Through a closely collaborative effort with OHD and ESRL, NCEP Environmental Modeling Center has developed Climatology-Calibrated Precipitation Analysis (CCPA), a new precipitation analysis at about 5km resolution with 6 hour accumulation for bias correction and downscaling. CCPA has been running in real-time and updating twice daily since July 14, 2010, and the product is available to users at five basic grids over the continental US from 2002 to present. This 6-hourly analysis product is generated by combining two widely used available datasets to take advantage of the higher reliability of the CPC Unified Global Daily Gauge Analysis and the higher temporal and spatial resolution of the Stage IV dataset based on multi-sensor observations. This product is being used in several important studies. In particular, bias correction and downscaling the precipitation forecast from GEFS has made progress and presented in the previous meeting.

Recent upgrades to improve CCPA are undergoing, consisting of 1) inclusion of 3-houly analysis; 2) update of the regression coefficients with extended historical data sets from 2002 to 2011; and 3) application of a non-linear regression model. In response to a need for higher temporal resolution precipitation analysis for use in regional short-range forecast calibration and verification, 3-hourly analysis has been developed and successfully implemented within the CCPA production package. Previous evaluation and cross validation studies suggest that the CCPA methodology is robust but subject to limitations due to the validity of the simple linear regression model and inadequate sample of high amount precipitation. There is evidence that a linear regression is likely dominated by the lower amount precipitation, and may not hold for high amount. To overcome this problem we will also employ a more realistic nonlinear regression approach into the CCPA software. Finally, comparison of both the original and new products will be performed and a summary of the presentation and results will be shown.