Validation of Vaisala's Global Lightning Dataset (GLD360) over the continental United States

Vaisala's Global Lightning Dataset (GLD360) was launched in September 2009. GLD360 is the first ground-based lightning detection network capable of providing both worldwide coverage and uniform, high performance without severe detection differences between daytime and nighttime conditions. Expected GLD360 cloud-to-ground (CG) flash detection efficiency is 70% and median CG stroke location accuracy is 5-10 km.

This paper will describe recent cloud-to-ground (CG) flash detection efficiency and stroke location accuracy validation results over the continental United States using Vaisala's National Lightning Detection Network (NLDN) as ground truth. A companion validation study has been carried out in southeast Brazil. These two studies are the first of many such studies that will be carried out around the globe as GLD360 coverage and performance evolve. Vaisala plans to use these validation studies to continually assess GLD360 performance and address differences between expected and validated performance.

Validation was performed for 22 select days from 1 December 2009 through 31 January 2010 where lightning occurred over both the continental U.S. and southeast Brazil. This ensured GLD360 network operational status was the same for both validation studies.

GLD360 CG flash detection efficiency ranged from 86% to 92% throughout the 24-hour UTC day, with little day/night variation. This variability in detection efficiency as a function of UTC time is much smaller than that observed in other existing long-range lightning detection systems. These results exceed the expected GLD360 70% CG flash detection efficiency over the continental U.S.

GLD360 median location accuracy was 10.8 km for the 770,421 matched GLD360/NLDN CG strokes during December 2009/January 2010 over the continental U.S. These results are slightly poorer than the expected GLD360 5-10 km median CG stroke location accuracy over the continental U.S.

Additional maps will show NLDN CG strokes overlaying GLD360 lightning strokes and GLD360 lightning strokes overlaying GOES-11/GOES-12 infrared satellite imagery. These maps clearly demonstrate that GLD360 highlights the appropriate areas of enhanced convective activity across the continental U.S., North Atlantic, and North Pacific. Some areas around convection show outlier (or scattered) lightning events. These GLD360 outlier lightning events tend to be more numerous in and around high lightning rate storms.