Dual Pol Radar Showing Us the Melting Level

We are already enjoying the benefits of the recent dual pol upgrade of the Fort Knox Doppler weather radar.  Take the image below, for example.  This is a screenshot of radar data taken this evening. 

Remember that as the radar beam goes out from the radar, it is angled slightly upward so that the beam becomes higher and higher above the ground as it travels away from the radar.  On the image below, the small circle around the radar near the center of the image is where the radar beam is about 600 feet off the ground.  Within that circle we see mostly purple colors, which indicate that the precipitation in that area is of one type (as opposed to a mix).  Above the 600 foot level, as we go away from the radar, to roughly 2000 feet above ground, the radar signal is very noisy.  Rather than a smooth purple appearance, there are lots of colors all jumbled together.  That tells us that there is a mix of precipitation at that height.  So, between 600 feet and 2000 feet above the ground, there is a mix of rain and snow.  Then, above 2000 feet, the relatively smooth purple color reappears, signifying that above 2000 feet there once again is just one main type of precipitation, rather than a mix. 

The conclusion at which we can arrive from all of this is that above 2000 feet we have snowflakes, between 2000 and 600 feet there is a mix of rain and snow, and below 600 feet there is just rain.   This gives meteorologists valuable information on the height at which the snow in the clouds transitions to rain at the surface.  We can then track this over time and see how the melting layer is rising or falling.  If the melting layer is getting lower and lower, then we know that we'll soon be seeing snow at the surface.

Correlation Coefficient on October 30, 2012

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