Dopler--Level 2 vs. L 3: what's the difference?

[Bob Hartig]

What is meant by the different radar levels? What are the pros/cons of one over the other?

 

[Jeff Snyder]

The difference is the level of processing done with the data.

Level I data is raw radar data (you don't want to see that stuff).

Level II is the radar data after a small amount of initial processing. Level II data only consists of Base Reflectivity (0.5 dBz increments), Radial Velocity (1kt increments), and Spectrum Width. The radial resolution of the velocity product is 250m. In terms of vertical resolution, there are typical 9-14 vertical tilts availab.e

Level III data is formerly known as NIDS data... More processing has been done with this data. This means that more products are available, but at a lower resolution (than Level II). Products include Base Reflectivity (5 dBz increments), Radial Velocity (5kt increments), Storm-Relative Radial Velocity (5kt increments), Echo Tops, Vertically Integrated Liquid (VIL), 1hr/3hr/Storm total precipitation estimates, and the Vertical Azimuth Display (VAD) wind profile. The radial resolution of the velocity products is 1km. In terms of vertical resolution, only 4 tilts are available.

So, not only are the increments smaller (higher resolution) for Level II data versus Level III (NIDS) data, but the spatial resolution (horizontal and vertical) is greater as well. For example, for the velocity products, there is less averaging for the Level II data than for the Level III data. For a very quick example of the two, head on over to http://nexrad.allisonhouse.com/faq/2v3/ for a look at the 5-9-03 OKC Supercell with Level II and Level III radar imagery.

There is a good PowerPoint presentation regarding the benefits of Level II radar imagery versus Level III, but I can't find it at the moment. I thought it was on the NSSL or OU domain...

 

[Bob Hartig]

Thanks, Jeff! That's interesting--I get the impression that it may be more beneficial to use L2 than L3 when it comes to details. I'd imagine it's a matter of different needs at different times, yes?

In practical application, how do you choose which level to use when you're chasing?

Also, am I right in assuming that the online Dopler sites use level 3 (i.e. the NOAA site offers a composite reading that I'd imagine is an elaborate synthesis of data such as you've described for L3)?

Where are good online sources of both L2 and L3 radar?

 

[John Diel]

Level II is only available from NOAA. They inturn make it available to Universities and Commercial companies as they can afford it. The full Level II data feed is very expensive (I think I read something on order of $2000 per month). There is at least one provider of Level II information that is reasonable (very reasonable) on a "per radar site" basis ($30 per month, per radar site). See www.allisonhouse.com for details there.

Level III information is publicly available just about anywhere. The radar info you see on NWS Sites and many other sites is this very information. I'm sure if you did a search via NOAA you could get the ftp site than carries all the info and instructions on how to access it. College of Dupage, and NCAR generally use the Level III displays on their sites. It generally updates every five or six minutes and by refreshing your web browser you can pick up on those updates. Of course this is dependant on the Web, so all bets are off when there's a severe weather around.

There are various other suppliers of radar information. I think Baron Services uses it's network of radars to come up with a different view. These are the radars that many Television stations have and use to give their updates. I'm sure there are others out there.

Most publicly available software uses the NWS Level III information though. Baron being the notable difference here. WxWorx and Srorm Hawk, I believe use the Baron Radar displays though I'm not sure on that.

 

[Rockwell Schrock]

Originally posted by John Diel
I'm sure if you did a search via NOAA you could get the ftp site than carries all the info and instructions on how to access it.

This URL provides information for accessing the encoded data:
http://www.nws.noaa.gov/tg/radfiles.html

You can find the GIF images for some products here:
ftp://tgftp.nws.noaa.gov/SL.us008001/DF.gif/DC.radar/

The naming conventions for the folders in the second link can be found following the first link.

 

[Bob Hartig]

Thanks to all of you for your very helpful information!

John, a couple questions for you:

There is at least one provider of Level II information that is reasonable (very reasonable) on a "per radar site" basis ($30 per month, per radar site). See www.allisonhouse.com for details there.

I've checked out the allisonhouse link and am puzzled. Maybe I'm just having a middle-aged moment here, but the pricing info doesn't seem very clear. It sounds like I can have a month's free trial once I've downloaded L2. But it mentions a price of $79.95 and says nothing about $30. I'm wondering whether that $79.95 price is the cost of the download--I pay that and then can use L2 free for a month, after which I pay $30 a month. But I'm just guessing here. I'd really appreciate it if you could fill in a few details for me.

Can you tell me:
* How much it cost you for the download.
* How the $79.95 figures in if $30 is the monthly rate (if you know).

Thanks!

 

[Tyler Allison]

I've checked out the allisonhouse link and am puzzled. Maybe I'm just having a middle-aged moment here, but the pricing info doesn't seem very clear. It sounds like I can have a month's free trial once I've downloaded L2. But it mentions a price of $79.95 and says nothing about $30. I'm wondering whether that $79.95 price is the cost of the download--I pay that and then can use L2 free for a month, after which I pay $30 a month. But I'm just guessing here. I'd really appreciate it if you could fill in a few details for me.

Can you tell me:
* How much it cost you for the download.
* How the $79.95 figures in (if you know).

Thanks!

Gibson Ridge software is the company that sells GRLevel2. That costs you $79.95 to purchase the software. You can use it to review Level2 data provided by the NCDC archive (not live). GRLevel2 is similar to other software you might purchase like Norton Anti-Virus, a game, etc. It's like going to wallmart and buying a piece of software. No monthly fees, etc.

If you want live Level2 data you go to allisonhouse, or other provider, and purchase a data subscription.

Though GRLevel2 works with the allisonhouse data feed they are totally different and run by different people. You can in fact use GRLevel2 with the IDD/LDM feed made available by Unidata to Universities, if you have access to it. Thus you wouldn't want to purchase allisonhouse data..it's the same data.

As this is not a Gibson Ridge or allisonhouse forum you may wish to drop me a private email and I can explain more if you need. I don't want to clutter up Stormtrack and get myself in the bad graces.

 

[Bob Hartig]

Thanks so much for clarifying, Tyler. I understand now; from here, I need to talk with my chase buddies, and will shoot you a note if I need to.

BTW, speaking of senior moments, I see you copied my original bullet about "is the $30 a monthly fee?" before I could edit it out. John stated clearly that it is--it just didn't register with me before I wrote!