Abstract
Abstract. Polar Mesosphere Summer Echoes (PMSE) have been studied at Andenes (69° N, 16° E), Norway, using VHF radar observations since 1994. One remarkable feature of these observations is the fact that {during 50% of the time,} the radar echoes occur in the form of two or more distinct layers. In the case of multiple PMSE layers, statistical analysis shows that the lower layer occurs at a mean height of ~83.4 km, which is almost identical to the mean height of noctilucent clouds (NLC) derived from observation with the ALOMAR Rayleigh/Mie/Raman lidar at the same site. To investigate the layering processes microphysical model simulations under the influence of tidal and gravity waves were performed. In the presence of long period gravity waves, these model investigations predict an enhanced formation of multiple PMSE layer structures, where the lower layer is a consequence of the occurrence of the largest particles at the bottom of the ice cloud. This explains the coincidence of the lowermost PMSE layers and NLC. During periods with enhanced amplitudes of the semidiurnal tide, the observed NLC and PMSE show pronounced tidal structures comparable to the results of corresponding microphysical simulations. At periods with short period gravity waves there is a tendency for a decreasing occurrence of NLC and for variable weak PMSE structures.
Highlights
During summer, the thermal state of the polar mesosphere is characterized by the lowest temperatures of the Earth’s at-mosphere allowing the formation of ice clouds, known as noctilucent clouds (NLC)
The height distribution shows a mean height of 84.8 km for single polar mesosphere summer echoes (PMSE) layers, whereas in the case of multiple PMSE layers, the lower layer occurs at a mean height of ∼83.4 km and the layer located above at about 86.1 km
We have investigated the influence of short and long period gravity waves as well as of tidal waves on layering processes in the polar summer mesopause region leading to NLC and PMSE
Summary
The thermal state of the polar mesosphere is characterized by the lowest temperatures of the Earth’s at-mosphere allowing the formation of ice clouds, known as noctilucent clouds (NLC). Starting from the initial observations by Hansen et al (1989); NLC have been routinely observed applying ground based lidars since 1997 (see Fiedler et al, 2003). These ice particles give rise to very strong radar echoes first detected by Czechowsky et al (1979) and Ecklund and Balsley (1981) and which are referred to as polar mesosphere summer echoes (PMSE). One remarkable feature of all PMSE is the fact that the radar echoes often occur in the form of two or more distinct layers (Hoffmann et al, 2005) and they show clear wavelike structures.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
