Support for NEXRAD Level 3 product 176, Digital Instantaneous Precipitation Rate (DPR)

[jjhelmus]

Py-ART cannot read NEXRAD Level 3 Digital Instantaneous Precipitation Rate (DPR) files (product 176). They are stored as the Generic Radial Product Format which is not supported by the nexrad_level3.py module.

This product stores data in Generic Data Package packets (packet code 28) which is defined in Figure 3-15c on page 3-132 of "INTERFACE CONTROL DOCUMENT FOR THE RPG TO CLASS 1 USER" RPG Build 13.0, Document Number 2620001T. This packet serializes the data using the External Data Representation (XDR) format, see Appendix E of the above document and RFC 1832.

Reading this data should be possible with the xdrlib module in the standard library

[dopplershift]

There was some weirdness in the ICD too--MetPy has a working implementation: https://github.com/metpy/MetPy/blob/master/metpy/io/nexrad.py#L2082

[jjhelmus]

@dopplershift Funny I was just look at that code :smile:

[dopplershift]

Let me know if you find any issues with it--bugs, docs, whatnot.

[jjhelmus]

Adding support for the product is not a high priority but when I get to it I let me know if I find anything.

[dcedgren]

Just a note that I ran across this issue wanting to bring in DPR Level-III data into Py-ART. Looked into it briefly and I don't know what I'm doing well enough for me to try to use the Metpy code, and Metpy does not currently appear to have an output function.

So mostly just a quick note to say I'd appreciate support for this if you ever get around to it, or else any recommendations for a (not too technical) alternative.

[scollis]

@dopplershift : Did you ever provide this in MetPy?

One day we should discuss some bridges between MetPy and Py-ART

[dopplershift]

We have the decoding working, we just don't have much of a data model around them; very ad-hoc data structures with dicts of dicts of lists of dicts...

[scollis]

Is the data range-az-el data?

[dopplershift]

Looks like it, yeah. Here's what I played with in MetPy:

from metpy.io import Level3File
f = Level3File('testdata/nids/KOUN_SDUS84_DPRTLX_201305202016')
f.sym_block[0][0]
f.sym_block[0][0]['components']

Looking over that code, it looks like that ICD was pretty damn sketchy...

[craddockME]

Hi, have there been any updates on this issue since 2016? Looks like pyART still does not support DPR. I see some code in metpy nexrad.py but I'm not clear if it's a placeholder or working code. Hoping to be able to process the DPR data parameter. Thanks in advance for any info!

[dopplershift]

As far as I’m aware, the code in MetPy should work (though the interface is hideous). I’m not sure if anyone is using it yet, so there may be a lurking bug or two. Feel free to let us know on the MetPy issue tracker if you run into any problems and we can try to get them fixed up.

[scollis]

A pr that uses metpy as a conditional dependency for level 3 would be welcome

But it’s not something the core dev team is doing any time soon

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On Jul 11, 2018, at 2:24 PM, Ryan May notifications@github.com wrote:

As far as I’m aware, the code in MetPy should work (though the interface is hideous). I’m not sure if anyone is using it yet, so there may be a lurking bug or two. Feel free to let us know on the MetPy issue tracker if you run into any problems and we can try to get them fixed up.

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[dcedgren]

I'm taking a look again at being able to use the DPA product. Metpy's implementation appears to be working (it ran without errors for me at least). But as @dopplershift noted the structure is ugly. I have a little time to dig into this next week (#coronavirus) so I'm going to try to rig something together and I'll give it a shot to add basic functionality for this product, likely by using metpy to do the heavy lifting and then just re-wrangle it to be a pyart radar object.

I'm still pretty new to programming and to pyart, so I'm open to comments if anyone feels this functionality should work in a certain way or another.@zssherman

[zssherman]

Hi @dcedgren, yeah using metpy and adding it as a dependency I think is fine. Really the only comment I would have, but you already mentioned, was conforming or feeding it into pyart radar object, but I can help with that. Whenever you have a basic product, feel free to submit a pull request and I can also answer questions and help get it going.