Advances in calibration of QPF/PQPF for the NCEP Global Ensemble Forecast System

Calibration of Quantitative Precipitation Forecasts (QPF) and Probabilistic Quantitative Precipitation Forecasts (PQPF) for the NCEP Global Ensemble Forecast System (GEFS) has been implemented in operation since May 2004 (Zhu and Toth, 2002, 2003 and 2005). This post-processing through statistical bias correction is made by defining an adjustment to the QPF value in such a way that the adjusted cumulative forecast distribution over a moving time window (most recent 30-day period) match the corresponding observed distribution accumulated over the entire continental US and different RFC regions. It improves NCEP GEFS model QPF/PQPF forecasts by reduced bias and enhanced probabilistic skill. Current study will base on May 2004's implementation, and focus on: 1). 1.0*1.0 (lat/lon) degree resolution, 6-hr forecast out to 384 hours, 2). statistical down scaling from 1.0*1.0 (lat/lon) degree resolution to 5km (NDGD) resolution, 3). using new developed CCPA (Climatology-Calibrated Precipitation Analysis) as proxy truth. After this application, NCEP GEFS QPF and PQPF will have higher temporal and spatial resolution which will satisfy various users in reality especially for hydro-meteorological and short-range weather forecast applications.