Polar mesosphere winter echoes during MaCWAVE

S Kirkwood,J Manninen,P Dalin,J D Mitchell,F Schmidlin,K.-H Fricke,C Croskey,U Blum,E Belova,R A Goldberg

doi:10.5194/angeo-24-1245-2006

Abstract

Abstract. During the MaCWAVE winter campaign in January 2003, layers of enhanced echo power known as PMWE (Polar Mesosphere Winter Echoes) were detected by the ESRAD 52 MHz radar on several occasions. The cause of these echoes is unclear and here we use observations by meteorological and sounding rockets and by lidar to test whether neutral turbulence or aerosol layers might be responsible. PMWE were detected within 30 min of meteorological rocket soundings (falling spheres) on 5 separate days. The observations from the meteorological rockets show that, in most cases, conditions likely to be associated with neutral atmospheric turbulence are not observed at the heights of the PMWE. Observations by instrumented sounding rockets confirm low levels of turbulence and indicate considerable small-scale structure in charge density profiles. Comparison of falling sphere and lidar data, on the other hand, show that any contribution of aerosol scatter to the lidar signal at PMWE heights is less than the detection threshold of about 10%.

Highlights

Polar mesosphere winter echoes (PMWE) are thin layers of strongly enhanced radar echo occasionally seen by high-latitude VHF radars such as the ESRAD (52 MHz) and EISCAT (224 MHz) radars in northern Scandinavia (Kirkwood et al, 2002a, 2002b; Stebel et al, 2004; Belova et al, 2005)
Measurements made at Esrange during the MaCWAVE sounding-rocket campaign in January 2003 have been used to test whether layers of enhanced radar echo in the winter mesosphere (PMWE) are likely to be caused by turbulence or by charged aerosol
Co-located measurements of atmospheric static stability and wind shear from the MaCWAVE falling spheres, and PMWE from the ESRAD radar have not provided any evidence of background conditions favouring turbulence associated with most PMWE

Summary

Introduction

Polar mesosphere winter echoes (PMWE) are thin layers of strongly enhanced radar echo occasionally seen by high-latitude VHF radars such as the ESRAD (52 MHz) and EISCAT (224 MHz) radars in northern Scandinavia (Kirkwood et al, 2002a, 2002b; Stebel et al, 2004; Belova et al, 2005). The appearance of PMWE during solar proton events has previously been reported and it has been argued that they are much too strong to be explained by layers of neutral turbulence and that they may be evidence for charged aerosol layers in the winter mesosphere (Kirkwood et al, 2002a, 2002b; Stebel et al, 2004; Belova et al, 2005).

Results

Conclusion