Extreme Horizontal Wind Perturbations in the Mesosphere and Lower Thermosphere Over South America Associated With the 2022 Hunga Eruption

Abstract

The 15 January 2022 eruption of Hunga volcano, Tonga (Global Volcanism Program, 2022), which began around 4:00 UT, ejected an immense amount of energy into the atmosphere, as well as volcanic tephra and gases into the stratosphere. The eruption released approximately the equivalent of 61 Mt, which is larger than the Tsar Bomba, and the famous 1980 eruption of Mount St. Helens (Díaz & Rigby, 2022).The event generated a wide spectrum of atmospheric waves (Matoza et al., 2022) with a salient surface-guided Lamb wave (Francis, 1973) that was detected all around the globe, propagating at ∼310 m/s. Carvajal et al. ( 2022) used globally distributed coastal tide gauge records and found a uniformly small amplitude leading wave moving faster than the expected tsunami. The velocity of the leading wave was very close to the velocity of the atmospheric Lamb wave, as measured by pressure pulses all over the world (Amores et al., 2022;Díaz & Rigby, 2022). Even though the kinetic energy of these waves falls away exponentially from the surface (Vallis, 2017), clear ionospheric perturbations were detected propagating at comparable velocities (≃300-320 m/s) (e.g., Lin et al., 2022;Verhulst et al., 2022;Zhang et al., 2022), which suggests that their energy leaked into the thermosphere. Since the neutral density also decreases exponentially with altitude, Lamb waves increase in amplitude with height. The ionospheric disturbances traveled around the world at least three times (Zhang et al., 2022).The eruption generated regionally localized perturbations as well. In South America, the strongest total electron content (TEC) variations on the day of the event were detected between around 17:00 and 22:00 UT (Takahashi et al., 2023). The onset time of these perturbations approximately coincides with the arrival time of the largest tsunami waves to the western coast of the continent (Carvajal et al., 2022).

The impact of the Hunga Tonga–Hunga Ha’apai volcanic eruption on the Peruvian atmosphere: from the sea surface to the ionosphere

“…On the other hand, the clear perturbation at ~ 18 UT on both systems at Jicamarca and Piura can be interpreted as an L1 Lamb-wave mode (Francis 1973). The phase speed of this mode is slower than 300-318 m/s and the perturbation was described in detail by Poblet et al (2023). They found MLT horizontal wind perturbations with horizontal phase velocity, period and wavelength of about 200 m/s, 2 h, and 1440 km that we confirmed.…”

“…The L 1 Lamb-wave mode was also found by Liu et al (2023) in WACCM-X simulations with a phase speed of about 245 m/s. One reason we can see the effects of the second Lamb wave ( L 1 ) in the MLT region and not an effect from the first one might be that it displays its kinetic energy peak in the mesosphere instead of the Earth's surface (Poblet et al 2023;Francis 1973). An alternative explanation of the MLT wind perturbation near 18 LT could be related to the gravity waves generated by the largest tsunami waves triggered by the eruption that arrived on the Peruvian coast near that LT period.…”

“…An alternative explanation of the MLT wind perturbation near 18 LT could be related to the gravity waves generated by the largest tsunami waves triggered by the eruption that arrived on the Peruvian coast near that LT period. These gravity waves travel faster than the tsunami waves and they might have reached Peru a couple of hours before the arrival of the largest tsunami waves (Poblet et al 2023) and could have produced TIDs that manifested in TEC perturbations. However, simulations performed by Vadas et al (2015) showed that tsunamiinduced gravity waves are generated in a continuum of frequencies (different propagation speeds) but Poblet et al (2023) did not find any indication of this polychromatic nature of the disturbances of the neutral winds in the MLT region.…”

“…Atmospheric pressure disturbances traveled in the form of Lamb waves and surrounded the Earth several times. The volcano eruption can produce effects in the lower atmosphere (varying atmospheric pressure), in the mesosphere and lower thermosphere (MLT) region (modifying neutral winds), as well as in the ionosphere (perturbing the horizontal magnetic field component-H, the vertical plasma drifts, the equatorial electrojet-EEJ, and the virtual height of the ionograms) (Poblet et al 2023;Stober et al 2023;Schnepf et al 2022;Le et al 2022;Sun et al 2022;Li et al 2023;Harding et al 2022;Qiu et al 2023).…”

“…Reports of perturbations in the MLT region have also shown signatures attributed to the volcano explosion. Utilizing three multistatic specular meteor radars spaced more than 3000 km apart, MLT horizontal wind disturbances were found over the west side of South America (Poblet et al 2023). A notorious wave was identified…”