Assessment of the Indian Lightning Location Network (ILLN) using ground-based and satellite observations

The Indian Lightning Location Network (ILLN), established by the Indian Institute of Tropical Meteorology (IITM), provides a comprehensive framework for investigating lightning phenomena, thunderstorm dynamics, and associated nowcasting/forecasting methodologies. ILLN is a ground-based lightning location system operating in VLF/LF/HF radio frequency bands, facilitating effective nationwide lightning mitigation strategies. The detection accuracy of ILLN was thoroughly evaluated using a comprehensive approach, including ground-based observations with electric field mills (EFMs) and C-band polarimetric radar, alongside satellite data from the Global Precipitation Measurement (GPM) mission and the ISS Lightning Imaging Sensor (LIS). The findings reveal that the ILLN exhibits a Relative Detection Efficiency (RDE) of 67.6 % in Pune, 69.4 % in Kohima, and 64.9 % in Rampurhat compared to electric field mill observations, closely aligned during high lightning activity during significant numbers of electric field changes. The average RDE for ILLN with reference to EFM is approximately 60 %, with lower values potentially due to a predominance of intra-cloud (IC) lightning. Lightning flashes detected by ILLN are primarily located within high reflectivity areas detected by GPM and ground radar, concentrated in regions exceeding 30 dBZ. Spatial RDE values concerning ISS ranged from 43 % to 97 %, with quartiles between 55 % and 84 % and median values between 67 % and 85 % across different cases, indicating occasional lower detection of IC lightning by ISS compared to ILLN. Factors such as IC:CG ratios may impact ISS-LIS detection, influencing discrepancies in the spatial pattern between ILLN and ISS over Northwest and Eastern regions. Despite minor regional differences, the overall alignment between ISS and ILLN lightning detections is close. These findings underscore the challenges and reliability of lightning detection methods, highlighting ILLN's consistent performance across diverse scenarios. The network's robust detection efficiency reinforces its utility for diverse applications, serving as a pivotal data source for esteemed organizations like the India Meteorological Department and national and state disaster management authorities. ILLN's widespread implementation significantly contributes to mitigating the adverse impact of lightning-induced incidents.