A modeling study of convection initiation prior to the merger of a sea-breeze front and a gust front

Vertical momentum budgets were conducted in the intermediate area as well as along the backward trajectories of parcels within a selected convective cell. The vertical acceleration was decomposed into dynamic and buoyant components, respectively. The diagnostic results showed that the dynamic acceleration dominated in the low level, while buoyant acceleration became evident only when the parcel reached a high altitude above 2 km. Therefore the dynamic forcing appeared to be more relevant to CI. The dynamic acceleration was further decomposed into four terms based on anelastic approximation. The positive dynamic acceleration was mainly caused by fluid extension associated with the low-level convergence, while fluid twisting in the vertical contributed negatively to the dynamic acceleration. The other two terms related to horizontal curvature and height variation of density were negligibly small.