Correlation between mars’ semidiurnal LOD amplitude variation and atmospheric dust cycle index

The Mars’ rotational rate, or equivalently its length-of-day (LOD), varies slightly due to global atmospheric changes. And the atmospheric dust cycle is considered to be one key process impacting the Mars’ atmosphere. Lewis and Barker (2005) demonstrated the close link of the semidiurnal tidal amplitude with the atmospheric dust content. In consideration of tidal effects in the Mars’ variable rotation, possible connection may exist between the Mars’ semidiurnal LOD amplitude variation and atmospheric dust cycles. In this study, the Mars’ LOD variations which are influenced by global atmosphere, and the atmospheric dust cycle index (ADCI) are computed based on eight realistic scenarios of the Martian Years (MY) 24–31 of the Martian Climate Database. The semidiurnal LOD amplitude change and the ADCI are found to be correlated at the 99% significance level, and they present similar time-varying wavelet spectral structures. In mature stages of global dust storms in MYs 25 and 28, relatively high LOD and ADCI values occurred synchronously across the time scales, ranging from a few months’ high frequency to seasonal and over one year’s lower frequency band. The close relation between the semidiurnal LOD amplitude variation and the ADCI reflects the strong coupling between the solid Mars and surficial atmosphere system, which relates primarily to the semidiurnal atmospheric tide.