Effects Of Mesospheric Wind Shears On Atmospheric Gravity Waves Induced By Tsunamis

In this paper, we numerically simulated the atmospheric gravity waves caused by tsunamis, andaimed to reveal the characteristics of the upward propagation of such waves in the middle atmosphere.Some of wave sources at lower altitudes are mainly related to weather and nature, such asthunderstorm, earthquake, tsunami, and cloud thermal effect, etc. Long waves propagating along theocean surface and excited by underwater earthquakes or volcanic eruptions are described qualitativelyas shallow-water gravity waves in scientific literature. Shallow-water gravity waves travel rapidly andtheir wavelengths are much greater than the depth of the ocean. Hines was the first who proposed thattsunami can generate atmospheric gravity waves, which propagate upwards into the ionosphere, andsubsequently the ionospheric disturbances can be served as a harbinger of an early tsunami warning.Using measurements from the GPS network, Japanese scientists have reported observations of anionospheric disturbance fluctuated by atmospheric gravity waves following a strong tsunami. On theother hand, with numerical simulations the works focus on a better understanding of the propagatingcharacteristics of atmospheric gravity waves driven by tsunamis. It could probably support a fewobservations of such atmospheric gravity waves in the ionosphere in the future, and would be veryhelpful to an early off shore detection of tsunami.A strategy of early tsunami warning is attempted to implement in the paper based on lineargravity wave theory. The effects of directional filtering are analyzed due to the mesospheric windshears on the propagation of atmospheric gravity waves induced by tsunamis. The paper has solelychosen the2004Sumatra tsunami and the2011Tohoku tsunami as two representatives of thelow-latitude and mid-latitude, respectively. A significant influence to the upward propagating gravitywaves was found in the zonal direction and in the presence of background winds. In the case for the2004Sumatra tsunami with a location of the low-latitude, it seems that both the westward andeastward waves were largely affected by the wind shears, but still freely propagating into theionosphere. However, the situation was different to the zonal wave propagation driven by the2011Tohoku tsunami with a mid-latitude location. Observable ionospheric response is favorable to tsunamipropagation towards the east that is far away from the west coast of Japan.