Statistical Properties of ENI IC/CG Flashes Relative to NLDN CG Flashes over the CONUS

The US National Lightning Detection Network (NLDN), developed and operated by Vaisala, Inc., has been providing useful cloud-to-ground (CG) lightning flash data over the contiguous United States (CONUS) for over two decades. With newer technology, the Earth Networks Total Lightning Network (ENTLN) developed by Earth Networks, Inc. has recently been providing not only CG data but also in-cloud (IC) flashes both in real time and data archives. In this study, these data together with radar reflectivity products from the Multi-Radar Multi-Sensor (MRMS) System developed by the National Severe Storms Laboratory are used to examine time series maps of gridded IC and CG flashes and radar products for 10 recent, notorious convective storm cases over the eastern CONUS. The cases were selected from 2012 - 2014, a period for which ENTLN data are believed to have reasonably stable properties. We also examine comparative summary statistics of all ENTLN and NLDN CG flashes for the full CONUS, as well as complementary statistics for ENTLN IC and TL (composite of IC and CG) flashes.

The case studies involve time series maps of 15-min CG and IC counts in 10-km gridboxes from ENTLN/NLDN together with “instantaneous” grids of maximum values of MRMS composite reflectivity (cref), vertically-integrated liquid (vil), and storm top height (stp). Among the storm events is the June 29-30, 2012 eastern US derecho, Hurricane Sandy (October 29-30, 2012), the June 3, 2014 Nebraska severe hailstorms, and the June 16, 2014 Nebraska twin tornadoes.

Careful inspection of maps across the 10 cases reveals that spatial patterns of NLDN and ENTLN CG flash counts are generally similar to one another, ENTLN IC flash patterns are similar to corresponding CG flash patterns, and all CG and IC patterns closely match patterns of high cref, vil, and stp. However, regarding summed flash counts substantial differences between the ENTLN CG and NLDN CG data emerge, and these depend on whether the case fell before or after ENTLN implemented a flash classification upgrade on June 4, 2013. The ratio of summed ENTLN CG flashes to summed NLDN CG flashes changed from 2.5 for before-upgrade cases to 0.8 for after-upgrade cases, which indicates a substantial improvement in consistency between the two CG data sources. Also, the upgrade resulted in a change in the ENTLN ratio of summed IC to summed CG flashes from 2.3 for pre-upgrade to 8.8 for post-upgrade cases, which shows a strong shift in the relative counts of ENTLN CG and IC flashes. Presently, the correctness of neither of these ENTLN IC/CG ratios can be assessed, as IC data from another source are not available.