Abstract
AbstractThe impact of gravity waves (GW) on diurnal tides and the global circulation in the middle/upper atmosphere of Mars is investigated using a general circulation model (GCM). We have implemented a stochastic parameterization of non‐orographic GW into the Laboratoire de Météorologie Dynamique (LMD) Mars GCM (LMD‐MGCM) following an innovative approach. The source is assumed to be located above typical convective cells ( 250 Pa), and the effect of GW on the circulation and predicted thermal structure above 1 Pa ( 50 km) is analyzed. We focus on the comparison between model simulations and observations by the Mars Climate Sounder (MCS) on board Mars Reconnaissance Orbiter during Martian Year 29. MCS data provide the only systematic measurements of the Martian mesosphere up to 80 km to date. The primary effect of GW is to damp the thermal tides by reducing the diurnal oscillation of the meridional and zonal winds. The GW drag reaches magnitudes of the order of 1 m/s/sol above 10 Pa in the northern hemisphere winter solstice and produces major changes in the zonal wind field (from tens to hundreds of m/s), while the impact on the temperature field is relatively moderate (10–20 K). It suggests that GW‐induced alteration of the meridional flow is the main responsible for the simulated temperature variation. The results also show that with the GW scheme included, the maximum day‐night temperature difference due to the diurnal tide is around 10 K, and the peak of the tide is shifted toward lower altitudes, in better agreement with MCS observations.
Highlights
Gravity waves (GW) are small-scale atmospheric waves frequently detected in terrestrial planet atmospheres
In this paper we describe the results of the implementation of a non-orographic gravity waves (GW) parameterization into the Mars Global Climate Model (MGCM) developed at the Laboratoire de Météorologie Dynamique (LMD), which already included an orographic GW scheme (Forget et al, 1999)
A stochastic parameterization of non-orographic GW was implemented into the Laboratoire de Météorologie Dynamique (LMD) Mars general circulation model (LMD-MGCM), following an innovative scheme, as described in Lott et al (2012) and Lott and Guez (2013)
Summary
Gravity waves (GW) are small-scale atmospheric waves frequently detected in terrestrial planet atmospheres. They are an intrinsic feature of all stably stratified planetary atmosphere and play an important role in the large-scale circulation and variability of the middle/upper atmospheres of the Earth and Mars (Angelats i Coll et al, 2005; Alexander et al, 2010; Barnes, 1990; Forget et al, 1999; Fritts et al, 2006; Fritts & Alexander, 2003; Joshi et al, 1995; Medvedev et al, 2011). GW propagation into the atmosphere provides a significant source of momentum and energy to the mean flow when they break or encounter critical values. The gravity wave drag (i.e., gravity wave momentum deposition to the mean flow) may cause wind acceleration or deceleration
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