On the detection and attribution of gravity waves generated by the 20 March 2015 solar eclipse

Abstract

Internal gravity waves are generated as adjustment radiation whenever a sudden change in forcing causes the atmosphere to depart from its large-scale balanced state. Such a forcing anomaly occurs during a solar eclipse, when the Moon’s shadow cools part of the Earth’s surface. The resulting atmospheric gravity waves are associated with pressure and temperature perturbations, which in principle are detectable both at the surface and aloft. In this study, surface pressure and temperature data from two UK sites at Reading and Lerwick are examined for eclipse-driven gravity wave perturbations during the 20 March 2015 solar eclipse over northwest Europe. Radiosonde wind data from the same two sites are also analysed using a moving parcel analysis method, to determine the periodicities of the waves aloft. On this occasion, the perturbations both at the surface and aloft are found not to be confidently attributable to eclipse-driven gravity waves. We conclude that the complex synoptic weather conditions over the UK at the time of this particular eclipse helped to mask any eclipse-driven gravity waves.This article is part of the themed issue ‘Atmospheric effects of solar eclipses stimulated by the 2015 UK eclipse’.

Investigation of sources of gravity waves observed in the Brazilian equatorial region on 8 April 2005

“…These findings are in close agreement with previous results from different studies at this laboratory (e.g. Medeiros et al, 2003 andEssien et al, 2018). It is expected that the GWs should propagate in all directions in accordance with the location of the ITCZ.…”

“…As these GWs propagate in the wind direction into the upper atmosphere, they become susceptible to the Doppler effect and critical level dissipation (Bretherton, 1966). The critical level marks the region where the horizontal wind component annuls the wave's horizontal phase speed (Medeiros et al, 2003). This region is very important, as it decides how and if a travelling wave would propagate further.…”

“…Sarkar and Scotti, 2017), and solar eclipses (e.g. Marlton et al, 2016). These atmospheric structures have been identified as a key component in the transportation of energy in the mesosphere-lower thermosphere (MLT) region (e.g.…”

“…Internal GWs are generated as adjustment radiations whenever a sudden change in forcing causes the atmosphere to depart from its large-scale balanced state. Such forcing anomaly occurs during a solar eclipse (Campos et al, 2016;Marlton et al, 2016). The intrinsic properties of the GWs (observed horizontal phase speed, propagation direction, observed period and horizontal wavelength) can be calculated directly from airglow images using spectral analysis.…”

“…GWs can be summarised as large-scale waves, medium-scale waves and small-scale waves. Small-scale GWs are characterised by horizontal wavelengths of tens of kilometres (Medeiros et al, 2003), medium-scale GW wavelengths range from ∼ 100 to 400 km, and large-scale waves have high phase speeds and travel larger horizontal distances than the small-and medium-scale waves .…”