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Chinook

radar clutter

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I have many times looked at radar images in the plains and midwest areas, and seen radar clutter indicating variations in the boundary layer, such as this:

 

post-1182-0-61984100-1407448529_thumb.jp

 

This is an image from KFDR today, which indicates a few showers and storms, and also some clutter. Since the weather is clear outside of those storms, what is reflecting the radar beam?  Bugs? The earth? Birds?

 

Obviously the radar clutter changes at nighttime to being a more uniform anomalous propagation clutter, indicating that the radar is bouncing off the earth (I think.)

 

 

 

 

 

 

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I have many times looked at radar images in the plains and midwest areas, and seen radar clutter indicating variations in the boundary layer, such as this:

 

attachicon.gif2014_08_07_2148_FDR1.jpg

 

This is an image from KFDR today, which indicates a few showers and storms, and also some clutter. Since the weather is clear outside of those storms, what is reflecting the radar beam?  Bugs? The earth? Birds?

 

Obviously the radar clutter changes at nighttime to being a more uniform anomalous propagation clutter, indicating that the radar is bouncing off the earth (I think.)

I'm confused -- are you asking what the clutter is composed of, or what the striations in the clutter are? If it is the former, it is almost certainly insects and possibly birds. It is a warm summer night, so there are plenty of insects out there. You know it is non-meteorological from the low ρhv values... and you can tell it is biological from the extremely higher ZDR values and the non-zero base velocities, whereas targets on the Earth will have velocities near zero. Additionally, the ZDR field has taken on the characteristic hourglass shape, which forms as the radar beam intersects either the side of the insect/bird (with a relatively comparable horizontal and vertical cross-sectional area) or directly head/tail-on (where the winds would result in a very large horizontal cross-sectional area compared to the vertical), resulting in larger ZDR values. You can see this ZDR pattern aligns very well with the base velocity field, as the birds fly and especially as insects will tend to move with the mean flow of the wind. Note that the "hourglass" signature can be reversed with respect to the angle at which the target is being viewed due to Mie scattering in the case of birds and some large insects... but you should still see the hourglass form in the ZDR field.

 

post-28-0-88473700-1407472991_thumb.png

post-28-0-78909900-1407473023_thumb.png

 

For a review on dual-pol signatures on clutter, check out the WDTB training module for non-precipitation radar echoes.

 

http://www.wdtb.noaa.gov/Courses/dualpol/Applications/nonPrecip/player.html

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