Articles | Volume 26, issue 5
Ann. Geophys., 26, 1057–1069, 2008

Special issue: Atmospheric studies by optical methods

Ann. Geophys., 26, 1057–1069, 2008

  28 May 2008

28 May 2008

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

D. Heinrich1, H. Nesse1, U. Blum1,*, P. Acott2, B. Williams3, and U.-P. Hoppe1 D. Heinrich et al.
  • 1Norwegian Defence Research Establishment (FFI), 2027 Kjeller, Norway
  • 2Department of Physics, Colorado State University, Fort Collins CO 80523-1875, USA
  • 3NorthWest Research Associates, Colorado Research Associates division, Boulder, CO 80301, USA
  • *now at: Fraunhofer-Institute for Technological Trend Analysis, Euskirchen, Germany

Abstract. We present summer Na-densities and atmospheric temperatures measured 80 to 110 km above the Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR). The Weber Na Lidar is part of ALOMAR, located at 69° 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.