Recent Variations in the Venus Atmospheric Temperature Detected by Meteorological Satellites

Kurzfassung

For understanding the Venusian atmosphere, thermal tides and planetary-scale waves have been considered important phenomena as sources of momentum transport [e.g., 1, 2]. Spatial and altitudinal patterns of both phenomena have been expected to be highly sensitive to various factors like static stability [e.g., 3]. Therefore, monitoring cloud-top temperature at various mid-infrared wavelengths of Venus provides hints to elucidate its atmospheric dynamics. In the last decade, only two planetary missions, Akatsuki and BepiColombo, have conducted spaceborne observations of Venus's cloud-top temperature [4, 5]. However, Akatsuki has a single-band camera at the mid-infrared wavelengths and cannot retrieve temperature at various altitudes. In addition, BepiColombo observed Venus only at its flyby, and the observed area is limited because of its close distance to Venus. Therefore, multiband observation of Venus at mid-infrared wavelengths is still missing. Meteorological satellites might be able to complement such a lack of mid-infrared Venus data. When the meteorological satellite observes the whole Earth, its observation extends to space adjacent to the Earth’s rim, where several solar-system bodies, such as the Moon and Venus, are sometimes captured simultaneously (Figure 1) [6]. Some meteorological satellites are equipped with multiband infrared cameras. For example, Japanese meteorological satellites Himawari 8 and 9 have nine bands within 6 – 14 μm. Therefore, their Venus images are potentially able to provide a new spaceborne dataset to study its atmospheric dynamics. In this study, Venus observations by the Himawari series are first archived as a new dataset for Venus science. Then, utilizing the archived multiband data, we demonstrate the temporal variations in thermal tide and Rossby-wave structures observed over the last decade.