Mars Science Laboratory diurnal moisture observations and column simulations

Hourly observations of air temperature and relative humidity at 1.6 m height from the surface (T 1.6 m, RH 1.6 m) measured by the Mars Science Laboratory (MSL) Rover Environmental Monitoring Station relative humidity (REMS-H) device are shown for MSL solar days 15–17 and 80–82, augmented with column model simulations. The diurnal range of T 1.6 m was 197–268 K in the first period, RH 1.6 m being small (<1%) in daytime but increasing to 45–49% by sunrise. During the warmer second period the T 1.6 m range was 201–275 K with RH 1.6 m only up to 16% in the morning. The modeled temperatures were quite close to those observed when the local albedo was set to 0.15 and thermal inertia to 300 tiu. The modeled RH 1.6 m was close to that observed when the well-mixed boundary layer values (0–4 km) of the mass mixing ratio q were 28–30 ppmm (suggesting a precipitable water content (PWC) of ~5.5 µm) during the first period and 12 ppmm (PWC of ~2 µm) during the second period. The REMS-H observations indicate systematic diurnal variation in the near-surface mixing ratio.