Terdiurnal signatures in sporadic &amp;lt;i&amp;gt;E&amp;lt;/i&amp;gt; layers at midlatitudes

T Fytterer,C Jacobi,C Arras

doi:10.5194/ars-11-333-2013

Abstract

Abstract. Global Positioning System radio occultation measurements by the FORMOsa SATellite mission-3/Constellation Observing System for Meteorology, Ionosphere and Climate satellites were used to analyse the behaviour of the signature of the terdiurnal tide in sporadic E (ES) layers at midlatitudes (43–63° N). According to theory, the occurrence of ES is expected when the vertical zonal wind shear, which is mainly owing to solar tides, is negative. 4 yr means, based on 3-monthly running mean zonal means from December 2006–November 2010, were constructed for the terdiurnal oscillation in the occurrence frequency of ES. Comparison of the results with VHF meteor radar observations of the terdiurnal tide and the 8 h oscillation in the vertical zonal wind shear at Collm, Germany (51.3° N, 13° E) shows a clear correspondence between the 8 h in ES and in wind shear signature.

Highlights

The wind fields of the mesosphere/lower thermosphere (MLT) are strongly influenced by atmospheric solar tides
Global Positioning System radio occultation measurements by the FORMOsa SATellite mission3/Constellation Observing System for Meteorology, Ionosphere and Climate satellites were used to analyse the behaviour of the signature of the terdiurnal tide in sporadic E (ES) layers at midlatitudes (43–63◦ N)
The occurrence of ES is expected when the vertical zonal wind shear, which is mainly owing to solar tides, is negative. 4 yr means, based on 3-monthly running mean zonal means from December 2006–November 2010, were constructed for the terdiurnal oscillation in the occurrence frequency of ES

Summary

Introduction

The wind fields of the mesosphere/lower thermosphere (MLT) are strongly influenced by atmospheric solar tides. These are global waves with periods of a solar day and its subharmonics and are named diurnal tide (DT), semidiurnal tide (SDT), terdiurnal tide (TDT), etc. The wind amplitudes are small (on the order of few ∼ cm s−1) near the region of forcing, but increase significantly with height due to the decreasing air density They maximise in the MLT at midlatitudes (Hagan et al, 1995). Sporadic E (ES) layers are thin clouds of enhanced electron density, at midlatitudes primarily occurring in summer They generally form in the upper MLT (90–120 km), which is equivalent to the lower ionospheric E region. TDT phases as seen in ES and wind shear will be compared as well

Measurements and data analysis

Results

Conclusions