Comments for Notes from the Field

Comment on Not Your Backyard Rain Gauge by Jim Perkins

Jim Perkins — Thu, 13 Jun 2013 16:02:43 +0000

Thanks for a great blog, Kara.

I once heard a poem from some satellite meteorologists, touting how metsat sensing could or would one day replace all other weather equipment. It started out: “Put away your anemometer, pibal and sling psychrometer; Put away your tipping bucket rain gauge….”

Anyway, that fine day has certainly not arrived yet.

I see from your background you have a love of travel and education. As a retired scientist, I’m in my second career as a high school science teacher and I urge you to volunteer in your local schools, if you don’t already. I bet you’d be great at inspiring kids and helping with their understanding of the world around them.

Thanks again
Jim Perkins

Comment on Multi-wavelength View of Mammatus by Jim in IA

Jim in IA — Wed, 05 Jun 2013 13:13:42 +0000

Interesting. I hope the studies are going well.

Comment on A Line of Snow in a Cold Spring Shower by Walt Petersen

Walt Petersen — Fri, 31 May 2013 13:14:40 +0000

Richard,
The correlation coefficient that the radar measures is essentially a correlation between the horizontally polarized and vertically polarized returns. For a collection of uniformly-shaped rain drops, you can imagine that the correlation between the two returns will almost always be very close to one (in fact, it is typically 0.98 or better). However, if you now through a mixture of particle types, sizes and shapes into the pulse volume, the correlation between the two returns decreases because the scattering at the two polarizations gets more complex when interacting with different particle shapes and phases (e.g., liquid water….frozen/snow etc.). So, what we see is a marked decrease in the correlation coefficient where the mixture occurs. The decrease is especially pronounced when there are both liquid and frozen particles (e.g., melting snow, or snow mixed with rain, wet hail etc.).

Hope that helps,
Walt

Comment on A Line of Snow in a Cold Spring Shower by Richard Ma

Richard Ma — Wed, 29 May 2013 14:36:16 +0000

Nice post series.

The most interested part I learnt from these post is the determination of mixture of raindrop-showflakes with correlation coefficient among the particles. But how it works? multiple-particales comparisons?

Comment on Tiny Things Matter by Richard Swann

Richard Swann — Wed, 29 May 2013 05:28:43 +0000

Along with the rainfall measurements, does anyone monitor the amount of dust and it’s origins? I suppose springtime plowing might be throwing a lot of dust in the air, later in the growing season is there less dust?

Comment on A Line of Snow in a Cold Spring Shower by Walt Petersen

Walt Petersen — Wed, 08 May 2013 17:30:56 +0000

Hi Folks- thanks for the nice comments and the questions. Let’s see If I can address Michael’s question.
1. Detecting precip: Each pulse of microwave radiation we send out is scattered by the volume of rain, snow or ice we are looking at. The “volume” of each pulse is determined by the beam width of the radar (about 1 Degree) adn the lenght of the pulse we transmit (about 120 meters). At a range of roughly 60 km, the pulse volume is out 1000 m wide by 120 m deep. So, there are huge numbers of precpitation particles in that single volume. In order to make sure we have a really good representation of the scattering from all those precipitation particles in the volume, we then collect about 60 different pulses from that one volume, and then repeat that for every pulse volume along an individual ray out to about 150 km from the radar. The radiation scattered back to the radar by the precipitation in that volume does indeed “reflect” differently depending on wavelength- and we use that information to say something more specific about both the size and type of precipitation. The processing of the data does sometimes invovle Fourier Transforms, but we also use a technique based on Autocorrelation (Pulse Pair Processing). You can google those for more info (too much to include in here).

The “artifacts” to the north and west that I *think* you are referring to are missing regions where the low-level beams are blocked by a clump of trees located northwest of the radar. We just can’t see through them…………………..

Hope that addresses your questions.
Walt P.

Comment on A Line of Snow in a Cold Spring Shower by Michael

Michael — Sat, 04 May 2013 19:37:00 +0000

How are the different types of precipitate detected ? Do they reflect different wave-length differently ? Is this the result of a fourier-analysis ?
And what are the artefacts at North-West by West on the map ?
sincerely Michael

Comment on A Line of Snow in a Cold Spring Shower by Jim in IA

Jim in IA — Fri, 03 May 2013 18:06:27 +0000

I am enjoying this series of posts. I learned something about the dual polarization radar and correlation coef.

Thanks for the posts… Jim

Comment on Waiting for the Rain near Traer, Iowa by bobwaiting4rain

bobwaiting4rain — Fri, 03 May 2013 18:02:37 +0000

Waiting for h.a.a.r.p to move rain over 5 states that have huge fires
we are also asking praying for Divine help from the Creator ,help is
needed urgent massive fires many thousands with out homes,

Dominus Vobiscum et tu Spiritus Sanctus in Jejus Christ amen
and Pax et Orbi

Comment on A Line of Snow in a Cold Spring Shower by Dorian Janney

Dorian Janney — Fri, 03 May 2013 16:23:56 +0000

This is really interesting stuff- fun to “be with you” as you explain the ins and outs of data collection. Thanks for making time to write this up!