Regional Dust Storms Research Articles

Water Vapor Vertical Profiles on Mars in Dust Storms Observed by TGO/NOMAD

AbstractIt has been suggested that dust storms efficiently transport water vapor from the near‐surface to the middle atmosphere on Mars. Knowledge of the water vapor vertical profile during dust storms is important to understand water escape. During Martian Year 34, two dust storms occurred on Mars: a global dust storm (June to mid‐September 2018) and a regional storm (January 2019). Here we present water vapor vertical profiles in the periods of the two dust storms (Ls = 162–260° and Ls = 298–345°) from the solar occultation measurements by Nadir and Occultation for Mars Discovery (NOMAD) onboard ExoMars Trace Gas Orbiter (TGO). We show a significant increase of water vapor abundance in the middle atmosphere (40–100 km) during the global dust storm. The water enhancement rapidly occurs following the onset of the storm (Ls~190°) and has a peak at the most active period (Ls~200°). Water vapor reaches very high altitudes (up to 100 km) with a volume mixing ratio of ~50 ppm. The water vapor abundance in the middle atmosphere shows high values consistently at 60°S‐60°N at the growth phase of the dust storm (Ls = 195°–220°), and peaks at latitudes greater than 60°S at the decay phase (Ls = 220°–260°). This is explained by the seasonal change of meridional circulation: from equinoctial Hadley circulation (two cells) to the solstitial one (a single pole‐to‐pole cell). We also find a conspicuous increase of water vapor density in the middle atmosphere at the period of the regional dust storm (Ls = 322–327°), in particular at latitudes greater than 60°S.

Eddy evolution during large dust storms

The evolution of eddy kinetic energy during the development of large regional dust storms on Mars is investigated using the Mars Analysis Correction Data Assimilation (MACDA) reanalysis product and the dust storm data derived from Mars Global Surveyor Mars Daily Global Maps. Transient eddies in MACDA are decomposed into different components according to their eddy periods: P≤1 sol, 1<P≤8 sols, 8<P≤60 sols. This paper primarily focuses on the Mars year 24 pre-solstice ”A” storm that starts with many episodes of frontal/flushing dust storms from the northern hemisphere and attains its maximum global mean opacity after dust expansion in the southern hemisphere. During the development of this storm, the dominant eddies in terms of eddy kinetic energy progress from the 1<P≤8 sol eddies in the northern mid/high latitudes to the P≤1 sol eddies (dominated by thermal tides) in the southern mid latitudes, and the 8<P≤60 sol eddies show a prominent peak with the increased global-mean dust opacity. The peaks of the 1<P≤8 sol eddies are found to best correlate with the average area of textured frontal/flushing dust storms within 40∘N–60∘N. The region where the 1<P≤8 sol eddies increase the most corresponds to the main flushing channel. The eddy kinetic energy of the P≤1 eddies, dominated by P = 1 and its harmonics, increases with the global mean dust opacity both before and after the winter solstice in Mars year 24. The 8<P≤60 sol eddies briefly spike during large, regional dust storms but remain weak if dust storm sequences do not lead to a major dust storm. Zonal wavenumber analysis of eddy kinetic energy shows that the peaks of the 1<P≤8 eddies often result from combinations of zonal wavenumbers 1 to 3, while the P≤1 eddies and 8<P≤60 sol eddies are each dominated by zonal wavenumber 1.

An Observational Overview of Dusty Deep Convection in Martian Dust Storms.

Deep convection, as used in meteorology, refers to the rapid ascent of air parcels in the Earth's troposphere driven by the buoyancy generated by phase change in water. Deep convection undergirds some of the Earth's most important and violent weather phenomena and is responsible for many aspects of the observed distribution of energy, momentum, and constituents (particularly water) in the Earth's atmosphere. Deep convection driven by buoyancy generated by the radiative heating of atmospheric dust may be similarly important in the atmosphere of Mars but lacks a systematic description. Here we propose a comprehensive framework for this phenomenon of dusty deep convection (DDC) that is supported by energetic calculations and observations of the vertical dust distribution and exemplary dusty deep convective structures within local, regional, and global dust storm activity. In this framework, DDC is distinct from a spectrum of weaker dusty convective activity because DDC originates from pre-existing or concurrently forming mesoscale circulations that generate high surface dust fluxes, oppose large-scale horizontal advective-diffusive processes, and are thus able to maintain higher dust concentrations than typically simulated. DDC takes two distinctive forms. Mesoscale circulations that form near Mars's highest volcanoes in dust storms of all scales can transport dust to the base of the upper atmosphere in as little as two hours. In the second distinctive form, mesoscale circulations at low elevations within regional and global dust storm activity generate freely convecting streamers of dust that are sheared into the middle atmosphere over the diurnal cycle.

Use of Low-Cost Ambient Particulate Sensors in Nablus, Palestine with Application to the Assessment of Regional Dust Storms

Few air pollutant studies within the Palestinian territories have been reported in the literature. In March–April and May–June of 2018, three low-cost, locally calibrated particulate monitors (AirU’s) were deployed at different elevations and source areas throughout the city of Nablus in Northern West Bank, Palestine. During each of the three-week periods, high but site-to-site similar particulate matter less than 2.5 µm in aerodynamic diameter (PM2.5) and less than 10 µm (PM10) concentrations were observed. The PM2.5 concentrations at the three sampling locations and during both sampling periods averaged 38.2 ± 3.6 µg/m3, well above the World Health Organization’s (WHO) 24 h guidelines. Likewise, the PM10 concentrations exceeded or were just below the WHO’s 24 h guidelines, averaging 48.5 ± 4.3 µg/m3. During both periods, short episodes were identified in which the particulate levels at all three sites increased substantially (≈2×) above the regional baseline. Air mass back trajectory analyses using U.S. National Oceanic and Atmospheric Administration’s (NOAA) Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model suggested that, during these peak episodes, the arriving air masses spent recent days over desert areas (e.g., the Saharan Desert in North Africa). On days with regionally low PM2.5 concentrations (≈20 µg/m3), back trajectory analysis showed that air masses were directed in from the Mediterranean Sea area. Further, the lower elevation (downtown) site often recorded markedly higher particulate levels than the valley wall sites. This would suggest locally derived particulate sources are significant and may be beneficial in the identification of potential remediation options.

Observations and transport modeling of dust storm event over Northeast Asia using HYSPLIT: case study

This study analyzes a regional dust storm event that occurred in spring 2016 using data from observation sites, Lidar measurements, and satellite imageries. PM10 concentrations at surface observation stations are considered as a primary indicator of the dust events. The dust events occurred on 3-12 March with PM10 reaching a maximum beyond 1682, 1498, 706, and 165 μg m−3 at observation sites in Mongolia, China, Korea and Japan, respectively. The dust event in Northeast Asia is captured by time series of PM10 concentrations at observation sites. On 3-4 March, the dust storm event originated from Mongolia move toward China, Korea and Japan. Vertical distributions of dust observed by Lidar measurements from stations in AD-Net capture a thick layer of nearly 2.2 km of high concentrations above surface in the area of origin. The maximum PM10 concentration drops with downwind transport. Dust source identification and dust-loaded air parcel trajectories are calculated using the HYSPLIT model. According to the HYSPLIT model, the dust storm started on 3-4 March from Mongolia and reached northern Japan in about 4 days passing over northern China and Korea.

Long-Term Ground-Based Measurements of Aerosol Optical Depth over Kuwait City

We analyze ten years (2008–2017) of ground-based observations of the Aerosol Optical Depth (AOD) in the atmosphere of Kuwait City, in Middle East. The measurements were conducted with a CIMEL sun-sky photometer, at various wavelengths. The daily average AOD at 500 nm (AOD500) is 0.45, while the mean Ångström coefficient (AE), calculated from the pair of wavelengths 440 and 870 nm, is 0.61. The observed high AOD500 values (0.75–2.91), are due to regional sand and dust storm events, which are affecting Kuwait with a mean annual frequency of almost 20 days/year. The long-term record analysis of AOD500 and AE, shows a downward and upward tendency respectively, something which could be attributed to the continuous expansion and industrialization of the main city of Kuwait, in combination with the simultaneous increase of soil moisture over the area. By utilizing back trajectories of air masses for up to 4 days, we assessed the influence of various regions to the aerosol load over Kuwait. The high aerosol loads during spring, are attributed to the dominance of coarse particles from Saudi Arabia (AOD500 0.56–0.74), a source area that contributes the 56% to the mean annual AOD500. Other dust sources affecting significantly Kuwait originated from the regions of Iraq and Iran with contribution of 21%.

Meteorological pressure at Gale crater from a comparison of REMS/MSL data and MCD modelling: Effect of dust storms

We examine the record of atmospheric pressure in Gale crater measured in-situ by the Rover Environmental Monitoring Station (REMS) instrument (Gómez-Elvira et al., 2012) on the Mars Science Laboratory (MSL) rover over two Martian years. We compare the data with pressure predictions from the Mars Climate Database (MCD) (Forget et al., 1999; Millour et al., 2015) version 5.2, which is a climatological database derived from numerical simulations of the Martian atmosphere produced by a General Circulation Model run over several Martian years. Seasonal and daily trends in pressure data from REMS are well reproduced by the standard climatology of the MCD using its high resolution mode. This high-resolution mode extrapolates pressure values from the nominal model into the altitude of each location using a high-resolution topography model and a fine tuning of the vertical scale height that was chosen to mimic effects of slope winds not directly accounted for in the General Circulation Model on which the MCD is based. Differences between the synthetic MCD pressure data and the REMS measurements are produced by meteorological features that are identified on particular groups of sols and quantified in intensity. We show that regional dust storms outside Gale crater and dust abundance at the crater are important factors in the behaviour of the pressure exciting larger amplitudes on the daily pressure variations and causing most of the largest REMS-MCD differences. We compare the pressure signals with published data of the dust optical depth obtained by the REMS ultraviolet photodiodes and the Mastcam instrument on MSL, and with orbital images of the planet acquired by the MARCI instrument on the Mars Reconnaissance Orbiter (MRO). We show that in some cases regional dust storms induce a characteristic signature in the surface pressure measured by REMS several sols before the dust arrives to Gale crater. We explore the capability of daily pressure measurements to serve as a fast detector of the development of dust storms in the context of the MSL, Insight and Mars 2020 missions.

Coarse Sediment Transport in the Modern Martian Environment

AbstractThe occurrence of regional and global dust storms, observations of migrating ripples and dunes, and the recognition of aeolian sandstone outcrops demonstrate that aeolian processes have been and continue to be a significant agent of surface modification on Mars. However, the mechanisms of aeolian transport within Mars' low atmospheric pressure surface environment are still not fully understood. This work presents a synthesis of change detection observations conducted with the Mars Science Laboratory Curiosity rover in Gale crater over three Martian years. Sediment mobility during this period was highly variable, consistent with previous orbiter‐based observations showing strong seasonal variability, with strongest winds expected during southern summer. Wind activity inferred at each change detection site helps test the accuracy of atmospheric models, as well as constrain the intensity of current atmosphere‐surface interactions and the physics of sand transport in the tenuous Martian atmosphere. Results indicate an apparent discrepancy between predicted wind speeds and the wind strengths required by classical incipient‐motion models to explain observed sediment motion. Observed mobilization of perched and/or isolated very coarse sand grains and fine pebbles (i.e., grain sizes 1 mm ≤d≤3 mm) likely requires an alternate explanation, such as very strong but infrequent wind gusts, drag‐induced rolling, or impact‐driven creep caused by smaller saltating particles.

The cascade from local to global dust storms on Mars: Temporal and spatial thresholds on thermal and dynamical feedback

We use the MarsWRF general circulation model to examine the temporal and spatial response of the atmosphere to idealized local and regional dust storm radiative heating. The ability of storms to modify the atmosphere away from the location of dust heating is a likely prerequisite for dynamical feedbacks that aid the growth of storms beyond the local scale, while the ability of storms to modify the atmosphere after the cessation of dust radiative heating is potentially important in preconditioning the atmosphere prior to large scale storms. Experiments were conducted over a range of static, prescribed storm sizes, durations, optical depth strengths, locations, and vertical extents of dust heating. Our results show that for typical sizes (order 105 km2) and durations (1–10 sols) of local dust storms, modification of the atmosphere is less than the typical variability of the unperturbed (storm-free) state. Even if imposed on regional storm length scales (order 106 km2), a 1-sol duration storm similarly does not significantly modify the background atmosphere. Only when imposed for 10 sols does a regional dust storm create a significant impact on the background atmosphere, allowing for the possibility of self-induced dynamical storm growth. These results suggest a prototype for how the subjective observational categorization of storms may be related to objective dynamical growth feedbacks that only become available to storms after they achieve a threshold size and duration, or if they grow into an atmosphere preconditioned by a prior large and sustained storm.

The Variability of Atmospheric Deuterium Brightness at Mars: Evidence for Seasonal Dependence

AbstractThe enhanced ratio of deuterium to hydrogen on Mars has been widely interpreted as indicating the loss of a large column of water into space, and the hydrogen content of the upper atmosphere is now known to be highly variable. The variation in the properties of both deuterium and hydrogen in the upper atmosphere of Mars is indicative of the dynamical processes that produce these species and propagate them to altitudes where they can escape the planet. Understanding the seasonal variability of D is key to understanding the variability of the escape rate of water from Mars. Data from a 15 month observing campaign, made by the Mars Atmosphere and Volatile Evolution Imaging Ultraviolet Spectrograph high‐resolution echelle channel, are used to determine the brightness of deuterium as observed at the limb of Mars. The D emission is highly variable, with a peak in brightness just after southern summer solstice. The trends of D brightness are examined against extrinsic as well as intrinsic sources. It is found that the fluctuations in deuterium brightness in the upper atmosphere of Mars (up to 400 km), corrected for periodic solar variations, vary on timescales that are similar to those of water vapor fluctuations lower in the atmosphere (20–80 km). The observed variability in deuterium may be attributed to seasonal factors such as regional dust storm activity and subsequent circulation lower in the atmosphere.

Limb clouds and dust on Mars from images obtained by the Visual Monitoring Camera (VMC) onboard Mars Express

The Visual Monitoring Camera (VMC) onboard the Mars Express (MEx) spacecraft is a simple camera aimed to monitor the release of the Beagle-2 lander on Mars Express and later used for public outreach. Here, we employ VMC as a scientific instrument to study and characterize high altitude aerosols events (dust and condensates) observed at the Martian limb. More than 21,000 images taken between 2007 and 2016 have been examined to detect and characterize elevated layers of dust in the limb, dust storms and clouds. We report a total of 18 events for which we give their main properties (areographic location, maximum altitude, limb projected size, Martian solar longitude and local time of occurrence). The top altitudes of these phenomena ranged from 40 to 85 km and their horizontal extent at the limb ranged from 120 to 2000 km. They mostly occurred at Equatorial and Tropical latitudes (between ∼30°N and 30°S) at morning and afternoon local times in the southern fall and northern winter seasons. None of them are related to the orographic clouds that typically form around volcanoes. Three of these events have been studied in detail using simultaneous images taken by the MARCI instrument onboard Mars Reconnaissance Orbiter (MRO) and studying the properties of the atmosphere using the predictions from the Mars Climate Database (MCD) General Circulation Model. This has allowed us to determine the three-dimensional structure and nature of these events, with one of them being a regional dust storm and the two others water ice clouds. Analyses based on MCD and/or MARCI images for the other cases studied indicate that the rest of the events correspond most probably to water ice clouds.

The seasonal and spatial distribution of textured dust storms observed by Mars Global Surveyor Mars Orbiter Camera

Local and regional dust storms observed by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) exhibit three main types of textures in their visible top structures which we describe as “pebbled”, “puffy”, and “plume-like.” In this paper, we present the temporal and spatial distribution of each texture type. There is a pause in activity near the solstices for all three texture types, but the pause is more pronounced for pebbled and plume-like dust storms than for puffy dust storms. The average size of each texture type is usually much larger during the northern summer and fall (Ls=90–270°) than during the rest of the Martian year. Although all three textures types can be observed at all latitudes, plume-like dust storms tend to dominate the northern mid-latitudes, pebbled dust storms tend to dominate the southern mid-latitudes, and puffy dust storms tend to dominate the low latitudes. During the 2001 global dust storm in Mars Year 25, we found a progression from a combination of all three texture types in the early stage to mostly plume-like dust storms in the expansion and decay phases.

Seasonal and spatial differences in source contributions to PM2.5 in Wuhan, China

Fine particle (PM2.5) samples were collected in 2011 and 2012 simultaneously at three sites in Wuhan in an industrial area (ID), downtown Wuhan (DT), and the Wuhan botanical gardens (BG). The annual average concentration of PM2.5 was highest in the industrial area at 180μgm−3 and lowest in the botanical gardens, with an average of 93μgm−3. The average downtown PM2.5 concentration was 113μgm−3. All sites had concentrations well above the World Health Organization (WHO) guidelines and the Chinese air quality standard. The concentration of major constituents of PM2.5 varied seasonally across all sites; specifically, sulfate, nitrate, and organic carbon varied most strongly during spring, followed by summer and fall. Organic carbon varied the most across sites for all seasons, which is attributable to large differences in local source emissions. The major primary sources contributing to OC were vehicle emissions (38.1±8.3%), coal combustion (7.0±6.2%), meat cooking (3.0±1.6%), and biomass burning (3.0±1.0%). All these sources had large seasonal variations across the three sites. Biomass burning had the largest impact at BG, mobile sources had the largest impact at DT, and coal combustion had the largest impact at ID. Mineral dust was a major contributor to PM2.5 (average 16.8±9.6μgm−3) and had very homogenous concentrations across the sites during springtime due to regional dust storms, but had much higher concentration at ID during the summer and fall. The results demonstrate the need for both regional and local air pollution control strategies to reduce air pollution in Wuhan. This research contributes to the field of particulate matter studies by providing information about seasonal and regional fluctuations in PM2.5 in large urban areas, which helps advance understanding of the sources responsible for urban haze.

Interannual perturbations of the Martian surface heat flow by atmospheric dust opacity variations

AbstractThe InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) mission will perform the first Martian in situ heat flow measurement by deploying the Heat Flow and Physical Properties Package (HP3) onto the Martian surface. In order to estimate the heat flow coming from the planetary interior, HP3 will measure the local subsurface thermal gradient as well as the local thermal conductivity to a depth of up to 5 m. From these measurements, local heat flow can be determined, but this will in general differ from the heat flow emanating from the planetary interior due to atmosphere‐induced perturbations. Here we quantify heat flow perturbation induced by dust loading of the Martian atmosphere using dust opacity data obtained by the Mars Exploration Rover Opportunity. Dust opacity data span the time period between Mars year (MY) 27 and MY 32, thus incorporating the global dust storm event of MY 28 as a signal. We consider two end‐member cases for the regolith thermal conductivity and find that the background planetary heat flow is superposed by atmosphere‐induced perturbations of less than 1.5 mW m−2 at depths below 2 m if regolith thermal conductivity is low and around 0.025 W m−1 K−1 on average. If thermal conductivity is high and around 0.05 W m−1 K−1 on average, perturbations are less than 2.5 mW m−2 at depths below 3 m. Overall, the influence of interannual variability on subsurface heat flow is found to be moderate following a global dust storm. Considerably smaller perturbations are introduced by regional dust storms, which are of shorter duration and smaller magnitude.

Variation of strong dust storm events in Northern China during 1978–2007

Dust storms have a great significance for global mineral aerosol cycle, marine ecosystem, air quality and human health. Dust storm frequency (DSF), often used as a primary index for understanding a regional characteristic of dust storms. However, DSF couldn't describe the frequency and the outbreak areas of a dust storm event (DSE) which was defined as a dust storm occurred at three or more meteorological stations during the same weather process, because a DSE might occur at several meteorological stations and continue for several days. We defined a new index DSE considering the factors including wind speed, wind direction and spatial variation during a dust storm process. To clarify which index of DSF or DSE is better to describe the characteristics of dust storms, we have used the data sets of dust storm from 319 meteorological stations to calculate the frequency of DSE, and the outbreak area and the duration of each DSE in 1978–2007, as well as to compare the differences between DSE and DSF in spatiotemporal distribution in Northern China. The results showed that the high-value locations of occurrence numbers of DSE and DSF were almost overlapped; from 1978 to 2007, the total values of DSE and DSF decreased from 558 to 201 and from 1273 to 467, respectively, but the mean values of outbreak area and duration of DSE have wavily increased since 1991. These implied that the differences existed between DSE and DSF in describing the characteristics of a regional dust storm, and DSE was a better index for a dust storm to identify the fact of occurrence frequency and outbreak area. The implication of this study was that the values of DSE and DSF have a decrease trends with increase of extreme precipitation events and decrease of mean wind speed under the global warming scenarios, but strong dust storms, which is defined as the outbreak area of an event >105km2 here, probably bring greater risk in future.

Long‐term variability of dust optical depths on Mars during MY24–MY32 and their impact on subtropical lower ionosphere: Climatology, modeling, and observations

AbstractDust optical depths (τ) for nine Martian years (MY24–MY32) in the subtropical region (25–35°S) have been used to classify distinct dust scenarios. These data are based on observations at 9.3 µm from the Mars Global Surveyor and Mars Odyssey missions and encompass the regional dust storms which occur every year around solar longitude (Ls) ~ 220° and the two major dust storms of MY25 and MY28. Constrained by these observations and the Mars Climate Sounder observations of detached dust layers, we estimate altitude profiles of dust concentrations. We discuss the characteristics of dust aerosol particles of different size between 0.2 and 3.0 µm by assuming a modified gamma distribution. We then use a comprehensive ion‐dust model to calculate ion densities and conductivities in the lower ionosphere of Mars in the absence of dust storm at τ = 0.1 and Ls = 150° and for three dust storm periods viz., (1) major dust storm at τ = 1.7 and Ls = 210°, (2) major dust storm at τ = 1.2 and Ls = 280°, and (3) regional dust storm at τ = 0.5 and Ls = 220°. The model with 12 neutral species considers galactic cosmic rays as a source of ionization. Results show that the density of the dominant hydrated cluster ions and the electrical conductivity are reduced by an order of magnitude near the surface for a few months until the dust storm settles down to its normal condition.

The effect of dust on the martian polar vortices

The influence of atmospheric dust on the dynamics and stability of the martian polar vortices is examined, through analysis of Mars Climate Sounder observations and MarsWRF general circulation model simulations. We show that regional and global dust storms produce “transient vortex warming” events that partially or fully disrupt the northern winter polar vortex for brief periods. Increased atmospheric dust heating alters the Hadley circulation and shifts the downwelling branch of the circulation poleward, leading to a disruption of the polar vortex for a period of days to weeks. Through our simulations, we find this effect is dependent on the atmospheric heating rate, which can be changed by increasing the amount of dust in the atmosphere or by altering the dust optical properties (e.g., single scattering albedo). Despite this, our simulations show that some level of atmospheric dust is necessary to produce a distinct northern hemisphere winter polar vortex.

A view-dependent spatiotemporal saliency-driven approach for time varying volumetric data in geovisualization

Geospatial datasets from satellite observations and model simulations are becoming more accessible. These spatiotemporal datasets are relatively massive for visualization to support advanced analysis and decision making. A challenge to visualizing massive geospatial datasets is identifying critical spatial and temporal changes reflected in the data while maintaining high interactive rendering speed, even when data are accessed remotely. We propose a view-dependent spatiotemporal saliency-driven approach that facilitates the discovery of regions showing high levels of spatiotemporal variability and reduces the rendering intensity of interactive visualization. Our method is based on a novel definition of data saliency, a spatiotemporal tree structure to store visual saliency values, as well as a saliency-driven view-dependent level-of-detail (LOD) control. To demonstrate its applicability, we have implemented the approach with an open-source remote visualization package and conducted experiments with spatiotemporal datasets produced by a regional dust storm simulation model. The results show that the proposed method may not be outstanding in some specific situations, but it consistently performs very well across different settings according to different criteria.

Atmospheric tides in Gale Crater, Mars

Atmospheric tides are the primary source of daily air pressure variation at the surface of Mars. These tides are forced by solar heating of the atmosphere and modulated by the presence of atmospheric dust, topography, and surface albedo and thermal inertia. This results in a complex mix of sun-synchronous and non-sun-synchronous tides propagating both eastward and westward around the planet in periods that are integer fractions of a solar day. The Rover Environmental Monitoring Station on board the Mars Science Laboratory has observed air pressure at a regular cadence for over 1Marsyear and here we analyze and diagnose atmospheric tides in this pressure record. The diurnal tide amplitude varies from 26 to 63Pa with an average phase of 0424 local true solar time, while the semidiurnal tide amplitude varies from 5 to 20Pa with an average phase of 0929. We find that both the diurnal and semidiurnal tides in Gale Crater are highly correlated to atmospheric opacity variations at a value of 0.9 and to each other at a value of 0.77, with some key exceptions occurring during regional and local dust storms. We supplement our analysis with MarsWRF general circulation modeling to examine how a local dust storm impacts the diurnal tide in its vicinity. We find that both the diurnal tide amplitude enhancement and regional coverage of notable amplitude enhancement linearly scales with the size of the local dust storm. Our results provide the first long-term record of surface pressure tides near the martian equator.

Extreme detached dust layers near Martian volcanoes: Evidence for dust transport by mesoscale circulations forced by high topography

AbstractModeling suggests that thermal circulations over Mars's highest volcanoes transport water vapor and dust from the surface into the middle atmosphere, forming detached layers in these constituents. Intense vertical mixing also takes place in regional and global dust storms, which can generate detached layers that are extreme in both altitude and magnitude. Here we employ observations by the Mars Climate Sounder (MCS) on board Mars Reconnaissance Orbiter, taking advantage of improved vertical coverage in MCS's aerosol retrievals, to discover a new class of extreme detached dust layers (EDDLs). Observed during minimal dust storm activity and furthermore distinguished by their potentially large and measurable horizontal extent (&gt;1000 km), these EDDLs cluster near Olympus Mons and the Tharsis Montes, from which they likely originate. The existence of these EDDLs suggests that vertical mixing by topographic circulations can be much stronger than previously modeled and more frequent than previously observed.