Bathymetry maps...

[oldo_nicho]

Cheers for the response everyone...

SAsurfa, that does sound like an interesting project. Is there already software out there that models this kind of thing or are you having to start from ground up? What are you using to model it? Matlab, or something more specific?

Also, thanks all for heads up on Boat Books. I'm planning a bit of a trip soon and there are heaps of books all about sailing there... Nice to know about.

[SAsurfa]

The model is based on the "COupled Hydrodynamical Ecological model for REgioNal Shelf seas" (COHERENS), but has been modified to suit the needs of the project by my supervisor so luckily I didn't have to build it from scratch, I think that would take a few good years to do anyway. I still have to do a little coding to calibrate it a little more accurately but at the moment it's all up and running fine. And yeah i'm just using matlab to analyse and process the data.

[oldo_nicho]

I just had a look at the COHERENS model site... Interesting stuff! It must be a pretty complex model to be able to take into account the biology, sediment, and contaminant transport within the system boundaries. What sort of grid size are you running, does the grid have a constant mesh size, and what kind of timeframe does it take to converge on a solution?

Also, where did you get your bathymetry data from?

[SAsurfa]

Ah, the model I am running is only dealing with the salinity, temperature, current/circulation and adding in a source concentration which can be traced. So not the biological or sediment sides of things.

The resolution of the gridboxes is about 2-3km if I remember correctly with 105 gridcells in the x direction and 130 in the y direction and 10 vertical ocean layers. We can go finer in resolution though.

The grid has a constant mesh size and the model takes around 85 hours on a supercomputer to get results 5 years into the future, but it reaches a steady state after about 3-4 years.

Oh and I don't know where the bathymetry is from but i'll ask my supervisor.

And what do you do old-nicho, do you do modelling of any sorts?

[oldo_nicho]

Wow, 85 hours...

How do you model current/circulation? I mean, is it a general sort of formula that is linked to the bathymetry of the ocean floor and shape of the coastline, or is it a model created by quantitative observations of the water movement in that area?

Me, well I finished a degree in mechanical engineering last year. Am looking to get into work within ecologically sustainable development. I haven't done a huge amount of modeling, though took an interesting course in computational fluid dynamics. It was pretty fascinating, and some of the programs that are being used are extremely sophisticated; as I am sure you know!

[SAsurfa]

It is based on formula, don't know if you've heard about the Navier Stoke's equations but there's 5 of them and you can basically describe any type of fluid motion with them, whether it be interactions with topography or density fronts, eddies etc. But meteorological forcing data is applied so that there is solar input factored in and evaporation/precipitation/run off etc.

So it's all fairly complex. I've done some initial runs just to get the feel of it and now I just have to play around with it a little to calibrate it so it simulates the tides a little more closely and make sure the temperatures and salinities fall with in reasonable values throughout the year.

And yeah I am doing a subject looking at the Educational Global Climate Model, EdGCM and that is quite interesting at all, it's a fairly large resolution but good for doin rough climate change scenarios and the like

[oldo_nicho]

That's sweet that the Navier Stoke's equations still yield accurate solutions with massive meshes.

Yeah, tidal simulation would be kind of interesting over there. I was over in that part of the world a couple of months ago and found that the tides were completely bizzare! Some days there would be just one phase, others two, three or four. And sometimes there was only 0.1m difference between high and low...

[SAsurfa]

Haha, yeah the tides go crazy over here and we are one of only a couple of places that experience a dodge tide which shows no tidal movement at all

[Butts]

Enough of the "technical intricacies", cause i don't understand a WORD youse are saying

WELL over my head

[daryl]

wholly smoke

[phil osofer]

What fascinates me is the bathymetry out off Cape Byron.
On tuesday the 4th of March there was a 14 second period SE swell refracting about 110 degrees into the Pass, nice long clean fat lines, and fortunately the banks are improving after being ordinary for about a year.

Out off the Cape there must be a huge sand ridge that has built up from the south to north sand flow.

How far does it extend out?
And how far out do the 14 second swells start to feel the sandy sea floor and start to change direction?

One way to alter the bathymetry out off our coastline is with Reefballs, (google reefballs) it is kind of like underwater permaculture.
Reefballs are already being sunk off our coastline to create fish habitats, the funding comes from fishing licences.
The reefball people are doing some very interesting stuff, I particularly like the reefball design that is suitable for lobsters to inhabit, kind of like under water terraced appartment living.

If surfers ever build surfing reefs, reefballs should be the top layer so as to create a new marine ecosystem.

Surfing reef design +reefballs = quality peeling waves + new marine ecosytems = a whole new frontier of creativity, science and study.

The collective surfing mind consciously designing the future.

[wanto]

i think they'd have to make these balls a little bigger for them to not move when a swell hits. maybe 10-20 times bigger. and filled with lead.

[puurri]

So pay for a feckin surf licence!!!

[LONGINUS]

One benefit of spending 13 years on submarines is that you collect a whoooole lot of bathy information. don't get too concerned that NSW has a whole lot of secret squirrel info, it's all just as well laid out in publically available hydro product. West Oz? Whole different story.

[puurri]

One benefit of spending 13 years on submarines is that you collect a whoooole lot of bathy information. don't get too concerned that NSW has a whole lot of secret squirrel info, it's all just as well laid out in publically available hydro product. West Oz? Whole different story.

Sub-mariner eh? Weell the yanks did a heap that way WW2 (largest sub fleet in Indian Ocean and now??? (don't ask, don't get a reply that offends)

Good old google earth gets you a bit but there's coastal areas that are fuzzed out and a whole heap of sensors out there on the sea bed.

[LONGINUS]

Oh yeah mate, US DOD had vetting rights on all imagery that google went public with. It amkes me laugh when I read blogs of mid western Americans complaining that their towns arent in very high resolution - thats because theres an ICBM silo in that old hayshed dummy.

Check out the approaches to all major beaches on Oahu, Hawaii - all obscured even with artificial cloud cover added in. No more Pearl Harbour 2.0 thank you very much.

It's a conspiracy I tell you!

[mozzquito]

Hey fellas,

My last quote turned to code when I tried to insert text to muzzquito's contribution and the best I could do was to embold.

I do note that he appears an earnest advocate For RAN.

Therefore is muzzquito a mole from RAN Hydro?

back from the land of no pc... its a beautiful place

not at all puurri - a bit tongue in cheek it was - I worked for a contracter to AHS for many years building IT systems etc and I reckon the AHS have a bloody cheek selling product for profit when it was our tax that paid for the info to be collected and utilised in the first place. IMO they are a slow moving, bureaucratic IT project disaster zone but they do have a lot of raw bathymetry data which they will make available to non-profit projects such as SASurfer sounds like he is into.

[LONGINUS]

From my experience, RAN hydo are some of the laziest pricks that god has ever shoveled shit into. It's often quicker to request charts of our waters from Canada than it is Wollongong. I used to cringe whenever visiting navies had to request charts from that fukcing sheltered workshop down there, guaranteed to embaris every time. The thing to keep in mind is that navy related stations are so badly undermanned that they struggle to deliver for their main client which is the international merchantman with a draught of 10-15 metres.

Anything less than that which is basically every surfing quality reef on the Australian station is background noise. All the info is just sitting there waiting for someone to pay for it to be printed.