Vertical winds and momentum fluxes due to equatorial planetary scale waves using all-sky meteor radar over Brazilian region. (November 2016)

• Record Type: Journal Article
• Authors: Egito, F.; Andrioli, V.F.; Batista, P.P.
• Is Part Of: Journal of atmospheric and solar-terrestrial physics. Volume 149(2016)
• Page Start: 108
• Page End: 119
• Publication Date: 2016-11
• Subjects: Vertical wind -- Planetary scale waves -- Meteor radar; Geophysics -- Periodicals; Atmospheric physics -- Periodicals; Géophysique -- Périodiques; Météorologie physique -- Périodiques; Electronic journals; 551.51
• DOI: 10.1016/j.jastp.2016.10.005
• Languages: English
• ISSNs: 1364-6826

Abstract

Abstract: In the equatorial region planetary scale waves play an important role transporting significant amount of energy and momentum through atmosphere. Quantifying the momentum transported by these waves and its effects on the mean flow is rather important. Direct estimates of the momentum flux transported by waves require horizontal and vertical wind measurements. Ground-based meteor radars have provided continuous and reliable measurements of the horizontal wind components in the Mesosphere and Lower Thermosphere (MLT) region and have contributed to improve our knowledge of the dynamics of this region. However, instrumental limitations hinder its use for measuring vertical winds and momentum fluxes. On the other hand, according to Babu et al (2012), all- sky meteor radars are able to infer tridimensional winds when using a large number of meteor echoes centered at the meteor ablation peak. Following this approach, we have used measurements performed by a Meteor Radar installed at São João do Cariri, Brazil (7.4°S; 36.5°W) in order to measure vertical winds and calculate the momentum flux transported by equatorial planetary scale waves. In order to evaluate the accuracy of vertical wind values we have performed several tests based on a simple model considering real meteor distributions and theoretical equations for the MLT winds motion. From our tests, we inferred that Brazilian meteor radar data can be used for this purpose with an accuracy of ~ 1.8 m/s. The results show that the vertical wind presents magnitudes of a few meters per second and occasionally reaches magnitudes around 10 m/s. Below 92 km the vertical wind is predominantly upward during the whole year and above exhibits a semi-annual oscillation with downward phase during the equinoxes. Variations associated to planetary scale waves in the vertical wind are also observed and some of them appear simultaneously in the zonal and meridional wind as well. Largest wave induced amplitudes in the vertical wind are found in the 3–4 d band, reaching up to 4 m/s. From the vertical and zonal wind measurements, we calculated the vertical transport of zonal momentum in the 3–4 d band and found it to be maximum near autumn equinox, when its value reaches almost 20 m 2 /s 2, while minimum momentum flux is observed after the winter solstice. Highlights: Vertical wind in the equatorial MLT from meteor radar. Testing method is proposed to evaluate the vertical wind confidence. Vertical wind in the equatorial MLT presents magnitudes of a few meters per second. Equatorial planetary waves induce time variability in the vertical wind of a few m/s. Momentum flux of 3–4 d wave is strong near autumn equinox reaching almost 20 m 2 /s 2 .