Scientific objective A-1: general circulation and climatological cycles

For general or global circulation and climate related observations the main measured variable is pressure, supplemented by the temperature, wind, relative humidity and optical thickness observations. The pressure observations provide ground truth for the orbiting atmospheric sounders’s observations for derivation of a 4-D image of the atmospheric state. As wide latitudinal coverage as possible on both hemispheres and at different terrains is required to sample a wide spectrum of phenomena and to provide good ground truth observations. As an example of identification of a class of general circulation phenomena, mid-latitude baroclinic eddies were observed by the Viking Lander spacecraft in the north, the models agree and predict their occurrence also in the south, but their existence there remains observationally unconfirmed in situ (Barnes et al, 1993). Longitudinal site coverage in turn can account for the effect of large topography features and resolve atmospheric waves extending over many longitudes.

Comprehensive global coverage will shed light into such features as characteristics of the CO2 sublimation-condensation cycle and—with the inclusion of H2O observations—into the global H2O cycle. Multiple sensors of the lander payload will provide data relevant to initiation and evolution of the dust-related processes: optical thickness, LIDAR, temperature (reduced nearsurface air temperatures during dust storms), and pressure (normal modes and their role in dust storm initialisation, passage of dust devils; Tillman (1988); Schofield et al (1997). Selection of a landing sites from known dust storm onset regions (e.g., Argyre, Hellas) can provide unique opportunities for monitoring the onset and growth phases of Martian dust storms.