Ok heres a q for ya

[mckpickle]

Ok I have a good interview question, and please excuse the spelling.

If you are using a Mono-chromatic radar how do you tell if weather is causing attenuation?

Any ideas or good books where I might find some info?

 

[avbug]

All weather causes attenuation; assume it's happening, because it is. The degree of attenuation, in addition to reflectivity, determines instensity.

With monochromatic radar, you don't have color coding for intensity, but you should always assume attenuation when painting weather with weaker returns behind, or a shadow. Always pretend that what you can't see can hurt you; and assume that shadows behind defined returns are from attenuation unless you can prove otherwise.

 

[sabreliner]

To gauge attenuation, I usually tilt the radar down a bit to paint the ground behind the weather. On the really bad stuff, you won't be able to paint behind the weather. I also try adjusting the gain down a notch to see how much goes away.

 

[mckpickle]

Im sorry i should have been more specific. What I meant was how do you tell if there is a shadow. In the ATR if the radar is atenuating, then there is a shadow, and if the feature (RTC) is used it shows up blue. So with only one color to look for a shadow, how do you tell that there is more stuff behind current cells? Is it just an absence of anything behind cells with a steep gradiant?

 

[enigma]

mckpickle, I too have been frustrated with undefined terms. You wrote, "What I meant was how do you tell if there is a shadow. " Wouldn't be nice if the experts like Archie Trammel would stop assuming that we all knew the definition of terms like shadow, 50Dbz, contouring, etc.

To answer your question, Yes.

I've never used monochrome radar, but a shadow is nothing more than a blank area on the screen behind a heavy return, and I assume that it looks that way on the monochrome display, blank.

I use the same technique as sabreliner to determine attenuation/shadow. If I can't paint ground behind the first heavy return, I know that I don't know what is there and avoid the area. As usual, Avbugs' advice is right on.

regards,
8N

 

[crosscut]

Im sorry i should have been more specific. What I meant was how do you tell if there is a shadow. In the ATR if the radar is atenuating, then there is a shadow, and if the feature (RTC) is used it shows up blue. So with only one color to look for a shadow, how do you tell that there is more stuff behind current cells? Is it just an absence of anything behind cells with a steep gradiant?

The monochrome radars have contour modes. If the radar can’t paint through a cloud (cell), it’ll give you a black or “empty” part of the cell interior that it can’t “see” through outlined by the shape of the return. If this is the case, you may also tilt the radar down till you paint ground on the other side of the convection. Unpainted areas immediately behind the contour are the “shadows”. What the radar can’t differentiate is moderate (or greater) precip from convective activity – it’ll contour both. That’s when the combination of the size of the contour, “normal” radar mode, wx & vicinity ride reports becomes important. If the radar works as it should, it is so accurate so as to be able to paint other airplanes in the 30 mile range.

 

[mckpickle]

Great replies! Thank you!