THE BOUNDARY-LAYER OF MARS - FLUXES, STABILITY, TURBULENT SPECTRA, AND GROWTH OF THE MIXED-LAYER

Spectra of wind from high-frequency measurements in the Martian atmosp heric surface layer, along with the diurnal variation of the height of the mixed surface layer, are calculated for the first time for Mars. Heat and momentum fluxes, stability, and z0 are estimated for early sp ring from a surface temperature model and from Viking Lander 2 tempera tures and winds at 44-degrees-N, using Monin-Obukhov similarity theory . Flow distortion by the lander is also taken into account. Model spec tra for two measuring heights and three surface roughnesses are calcul ated using the depth of die mixed layer and the surface-layer paramete rs. These experiments indicate that z0 probably lies between 1.0 and 3 .0 cm, and most likely is closer to 1.0 cm. The spectra are adjusted t o simulate aliasing and high-frequency rolloff, the latter caused by b oth the sensor response and the large Kolmogorov length on Mars. Since the spectral models depend on the surface parameters, including the e stimated surface temperature, their agreement with the calculated spec tra indicates that the surface-layer estimates are self-consistent. Th is agreement is especially noteworthy in that the inertial subrange is virtually absent in the Martian atmosphere at this height, due to the large Kolmogorov length scale. These analyses extend the range of app licability of terrestrial results and demonstrate that it is possible to estimate the effects of severe aliasing of wind measurements, to pr oduce models that agree well with the measured spectra. The results sh ow that similarity theory developed for Earth applies to Mars, and tha t the spectral models are universal.