Climatology and Diurnal Variation of Ozone Column Abundances for 2.5 Mars Years as Measured by the NOMAD-UVIS Spectrometer

Abstract

The distribution of Mars ozone (O₃) is well established; however, our knowledge on the dayside diurnal variation of O₃ is limited. We present measurements of Mars O₃ column abundances, spanning Mars Year (MY) 34 to the end of MY 36, by the Ultraviolet and VIsible Spectrometer (UVIS), part of the Nadir and Occultation for MArs Discovery (NOMAD) instrument, aboard the ExoMars Trace Gas Orbiter. UVIS provides the capability to measure dayside diurnal variations of O₃ and for the first time, a characterization of the dayside diurnal variations of O₃ is attempted. The observed O₃ climatology for Mars Years (MY) 34–36 follows the established seasonal trends observed through previous O₃ measurements. At aphelion, the equatorial O₃ distribution is observed to be strongly correlated with the water ice distribution. We show that the early dust storm in MY 35 resulted in a near-global reduction in O₃ during northern spring and the O₃ abundances remained 14% lower in northern summer compared to MY36. Strong latitudinal and longitudinal variation was observed in the diurnal behavior of O₃ around the northern summer solstice. In areas with a weak O₃ upper layer, O₃ column abundance peaks in the mid-morning, driven by changes in the near-surface O₃ layer. In regions with greater O₃ column abundances, O₃ is observed to gradually increase throughout the day. This is consistent with the expected diurnal trend of O₃ above the hygropause and suggests that in these areas an upper O₃ layer persists throughout the Martian day.