Monday, February 18, 2013

Hurricanes and SST - movies


I have posted animations of daily high-resolution NOAA/NCDC satellite SST data in various regions, including the North Atlantic. There are patterns there that can be associated with known ocean fluid mechanics, but others that can't. So I extended the movies to include hurricane tracks in the N Atlantic in recent years. I was curious to see whether they would leave footprints of cooler water.

The answer seems to be - sometimes. For example, Gordon in 2012 left a marked trail. But our SST data is daily and hurricanes can move a long way in a day. I've shown just the midday (UTC) positions.

In the process, I've experimented with yet another visual mechanism. This time I've gone back to a sort of animated slide show of jpg's. This gives best quality and control, but no video compression. For the N Atlantic, this seems to work because the number of data points is not so large. The controls are explained below the graphic.

Update - I've added a highlight collection of the best streakers. Click on the bottom selection (below 2005), labelled "Tops".








Choose Year




Pause Loop




Stepmillisec

Details

Hurricanes and storms are marked by their midday (UTC) position. Track data comes from the NCDC 5.5Mb HURDAT2 data file. SST data is as described here.

Each storm is marked by a black circle with central color. The colors are grey for "Low", cyan for "Tropical Depression", pink for "Tropical Storm" and red for "Tropical Hurricane" or "Extratropical Cyclone".

You can select a year from the top dropdown. When you do, the requisite jpg files will be preloaded, which will take a second or two. It's likely the sequence will start at once; otherwise clicking on Pause should get it going. Loop toggles loop mode. The move buttons below move one step forward or back. This works best when paused.

There is a text box where you can enter the time you'd like each frame to show, in millisecs. It works immediately - indeed even as you type. But it won't let the time go below 100 millisec.

You can click on the timeline below the plot to go to a specific date.


2 comments:

  1. I like the hurricane animation. You'd only expect to see a "footprint" if there is enough pressure to cause an upwelling of deep water.

    A couple of comments with climate, there are places where even a 24-hour sampling period is too coarse (just underlines how much of the picture we're missing by sticking with monthly data).

    Secondly, there's a related, I thought very interesting papaer

    Estimating Local Memory of Tropical Cyclones through MPI Anomaly Evolution plus there's a shorter write-up here.

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    Replies
    1. Thanks, Carrick,
      I haven't got to the long paper yet, but the BAMS writeup is interesting.

      I had thought of the footprint in terms of the energy transfer that drives the hurricane, and also surface churning. But the BAMS people are focussing on upwelling too.

      Yes, we're always short of resolution. I suppose that with the satellite data you can't assemble a whole globe picture in much less than a day.

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