Generation of Convectively Forced Gravity Waves and Their Impacts on Convection

Convectively forced gravity waves (CGWs) are atmospheric phenomena that influence convection through feedback mechanisms. These waves, generated by convective heating, can either suppress or enhance convection. In this study, we explore the generation mechanisms of CGWs and their impacts on convection using a combination of analytical models and numerical simulations. We introduce a new linear analytical model for CGWs, driven by periodic heating to represent both short-lived and long-lived convection. The model shows that deep convection generates n=1 gravity waves, which stabilize the atmosphere by increasing Convective Inhibition (CIN) and decreasing CAPE, thereby suppressing convection. In contrast, stratiform convection produces n=2 waves, destabilizing the atmosphere and promoting elevated convection by lowering the Level of Free Convection (LFC). We analyze the sensitivity of wave propagation to the vertical and horizontal scales of convective heating. The results indicate that the vertical scale of heating primarily determines wave characteristics, with larger horizontal scales leading to slower propagation speeds and longer wavelengths. The presence of a tropopause further enhances wave propagation by reflecting waves, allowing them to travel longer distances. Numerical simulations of squall lines under vertical wind shear reveal that CGWs contribute to the asymmetric development of squall lines. n=1 waves suppress convection on the downshear side, while n=2 waves enhance cloud formation and destabilize the environment. A real case from South China demonstrates that CGWs generated by frontal rainbands can influence warm-sector convection, increasing low-level humidity and reducing CIN, thus aiding convection initiation. This study enhances our understanding of the interactions between convection and CGWs, with implications for weather prediction, particularly in squall lines and warm-sector rainfall.