Adverse weather effects on the power production of a utility-scale wind turbine

Wind turbines are commonly characterized under idealized atmospheric conditions, yet real-world operation often occurs in rain and other adverse weather that can substantially alter their aerodynamic performance. Here, we combine nearly 10 years of operational data from a 2.5 MW utility-scale wind turbine with controlled wind-tunnel experiments under heavy rain to quantify these effects and identify the mechanisms underlying rain-induced power losses. All five common adverse weather types examined reduce power production. Rain is the most frequent, occurring during 41.9% of the evaluated turbine operating period, and reduces power output by 6.3% on average, with losses reaching approximately 10% near the rated wind speed. Flow-field and force measurements reveal that droplet impacts generate non-uniform water films and rivulets, triggering premature boundary-layer transition and separation, while droplet splashing-back near the blade frontal region extracts momentum from the near-surface airflow. Together, these mechanisms reduce lift and increase drag; near stall, lift decreases by approximately 10% and drag increases by approximately 17% relative to dry conditions. By bridging long-term field observations with controlled laboratory measurements, this study establishes a mechanistic basis for predicting rain-induced turbine performance losses and highlights the need to account for precipitation in turbine design, control, and power-production forecasting.