Using objective comparisons of observed and simulated precipitation to help guide the improvement of Earth System Models

In this presentation we discuss a community-based effort to establish the benchmarking of simulated precipitation in Earth System Models.   We first summarize the impetus and outcomes of a recent workshop dedicated to the topic.    This includes the identification of a tiered system of objective tests (metrics) for the following climatological characteristics:  the mean state, seasonal cycle, variability across time scales, intensity/frequency distributions, extremes and drought.   Preliminary results are shown gauging model performance changes across multiple generations of CMIP.   The performance tests we describe are part of an open-source analysis framework being made available to model developers to help them make judgements about the quality of simulated precipitation during the model development process.