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Ensemble Sensitivity Analysis Applied to a Heavy Rainfall Event in Beijing

A high-impact heavy rainfall event occurred in Beijing, China on 16 July 2018, which is a typical warm sector heavy rainfall associated with Mesoscale Convective System (MCS) of multi cells. To clarify the key factors influencing the heavy rainfall, ensemble sensitivity analysis (ESA) is conducted using the state-of-the-art European Centre for Medium-Range Weather Forecasts (ECMWF) ensemble prediction system. The ESA is a new efficient tool utilizing the information contained in ensemble forecast to calculate a linear relationship between a forecast metric and model perturbation variable. Results show that the low-level southwestly moist flow plays a significant role in the heavy rainfall in Beijing which is favorable for abundant water vapor and dynamic lifting. Keywords—ensemble sensitivity analysis; heavy rainfall; ensemble prediction system