Evaluating the impact of initial conditions on lightning simulation over Rajasthan: A synoptic and modelling approach using the WRF model

An intense thunderstorm accompanied by lightning strikes claimed the lives of more than 11 people in Jaipur, Rajasthan, on 11th July 2021. This study investigates the influence of different Initial Conditions (ICs) on the simulation of this lightning event using the Weather Research and Forecasting (WRF) model. Various datasets Global Forecast System GFS (0.25° x 0.25°), Global Data Assimilation System (GDAS)/ (FINAL) GDAS-FNL (0.25° x 0.25°), FNL (1° x 1°), and ERA5 (0.25° x 0.25°) were used as to assess their impact on model performance. The objectives of this study are to analyses the synoptic conditions associated with the thunderstorm and lightning event, evaluate the sensitivity of lightning simulations to different initial condition, and understand how these conditions influence the spatial and temporal distribution of lightning. The study also aims to assess how ICs affect the accuracy and predictability of lightning simulation. A comprehensive examination of meteorological factors during the onset of the monsoon season highlights the conditions that triggered this severe lightning event. Results show that between 1400 and 1600 UTC, when the event occurred, simulations using ERA5 outperformed FNL, GDAS-FNL, and GFS. ERA5 yielded the highest accuracy (0.67), along with improved scores for Probability of Detection (POD = 0.85), Critical Success Index (CSI = 0.53), and Heidke Skill Score (HSS = 0.36). The simulated lightning flash counts from ERA5 closely aligned with lightning observations over Rajasthan. Furthermore, the study evaluates the strengths and limitations of each ICs in representing key meteorological parameters such as temperature, humidity, precipitation, and lightning activity. Overall, the findings suggest that the ERA5 dataset provides the most reliable input for simulating precipitation and lightning over the region.