Introducing Dual Polarization Radar

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By Scott Cimini on December 26, 2012, 10:10pm Last modified: December 28, 2012, 12:23pm

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In the years before radar, people had very little advanced warning of severe weather.  Because of this many died in floods, snowstorms, hurricanes, etc.  When Doppler radar came around it helped save millions of lives!  For many years scientists and inventors have upgraded the capabilities of radar and now we have a brand new one!  It’s called dual polarization radar and it’s being rolled out by the National Weather Service on all of their radars.  The process has already begun and will continue in 2013 and 2014.  I’m excited because this will help tremendously in forecasting and warning people of what to expect in a storm.

Conventional Radar tells us about the relative size of objects whereas dual polarization radar tells us about the size, shape, and variety of objects.  Here are a few things that the new radars will have:

Differential Reflectivity (ZDR) will help meteorologists locate hail cores in Thunderstorms.  Also, vertical columns of ZDR will also help in determining updraft location and strength.

              Specific Differential Phase (KDP) is a great new feature.  If you have similar reflectivity values, this feature can let you know if the area is experiencing many small raindrops or fewer but larger raindrops.  It will give you better insight about how light or heavy the rain is falling in a particular area.

        The Correlation Coefficient is a measure of strength or weakness between 2 (or more) variables.  A CC will have a value between -1 and 1 where -1 would be a very weak relationship and +1 a very positive one.  CC is helpful in find the melting layer by comparing all the different shapes and sizes of the wet and frozen particles.  It’s also helpful in determining how wet or dry snow is falling.  There are many other applications of the CC but I won’t go into that here.  

If you are interested in learning more about dual polarization radars, the National Weather Service has provided a large set of training  modules online to educate weather geeks and meteorologists alike.  I took an overview course in writing this article.  Lots of great information to look at! 


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Scott Cimini

Town: Wallingford, CT  

Reporting for WXedge since January 2012.

Articles: 149

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