Investigating the Uncertainties in Future Lightning Activity over Eastern Japan Using Convective-Permitting Climate Simulations

This study investigates the uncertainties in future lightning activity over eastern Japan using a convective-permitting model coupled with an explicit-bulk lightning model (BLM). Projected changes to four commonly used lightning flash parameterizations (LFP), the product of Convective Available Potential Energy and precipitation (CP), Updraft Volume (UV), updraft Ice Flux (IFlux), and the McCaul Lightning Flash Algorithm (MLFA), in addition to results from the BLM, are computed by applying the pseudo-global warming method on two highly active lightning cases. Results from LFPs exhibited high uncertainty in future flash counts, with increasing CP and UV, and decreases or minimal change using the IFlux and the MLFA for both cases. The BLM alone exhibits a large decrease in projected flash counts for both cases. The BLM explicitly computes various cloud-electric properties, such as charge separation due to graupel and ice/snow collision, which is widely believed to be an important mechanism for lightning. In future climates, less charge separation per collision and fewer collisions are projected due to changes in cloud ice properties that are not considered in LFPs. The BLM, therefore, offers an alternative assessment of projected lightning activity.