Traditional aerodynamic analyses of electric vertical take-off and landing (eVTOL) urban air mobility (UAM) aircraft predominantly assume uniform inflow conditions, neglecting the complex atmospheric environments encountered during actual operations. In fact, atmospheric stability has a significant effect on the temporal and spatial distribution of turbulent inflow, hence further affect the safety, stability, and operational efficiency of the aircraft[1]. Under stable atmospheric conditions, vertical motion is suppressed, leading to generally calm and laminar airflow that is conducive to stable flight control. Conversely, unstable conditions promote thermal convection, generating hazardous phenomena such as turbulence, gusts, and vertical wind shear. These pose substantial risks to eVTOLs, particularly during low-speed, high-power phases like hover and landing. They can cause aircraft attitude instability, increase control system workload and energy consumption, and may exceed operational wind limits, leading to flight cancellations or delays. This study employs an efficient mid-fidelity coupled vortex method[2] integrated with a turbulent inflow generator to investigate the aerodynamic characteristics of a lift-cruise eVTOL rotor system during transition flight under different atmospheric stabilities. Results indicate that under uniform inflow conditions, aerodynamic loads exhibit steady periodic variations once the rotor wake reaches a fully developed state. However, under unstable atmosphere, increasing turbulence intensity progressively disrupts the organized wake structures, culminating in significant wake deterioration under high-turbulence conditions. Compared with the uniform flow baseline, turbulent inflow substantially amplifies unsteady load fluctuations. These findings underscore the necessity of incorporating realistic atmospheric turbulence in UAM aerodynamic design process, thereby deepening the understanding of rotor-turbulence interaction physics and informing the development of more robust UAM aircraft.