Saturday, July 14, 2007

500mb in 3D

The GRIB files can also contain data related to the 500mb charts. A 500mb fax would typically look like this:

It is really supposed to represent the topography of the atmosphere...
Other rendering(s) of the same data might be helpful, like this one:

Plus it is really animated, you can orient it the way you want, just with the mouse.
The four lows are really easy to spot, notice that the one in the Gulf of Alaska is not that impressive, and look - it is not on the fax, it's beyond its edge - how much fun they're going to have in the south Japan...
Sea temperature and PRMSL (Pressure at Mean Sea Level) can also be represented the same way. I want to check if wave heights can be represented the same way...

Tuesday, July 10, 2007

Smoothing the GRIB

The smoothing algorhythm mentioned in an earlier post can be adapted to the GRIB Data.
It allows you to turn this:

into that:

This smoothing is spatial, in other words, it fills the gap between the points.
This can reduce substantially the size of the GRIB data to download, as it gives the possibility to rebuild the data between the actual points. This will need some validation, but that sounds promising. SailMail users might be concerned; on the example above, the size of the GRIB file is ~15 times smaller.
The next step will be to add a time dimension, smoothing the wind across several frames.
Keep posted!