Precipitation accumulation analysis – assimilation of radar-gauge measurements and validation of different methods

Abstract. We investigate the appropriateness of four different methods to produce precipitation accumulation fields using radar data alone or combined with precipitation gauge data. These methods were validated for high-latitude weather conditions of Finland. The reference method uses radar reflectivity only, while three assimilation methods are used to blend radar and surface observations together, namely the linear analysis regression, the Barnes objective analysis and a new method based on a combination of the regression and Barnes techniques (RandB). The Local Analysis and Prediction System (LAPS) is used as a platform to calculate the four different hourly accumulation products over a 6-month period covering summer 2011. The performance of each method is verified against both dependent and independent observations (i.e. observations that are or are not included, respectively, into the precipitation accumulation analysis). The newly developed RandB method performs best according to our results. Applying the regression or Barnes assimilation analysis separately still yields better results for the accumulation products compared to precipitation accumulation derived from radar data alone.