woodcreeper

But, are you saying the base reflectivity image is showing a false picture of active mgration? Why did you replace the zero migration with the base reflectivity? Does it show that the bright green of the (precip mode) matches exactly to the grey of the zero velocity?

And I don’t understand the velocity plot. I don’t see just grey, I see yellow and greenish yellow, actually more than the grey. What do they mean?

Thanks for trying to put some tutorials up!

Susan

David,
My questions were going to be the same as Susans especially about the area of zero velocity. By the way…nice site, I visit it often.
Jamie

Reading the velocity plot:

This plot shows movement through the radar’s view. In this case, the movement looks to be from the N/NE (blues), over the radar, and then out to the S/SW (yellows/oranges). The “stuff” coming into the radar has a negative value (again, the blues) and the “stuff” going away from the radar has a positive value (again, the yellows/oranges). That’s how you would read the plot, “stuff “ is entering from the blue area, and heading in the direction of the yellow area. Areas of zero velocity are in gray, and areas of very low velocity are that dark yellow/green color and the dark teal (my brain’s color wheel is pretty minimal).

Using velocity to interpret the radar:

Most bird migration occurs at a velocity 10 - 20kts greater than the prevailing winds. In this case, most of the base reflectivity (radar) signal is occurring in an area with either zero, or very little velocity. Therefore I interpret this as anomalous propagation, a signal caused by temperature inversion after sunset (there’s a link to a paper under the radar study links). It might have been a little confusing since I only blocked out the zero-velocity area, but I was trying to be conservative. I would suspect that that entire large signal in the west/central area was caused by anomalous propagation, and that the only migration picked up in the radar was the stuff near the coast. I hope this helps.

Cheers