11:45 AM - 12:00 PM
[PCG21-10] Study of observational methods for seasonal and latitudinal/longitudinal dependence of Martian atmospheric gravity waves using terahertz heterodyne spectroscopy
Keywords:Terahertz hetrodyne spesctroscopy, Mars, Atmospheric gravity wave
We are currently advancing the design study of a Terahertz Heterodyne Spectroscopy Sensor (THSS) for MACO+, considering the inclusion of next-generation Mars exploration payloads such as the Mars Ice Mapper. The THSS is capable of observing trace molecules relayed to atmospheric oxidation processes, including water vapor, carbon monoxide, their isotopes, and HOx species even during periods of dust storms, as it is less affected by dust and aerosol absorption and scattering effects. Furthermore, it does not require a background light source like the Sun, which allow us to carry out limb-sounding across a wide range of latitudes, longitudes, altitudes, and local times. Additionally, Doppler measurements enable the observation of atmospheric wind fields. This allows for the capture of the atmospheric coupling from near-surface to altitudes exceeding 100 km, providing valuable insights into Martian atmospheric material cycling, dynamics, and meteorological and climatological predictions through data assimilation with General Circulation Models (GCM).
In recent years, atmospheric gravity waves on Earth have been discussed in relation to sudden weather events, as well as their contribution to radiation forcing, cloud formation, aerosols, and climate. On Mars, breaking gravity waves at altitudes of 100-130 km were observed through mid-infrared band observations by TGO (Starichenko et al. JGR Planets, 128, 2021), suggesting the importance of understanding their contribution to the upper atmospheric environment. In this study, using the time-dependent three-dimensional data of temperature, pressure, and carbon monoxide simulated by Kuroda's GCM, the 460GHz band spectrum of carbon monoxide was pseudo-observed at Nadir. The temporal and spatial resolutions were 10 seconds and 1.1 degrees (67km), respectively. The calculations were performed assuming that the orbiter at an altitude of 250km passed at LST 15:00 along the longitudes of Olympus Mons and low-elevation regions. As a result, during the summer period in the southern hemisphere at Ls=270 degrees, where temperature disturbances induced by breaking gravity waves were prominent in the result of the GCM simulation, sharp fluctuations in the depth of CO absorption lines were observed, particularly around Olympus Mons. Conversely, during the summer period in the northern hemisphere at Ls=90 degrees, amplitude variations in the CO absorption spectrum were observed in the southern hemisphere. However, these variations were smaller in magnitude and extent compared to those at Ls=270 degrees. These results suggest that the seasonal and latitude and longitude dependence of atmospheric gravity waves on Mars can be detected using THSS.
In recent years, atmospheric gravity waves on Earth have been discussed in relation to sudden weather events, as well as their contribution to radiation forcing, cloud formation, aerosols, and climate. On Mars, breaking gravity waves at altitudes of 100-130 km were observed through mid-infrared band observations by TGO (Starichenko et al. JGR Planets, 128, 2021), suggesting the importance of understanding their contribution to the upper atmospheric environment. In this study, using the time-dependent three-dimensional data of temperature, pressure, and carbon monoxide simulated by Kuroda's GCM, the 460GHz band spectrum of carbon monoxide was pseudo-observed at Nadir. The temporal and spatial resolutions were 10 seconds and 1.1 degrees (67km), respectively. The calculations were performed assuming that the orbiter at an altitude of 250km passed at LST 15:00 along the longitudes of Olympus Mons and low-elevation regions. As a result, during the summer period in the southern hemisphere at Ls=270 degrees, where temperature disturbances induced by breaking gravity waves were prominent in the result of the GCM simulation, sharp fluctuations in the depth of CO absorption lines were observed, particularly around Olympus Mons. Conversely, during the summer period in the northern hemisphere at Ls=90 degrees, amplitude variations in the CO absorption spectrum were observed in the southern hemisphere. However, these variations were smaller in magnitude and extent compared to those at Ls=270 degrees. These results suggest that the seasonal and latitude and longitude dependence of atmospheric gravity waves on Mars can be detected using THSS.