The U.S. National Lightning Detection Network: Post-upgrade status

U.S. National Lightning Detection Network (NLDN™) has been providing real-time U.S. continental-scale lightning information to research and operational users since 1989, and has been the lightning data source for the U.S. National Weather service for more than a decade. This network has undergone regular improvements during its 15-year life. The intent of this paper is to provide research and operational users of NLDN data with a contemporary view of the strengths and limitations of this national data resource.

Beginning in the spring of 2002 the NLDN underwent its most-recent system-wide upgrade. The objectives of the upgrade were to increase sensor reliability and reduce maintenance costs, to improve detection efficiency and location accuracy on the boundaries of the network, and to provide the capability to detect some cloud discharges. The original (1995) time-of-arrival LPATS sensors and early IMPACT sensors were replaced by new IMPACT ESP sensors. Several additional sensor sites have been installed or are being installed. The new IMPACT ESP sensors provide accurate time-of-arrival and direction information, as well as increased sensitivity. The model-estimated stroke detection efficiency (DE) is now in the range of 60-80%, and the overall modeled cloud-to-ground (CG) flash DE is in the range of 90-95% throughout the continental U.S.

In conjunction with this upgrade, validation field campaigns were carried out in Southern Arizona and in Oklahoma/Texas in 2003 and 2004, and at the International Center for Lightning Research and Testing (ICLRT) in Florida in 2001-2003. Data from these studies were used to validate the performance of the NLDN and to evaluate classification of lightning type.

This paper provides an overview of the current NLDN configuration and processing, a description of the on-going changes to the NLDN, and a comparison of modeled and measured performance before, during, and after the upgrade. The effect of the upgrade on CG peak current distributions and flash multiplicity will also be presented. Finally, national-scale thematic maps of selected lightning parameters will be shown in order to illustrate the range of instrumentation effects, measurement effects, and true regional variations in lightning climatology.