TITLE

Pre- and Postupgrade Distributions of NLDN Reported Cloud-to-Ground Lightning Characteristics in the Contiguous United States

AUTHOR(S)
Rudlosky, Scott D.; Fuelberg, Henry E.
PUB. DATE
September 2010
SOURCE
Monthly Weather Review;Sep2010, Vol. 138 Issue 9, p3623
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
The National Lightning Detection Network (NLDN) underwent a major upgrade during 2002-03 that increased its sensitivity and improved its performance. It is important to examine cloud-to-ground (CG) lightning distributions before and after this upgrade because CG characteristics depend on both measurement capabilities and meteorological variability. This study compares preupgrade (1996-99, 2001) and postupgrade (2004-09) CG distributions over the contiguous United States to examine the influence of the recent upgrade and to provide baseline postupgrade averages. Increased sensitivity explains most of the differences in the pre- and postupgrade distributions, including a general increase in total CG and positive CG (+CG) flash densities. The increase in +CG occurs despite the use of a greater weak +CG threshold for removing ambiguous +CG reports (post 15 kA versus pre 10 kA). Conversely, the average +CG percentage decreased from 10.61% to 8.65% following the upgrade. The average +CG (−CG) multiplicity increased from 1.10 (2.05) before to 1.54 (2.41) after the upgrade. Since true +CG flashes rarely contain more than one return stroke, explanations for the greater than unity +CG multiplicities remain unclear. Postupgrade results indicate that regions with mostly weak peak current +CG flashes now exhibit greater average +CG multiplicities, whereas regions with mainly strong +CG flashes now exhibit smaller average +CG multiplicities. The combination of NLDN performance, meteorological conditions, and physical differences in first −CG return strokes over saltwater produce maxima in −CG multiplicity and peak current over the coastal waters of the southeast United States.
ACCESSION #
54005569

 

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