17:15 〜 18:45
[PCG21-P07] Relationship between equatorial waves and 7-sol period wind oscillations in low latitudes on Mars
キーワード：火星、InSight、赤道波
The unmanned InSight spacecraft landed near the equator of Mars in the winter of 2018 and operated for the next four years. InSight measured atmospheric pressure, temperature, wind direction and wind speed. This study started with seeking for features of meteorological data observed by Insight. TWINS (The Temperature and Wind for InSight) and PS are equipped onboard InSight (Banfield et al., 2019). We divided wind speed and direction data included in the derived data of TWINS into zonal and meridional wind components, and converted the temporal resolution of the derived data from 1 second into 10 min by resampling and averaging. The preliminary analysis showed seven-sols oscillations in horizontal wind speed data as well as its zonal and meridional components during the period from Ls = 270° to 340° (the northern winter).
We examined oscillation periods of westward-propagating inertial-gravity wave, eastward-propagating inertial-gravity wave, Rossby wave, and Kelvin wave using the dispersion relation of equatorial waves and found that Rossby waves can explain the seven-sols oscillation for some combinations of wavenumber, meridional structure, and equivalent depth. However, the zonal and meridional wind components were 180° out of phase. This means that the seven-sols oscillation in wind may not be explained by equatorial waves because the two wind components should be 90° out of phase. Therefore, we may need to additionally investigate the coupling between the atmospheric waves and some kinds of the atmospheric phenomena (e.g. dust storm, ice cloud) like Madden Julian Oscillation in low latitudes on Earth.
We examined oscillation periods of westward-propagating inertial-gravity wave, eastward-propagating inertial-gravity wave, Rossby wave, and Kelvin wave using the dispersion relation of equatorial waves and found that Rossby waves can explain the seven-sols oscillation for some combinations of wavenumber, meridional structure, and equivalent depth. However, the zonal and meridional wind components were 180° out of phase. This means that the seven-sols oscillation in wind may not be explained by equatorial waves because the two wind components should be 90° out of phase. Therefore, we may need to additionally investigate the coupling between the atmospheric waves and some kinds of the atmospheric phenomena (e.g. dust storm, ice cloud) like Madden Julian Oscillation in low latitudes on Earth.