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Thebarton, Australia

Reid I.M.,University of Adelaide | Spargo A.J.,University of Adelaide | Woithe J.M.,ATRAD Pty Ltd
Journal of Geophysical Research: Atmospheres | Year: 2014

We analyze 15years of atomic oxygen (OI) 558nm and hydroxyl (OH) (8-3) 730nm nightglow emission intensities from heights near 96 and 87km, respectively, measured using filter photometers at the Buckland Park Field Station (34.6S, 138.6E) near Adelaide, Australia. The intensity of both emissions exhibits clear seasonal and interannual periodicities, with annual, semiannual, and quasi-biennial oscillations, as well as a solar cycle influence. In addition, there is a terannual and 4.1year component in the OI airglow intensity and both a quasi-biennial and quasi-triennial oscillation in the OH intensity. The results are in very good agreement with simultaneous collocated measurements made with an imager, and with global satellite climatologies of OI and OH intensities reported for the Wind Imaging Interferometer instrument. The mean value of the OI annual oscillation intensity is the same as that of the semiannual oscillation at this location to within the experimental uncertainty. The OI annual oscillation maximizes in summer, and the semiannual oscillation maximizes in autumn and spring, with the largest maximum in autumn. The terannual component in the OI nightglow maximizes in early summer, autumn, and spring. The quasi-biennial oscillation in the OI nightglow takes its first maximum value in autumn 1996, and the 4.1year period in this emission first maximizes in summer 1998. The OH annual and semiannual oscillation intensities also agree to within the experimental uncertainties and are observed to peak in early winter. The quasi-biennial and quasi-triennial oscillations in this emission take their first maximum value in summer 1996. Key Points Fifteen years of airglow intensity measurements Seasonal and interseasonal variations Similarity to conjugate observations ©2014. American Geophysical Union. All Rights Reserved. Source

Dolman B.K.,ATRAD Pty Ltd | Dolman B.K.,University of Adelaide | Reid I.M.,University of Adelaide
Journal of Atmospheric and Solar-Terrestrial Physics | Year: 2014

Wind profiling radars are now in general use by a number of weather agencies worldwide. These use the Doppler Beam Swinging approach exclusively. The Australian Government Bureau of Meteorology has adopted a Boundary Layer wind profiling radar using the Spaced Antenna technique. This paper describes the performance of these radars and discusses some of the issues that needed to be addressed for appropriate performance in an operational environment, namely the known wind magnitude underestimation. The underestimation was successfully addressed with an empirical correction. Quality control and hardware improvements to minimize internal clutter have been implemented, resulting in largely outlier free wind estimates on presentation to forecasters, and excellent height coverage. © 2014 Elsevier Ltd. Source

Walterscheid R.L.,The Aerospace Corporation | Hecht J.H.,The Aerospace Corporation | Gelinas L.J.,The Aerospace Corporation | Mackinnon A.,University of Adelaide | And 7 more authors.
Journal of Geophysical Research D: Atmospheres | Year: 2015

The Southern Hemisphere summer 2 day wave (TDW) is the most dramatic large-scale event of the upper mesosphere. The winds accelerate over ∼1 week, may attain > 70 m/s, and are often accompanied by a near disappearance of the diurnal tide and stabilization of the period close to 48 h. We denote this as the phase-locked 2 day wave (PL/TDW). We have examined airglow and meteor radar (MR) wind data from the Andes Lidar Observatory (Cerro Pachon, Chile:30°S, 289.3°E), MR data from Darwin (12.5°S, 131°E) and airglow and medium frequency radar data from the University of Adelaide (34.7°S, 138.6°E) for the behavior of the TDW during the austral summers of 2010, 2012, and 2013. The Cerro Pachon and Adelaide sites are located at similar latitudes separated in longitude by about 120°. We find a remarkable coincidence between the TDW oscillations at Chile and Adelaide for the period January-February 2010. The oscillations are nearly in phase in terms of local time and the minima and maxima repeat at nearly the same local time from cycle to cycle consistent with a phase-locked wave number 3 TDW. Data for this and other years (including Darwin) show that the amplitude of the diurnal tide decreases when the TDW is largest and that this occurs when the period is close to 48 h. These observations support the proposal that the PL/TDW is a subharmonic parametric instability wherein the diurnal tide transfers energy to a TDW that is resonant at nearly 48 h. ©2015. American Geophysical Union. All Rights Reserved. Source

Li G.,CAS Institute of Geology and Geophysics | Ning B.,CAS Institute of Geology and Geophysics | Hu L.,CAS Institute of Geology and Geophysics | Chu Y.-H.,National Central University | And 4 more authors.
Journal of Geophysical Research: Space Physics | Year: 2012

Interferometry measurements of range spread meteor trail echoes (RSTEs; also known as nonspecular echoes) have provided new insights into both the irregularity structures in meteor trails and lower-thermospheric winds (LTWs). In this study, we used trail echoes observed with the newly installed Sanya (18.4°N, 109.6°E) 47.5 MHz VHF coherent radar and the Sanya all-sky meteor radar to estimate instantaneous zonal and hourly averaged meridional winds from RSTEs and hourly averaged zonal and meridional winds from large numbers of specular meteor echoes. The mean height variations in both the zonal and meridional winds estimated from the RSTEs were generally consistent with those estimated from specular meteor echoes below 96 km. This gives validity to the technique proposed recently by Oppenheim et al. (2009) and suggests that RSTE measurements made with a small radar can be used to investigate LTWs, whereas this had previously been limited to larger radars such as the Jicamarca radar. However, some observations show significant differences in wind magnitude at individual heights at times. The results of RSTE measurements show the presence of an intense westward wind with a speed near 100 ms-1. In contrast, the specular meteor zonal winds were generally less than 50 ms -1. On the other hand, the meridional drift of RSTEs derived from the meridional Doppler velocity at higher altitudes shows a very poor correlation with the specular meteor meridional wind. Potential causes for the discrepancy in wind estimates obtained from RSTE and specular meteor trail echoes are discussed. Source

Younger J.P.,ATRAD Pty Ltd | Younger J.P.,University of Adelaide | Reid I.M.,ATRAD Pty Ltd | Reid I.M.,University of Adelaide | And 3 more authors.
Icarus | Year: 2015

The Camelopardalids meteor shower was predicted to occur for the first time on 24 May 2014, based on optical observations of the comet 209P/LINEAR. Using a 38.9MHz meteor radar located at Mohe, China, we were able to detect approximately 590 shower meteors originating from an average pre-infall radiant of R.A.=129.1°±9.8°, declination=79.4°±1.6° (J2000) with a geocentric velocity of 16.0±1.6kms-1. Measurements of the shower duration, direction, velocity, and individual meteor detection heights facilitated a detailed analysis of the parent debris stream. Orbital parameters were calculated including a semi-major axis of 2.86AU, eccentricity of 0.659, and inclination of 21.1°. Combining orbital parameters with the shower activity duration FWHM of 5.09h, it was found that the stream has a FWHM of at least 211,000km at 1AU, as measured perpendicular to the direction of orbital motion. A comparison of shower meteor detection heights and diffusion coefficient estimates with the sporadic background is consistent the prediction of Ye and Wiegert (Ye, Q., Wiegert, P. [2014]. Mon. Not. R. Astron. Soc. 437, 3283-3287) that Camelopardalid meteoroids are biased towards larger sizes or that Cameloppardalid meteoroids are less fragile than sporadic background meteoroids. © 2015 Elsevier Inc. Source

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