Kylash Rajendran
Gather.town id
FMM04
Poster Title
Super-rotation and the 2018 Mars Global Dust Storm
Institution
The Open University
Abstract (short summary)
The presence of a prograde jet at the equator in a planetary atmosphere is often referred to as super-rotation. On Mars, the strength of the equatorial jet is dynamically coupled to the amount of dust in the atmosphere; strengthening of the equatorial jet by the presence of dust affects dust transport in the tropics, which in turn determines the locations of further dust-driven heating. We used data assimilation to study the interaction between dust and the equatorial jet during the 2018 Mars global dust storm (GDS). The data assimilation scheme integrated temperature and dust information from instruments aboard the Mars Reconnaissance Orbiter and ExoMars Trace Gas Orbiter satellites into a numerical model of the Martian atmosphere, creating a better representation of the atmospheric state than could be achieved from observations or models alone. We found that super-rotation increased by a factor of two at the peak of the GDS, due to enhanced winds in the tropics. A strong westerly jet formed in the tropical lower atmosphere, and easterlies were strengthened above 60 km, as a result of momentum transport by dust-driven thermal tides. We found that the atmosphere was in a state of enhanced super-rotation even before the onset of the GDS, as a result of equatorward advection of dust from the southern mid-latitudes into the tropics. The redistribution of dust across the hemispheres resulted in a more uniform dust distribution across the tropics, leading to a symmetric Hadley cell with a tropical upwelling branch that was closely aligned to the vertical. We argue that the symmetrical circulation and enhanced super-rotation would have been important environmental factors that encouraged the development of the GDS in 2018.
Plain text (extended) Summary
Slide 1: Title, author list, affiliations and funding agencies at top.
A single figure in the middle of the slide is surrounded by the main text. On the left the text introduces Global Dust Storms (GDS) on Mars, and highlights that it is still unknown why these storms form in some years and not in others. The text on the right explains how dust in the martian atmosphere can lead to super-rotation and enhanced prograde tropical winds. Super-rotating winds may have a role to play in enabling GDS formation by enabling rapid dust transport across the planet.
The main figure shows two side-by-side images of Mars as taken from space. The left image shows Mars with a clear atmosphere, indicating non-dusty conditions, and the right image shows Mars in dusty conditions. Eastward-pointing arrows stretch across the equator in both plots, with the arrow on the right plot much thicker than the arrow on the left plot, indicating enhanced super-rotating winds due to the presence of dust.
Slide 2: Title: “2018 Mars Global Dust Storm (GDS) & Data Assimilation”. Main text on right half of slide explains that the study used data assimilation to study super-rotation during the 2018 GDS. The satellite data used in the assimilation are listed, together with the metrics used to diagnose super-rotation.
Left half of the slide consists of a single image, consisting of two small globes on the left (aligned in the vertical) and a large globe on the right. The left globes show atmospheric field data of the Martian atmosphere as derived from observations (top globe) and models (bottom globe). The large globe on the right is a combination of the two globes on the left, demonstrating how data assimilation works.
Two equations at the bottom of the slide give the mathematical definitions of the global and local super-rotation indices.
Slide 3: Title: “Results”. Main text at top-left describes the main findings that super-rotation doubled at the peak of the storm and that these winds facilitated dust transport across the globe.
There are two figures on this slide. The figure on the bottom-left shows how global super-rotation changes over the course of a year with a dust storm and a year without a dust storm. There is a large peak in the year with the dust storm, indicating that super-rotation doubled during the storm. The figure on the left of the slide has 4 subplots that show how equatorial winds change at the onset and peak of the GDS. The plot demonstrates how local super-rotation was very strong in tropical regions during both storm phases, as compared to the non-GDS year.
Slide 4: Main text at top-left explains that super-rotation was found to have been enhanced even prior to storm onset in the GDS year. The cause was dust from the southern hemisphere encroaching into the tropics and altering the heating distribution. This led to a symmetric distribution of dust heating that enhanced the circulation and created a tropical upwelling branch closely aligned to the vertical, enabling efficient vertical transport. It is suggested that the enhanced pre-storm winds may have significantly contributed to the later rapid expansion of the storm.
The text is supported by a series of plots showing the evolution of the dust and circulation fields 50, 40, and 30 sols before the onset of the global dust storm. The poster ends with a link to the submitted paper describing these results, and a DOI to the preprint.
A single figure in the middle of the slide is surrounded by the main text. On the left the text introduces Global Dust Storms (GDS) on Mars, and highlights that it is still unknown why these storms form in some years and not in others. The text on the right explains how dust in the martian atmosphere can lead to super-rotation and enhanced prograde tropical winds. Super-rotating winds may have a role to play in enabling GDS formation by enabling rapid dust transport across the planet.
The main figure shows two side-by-side images of Mars as taken from space. The left image shows Mars with a clear atmosphere, indicating non-dusty conditions, and the right image shows Mars in dusty conditions. Eastward-pointing arrows stretch across the equator in both plots, with the arrow on the right plot much thicker than the arrow on the left plot, indicating enhanced super-rotating winds due to the presence of dust.
Slide 2: Title: “2018 Mars Global Dust Storm (GDS) & Data Assimilation”. Main text on right half of slide explains that the study used data assimilation to study super-rotation during the 2018 GDS. The satellite data used in the assimilation are listed, together with the metrics used to diagnose super-rotation.
Left half of the slide consists of a single image, consisting of two small globes on the left (aligned in the vertical) and a large globe on the right. The left globes show atmospheric field data of the Martian atmosphere as derived from observations (top globe) and models (bottom globe). The large globe on the right is a combination of the two globes on the left, demonstrating how data assimilation works.
Two equations at the bottom of the slide give the mathematical definitions of the global and local super-rotation indices.
Slide 3: Title: “Results”. Main text at top-left describes the main findings that super-rotation doubled at the peak of the storm and that these winds facilitated dust transport across the globe.
There are two figures on this slide. The figure on the bottom-left shows how global super-rotation changes over the course of a year with a dust storm and a year without a dust storm. There is a large peak in the year with the dust storm, indicating that super-rotation doubled during the storm. The figure on the left of the slide has 4 subplots that show how equatorial winds change at the onset and peak of the GDS. The plot demonstrates how local super-rotation was very strong in tropical regions during both storm phases, as compared to the non-GDS year.
Slide 4: Main text at top-left explains that super-rotation was found to have been enhanced even prior to storm onset in the GDS year. The cause was dust from the southern hemisphere encroaching into the tropics and altering the heating distribution. This led to a symmetric distribution of dust heating that enhanced the circulation and created a tropical upwelling branch closely aligned to the vertical, enabling efficient vertical transport. It is suggested that the enhanced pre-storm winds may have significantly contributed to the later rapid expansion of the storm.
The text is supported by a series of plots showing the evolution of the dust and circulation fields 50, 40, and 30 sols before the onset of the global dust storm. The poster ends with a link to the submitted paper describing these results, and a DOI to the preprint.
URL
kylash.rajendran@open.ac.uk
Poster file