Publication Date:
2014-07-29
Description:
Global Positioning System radio occultation measurements by FORMOsa SATellite mission-3/Constellation Observing System for Meteorology, Ionosphere and Climate satellites were used to analyse the characteristics of the 8-h oscillation in sporadic E (ES) layers. Six-year averages based on the 3-monthly mean zonal means from December 2006 to November 2012 were constructed for the amplitude of the terdiurnal oscillation in the occurrence frequency of ES. A global distribution from 60[degree sign] S to 60[degree sign] N is given, revealing two peaks above 100 km during solstice with one maximum at low and midlatitudes (approximately 10[degree sign] to 40[degree sign]) in each hemisphere. During equinox, the global distribution is marked by two dominant peaks centred at midlatitudes, while an additional weak maximum is located at very low southern latitudes. The seasonal characteristics around 110 km reveal large values during equinox at low and midlatitudes ( 40[degree sign] S and in July near 30[degree sign] S. The pattern around 90 km is dominated by a broad peak between 20[degree sign] and 30[degree sign] S from March to September. Comparisons with the terdiurnal oscillation in the neutral atmosphere derived from zonal wind and vertical zonal wind shear simulated with a circulation model of the middle atmosphere, as well as with satellite observations of the terdiurnal tide in temperature, fit quite well for the results above 100 km, but do not show agreement for lower altitudes.
Print ISSN:
1343-8832
Electronic ISSN:
1880-5981
Topics:
Geosciences
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