One Martian year of MEDA HS humidity sensor observations and comparisons with models

The Mars 2020 mission rover “Perseverance”, launched on 30 July 2020 by NASA, landed successfully 18th Feb. 2021 at Jezero Crater, Mars (Lon. E 77.4509° Lat. N 18.4446°). The landing took place at Mars solar longitude Ls = 5.2°, close to start of the northern spring. Perseverance’s payload includes the relative humidity sensor MEDA HS (Mars Environmental Dynamics Analyzer Humidity Sensor), which almost one Martian year of observations are described here. The relative humidity measured by MEDA HS is reliable from late night hours to few tens of minutes after sunrise when the measured relative humidity is greater than 2% (referenced to sensor temperature). Observations show seasonal and diurnal trends and short term temporal fluctuations, which are discussed.

Nighttime observations are compared with the Finnish Meteorological Institute and Helsinki University adsorptive Single Column Model in various conditions and seasons. The model allows estimating daytime humidity levels. Model comparisons suggest water vapor nighttime adsorption into the soil.

Short period fluctuations in the surface humidity data may be due to turbulence caused by downslope winds and nighttime jets. These turbulences break nighttime boundary layer and bring humid air from above. Observed data is compared with the numerical simulations of turbulence over Jezero given by Mars Regional Atmospheric Modeling System (MRAMS).

Data is also compared with the Mars Science Laboratory rover Curiosity humidity instrument data.