Tuesday, September 14, 2010
The Birds Are Back
I have mentioned before that birds can be viewed on weather radar, and we have a great example tonight.
It seems like the big migrations tend to occur at night (less chance of being caught by predators?). Here is the radar image that shows the amount scattered by targets in the atmosphere (we call this reflectivity) at 5 PM. Not much there, just ground clutter and some weak returns from a few birds, planes, density discontinuities in the atmosphere.
But here is at 8 PM....the sky is filled with echos..the birds!
And which way are the birds going? We can tell, because we have Doppler Radars, which reveal the velocity towards or away from the radar. Cold colors (e.g., green) indicate a velocity towards the radar, warm colors (e.g, yellow) motion away. Clearly, the birds are generally heading to the south or southeast, just what one would expect.
This is is good time for the birds to get going---it is about to get wet here again, as a frontal system makes landfall later tomorrow.
Posted by Cliff Mass at 9:47 PM