A review of research progress on horizontal convective rolls

Horizontal convective rolls (HCRs) are defined as horizontal vortices that rotate in the opposite direction within the convective boundary layer. They are one of the common forms of shallow convection in the atmosphere. HCRs can cause strong turbulence and water vapor mixing in the boundary layer, as well as the exchange of material, momentum, and heat flux between the boundary layer and the free atmosphere. Meteorologists have conducted systematic research on the structural characteristics, formation mechanisms, and impact on the boundary layer of HCR through field observation experiments, theoretical derivation, flume experiments, and numerical simulations. The results indicate that inflection-point instability and thermal instability are the main mechanisms for the formation of HCRs. The turbulent flux transport of HCRs can cause non-uniform distribution of flux in the horizontal direction of the boundary layer. The vertical motion, high specific humidity, and positive temperature anomalies of the HCRs ascending branch provide favorable conditions for cold-flow snowstorm and deep convection. At present, large eddy simulation is the main numerical simulation method for studying HCRs. However, the mechanism by which HCRs triggers heavy snowfall and HCRs independently triggers deep convection is still unclear. To accelerate the application of new remote sensing technology in field experiments to establish three-dimensional structural model of HCRs. Conduct cloud penetration experiments on cold flow snow processes to study the effects of HCRs aerosols and flux transport on ice microphysical processes. To develop a simple and efficient HCRs triggering deep convection nowcasting model or operation process based on the comparative analysis of the structural characteristics of HCRs and environmental conditions that can trigger deep convection. Aim to improve the operational forecasting level of catastrophic weather caused by HCRs.