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Cyclic absorption of solar radiation generates oscillations in atmospheric fields. These oscillations are called atmospheric or thermal tides, which are furthermore modified by topography and surface properties. This leads to a complex mix of sun‐synchronous and non‐sun‐synchronous tides that propagate around the planet eastward and westward. This study focuses on analyzing the ter‐diurnal component (period of 8 hr) from surface pressure observations by Mars Science Laboratory (MSL), InSight, Viking Lander (VL) 1, and VL2. General Circulation Model (GCM) results are used to provide a global context for interpreting the observed ter‐diurnal tide properties. MSL and InSight have a clear and similar seasonal cycle, with local amplitude peaks at around solar longitude (Ls) 60°, Ls 130°, and Ls 320°. The amplitude peak at Ls 320° is related to the annual dust storm, while the Ls 230° dust storm is not detected by either platforms. During global dust storms, MSL, VL1, and VL2 detect their highest amplitudes. The GCM predicts the weakest amplitudes at the equinoxes, while the strongest ones are predicted in summer for both hemispheres. GCM amplitudes tend to differ from the observations but match slightly better around the aphelion season. During this time, model results suggest that the two most prominent modes are the sun‐synchronous ter‐diurnal tide and an eastward propagating resonantly enhanced Kelvin wave. Simulations with and without the effect of radiative heating by water ice clouds indicate the clouds may play a significant role in forcing the ter‐diurnal tide during northern hemisphere summer season. Plain Language Summary: Atmospheric pressure is a crucial meteorological parameter, since many weather phenomena on Mars, such as the condensation and sublimation of the seasonal polar caps, global scale atmospheric tides, and local turbulent flows, are associated with changes in surface pressure. On a diurnal time scale, atmospheric tides dominate surface pressure daily variations in the Martian tropics. They are generated by the diurnally varying solar radiation and additionally modified by topography, surface properties, and atmospheric absorbers. Here, we use pressure observations from Mars Science Laboratory, InSight, Viking lander 1, and 2 to characterize the Martian atmospheric tide that has a period of 8 hr, known as the ter‐diurnal tide, and compare results with model simulations. The results show that the Mars Science Laboratory and InSight observe similar seasonal cycles for the amplitude and phase of the ter‐diurnal tide. In addition, both these platforms react similarly to atmospheric dust content. The Viking landers and Mars Science Laboratory observe their highest amplitudes during the global dust storms. We find that modeled amplitudes are the strongest during summertime for both hemispheres and typically lower than those observed throughout the year. Moreover, the ter‐diurnal tide may be significantly affected by water ice clouds. Key Points: We analyze the ter‐diurnal atmospheric tide from pressure observations at four surface stations and compare them with model predictionsModel and observations suggest a clear wavenumber 6 amplitude and phase patterns in longitude at northern hemisphere (NH) summerThis study suggests the ter‐diurnal component's sensitivity to water ice clouds and a resonantly enhanced Kelvin wave near the NH summer solstice [ABSTRACT FROM AUTHOR]

The Mars2020 Perseverance Rover landed successfully on the Martian surface on the Jezero Crater floor (18.44°N, 77.45°E) at Martian solar longitude, Ls, ∼5° in February 2021. Since then, it has produced highly valuable environmental measurements with a versatile scientific payload including the MEDA (Mars Environmental Dynamics Analyzer) suite of environmental sensors. One of the MEDA systems is the PS pressure sensor system, which weighs 40 g and has an estimated absolute accuracy of better than 3.5 Pa and a resolution of 0.13 Pa. We present initial results from the first 414 sols of Martian atmospheric surface pressure observations by the PS, whose performance was found to meet its specifications. Observed sol‐averaged atmospheric pressures follow an anticipated pattern of pressure variation in the course of the advancing season and are consistent with data from other landing missions. The observed daily pressure amplitude varies by ∼2%–5 % of the sol‐averaged pressure, with absolute amplitude 10–35 Pa in an approximately direct relationship with airborne dust. During a regional dust storm, which began at Ls ∼ 135°, the daily pressure amplitude roughly doubled. The daily pressure variations were found to be remarkably sensitive to the seasonal evolution of the atmosphere. In particular, analysis of the daily pressure signature revealed diagnostic information likely related to the regional scale structure of the atmosphere. Comparison of Perseverance pressure observations with data from other landers reveals the global scale seasonal behavior of Mars' atmosphere. Plain Language Summary: Mars2020 Perseverance Rover successfully arrived on Mars in February 2021. It landed in an early Martian spring afternoon in a crater north of Mars' equator called Jezero crater. The rover is equipped with meteorological instruments that have so far produced extensive and valuable data for understanding the Martian atmosphere. One of the meteorological instruments is an accurate and precise pressure sensor. The pressure sensor has revealed large changes in the pressure over the seasons that are related to large changes in the actual mass of the Martian atmosphere. This is in line with seasonal pressure changes measured during previous Mars missions and can be explained as the condensation of the atmosphere onto the Martian poles and its subsequent sublimation. On a shorter time scale, the pressure sensor revealed complex pressure changes over a Martian day. These variations are thought to be related to atmospheric dust, whose ubiquitous nature is known to have a strong influence on the Martian climate. As the seasons progressed, the daily pressure variations morphed to exhibit different patterns likely related to the large‐scale regional changes in the atmosphere. Comparison of Perseverance pressure observations with other landers revealed the global nature of the atmosphere. Key Points: The atmospheric pressure observations by Perseverance Rover have proved to be of excellent quality fulfilling expectationsJezero crater pressure exhibits significant differences to other Martian areas likely due to varying regional geography and solar forcingOverall, the diurnal and seasonal atmospheric pressure cycles at Jezero Crater follow an anticipated pattern of pressure variation [ABSTRACT FROM AUTHOR]

In this paper we present new calibration measurements that have been performed with the ground reference models of the relative humidity instruments of the MSL, Mars 2020 and ExoMars missions. All instruments are based on capacitive sensor head technology, and they are developed, manufactured and tested by The Finnish Meteorological Institute (FMI). Calibration of capacitive humidity sensors for the Martian environment has been a challenging task and special facilities are needed in order to create Martian conditions including all relevant environmental parameters: low pressure, low temperature, carbon dioxide environment, and especially humidity that can be accurately controlled and measured. A measurement campaign was performed at DLR PASLAB (Planetary Analog Simulation Laboratory) determining relative humidity calibration data sets for REMS-H, MEDA HS and METEO-H instruments in temperatures from -30 °C down to -70 °C in low pressure CO2. In addition to the stable point humidity calibration measurements in CO2, the instrument performance was tested with the actual Martian atmosphere composition, and during long continuous measurements. The new calibration data set has already been used in the flight calibration of the MEDA HS instrument resulting in successful calibration and excellent accuracy. The results from this campaign will further improve relative humidity measurements on Mars by providing the means to reanalyse the current calibration of the REMS-H flight model, and by allowing more accurate comparison between the two instruments currently on the Martian surface. [ABSTRACT FROM AUTHOR]

An extensive sensitivity analysis was performed for a horizontally homogeneous and hydrostatic 1-D column model at the Mars Science Laboratory (MSL) location. Model experiments were compared with observations from the Curiosity Rover Environmental Monitoring Station humidity (REMS-H) device. Based on our earlier column model investigations, model surface temperature and pressure, dust optical depth (τ) and column precipitable water content (PWC) were the initial parameters that we investigated by our sensitivity analysis. Our analysis suggests that the most sensitive initial parameters for the column model temperature profile are τ and the surface temperature. The initial value of PWC does not affect the temperature profile of the model, but it is the most important parameter for the humidity profile. The initial value of τ also seems to have some effect on the humidity profile of the model. Based on our analysis, variations in surface pressure initialization are negligible for the model's humidity and temperature predictions. The model simulations are generally in good agreement with the observations. Our analysis suggest that a slightly different shape of the model's initial humidity profile could yield better results in the predicted water vapor volume mixing ratios at 1.6 m. [ABSTRACT FROM AUTHOR]