Lightning Prediction Using Electric Field Measurements Associated with Convective Events at a Tropical Location SOUMYAJYOTI JANA, 1 ROHIT CHAKRABORTY, 2 and ANIMESH MAITRA 3 Abstract—Nowcasting of lightning occurrences is essential in tropical locations as lightening causes severe damage to life and property. This study attempts to nowcast lightning events during convective phenomena using an electric field monitor (EFM) at a tropical urban location, Kolkata (22.65°N, 88.45°E). Before the onset of heavy lightning occurrences, definite changes in the atmospheric electric field (EF) are observed, which in turn are associated with high cloud liquid water content (LWC) and low cloud base height (CBH). A model has been proposed to nowcast lightning strikes within about 17.5 km radius of the present loca- tion based on the EF standard deviation (EFSD) values. The proposed technique is tested with the lightning data provided by a collocated lightning detector, which yields a prediction efficiency of * 0.91 (* 0.86), a false alarm rate of * 0.23 (* 0.18), and a critical success index of * 0.71 (* 0.72) with an optimal range of other performance parameters during the monsoon (pre-monsoon) periods, thereby generating an alarm 45 min before lightning events. Keywords: Atmospheric electric field, tropical thunderstorm, lightning strikes, cloud, nowcasting. 1. Introduction Convective phenomena are prevalent in the pre- monsoon and monsoon periods in various parts of the Indian subcontinent (Madhulata et al., 2013; Chak- raborty et al., 2018, 2021; Maitra et al., 2019). These events are often associated with large clouds, heavy rain, and many lightning strikes (Maitra et al., 2014), causing severe socioeconomic destruction (Livemint, 2020). Also, recent years have seen some catastrophic thunderstorms and lightning events, and [ 100 lives were lost on 25 June 2020 (Washington Post, 2020). A typical convective cloud contains a huge amount of water vapor (Madhulata et al., 2013), which forms cloud hydrometeor particles like grau- pel, ice crystals, and supercooled water droplets that become charged particles after undergoing up- and downdrafts within the cloud (Phillips and Kinzer, 1958). The electrical charges within the cloud are typically distributed across the troposphere along different layers (Bateman et al., 1995; Marshall & Stolzenburg, 1998). The influence of these charge distributions inside the cloud can be simplified with the help of surface electric field variations consider- ing a positively charged cloud top with a negatively charged layer underneath (Phillips and Kinzer 1958). This creates an increased electric field between the ground and cloud charge centers creating cloud-to- ground (CG) lightning flashes. These lightning fla- shes are highly correlated with the atmospheric moisture content and aerosol-cloud nucleation effects. They greatly help to form excess hydrome- teors in the mixed layer, which is necessary for lightning genesis (Shi et al., 2015, 2018; Siingh et al., 2011). Additionally, higher instability values are instrumental in uplifting this moisture above freezing level to produce ice and graupel, which collide with each other to become charge particles and help in cloud electrification (Galanaki et al., 2015; Saha et al., 2017). For decades, forecasting and detailed analysis of this lightning have been challenging 1 Space Physics Laboratory, Vikram Sarabhai Space Centre, Indian Space Research Organisation, Thiruvananthapuram, India. E-mail: mantu.abc@gmail.com 2 Divecha Centre for Climate Change, Indian Institute of Science, Bangalore, India. E-mail: rohitc744@gmail.com 3 Institute of Radio Physics and Electronics, University of Calcutta, 92, Acharya Prafulla Chandra Road, Kolkata 700009, India. E-mail: animesh.maitra@gmail.com; am.rpe@caluniv.ac.in Pure Appl. Geophys. Ó 2023 The Author(s), under exclusive licence to Springer Nature Switzerland AG, corrected publication 2023 https://doi.org/10.1007/s00024-023-03229-7 Pure and Applied Geophysics