Seasonal variations of MLT tides revealed by a meteor radar chain based on Hough mode decomposition

Abstract

Seasonal variations of different tides in the mesosphere and lower thermosphere are investigated from wind observations of a meteor radar chain on the basis of Hough mode decomposition. First, the observed winds are decomposed into different (diurnal, semidiurnal, and terdiurnal) tidal components. Different seasonal patterns are revealed for each component. Pronounced semiannual oscillation (SAO) is presented in the diurnal component, while latitude‐dependent seasonal variation is found in the semidiurnal and terdiurnal components. At the low/midlatitude stations, the semiannual/annual oscillation is relatively stronger. Then, Hough mode decomposition is utilized to extract the dominant tidal modes of each decomposed component. It is found that each component is dominated by one of its symmetric tidal modes with strong seasonal dependency. Apparent SAO is observed in the dominant (1, 1) mode; (2, 4) mode is strong in the autumn and winter months (after the September equinox). Based on the extracted results we further map the three‐dimensional distribution (latitude × altitude × season) of each tidal component. The mapped results are finally compared with the corresponding values observed by the Thermosphere Ionosphere Mesosphere Energetics and Dynamics Doppler Interferometer (TIDI) and modeled from the global scale wave model (GSWM). Each mapped tidal component agrees well with corresponding TIDI observation in the seasonal variation. Meanwhile, coincidences are found in the seasonal dependency of the diurnal component between the mapped values and the modeled results from GSWM, while difference between them exists in that of the semidiurnal one.

Multiyear Observations of Gravity Wave Momentum Fluxes in the Midlatitude Mesosphere and Lower Thermosphere Region by Meteor Radar

“…In addition, a semiannual variation with maxima eastward wind in summer and a secondary maximum during winter were observed between 85 and 96 km over Mohe. These results are comparable with that of previous study along 120°E longitude in NH (Yu et al, 2015). The differences in structure between the four stations are mainly due to different latitudes, which are consistent with previous global model studies and the observational result referenced therein Fleming et al, 1990;Fomichev et al, 2002;Hedin et al, 1996;Portnyagin et al, 2004;Portnyagin & Solovjova, 2000).…”

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

“…The semidiurnal tide is the main dominant tidal component in both systems, which fits with the results of Hoffmann et al (2010). Yu et al (2015) showed, however, increasing tidal amplitudes with increasing heights for several locations. The amplitudes in tidal modes vary with height, season, component, and location.…”

Variations of Mesospheric Neutral Winds and Tides Observed by a Meteor Radar Chain Over China During the 2013 Sudden Stratospheric Warming

“…With the support of Chinese Meridian Project, four meteor radars were installed at Mohe (53.5°N, 122.3°E), Beijing (40.3°N, 116.2°E), Wuhan (30.5°N, 114.6°E), and Sanya (18.3°N, 109.6°E) in 2011 around the geographic longitude of 120°E. Further details regarding these meteor radars can be found in previous literatures (Liu et al, 2017; Ma et al, 2017; Xiong et al, 2013; Yu et al, 2013, 2015). Besides these four radars, the Kunming meteor radar (25.6°N, 103.8°E), which belongs to the China Research Institute of Radio Wave Propagation, has been operated since year 2011.…”