Tau Chart, Comparing both rovers Options

[djellison]

I visited this data early on, but there's 600+ sols worth now, so I've revisited it

I thought it would be interesting to comapre Tau values form both rovers at the same time - so to that end I added 21 to the sol number of each Opportunity tau observation to bring it in to line, within a sol, of Spirit observations.

What does it show? (remember to subtract 21 to get ACTUAL Opportunity Sol numbers)

Well - both rovers experience a large increase from around Sol 350-370, but for Opportunity it peaked briefly significantly higher. Spirit experienced two local events, 380 and 420, Opportunity a long, small peak around 450 and another, shorter one at 480, and the share the big spike at 510ish.

Interesting stuff anyway - when you match them up, time wise ( i.e. +21 on MERB sol numbers ) they match quite closely.

Doug

Attached File(s)

 MER_tau.pdf ( 369.71K ) Number of downloads: 549

 

[Marz]

I visited this data early on, but there's 600+ sols worth now, so I've revisited it

I thought it would be interesting to comapre Tau values form both rovers at the same time - so to that end I added 21 to the sol number of each Opportunity tau observation to bring it in to line, within a sol, of Spirit observations.

What does it show? (remember to subtract 21 to get ACTUAL Opportunity Sol numbers)

Well - both rovers experience a large increase from around Sol 350-370, but for Opportunity it peaked briefly significantly higher. Spirit experienced two local events, 380 and 420, Opportunity a long, small peak around 450 and another, shorter one at 480, and the share the big spike at 510ish.

Interesting stuff anyway - when you match them up, time wise ( i.e. +21 on MERB sol numbers ) they match quite closely.

Doug

Nice chart: weird how Tau always increases as a huge spike that then levels off. I guess dust only is replenished back up into the high levels of the atmosphere during storm-like events, so a sudden burst of dust hits a site all at once and then tapers off slowly as the dust settles out?

Do we have about another 100 Sols before the next storm season begins?

[remcook]

sorry for my ignorance- tau=optical depth?

[djellison]

I'm not sure of the actual units, but a high number is murkier, dustier air.

Doug

[RNeuhaus]

The Tau chart would be much nice if the x-axis is labeled as Summer, Winter, Fall or Spring Southern Hemisphere so that I can correlate better the periodicity of Tau among the sessons: Winter: Low Tau (clear time with index lower than 1.0) and Summer: High Tau (if the index is above than 3.0, the sky is murky due to the increased winds and DD).

Rodolfo

[helvick]

sorry for my ignorance- tau=optical depth?

Yep Tau is optical depth. Direct insolation is e(-tau)*top of atmosphere insolation. Indirect insolation is a whole other ball of wax. Generally correlates to some degree with atmospheric dust levels on mars. AFAIK it's dimensionless, like a coefficient of friction or drag.

[mwolff]

The Tau chart would be much nice if the x-axis is labeled as Summer, Winter, Fall or Spring Southern Hemisphere so that I can correlate better the periodicity of Tau among the sessons: Winter: Low Tau (clear time with index lower than 1.0) and Summer: High Tau (if the index is above than 3.0, the sky is murky due to the increased winds and DD).

"low tau" would be more like < 0.2-0.3. the "high tau" values mentioned would most likely be associated with a large dust storm. however, tau > 1 is typically considered "high"...for dust. water ice clouds would be another story.

[mwolff]

Yep Tau is optical depth. Direct insolation is e(-tau)*top of atmosphere insolation. Indirect insolation is a whole other ball of wax. Generally correlates to some degree with atmospheric dust levels on mars. AFAIK it's dimensionless, like a coefficient of friction or drag.

tau is dimensionless.