Abstract

Data assimilation is the term used in geophysics for combining information from observations with predictions from a numerical model. Assimilation can be used to produce improved analyses and forecasts of a geophysical system, to improve numerical models, and to design and evaluate observing syst... Show moreData assimilation is the term used in geophysics for combining information from observations with predictions from a numerical model. Assimilation can be used to produce improved analyses and forecasts of a geophysical system, to improve numerical models, and to design and evaluate observing systems. The Data Assimilation Research Testbed (DART) is a mature community software facility providing researchers access to state-of-the-art ensemble assimilation tools. The freely-available DART distribution includes fully functional low-order and high-order models, support for commonly available observations, hooks to easily add both new models and observation types, diagnostic programs to interpret the results, and a full tutorial suitable for self-study or teaching data assimilation concepts, including exercises using the models distributed with DART. Recent applications of DART with both global and regional atmospheric models are presented to provide an overview of capabilities. DART has been used with the WRF regional atmospheric model to produce ensemble analyses and predictions of Pacific and Atlantic tropical storms. The impact of using radio occultation observations from the COSMIC satellites has been evaluated in these cases. DART has also been applied to global prediction with the CAM general circulation model. Analysis of the assimilated fields has led to the discovery of a significant coding error in the polar filtering in the CAM finite volume core. Ensemble assimilation has also identified noise due to a previously undocumented numerical instability that is found in the finite volume cores that have been used for several major climate models. DART was also used with the CAM/CHEM model to provide operational support during the ARCTAS field campaign. New tools to improve and simplify the use of ensemble assimilation continue to be added to the DART facility. In the past year, improved tools for automatically adapting to model error (adaptive damped inflation) and a new nonlinear filtering variant have been introduced. Examples of improvements to global analyses and forecasts are presented. New models, both small and large continue to be added to the set compatible with DART. For instance, During the past year, a version of the MIT/OCEAN model was added by Ibrahim Hoteit and the Navy's COAMPS model was added by Tim Whitcomb. An overview of requirements for adding a new large model are presented. Show less