Tuesday, February 12, 2013

High Resolution SST regional movies

Recently I posted some screencap videos derived from the WebGL displayed sea surface anomaly temperatures. These excellent data are supplied by NOAA/NCDC, based on their OISST processing of AVHRR satellite data.

I have now been able to mechanize the process of production. I no longer use screen grabs, which was a major holdup. So I have now posted a page which has a much greater number of videos installed, covering various regions of interest. Some of these are up to date, and I plan to maintain them so. You should be at any stage able to replay the last 50 days of ENSO, or the last 100 days at 2-day resolution etc. Same for Arctic, Antarctic and N Atlantic.

I've tinkered a lot to try to get something working in each browser type. There are various difficulties; IE and Safari support for the HTML5 movie tag is patchy. Currently Firefox and Chrome should see OGG videos with controls, while Safari and IE see .swf videos looping without controls. In both cases you should be able to select. There is now a little string at the bottom of the selection area that you can use to link to your current view. I'll use that in this post.

The movie sequences, apart from the ones ending now, are generally full years at 4 day intervals. For ENSO, we currently have 2012,2011,2010,2008,2007,2006,2005,1999 and 1998. For Arctic, 2012,2011,2010,2007 and 2000.


The main point of interest is the strong jet which forms directly along the Equator. This is warm in El Nino, cold in La Nina. It shows marked character of an alternating vortex street. It's also interesting to see how far it goes, and how it dissipates. Here's the last 50 days

Update - as an experiment, I've tried longer, faster sequences. They didn't add to the download time nearly as much as I expected, and the results are very good. Here is 2012 at five days a second.


The first notable feature is a large region at zero anomaly. This is ice. It isn't true that all ice is at zero anomaly, but it's mostly true that zero anomaly is ice. You can see the ice melt and refreeze. The melt is streaky because melt ponds etc may report a positive temperature, but the refreeze is clear and dramatic. Here's the 2010 annual movie.

You can also see warm SST that may be influencing melting. One thing to watch for recently is the persistence of clear water north of Svalbard, well into the winter.


Again there is the annual melt and freeze, without the geometric intricacy of the Arctic melt. But there are also interesting currents to watch, especially through the Drake passage. Here is the latest period

N Atlantic

The patterns, Gulf Stream etc are familiar, but show up dramatically here. On a finer scale it is possible to see some effects of hurricanes. I'll show soon a video of the SST footprint of Hurricane Sandy.


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