Long‐term changes of polar mesosphere summer echoes at 69°N

Abstract

[1] Polar mesosphere summer echoes (PMSE) are strong enhancements of received signal power at very high radar frequencies occurring at altitudes between about 80 and 95 km at polar latitudes during summer. PMSE are caused by inhomogeneities in the electron density of the radar Bragg scale within the plasma of the cold summer mesopause region in the presence of negatively charged ice particles. Thus, the occurrence of PMSE contains information about mesospheric temperature and water vapor content but also depends on the ionization due to solar electromagnetic radiation and precipitating high energetic particles. Continuous and homogeneous observations of PMSE have been done on the North-Norwegian Island Andøya (69.

Gravity wave influence on NLC: experimental results from ALOMAR, 69° N

“…As PMSE (polar mesospheric summer echoes, see Rapp and Lübken, 2004 for a review) are closely related to the existence of ice particles in the mesopause region, the mean PMSE occurrence rates could also hint at special background conditions. Nonetheless, the mean PMSE occurrence rate at ALOMAR in 2008 was not exceptional in any sense (Latteck and Bremer, 2013). The wind spectra and total wind variances do not show any peculiarities as well.…”

On the early onset of the NLC season 2013 as observed at ALOMAR

“…The Middle Atmosphere Alomar Radar System (MAARSY) as well as its precursor, the ALWIN-radar, operate at 53 MHz and observe PMSE on a regular basis since 1999 (Latteck and Bremer, 2013). As the radar operations are weather independent, the onset of the PMSE season is determined very precisely during each year.…”

Patches of polar mesospheric summer echoes characterized from radar imaging observations with MAARSY

“…To study PMSEs with different radar systems, the volume reflectivity is commonly used (Hocking, 1985;Li et al, 2010;Smirnova et al, 2011;Latteck and Bremer, 2013). The assumption is that the scattering mechanism is isotropic and also homogeneous.…”

“…This can be solved by calculating a beamfilling factor for the volume reflectivity or, following the approach of Sommer et al (2016b), by using longer integration periods. Latteck and Bremer (2013) used integration times of 5 min, which smoothes the localized signals and is already 10 times longer than the data sets presented here, while even longer integration periods would be more favourable.…”