The Interaction Between Low-level Jets and Cold Pools and Their Impacts on Convection Initiation

Previous studies have investigated the optimal configuration of squall lines affected by linear vertical wind shear and cold pools, as described by the RKW theory. However, the interaction dynamics between low-level jets (LLJs) with nonlinear vertical wind shear, and cold pools remain insufficiently understood. This study utilizes idealized numerical simulations to examine the impacts of LLJs on cold pools and their subsequent role in initiating convection, focusing on the sensitivity to LLJ height and strength. The simulations reveal that, under the influence of an LLJ, a cold pool typically evolves into a two-step structure with two distinct heads, and its intensity diminishes more rapidly compared to scenarios with quasi-linear shear or no wind. Two prominent regions of vertical velocity are identified near these heads, with oneassociated with the elevated cold pool head and elevated convection initiation. Variations in parcel lifting above and below the jet core arise from differences in horizontal vorticity induced by LLJ shear, resulting in two distinct clusters of parcel trajectories. A lower or weaker LLJ leads to earlier convection initiation due to larger initial vertical velocity driven by LLJ-cold pool interactions. Convection intensity peaks when the LLJ height aligns with levels of high CAPE and when vorticity pairing above the jet core reaches its optimal state, consistent with RKW theory.