A New Method for Generating Initial Condition Perturbations in a Regional Ensemble Prediction System: Blending

作者：Wang, Yong^*; Bellus, Martin; Geleyn, Jean-Francois; Ma, Xulin; Tian, Weihong; Weidle, Florian

来源：Monthly Weather Review, 2014, 142(5): 2043-2059.

DOI：10.1175/MWR-D-12-00354.1

• Short-range prediction
• Ensembles
• Forecasting techniques
• Forecast verification/skill

A blending method for generating initial condition (IC) perturbations in a regional ensemble prediction system is proposed. The blending is to combine the large-scale IC perturbations from a global ensemble prediction system (EPS) with the small-scale IC perturbations from a regional EPS by using a digital filter and the spectral analysis technique. The IC perturbations generated by blending can well represent both large-scale and small-scale uncertainties in the analysis, and are more consistent with the lateral boundary condition (LBC) perturbations provided by global EPS. The blending method is implemented in the regional ensemble system Aire Limitee Adaptation Dynamique Developpement International-Limited Area Ensemble Forecasting (ALADIN-LAEF), in which the large-scale IC perturbations are provided by the European Centre for Medium-Range Weather Forecasts (ECMWF-EPS), and the small-scale IC perturbations are generated by breeding in ALADIN-LAEF. Blending is compared with dynamical downscaling and breeding over a 2-month period in summer 2007. The comparison clearly shows impact on the growth of forecast spread if the regional IC perturbations are not consistent with the perturbations coming through LBC provided by the global EPS. Blending can cure the problem largely, and it performs better than dynamical downscaling and breeding.

• 出版日期2014-5
• 单位南京信息工程大学