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We present kinetic temperatures at ~87 km and ~94 km altitudes inferred from OH (6,2) and O2 At(0,1) airglow observations, respectively, at South Pole (90° S), Antarctica in the austral winter of 2002. These OH and O2 rotational temperatures measurements show mesosphere and lower thermosphere (MLT) temperature anomalies prior to the 2002 Southern Hemisphere Sudden Stratospheric Warming (SSW) . In this paper we focus on the first of the three minor stratospheric warmings which preceded the major SSW event. Temperature anomalies observed in the MLT region show sudden cooling (ΔT=~30 K) in OH temperatures accompanied by warming (ΔT=~15 K) in O2 temperatures preceding the onset of SSW event by about three to four weeks. This shallow vertical extent of mesospheric cooling is in agreement with the numerical simulation of Coy et al. (2005), however, the model cooling was centered well below the mesopause level. The other observed feature of the South Pole MLT temperature dataset is the intensification of planetary wave activity prior to the onset of SSW event. Fourier analyses of both OH and O2 temperatures show amplification of planetary wave activity in the 5–10 day range prior to the onset of SSW. The timing of wave amplification seen in the wave spectra coincides with the peak in OH and O2 temperature anomalies.

A technique is developed for reducing the amount of aliasing in the spectral analysis of TIDI observations, by ingestion of ground-based data into the satellite data set. A multi-dimensional (space-time) least squares fitting approach is applied to the satellite and ground-based data to determine the aliasing spectra. The addition of ground-based data to the TIDI data set reduces the aliased components in the aliasing spectrum. For example, at 20° latitude, the combined ground-based and TIDI data set of a sampled input semidiurnal (frequency of 2 days−1) signal with zonal wavenumber 2 results in a factor of 2 reduction in the amount of power aliasing into a signal with zonal wavenumber 0 and frequency 0 days−1.

Data obtained by Sondre Stromfjord incoherent scatter radar during recent Lower Thermospheric Coupling Study (LTCS) campaigns have been analyzed to examine seasonal changes in high-latitude lower thermosphere neutral winds. Data included in this study were obtained with a 2 × 160 μs multipulse as well as with higher-resolution multipulse and alternating code techniques and were analyzed with different auto correlation function (ACF) fitting routines. We report neutral wind results obtained during LTCS experiments with the new acquisition and analysis system and compare these results with those acquired using earlier versions of the software. We investigate the effects of different assumptions in the ACF fitting program on the data return and quality. Wind results are intercompared to examine average seasonal structure and variability. Strong semidiurnal oscillations characterize high-latitude lower thermospheric winds at 105 km irrespective of season; however, summer amplitudes are nearly a factor of 2 greater than those observed during winter. Average winter winds appear to have more variability than those deduced for summer. Equinox winds at fall and spring show similar oscillations but are nearly reversed in phase. At 115 km, diurnal oscillations grow and their amplitudes often exceeds typical semidiurnal amplitudes. Tidal amplitudes observed in radar data are compared with the predictions of several models, including National Center for Atmospheric Research thermosphere-ionosphere-general-circulation model (TIGCM) [Roble et al., 1988], global scale wave model (GSWM) [Hagan et al., 1994], and Forbes-Vial model (FV91) [Forbes and Vial, 1991]. These comparisons suggest that theoretical predictions significantly underestimate tidal amplitudes calculated from Sondrestrom incoherent scatter radar measurements.

[1] We present new observations made by the Coupled Ion Neutral Dynamics Investigation (CINDI) Ion Velocity Meter (IVM) instrument onboard the Communication/Navigation Outage Forecasting System (C/NOFS) satellite that show the effects of the January 2009 sudden stratospheric warming (SSW) event on equatorial electric fields. We have used IVM observations to construct composite curves of mean equatorial vertical plasma drifts as a function of local time and longitude sector. These curves show large upward vertical drifts during morning hours and downward drifts during afternoon. Our analysis indicates that this pattern could be observed over the range of longitudes where adequate IVM measurements were available, from approximately 165°E to about 315°E longitude. A clear day-to-day, quasi-deterministic variability in the drifts is also observed, with the transition from upward to downward drifts occurring at increasing local times from 25 to 30 January 2009. The analysis also suggests some level of longitudinal variability in the magnitude of the drifts. These in-situ observations are in good agreement with previous ground-based measurements of the response of equatorial electric fields to SSW events. In particular, we found that IVM drift measurements centered around 285°E depart significantly from climatological values but agree exceptionally well with ground-based measurements of vertical drifts made by the Jicamarca incoherent backscatter radar. Overall, the results agree well with previous studies of SSW events, demonstrate the usefulness of the IVM observations and motivate further studies of the variability of the equatorial ionosphere using C/NOFS.

[1] Tidal amplitudes and phases deduced from Austral winter observations of OH Meinel (3,1) rotational temperatures at South Pole, Antarctica over the period 1994-2007 are presented here. Dominant periodicities in temperature data are seen at 24, 12, and 8 h. The amplitude of these wave oscillations shows significant variability during the months analyzed herein (April through September). In contrast to 12- and 8-h waves, the 24-h wave is stronger, more persistent, and coherent at South Pole. The observed amplitude variability in 24-, 12-, and 8-h waves during the majority of the years analyzed is shown to be correlated. Phase variations of 24- and 8-h waves with longitudes indicate that these waves are standing zonal wave number 0 waves.

[1] We have examined Michelson Interferometer OH airglow temperature data to investigate solar cycle and long-term variations of mesospheric temperatures at South Pole Station (SPS), Antarctica (90°S). The data set used here is continuous (24 hours a day) and taken during 1994–2004 austral winters. We have used a Multiple Linear Regression (MLR) technique to elucidate solar cycle and the trend term in the MI temperature time series data. The 11-year time series of OH rotational temperature shows a strong correlation with F10.7 radio flux (R = 0.60). The amplitude of solar cycle response seen in the mesopause temperature records at South Pole is about 0.04 ± 0.01 K/sfu (Solar Flux Units), however, the trend term is statistically insignificant and is about 0.1 ± 0.2 K/year. Superposed epoch studies have been carried out in order to determine climatological variations in OH temperatures above South Pole derived from 11 years of austral winter observations. The mean amplitude of this variation is about 12.6 K and its maximum occurs near 30 May which is in agreement with the Fabry-Perot Spectrometer (FPS) observations of OH temperatures at SPS (Hernandez, 2003). However, whereas Hernandez (2003) reported 35 K cooling in 2002, MI OH temperatures at SPS do not show any significant deviation from previous years.

[1] We have examined the Michelson Interferometer (MI) OH airglow measurements at the South Pole Station and the National Center for Environment Prediction (NCEP) temperatures to investigate the dynamical effects of sudden stratospheric warming (SSW) events on the Antarctic mesosphere and stratosphere. Comparisons of stratospheric and mesospheric temperatures at the South Pole during the 1995 and 2002 observing seasons show evidence of mesospheric cooling preceding the SSW events. Spectral analyses of South Pole OH air glow brightness measurements from the 1995 and 2002 observing season and NCEP stratospheric temperatures show amplification of the 4-day wave planetary wave before the start of the mesospheric cooling trend, the latter preceding the onset of SSW event. A similar behavior of planetary wave is also seen in the stratosphere where the 4-day wave is seen to grow in amplitude just before the peak of the sudden increase in temperatures.