pretoria 0001, Republic of South Africa
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Kevin Brassel;
Kevin Brassel
Atmospheric Impacts Management, CSIR, Ematek, P.O. Box 395, Pretoria 0001, Republic of South Africa
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Sean O’Beirne;
Sean O’Beirne
Atmospheric Impacts Management, CSIR, Ematek, P.O. Box 395, Pretoria 0001, Republic of South Africa
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Frank Sokolic
Frank Sokolic
Department of Geographical and Environmental Sciences, University of Natal, Durban 4001, Republic of South Africa
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J. Acoust. Soc. Am. 101, 1710–1717 (1997)
Article history
Received:
November 22 1995
Accepted:
October 06 1996
Citation
David Larom, Michael Garstang, Malan Lindeque, Richard Raspet, Mark Zunckel, Yvonne Hong, Kevin Brassel, Sean O’Beirne, Frank Sokolic; Meteorology and elephant infrasound at Etosha National Park, Namibia. J. Acoust. Soc. Am. 1 March 1997; 101 (3): 1710–1717. https://doi.org/10.1121/1.418180
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