Tuesday, May 17, 2011

Chladni patterns

At Climate Audit, Steve McIntyre has been frequently writing about Chladni patterns in connected with principal components of autocorrelated data. He developed it for the Steig paper, and was disappointed when J Climate wouldn't allow its inclusion in the response. And he's recently claimed an appearance in another paper.

Chladni patterns are modes of oscillation, originally of a vibrating plate. Now people more often think of a drum membrane, which is a slightly different wave equation, but the idea, and patterns, are similar.

I must admit that I hadn't heard of Chladni before Hans Erren drew attention to them in Steve's first post. Some interesting history there. But I am familiar with the modes in question.

Steve thinks that if a Chladni pattern emerges, that somehow means that the result is showing that rather than the information about the climate pattern being sought, so the information content is reduced. I don't agree - there are reasons why the patterns arise, and they are just as informative in PCA as they are in wave studies. I'll try to show why.

Warning - mathematics (and \(\LaTeX\)) after the jump.

Latex now works here

I have implemented Latex (the MathJax version). It seems to work in comments too. You can just write normal Latex between these symbols(remove the _s)
  • \_(...\_) for inline
  • \_[...\_] or $_$...$_$ for display equations - note the doubled $'s
The next post should give this a workout.

The Woody Guthrie Award - Bart Verheggen


Last November, I was very pleased and flattered when ScienceofDoom chose Moyhu as the recipient of the Woody Guthrie award.

This award has an interesting history - it was initiated as a commendation of a "thinking blogger". The award was passed to SoD from Skeptical Science. I think both have been highly respected for their dedication to dispassionate analysis, and Moyhu has sought to live up to that.

I think Bart impressed all sides of the climate debate with his hosting of the very popular discussion on comparing temperature indices, which evolved into a debate about time series, unit roots and random walks. Strong views were expressed by well-informed commenters led by VS. Bart kept the discussion on track and constructive, with 2186 comments made. I think it is the best technical climate discussion I have seen.

But his blog isn't just technical - there is thoughtful, well-informed and inclusive discussion of policy as well. Bart always takes a broad view.

And there are brilliant cartoons as well.

I commend Bart's blog to readers, and I am very pleased to pass on the Award to him.



Here it is:
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