On Forcing the Winter Polar Warmings in the Martian Middle Atmosphere during Dust Storms

Abstract

Using a Martian general circulation model, we investigated the changes in the meridional circulation during planet-encircling dust storms on Mars that produce strong temperature vertical inversions in the middle atmosphere over winter polar regions. It is shown that vigorous poleward and downward transport, and, consequently, the adiabatic heating are caused by dissipating thermal tides, planetary and resolved small-scale gravity waves and eddies in almost equal degree. The increase of tidal forcing is mainly due to a stronger excitation in the summer hemisphere. Contribution of the stationary planetary wave (SPW) with the zonal wavenumber s ¼ 1 increases during dust storms due to intensified generation in the lower atmosphere as well as due to more favorable vertical propagation. SPW ðs ¼ 2Þ varies less with the dust load, dissipates lower, and contributes to the warming only below @ 0.1 mb. Transient planetary wave (s ¼ 1, period @ 5 sols) with a barotropic/baroclinic vertical structure provides up to 1/3 of the forcing by SPW ðs ¼ 1Þ. For the first time, we demonstrated a significance of small-scale gravity waves and eddies in maintaining the meridional circulation in Martian middle atmosphere, at least in high winter latitudes during dust storms.

Structure and dynamics of the Martian lower and middle atmosphere as observed by the Mars Climate Sounder: 2. Implications of the thermal structure and aerosol distributions for the mean meridional circulation

“…The resulting circulation strongly upwelled at the surface near the south pole, vigorously crossed the equator at altitudes as high as 70 km above the surface, strongly downwelled near the north pole, and returned toward the south pole near the surface, forming a “pole‐to‐pole” PMOC first proposed by Schneider [1983]. Other GCM simulations by Forget et al [1999] and Kuroda et al [2009] differ from that of Wilson [1997] with respect to the atmospheric dust levels or wave forcings necessary to produce a polar warming event, but both simulations produce latitudinally broad and vertically deep mean meridional circulations. Thus, in order to ensure that such a cell can be vertically resolved, current Martian GCMs [e.g., Wilson and Hamilton , 1996; Forget et al , 1999; Takahashi et al , 2003; Moudden and McConnell , 2005; Angelats i Coll et al , 2005; Hartogh et al , 2005; Kuroda et al , 2005; Kahre et al , 2006; Richardson et al , 2007] generally simulate both the lower and middle atmosphere.…”

“…Because of the similarity between the temperature of the polar warming simulated by Forget et al [1999] and observed dust storm polar warmings, it is possible that dust storm polar warmings are the result of a fully kinematically coupled lower and middle atmospheric meridional circulation. In other words, the “pole‐to‐pole” circulation in the simulations of Wilson [1997], Forget et al [1999], and Kuroda et al [2009] is a fully kinematically coupled lower and middle atmospheric meridional circulation. From the observations alone, we cannot infer anything about the vertical structure of tropical upwelling.…”

A laboratory study of global-scale wave interactions in baroclinic flow with topography II: vacillations and low-frequency variability

“…The occurrence of SSWs is also not necessarily confined solely to the Earth, but there is some evidence from numerical simulations that a dynamically similar phenomenon may occur in the Martian atmosphere (Barnes and Hollingsworth 1987, Wilson 1997, Kuroda et al 2009, where the amplitude of continent-scale topography is larger even than for the Earth. Downloaded by [University of Regina] at 23:37 30 September 2015…”

Carbon dioxide ice clouds, snowfalls, and baroclinic waves in the northern winter polar atmosphere of Mars

“…It utilizes a spectral solver for the three-dimensional primitive equations, and has a set of physical parameterizations for the martian atmosphere as described in Kuroda et al [2005], which account in particular for the radiative effects of gaseous CO 2 and airborne dust. The model has been validated against the observed zonal mean climatology [Kuroda et al, 2005], and has been applied to the study of baroclinic planetary waves ,zonal-mean variability in mid-andhigh-latitudes [Yamashita et al, 2007], equatorial semiannual oscillations [Kuroda et al, 2008], and winter polar warmings during global dust storms [Kuroda et al, 2009].…”