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Summer sudden Na number density enhancements measured with the ALOMAR Weber Na Lidar

: Heinrich, D.; Nesse, H.; Blum, U.; Acott, P.; Williams, B.; Hoppe, U.-P.

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Annales Geophysicae 26 (2008), Nr.5, S.1057-1069
ISSN: 0939-4176
ISSN: 0980-8752
ISSN: 0992-7689
ISSN: 0980-8760
ISSN: 1432-0576
Zeitschriftenaufsatz, Elektronische Publikation
Fraunhofer INT ()
atmospheric composition and structure; middle atmosphere - composition and chemistry; meteorology and atmosphere dynamics; middle atmosphere dynamics; instruments and techniques

We present summer Na-densities and atmospheric temperatures measured 80 to 110 km above the Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR). TheWeber Na Lidar is part of ALOMAR, located at 69 degree N in Norway, 150 km north of the Arctic Circle. The sun does not set here during the summer months, and measurements require a narrowband Faraday Anomalous Dispersion Optical Filter (FADOF). We discuss an observed sudden enhancement in the Na number density around 22:00 UT on 1 to 2 June 2006. We compare this observation with previous summer measurements and find a frequent appearance of Na number density enhancements near local midnight. We describe the time of appearance, the altitude distribution, the duration and the strength of these enhancements and compare them to winter observations. We investigate possible formation mechanisms and, as others before, we find a strong link between these Na number density enhancements and sporadic E layers.