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Dual Polarization, or "Dual-Pol", is a new advancement in radar technology. Now installed on all WSR-88D radars and many research radars, dual polarization technology allows the operator to better discern different weather phenomena by emitting pulses in both the vertical and horizontal planes. This also improves general data quality, and vastly improves the rainfall estimation products provided by the radar. We won't go into great detail about all of this here, since you'll likely be taking a course in radar meteorology in the not too distant future, but we'll quickly summarize the dual pol products.
Correlation Coefficient: This product is a measure of how similar the returns are for the horizontal and vertical pulse. This product can help distinguish meteorological echos from non-meteorological ones. Targets such as rain and large hail will usually have high CC values, near 1, while non-meteorological echos will have lower CC values, below 0.8.
Differential Reflectivity (ZDR): The differential reflectivity product shows the difference in the returned energy of the two pulses, measured in dB. A positive value shows that the target is longer in the horizontal plane than the vertical, and a negative value shows the opposite. Thus, a value near 0 shows that the target is nearly spherical.
Specific Differential Phase (KDP): The product is a measure of the phase shift between the horizontal and vertical pulses. This gets quite complicated to explain, and as stated above, you'll hear about it more later on in radar meteorology.
Hydrometeor Classification (HCA): This product is the result of an algorithm that produces a best guess at what the radar is detecting, based off of all the values the radar measures about a target. While useful, this product is not always accurate, so always evaluate all available products in conjunction with the hydrometeorological classification product.
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