Relationship between variability of the semidiurnal tide in the Northern Hemisphere mesosphere and quasi-stationary planetary waves throughout the global middle atmosphere

Abstract

Abstract. To investigate possible couplings between planetary waves and the semidiurnal tide (SDT), this work examines the statistical correlations between the SDT amplitudes observed in the Northern Hemisphere (NH) mesosphere and stationary planetary wave (SPW) with wavenumber S=1 (SPW1) amplitudes throughout the global stratosphere and mesosphere. The latter are derived from the Aura-MLS temperature measurements. During NH summerfall (July-October), the mesospheric SDT amplitudes observed at Svalbard (78 • N) and Eureka (80 • N) usually do not show persistent correlations with the SPW1 amplitudes in the opposite hemisphere. Although the SDT amplitudes observed at lower latitudes (∼50-70 • N), especially at Saskatoon (52 • N), are often shown to be highly and positively correlated with the SPW1 amplitudes in high southern latitudes, these correlations cannot be sufficiently explained as evidence for a direct physical link between the Southern Hemisphere (SH) winter-early spring SPW and NH summer-early fall mesospheric SDT. This is because the migrating tide's contribution is usually dominant in the mid-high latitude (∼50-70 • N) NH mesosphere during the local late summerearly fall (July-September). The numerical correlation is dominated by similar low-frequency variability or trends between the amplitudes of the NH SDT and SH SPW1 during the respective equinoctial transitions. In contradistinction,Correspondence to: X. Xu (xix303@mail.usask.ca) during NH winter (November-February), the mesospheric SDT amplitudes at northern mid-high latitudes (∼50-80 • N) are observed to be significantly and positively correlated with the SPW1 amplitudes in the same hemisphere in most cases. Because both the SPW and migrating SDT are large in the NH during the local winter, a non-linear interaction between SPW and migrating SDT probably occurs, thus providing a global non-migrating SDT. This is consistent with observations of SDT in Antarctica that are large in summer than in winter. It is suggested that climatological hemispheric asymmetry, e.g. the SH and NH winter characteristics are substantially different, lead to differences in the inter-hemispheric SPW-tide physical links.

Characteristics of Arctic tides at CANDAC-PEARL (80° N, 86° W) and Svalbard (78° N, 16° E) for 2006–2009: radar observations and comparisons with the model CMAM-DAS

“…10), in particular the NMT s = +1 (related to SPW S = 1) in the southern summer. This feature has also been observed, as noted in the Introduction (Paper 1; Hibbins et al, 2010;Xu et al, 2009a, c;Murphy et al, 2009;Baumgaertner et al, 2005Baumgaertner et al, , 2006. These 3 groups of authors also demonstrate that there are significant correlations and probable causal linkages between the SPW S = 1 of the NH-winter and both the directly observed winter-SDT and the related NMT s = +1 of the SHsummer.…”

“…(Manson et al, 2004a and b;Forbes et al, 2003;Cierpik et al, 2003). It is therefore possible for radars to have been located, by the chances provided for available land, so that positive, negative or minimal correlations (in time) are found between observed tides and the SPW (Baumgaertner et al, 2006;Xu et al, 2009a, c;Hibbins et al, 2010).…”

“…There was little to no indication of significant diurnal NMT forcing (in the Arctic) from the Southern Hemisphere's winter SPW. Regarding the semidiurnal tide, it was considered probable, and since then demonstrated clearly by Xu et al (2009a, c), that the large SPW of the NH winter and their associated NMT are linked through trans-equatorial propagation to the observed summer SDT at Rothera in Antarctica. It was proposed to use a GCM model with data assimilation for comparisons with the observed and calculated NMT in future studies: this is also a major feature of the present paper.…”

Vertical and interhemispheric links in the stratosphere-mesosphere as revealed by the day-to-day variability of Aura-MLS temperature data

“…Therefore, additional work is necessary for a better understanding of the interhemispheric SPW-tidal coupling processes. This is the subject of scrutiny in another paper by the present authors (Xu et al, 2009).…”

Asymmetry in the interhemispheric planetary wave-tide link between the two hemispheres

“…Using the semidiurnal tide (SDT) data from meteor radars (MWR) at Eureka (801N, 861W), Svalbard (781N, 161E) and Collm (511N, 151E), and medium frequency radars (MFR) at Tromsø (701N, 191E) and Saskatoon (521N, 2531E), Xu et al (2009) discussed the relationships between the day-to-day variability of the SDT in the Northern Hemisphere (NH) mesosphere and stationary planetary wave (SPW) with zonal wavenumber S ¼ 1 (SPW1) in the Southern Hemisphere (SH) during NH summer-fall (July-October). Their results showed that the SDT amplitudes observed at Arctic latitudes (801N) usually do not provide persistent correlations with the SH SPW1 amplitudes.…”