The Data Assimilation Research Testbed: A Community Facility for Ensemble Data Assimilation

The Data Assimilation Research Testbed (DART) is a novel community facility for ensemble data assimilation developed and maintained at the National Center for Atmospheric Research. DART provides state-of-the-art tools for data assimilation along with interfaces to a large assortment of geophysical prediction models, observational datasets, and diagnostic tools. By confronting models with observations, data assimilation provides a key tool for the development and improvement of geophysical models, observational systems, and numerical prediction capabilities. The probabilistic analyses and forecasts produced by the DART ensemble algorithms are especially useful for detecting deficiencies in models and observing systems.

Examples from a variety of geophysical applications will be presented to demonstrate the diversity of prediction problems that can be addressed by using the DART facility. First, the results of fully-cycling mesoscale ensemble data assimilation experiments with the Weather Research and Forecast model during the last two springs are presented. Ensemble assimilation results from the first season led to revised choices for model parameterization and observation sets in the second season, and resulted in improved short-term forecasts of severe weather.

Second, DART assimilations with the Community Atmosphere Model (CAM) climate general circulation model have identified model implementation problems and led to the development of enhanced parameterizations that improve both climate simulations and short-term predictions. The process by which ensemble assimilation can lead to improved models is highlighted.

Finally, DART ensemble assimilations with CAM coupled to the Parallel Ocean Program are being used as initial conditions for decadal predictions of the climate system. Highlights of the ocean analyses and plans for innovative fully-coupled climate system assimilation systems are discussed.