The Impact of Cloud-Radiative Forcing on the Boundary Layer Evolution for Landfalling Tropical Cyclones

This study investigates how cloud-radiative forcing interacts with continental thermodynamic environments to influence the evolution of the tropical cyclone boundary layer (TCBL) during landfall using high-resolution, full-physics numerical simulations. Three idealized landfall experiments representative of Atlantic continental environments are analyzed to examine how cloud-radiative processes respond to progressively stronger environmental thermodynamic forcing. The simulations show that cloud-radiative forcing influences the TCBL through a coupled thermodynamic pathway in which cloud condensate modifies radiative heating and cooling, altering boundary-layer stability and equivalent potential temperature. These thermodynamic changes, in turn, reorganize the secondary circulation, leading to changes in hurricane boundary-layer depth (HPBL), turbulent mixing, and radial inflow. The strength of this feedback depends strongly on the surrounding continental environment. Under warm-moist conditions, an extensive cloud shield at landfall generates longwave radiative forcing that broadens the inflow layer and deepens the HPBL. In warm-dry environments, dry-air intrusion fragments the onshore cloud shield, confining the radiative forcing and its boundary-layer response to localized regions. Under cool-moist conditions, environmental thermodynamic forcing increasingly competes with cloud-radiative forcing, shifting the secondary circulation rearward as cool continental air is advected cyclonically into the vortex. Taken together, these experiments identify three distinct regimes of TCBL evolution during landfall and show that the dominant control shifts from cloud-radiative forcing to environmental thermodynamic forcing as the strength of the continental thermodynamic forcing increases. These results provide a conceptual framework for understanding the transition from cloud-radiation-dominated to environmentally dominated TCBL evolution during tropical cyclone landfall, with implications for inland intensity forecasts and the evolution of the hurricane boundary layer.