Nocturnal turbulence at Jezero crater, as determined from MEDA
measurements and modeling
Abstract
Mars 2020 Mars Environmental Dynamics Analyzer (MEDA) instrument data
acquired during half of a martian year (Ls 13º-180º),
and modeling efforts with the Mars Regional Atmospheric Modeling System
(MRAMS) and Mars Climate Database (MCD) allow us to study the seasonal
evolution and variability of nocturnal atmospheric turbulence at Jezero
crater. Nighttime conditions in Mars’s Planetary Boundary Layer are
highly stable because of strong radiative cooling that efficiently
inhibits convection. However, MEDA nighttime observations of
simultaneous, rapid fluctuations in horizontal wind speed and air
temperatures suggest the development of nighttime turbulence in Jezero
crater. Mesoscale modeling with MRAMS also shows a similar pattern and
enables us to investigate the origins of this turbulence and the
mechanisms at play. As opposed to Gale crater, less evidence of
turbulence from breaking mountain/gravity wave activity was found in
Jezero during the period studied with MRAMS. On the contrary, the model
suggests that nighttime turbulence at Jezero crater is explained by
mechanical turbulence produced by increasingly strong wind shear related
to the development of a bore-like disturbance at the nocturnal inversion
interface. The enhanced wind shear leads to a reduction in the Ri and an
onset of mechanical turbulence. Once the critical Richardson Number is
reached (Ri ∼< 0.25), shear instabilities can mix warmer air
aloft down to the surface.