Stationary planetary waves in the atmosphere of Mars during southern winter

Abstract

We report new observation of stationary planetary waves in the Southern Hemisphere of Mars by Mars Global Surveyor (MGS). We focus on a period during midwinter (Ls = 134°-160°) when independent observations were acquired by two techniques. Radio occultation experiments sounded the atmosphere at essentially fixed latitude (∼68°S) and local time (∼1030), yielding profiles of geopotential and temperature between the surface and the 9 Pa pressure level. Observations by the Thermal Emission Spectrometer (TES) included systematic limb sounding at nine discrete latitudes and two local times (∼0200 and ∼1500), yielding temperature profiles at pressures of 1-100 Pa. We supplemented these data with a simulation by a Mars general circulation model (MGCM), which provides an accurate synthesis of the observations. These stationary planetary waves have significant amplitudes at zonal wave numbers s = 1 and 2. The s = 1 component propagates vertically, as reflected by a westward tilt with increasing height in the geopotential and temperature fields and a net poleward eddy heat flux. The peak amplitude at s = 1 is ∼1 km in geopotential height and ∼7 K in temperature. The geopotential field of the s = 2 component is "barotropic" in character, which results through hydrostatic balance in a distinctive temperature field. The amplitude at S = 2 is ∼700 m in geopotential height and 4-6 K in temperature.