Characterization of spread in a mesoscale ensemble prediction system: Multiphysics versus Initial Conditions

Abstract

In this research, uncertainty associated with initial and boundary conditions is evaluated for short-term wind speed prediction in complex terrain. The study area is the Alaiz mountain range, a windy region in the northern Iberian Peninsula. A multiphysics and multiple initial and boundary condition ensemble prediction system (EPS) was generated using the Weather Research and Forecasting model. Uncertainty of the EPS is analyzed using an index based on the spread between ensemble members, considering its behavior under different wind speed and direction events, and also during distinct atmospheric stability conditions. The results corroborate that physical parameterization uncertainty is greater for short-term forecasts (63.5 %). However, it is also necessary to consider the uncertainty associated with initial conditions, not only for its quantitative importance (36.5 %) but also for its behavior during thermal inversion conditions in the narrow valleys surrounded by mountains.