Interhemispheric structure and variability of the 5-day planetary wave from meteor radar wind measurements

Abstract

Abstract.A study of the quasi-5-day wave (5DW) was performed using meteor radars at conjugate latitudes in the Northern and Southern hemispheres. These radars are located at Esrange, Sweden (68 • N) and Juliusruh, Germany (55 • N) in the Northern Hemisphere, and at Tierra del Fuego, Argentina (54 • S) and Rothera Station, Antarctica (68 • S) in the Southern Hemisphere. The analysis was performed using data collected during simultaneous measurements by the four radars from June 2010 to December 2012 at altitudes from 84 to 96 km. The 5DW was found to exhibit significant short-term, seasonal, and interannual variability at all sites. Typical events had planetary wave periods that ranged between 4 and 7 days, durations of only a few cycles, and infrequent strongly peaked variances and covariances. Winds exhibited rotary structures that varied strongly among sites and between events, and maximum amplitudes up to ∼ 20 m s −1 . Mean horizontal velocity covariances tended to be largely negative at all sites throughout the interval studied.

Structure, Variability, and Mean‐Flow Interactions of the January 2015 Quasi‐2‐Day Wave at Middle and High Southern Latitudes

“…To assess the consistency between meteor and MF radars, we compare Q2DW amplitude and phase assessments using the two radars at Rothera. Our radar data analysis included the following steps: Hourly horizontal wind estimates were performed where at least five radial wind estimates were available in 2‐km altitude bins at Adelaide, Kingston, Rothera (MF), Davis, Syowa, and Halley and in 3‐km bins at CP, TdF, and Rothera (meteor); Missing hourly winds at each altitude were interpolated with 3 degrees of freedom for intervals less than 12 hr; intervals between 12 and 48 hr were fitted with a linear trend and components having periods of 8, 12, 24, and 48 hr consistent with adjacent radar data in order to enable S‐transform and band‐pass analyses using continuous data; A band‐pass filter from 42 to 54 hrs centered on the expected W3 period of 48 hr, and including the periods of other prominent Q2DW modes, was applied to the resulting hourly‐mean radar winds from December 2014 to February 2015; As in previous planetary wave (PW) studies using MLT radar winds (Fritts et al, ; Iimura et al, ), the S‐transform (Stockwell et al, ) was used to assess the event periods and durations using a Gaussian 10‐day full‐width/half‐maximum window; however, intervals of missing data longer than 12 hr were left blank in the relevant figures; the S‐transforms were used to infer the optimal Q2DW period and amplitude fit at each altitude for comparisons with MLS inferred winds at the radar sites, and local Q2DW amplitudes and phases at each altitude were estimated by least squares fits to sinusoids with periods having the maximum amplitudes in the S‐transform spectra. …”

“…A band-pass filter from 42 to 54 hrs centered on the expected W3 period of 48 hr, and including the periods of other prominent Q2DW modes, was applied to the resulting hourly-mean radar winds from December 2014 to February 2015; 4. As in previous planetary wave (PW) studies using MLT radar winds (Fritts et al, 2012;Iimura et al, 2015), the S-transform (Stockwell et al, 1996) was used to assess the event periods and durations using a Gaussian 10-day full-width/half-maximum window; however, intervals of missing data longer than 12 hr were left blank in the relevant figures; 5. the S-transforms were used to infer the optimal Q2DW period and amplitude fit at each altitude for comparisons with MLS inferred winds at the radar sites, and 6. local Q2DW amplitudes and phases at each altitude were estimated by least squares fits to sinusoids with periods having the maximum amplitudes in the S-transform spectra.…”

Intercomparison of middle-atmospheric wind in observations and models

“…Meteor radars providing wind observations through the evaluation of the drift of meteor trails in the wind field of the mesosphere-lower thermosphere region are a wellestablished technique (Hocking et al, 2001a;Jacobi, 2011;Fritts et al, 2012;Iimura et al, 2015). The reliability has also been demonstrated in recent comparisons to other remote sensing techniques and the Navy Global Environmental Model (NAVGEM) (Reid, 2015;McCormack et al, 2017;Wilhelm et al, 2017).…”

A comparison of 11-year mesospheric and lower thermospheric winds determined by meteor and MF radar at 69 ° N

“…Andrews et al, 1987, Fritts et al, 2012, Iimura et al, 2015. Mesospheric radars are distributed over the whole globe and depending on their antenna arrays, frequencies, locations, and transmitting power, they provide valuable information about winds at different vertical and spatial scales.…”