Latitudinal variation of quasi‐biennial oscillation modulation of the semidiurnal tide in the lower thermosphere

Abstract

Abstract. Perturbations in the geomagnetic field at the Earth's surface can result from variations in the neutral wind field in the lower therrnosphere through dynamo action in the interfused ionospheric E region. Thus spectral analysis of the $q variations in ground-based geomagnetic data extending continuously over many years, and from several sites worldwide, has been carried out to investigate the variation with latitude of quasi-biennial oscillation (QBO) effects in the semidiurnal tide in the lower therrnosphere. This QBO modulation of the tide appears to be greatest around •60 ø latitude. The phase of the oscillation is largely latitude independent and implies QBO modulation of the upward propagating semidiurnal tide close to its source region. The semidiurnal tide appears to propagate upward more easily during the easterly phase of the tropical stratospheric QBO at 30 rnbar than during the westerly phase.

Interannual variability of the S=1 and S=2 components of the semidiurnal tide in the Antarctic MLT

“…Angelats i Coll and Forbes, 2002). Such a QBO dependence of the semidiurnal tides had previously been observed in the dynamo region (100-140 km) derived from the Sq variation in the H component of the geomagnetic field at high southern latitudes (Jarvis, 1996(Jarvis, , 1997. More recently Xu et al (2009) have presented evidence for a similar biennial periodicity in the summer time semidiurnal tide in the MLT above Rothera.…”

Geomagnetic lunar and solar daily variations during the last 100 years

“…Similarly, the quasi‐biennial oscillation (QBO) in the stratosphere and mesosphere has some influence on tidal propagation [ Hagan et al , ; Xu et al , ]. Indeed, Olsen [] and Jarvis [, ] reported small but significant QBO signatures in the S variation. The effect of ENSO and QBO on the lunar tide, however, has not been studied.…”

Planetary wave trends in the lower thermosphere—Evidence for 22-year solar modulation of the quasi 5-day wave

“…For instance, a signature of the quasi biennial oscillation exists in the amplitude of the semidiurnal geomagnetic variation at the equator (Olsen, 1994) and at a range of other latitudes (Jarvis, 1996(Jarvis, , 1997. Kohsiek et al (1995) reported 10-and 16-day oscillations, indicative of planetary wave action associated with natural resonances or Rossby normal modes of the atmosphere (Salby, 1984), in geomagnetic data from two mid-latitude stations in the northern hemisphere.…”