Wednesday, August 17, 2016

How Reliable Is The World Ocean Database?

Fig. 1 Golomb Ruler
After working with the data for awhile, I like it.

I downloaded updates which I will be posting in a day or so (WOD Updates).

They are the May, 2016 updates.

They threw me a curve by mixing casts from different zones in 4 large files (CTDS, CTDO, PFLS, and PFLO) of 205.7 MB + 15.6 MB +703.5 MB +83.1 MB = 1.008 GB, covering 436 of 648 different WOD zones (note that many of the WOD zones cover only land, no ocean - see WOD Map).

I had to write a C++ module to go through those files, byte by byte, to identify, then separate the casts in those 4 files, and then place them in files with other casts from the same zone (e.g. all 1212 zone casts in one file named "1212").

Fig. 2
This is important, because if they are all mixed up one can't really get a handle on what is going on (Fig. 4).

That meant that I also had to rewrite the WOD zones database engine, because the only way in general you can tell what WOD zone a cast came from is the name of the file (e.g. CTD01212, and all casts in it, are from zone 1212).

Absent that, when they are all mixed up, the latitude and longitude furnish the only clues as to where the measurements came from.

Fig. 3
Finding those particular latitude and longitude values within "the PI stream" is at first daunting.

Now that I am accustomed to it, it does not take too long.

Nevertheless, I have been busy, as you can see by Fig. 2 and Fig. 3.

Fig. 4 (from 1.008 GB of data)
Those are screen captures of the directory the resulting files were stored in after the module extracted and collated the mixed casts (the 4 files at the end of Fig. 3 are the WOD update files; the other 436 files came out of those 4).

Those 436 files are now named according to the WOD zone the data came from (the ocean area where the water was tested - see WOD Map).

Anyway, that said, let's admit that WOD is a popular, quality place for the scientists who study the ocean and the influence the ocean has on weather and climate:
"Also, forecasters at NOAA’s Ocean Prediction Center, part of NOAA’s National Weather Service, use the information from the database for quality control of real-time oceanographic information it distributes."
(News Release). That is why I use it along with the PSMSL database.

Let's hope that the others using the updates noticed the mix (compare Fig. 4 to single-zone graphs here and here).


1 comment:

  1. Hmmm ... what if Fig. 4 is an apt rendition of what is going on in the vast expanse of the entire oceans?

    It is like single WOD zone graphs in the sense that they are averages of many measurements at different depths and different locations.

    Hmmmmmm ...