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Dust Storm
serpens
post Today, 12:13 AM
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The effect of dust storms is to loft water vapor into the middle atmosphere, with a significant decrease in absolute humidity near the ground. This reduction in the amount of water vapor means that the formation of films or brines is even less likely during a dust storm despite higher minimum temperature or minor variations in atmospheric pressure.
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marsophile
post Today, 12:38 AM
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QUOTE (serpens @ Jun 24 2018, 04:13 PM) *
...the formation of films or brines is even less likely during a dust storm....


I am more interested in the aftermath of the dust storm, when (hopefully) Opportunity will be able to observe changes in the resultant dust deposits. Is the above hypothesis still applicable at that point?
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mcaplinger
post Today, 01:17 AM
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QUOTE (marsophile @ Jun 24 2018, 04:38 PM) *
Is the above hypothesis still applicable at that point?

I don't think there's really an appreciable pressure signature from dust storms, but this has been measured. Note that some of the graphs below are more about diurnal variation in pressure and less about absolute pressure.

https://www-k12.atmos.washington.edu/k12/re...ion/overlay.gif

https://mars.nasa.gov/resources/4902/atmosp...ing-dust-storm/


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marsophile
post Today, 02:57 AM
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https://mars.nasa.gov/msl/mission/instrumen...onsensors/rems/

Dates (2018) Mean Pressure (Pascals)

June 05--June 10
758 756 758 762 764 765
June 11--June 16
766 767 768 770 768 769
June 17--June 21
771 772 776 780 778

Looks quite suggestive. Of course it might be just the normal seasonal signal.

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djellison
post Today, 03:28 AM
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QUOTE (serpens @ Jun 24 2018, 05:13 PM) *
The effect of dust storms is to loft water vapor into the middle atmosphere, with a significant decrease in absolute humidity near the ground. This reduction in the amount of water vapor means that the formation of films or brines is even less likely during a dust storm despite higher minimum temperature or minor variations in atmospheric pressure.


And the maximum temperatures are also decreased, dramatically, during the storm. Rendering windows when such events might occur astonishingly small, if they existed at all.
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serpens
post Today, 07:39 AM
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QUOTE (mcaplinger @ Jun 25 2018, 02:17 AM) *
I don't think there's really an appreciable pressure signature from dust storms, but this has been measured.

The second linked graph measures atmospheric pressure hundreds of miles from a dust storm and compares pressure changes above the daily minimum. Given the general atmospheric heating and the localised heating referred to wouldn't the minimum absolute pressure be different for each of the graphs, possibly implying that the absolute maximum temperatures would tend to align?
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mcaplinger
post Today, 02:54 PM
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QUOTE (serpens @ Jun 24 2018, 11:39 PM) *
wouldn't the minimum absolute pressure be different for each of the graphs...

Of course. Without finding the raw data I can only show what the team chose to plot. My only point in posting this was to indicate that the pressure was being measured and eventually we would be able to see those measurements (see http://pds-atmospheres.nmsu.edu/data_and_s.../Mars/Mars.html although if this page is right the REMS team is way behind on releasing data.)

Going back to the Viking 1 data would be the best way to look at the pressure through a dust storm as of today, probably.


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scalbers
post Today, 03:58 PM
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This simulated version shows the blue scattering surrounding the sun a bit better. Tau ranges from 0.5 to 10.

Attached Image


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Deimos
post Today, 04:03 PM
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Pressure is of course modified by the storm--but there is no measurable enhancement from the dust loading, the original question (I think). The modification is not as simple as a perturbation to the existing profile (e.g., shifting the absolute minimum pressure up or down or compressing/expanding the range of variation).

There are many modes, and they interfere. There's a diurnal tide--the surface gets warmer and heats the air, warm air rises, circulation happens--that can be diminished by the the diminished temperature cycle, but also by more complex interactions (VL1 diurnal tide went away, http://science.sciencemag.org/content/213/4506/437--at least the abstract can be seen). There's a semi-diurnal tide from heating by dust in the air and can be seen from orbit and the ground (http://www.planetary.org/blogs/guest-blogs/2013/mysterious-tides-martian-atmosphere.html). It increases in amplitude significantly when there is a lot of dust in the hemisphere or globe (Fig. 2 in https://journals.ametsoc.org/doi/full/10.1175/JAS3718.1)

The tides are enhanced in Gale as opposed to Meridiani; they correlate with dust as seen by Curiosity--two pay-walled papers discuss this: https://www.sciencedirect.com/science/artic...0531?via%3Dihub and https://www.sciencedirect.com/science/artic...5850?via%3Dihub. It might be cool if Scott (or Scot) would do a blog post at Planetary Society.

To visualize the modes, see Figs. 3, 9, 10 in http://sirius.bu.edu/withers/pppp/pdf/with...014atmo_v02.pdf.

So, there is no particular effect from the dust mass; but there will be a substantial impact from the dust heating and cooling effects, and those would be expected to significantly alter the shape of the pressure wave, based on how much the first two modes would be expected to change with tau>5 over possibly large regions.
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