Nonmigrating semidiurnal tide over the Arctic determined from TIMED Doppler Interferometer wind observations

Abstract

[1] The TIMED Doppler Interferometer (TIDI) on the NASA Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite has been measuring horizontal winds in the mesosphere and lower thermosphere (MLT) since 2002. Because of the high inclination of the TIMED orbit, TIDI measures the horizontal winds from pole to pole every orbit. This paper presents the first assessment of the spatial structure and temporal evolution of the nonmigrating semidiurnal tides over the Arctic determined from the TIDI wind measurements and a comparison of the structure of the nonmigrating semidiurnal tide between the Arctic and Antarctic. The nonmigrating semidiurnal tides were determined as a 60 day average based on the yaw cycles of the spacecraft. The nonmigrating semidiurnal tidal wind field over the Arctic comprises mainly the westward-propagating zonal wave numbers 1 (W1) and 3 (W3) and standing zonal wave number 0 (S0) modes. The W1 mode is the most prominent, maximizing above 90 km poleward of 60°N during the yaw interval ranging from mid-March to mid-May. While this mode exhibits a slight amplitude increase toward the North Pole during this interval, its phase is nearly constant with latitude. The S0 mode is enhanced over two yaw intervals ranging from mid-January to mid-May, but its amplitude decreases toward the North Pole. Compared to the W1 semidiurnal tide over the Antarctic, that over the Arctic is smaller in amplitude, of less extended duration, achieves maximum amplitudes at higher altitudes by ∼10 km, and exhibits a weaker amplitude increase toward the pole. These differences likely result from differences in excitation mechanisms and efficiency and/or in propagation conditions in the two responses for the nonmigrating semidiurnal tides between the Arctic and Antarctic.

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

“…Generally, over the three years, the NMT was either dominant, or comparable to the MT, 77 % of the available month-height possibilities. Late in the reviewing process a referee provided us with the Iimura et al (2010) reference; their paper, using TIMED-TIDI data, provided SDT NMT values for the high Arctic (circa 80 • N). The resulting dominance of s = +1 in the spring, and the weaker s = +3 in fall and winter are in good agreement with the NMT results reported here, originating from the two MWR radars.…”

“…The dominance of QSPW S = 1 and 2 in the Arctic was demonstrated in Paper 1, but also by recent assessment of Aura MLS temperatures; these latter results will be published elsewhere. Finally, the recent NMT results from Iimura et al (2010), using the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite with its Doppler Interferometer (TIDI), involved wave-numbers consistent with SPW S = 1 and 2.…”

“…there will be discussion of this in the final section of the paper. We appreciate that one of the referees informed us, during the late stages of the reviewing process, of the recent paper by Iimura et al (2010), using data from TIMED-TIDI, which provided unique satellite Arctic NMT information for the SDT: mainly the westward propagating wavenumbers s = +1, +3, and standing wave number s = 0. The s = +1 was most prominent (∼10 m s −1 ), 90 to ∼105 km, for months mid-March to mid-May, and reaching the high Arctic (80-87 • N).…”

“…in the desirable Russian Arctic Islands. However satellite Arctic tidal data from the TIDI system (TIMED Doppler Interferometer) were published while this paper was in review (Iimura et al, 2010), and brief remarks of a comparative nature are included in our "Summary and Discussion". For this paper, we had already chosen to compare tides from the first three years of data (2006)(2007)(2008)(2009) resulting from operation of the Eureka and Svalbard MWR radars, with a general circulation model (GCM) with a data assimilation system: Canadian Middle Atmosphere Model, CMAM-DAS (Ren et al, 2008).…”

Model of semidiurnal pseudo-tide in the high-latitude upper mesosphere

“…Recently, Iimura et al [2009Iimura et al [ , 2010 examined the non-migrating semi diurnal tide over the Antarctica and Arctic respectively using data from TIMED/TID!. The observed dominant non-migrating modes were found to be the westward propagating tides with m = 1 (and m 3).…”