Abstract
We report on the polar mesosphere summer echoes (PMSE) occurrence probability over SANAE (South African National Antarctic Expedition) IV, for the first time. A matching coincidence method is described and implemented for PMSE extraction from SuperDARN (Super Dual Auroral Radar Network) HF radar. Several SuperDARN-PMSE characteristics are studied during the summer period from years 2005-2007. The seasonal and interannual SuperDARN-PMSE variations in relation to the mesospheric neutral winds are studied and presented in this paper. The occurrence probability of SuperDARNPMSE on the day-to-day scale show, predominantly, diurnal variation, with a broader peak between 12-14 LT and distinct minimum of 22 LT. The SuperDARN-PMSE occurrence probability rate is high in the summer solstice. Seasonal variations show a connection between the SuperDARN-PMSE occurrence probability rate and mesospheric temperature from SABER (Sounding of the Atmosphere using Broadband Emission Radiometry). The seasonal trend for both meridional and zonal winds is very stable year-to-year. Analysis of the neutral wind variations indicates the importance of pole-to-pole circulations in SuperDARN-PMSE generation.
Highlights
It is generally accepted that during the polar summer time the charged ice aerosol particle and mesospheric neutral air turbulence interactions result in strong radar backscatter echoes within 90 - 100 km altitudes
In order to quantitatively eliminate other overlapping echoes, a SuperDARN-polar mesosphere summer echoes (PMSE) event is selected when the backscatter power is above 6 dB and the Doppler velocity and spectral width are below 50 m s-1
Based on the obtained results the following are the noted salient features: (1) The SuperDARN-PMSE seasonal rate is enhanced at the beginning of December, remains at the highest level until several days after the summer solstice and gradually decreases towards the end of February
Summary
It is generally accepted that during the polar summer time the charged ice aerosol particle and mesospheric neutral air turbulence interactions result in strong radar backscatter echoes within 90 - 100 km altitudes. Some studies have observed PMSE in the VHF band in correlation and anti-correlation to temperature, neutral winds, particle precipitation, cosmic noise absorption and gravity waves (Cho et al 1992; Kirkwood 1993; Röttger 1994; Hoffmann et al 1999; Klostermeyer 1999; Liu et al 2002; Klekociuk et al 2008). These complex phenomena range from periodic and episodic perturbations to those on a global scale. We discuss the possible temperature changes in relation to SuperDARN-PMSE probability peaks
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