Multisegment statistical bias correction of daily GCM precipitation output

An improved bias correction method for daily general circulation model (GCM) precipitation is presented. The method belongs to the widely used family of quantile mapping correction methods. The method uses different instances of gamma function that are fitted on multiple discrete segments on the precipitation cumulative density function (CDF), instead of the common quantile-quantile approach that uses one theoretical distribution to fit the entire CDF. This imposes to the method the ability to better transfer the observed precipitation statistics to the raw GCM data. The selection of the segment number is performed by an information criterion to poise between complexity and efficiency of the transfer function. The global precipitation output of Institut Pierre Simon Laplace Coupled Model for the period 1960-2000 is bias corrected using the precipitation observations of WATCH Forcing Data. The 1960-1980 period of observations was used to calibrate the bias correction method, while 1981-2000 was used for validation. The proposed method performs well on the validation period, according to two performance estimators.