tag:blogger.com,1999:blog-8524070301101240472.post599512952664692851..comments2023-09-28T08:13:11.489-07:00Comments on Only In It For The Gold: Climate Models - Is There a Better Way?Michael Tobishttp://www.blogger.com/profile/08229460438349093944noreply@blogger.comBlogger7125tag:blogger.com,1999:blog-8524070301101240472.post-17631221973857746132008-08-31T09:58:00.000-07:002008-08-31T09:58:00.000-07:00You should REALLY correspond with John Mashey at s...You should REALLY correspond with John Mashey at some point, Michael.<BR/><BR/>That's more or less what he's about right now, or at least one of his hats.Marion Delgadohttps://www.blogger.com/profile/09493068399042656060noreply@blogger.comtag:blogger.com,1999:blog-8524070301101240472.post-81824929629092948372008-08-22T15:39:00.000-07:002008-08-22T15:39:00.000-07:00Michael Tobis --- Thanks, now I understand.I'll su...Michael Tobis --- Thanks, now I understand.<BR/><BR/>I'll surmise that you will do at least as well with a mesh of spherical triangles. Indeed, you ought to be able to do better, esaily, because the spherical trianlges can easily be subdivided in regions of hish spacial/temporal derivatives.David B. Bensonhttps://www.blogger.com/profile/02917182411282836875noreply@blogger.comtag:blogger.com,1999:blog-8524070301101240472.post-58891544874038233992008-08-21T19:15:00.000-07:002008-08-21T19:15:00.000-07:00David, there was a time in my life that I discover...David, there was a time in my life that I discovered <A HREF="http://www.gfdl.noaa.gov/~aja/" REL="nofollow">Alistair Adcroft</A> with great relief. His existence means that I don't have to try to be Alistair Adcroft. It's a good thing. That's too hard for me. <BR/><BR/>He's the computational fluid dynamics guy behind the MIT GCM (I think); the cubed sphere grid underlies their implementation of atmosphere, ocean, and any other geophysical fluid (presumably another planet) that they choose to aim their code at.<BR/><BR/>There is an old joke that you can write Fortran in any language. Adcroft has rather tried to write C++ in Fortran. It's impenetrable but it works.<BR/><BR/>Anyway, the idea of the grid is to imagine a rectangular mesh forming the faces of a cube, and a light bulb at the exact center projecting those faces onto a sphere.<BR/><BR/>The <A HREF="http://mitgcm.org/cubedsphere/cubicgrids.html" REL="nofollow">resulting mesh</A> has very nice properties at all three levels: it's cognitively easy, less mathematically intractable than a lat/lon grid, and works well with multiple cores, distributed memory, cache and the like.Michael Tobishttps://www.blogger.com/profile/08229460438349093944noreply@blogger.comtag:blogger.com,1999:blog-8524070301101240472.post-56942043733434255212008-08-21T15:46:00.000-07:002008-08-21T15:46:00.000-07:00What is an MIT "cubed sphere" and why do you want ...What is an MIT "cubed sphere" and why do you want it?David B. Bensonhttps://www.blogger.com/profile/02917182411282836875noreply@blogger.comtag:blogger.com,1999:blog-8524070301101240472.post-3163385328467436372008-08-21T14:43:00.000-07:002008-08-21T14:43:00.000-07:00I'm thinking out loud her: maybe the simplest clim...I'm thinking out loud her: maybe the simplest climate model is not coupled, and not 3D - maybe it's along the lines of a lattice gas model.<BR/><BR/>Can you define simplicity a bit further. I've got: a) Simplicity of software design, encompassing literate source code, modularity and 'good practice'; b) Simplicity of the numerical solver (simplest thing might just be to farm this out to pre-exisiting componenents, but last time I looked there weren't any easily findable mature finite difference or spectral n-dimensional PDE solvers.); c) Simplicity of the model physics ; and d) The simplicity of a coarsely resolved model.<BR/><BR/>The resolution of the model interest me, because phenomenological models tend only to be valid across limited length and time scales. I'm fast leaving territory I know something about for territory that I think I might have an idea about, but isn't it the case that the sub-grid parameterisations of atmospheric models are one such example of a length scale (and time scale) contingent phenomenological model.<BR/><BR/>So this leads to two approaches to simplicity: on the one hand a ruthless coarse-graining that reduces the number and complexity of sub-grid physics, and on the other hand, increasing resolution to reduce the need for sub grid parameterisations in the first place so that all you need is continuum mechanics.achttps://www.blogger.com/profile/08817718132877704613noreply@blogger.comtag:blogger.com,1999:blog-8524070301101240472.post-5523256455009058152008-08-21T01:01:00.000-07:002008-08-21T01:01:00.000-07:00I've recently been dabbling in photorealistic comp...I've recently been dabbling in photorealistic computer graphics, and there exists something of this sort in that field.<BR/><BR/>The pbrt renderer (http://www.pbrt.org/) is written in the literate programming style and is accompanied by a rather nice book. It's principally designed as a teaching tool for undergraduate / graduate students, but it has been used by other researchers as a basis for further research. It's written to be easily extendable by the use of plugins.<BR/><BR/>Universities / organisations involved in photorealistic rendering research seem to each hold their own base rendering system which individuals or groups modify according to their own research needs. It seems to me that this has strong parallels with the way GCM works.SomeBeanshttps://www.blogger.com/profile/11076372969807940310noreply@blogger.comtag:blogger.com,1999:blog-8524070301101240472.post-91949521160218796892008-08-20T22:23:00.000-07:002008-08-20T22:23:00.000-07:00You had to figure I couldn't ignore this.Perhaps y...You had to figure I couldn't ignore this.<BR/><BR/>Perhaps you're wanting to runn before you can walk? I'm confident that one good scientist/developer working for six months, starting with a simple fortran code as "advice", could build a pretty useful python numpy based model. It wouldn't be a GCM. But you could do useful things with it, and it would be a step along the road. I think that's what's missing: Mozart didn't spring fully formed into existence. I bet he started with a few bars ...<BR/><BR/>(But why start with a cubed sphere, why not start with something understandable :-)Bryan Lawrencehttps://www.blogger.com/profile/15262374835889009894noreply@blogger.com