Sunday, May 8, 2011

Coastal Radar Site and The Radars You Don't Hear About

Several of you have asked questions about the new coastal radar at Langley Hill. To address these inquiries I have created a web site dedicated to this new system (click on link to open):

http://www.atmos.washington.edu/~cliff/Langleyradar.html


If there is anything I am missing, let me know. The site will be regularly updated.

There some other local radars you might not know about. For example, at Seattle and at Westport there are two radar wind profilers. I have shown you the output of this machine quite a few times. Here is a sample:

The plot shows the winds and temperatures from the surface to 2-km in time for ONE location: Seattle Sand Point. Very different from radars, which give you lots of 3-D spatial information. But radars don't give you high resolution temperatures and winds above one point--something that can be very useful at times (like deciding how the freezing level is changing).

Here is what the device looks like (this is not the Seattle or Westport unit but ours look very similar):

The central unit is a Doppler radar with three beams: up and two perpenicular directions. Instead of tracking precipitation, they follow variations of atmospheric density. Doppler radars tell you whether the target is approaching or moving away, and it turns out that using the Doppler information from the three beams and a little trigonometry (that's right kids, trig has its uses!) one can figure out the winds with height. Pretty neat.

But there is more! You see those castle-like towers around the radar? Those are BIG speakers that emit powerful multi-frequency tones (you should hear my version of it!). This sound propagates into the atmosphere and disturbs the density variations aloft. The radar unit can then track the density variations and thus the sound waves. Since the speed of sound depends on temperature, this unit can determine the speed of the sound waves and thus temperature variations with height. The fancy name for this hardware is RASS--Radio Acoustic Sounding System.

In another blog I will talk about the Canadian and TV radars.....

Two nice days ahead, by the way. But don't worry, it won't last....

11 comments:

Tiffany said...

Cliff - I wish you did the weather on any nighttime local station....I get more out of your few paragraphs than I have in years of watching the other guys. Thanks for the heads up on the great days ahead - now I can leave my umbrella at home and take my coffee instead.

Mike DeMarco said...

About now I could stand to worry about the good weather lasting. Even the Rhododendrons are getting schizophrenic. Thanks for the additional radar info. That was completely new to me.

Justin W said...

Wow, I hadn't heard about that radar system. That sounds really interesting. I can see many uses for such a system.

Avalanche said...

I'll be honest, love the new radar. However they work amazes me, super excited.

But there will be a day soon like clouds, precip. will be measured from outspace, not on the ground.

Just AboveNOAA said...

"Those are BIG speakers that emit powerful multi-frequency tones (you should hear my version of it!)."

your ardent fans demand that a suitable audio file (mp3 for choice) be posted on this site of "your version of it" ...yep.

oh, and approximately what are these multi-frequencies? (...could explain much that i've previously ascribed to the call of inebriated teen-age banshees) thankee!

Scott said...

When are those nice days supposed to get here? Cuz it ain't nice out there today.

Ansel said...

Cliff, please tell me we are not going to get another summer like 1993 or 1999. Those were the worst ones that I can remember. I know La Nina is fading. But there is always a lag.

BTW, what set of ocean conditions results in ABOVE average spring temperatures?

Ansel

Scott said...

@Ansel, It's possible to have a summer worse than 2010? Groan.

Patrick said...

I think they mixed up our radar order with an extra-large:

http://www.king5.com/news/local/Huge-radar-vessel-on-its-way-to-Seattle-121581254.html

Kevin Purcell said...

You can hear what the RASS sounds like in this WAV file.

http://www.atmos.anl.gov/ABLE/rass.wav

It's high frequency audio so you can make the speakers upward firing without annoying the neighbors too much. More like demented RTTY or FAX or perhaps a digital yodeling banshee.

isnoop said...

Is this installation only intended for weather information, or will the doppler also have some interest to the FAA?