OSSE Assessment of Underwater Glider Arrays to Improve Ocean Model Initialization for Tropical Cyclone Prediction

OSSEs are performed to quantitatively assess the ability of ocean observing systems to improve ocean model initialization for coupled hurricane prediction in the North Atlantic Ocean. A particular focus of this work is to determine the impact of deploying arrays of underwater gliders over a defined ocean region, emphasizing the additional positive impact realized by using moving ocean profiling platforms compared to using stationary platforms, such as moorings. Maps of RMSE with respect to the truth represented by the Nature Run calculated over the time interval July to October 2014 are presented for dynamic height at the surface relative to 1000 m and for temperature vertically averaged over the upper 100 m. For profiles collected from stationary platforms, large RMSE reduction is concentrated around each measurement location. Observations collected at fixed locations therefore have a limited radius of influence. By contrast, the ability of each moving glider to map a subset of the defined ocean region substantially extends the radius of influence of each glider. This extension roughly equalizes error reduction across the domain and leads to larger overall error reduction in ocean analyses used to initialize forecast models. The dependence of the radius of influence on properties of the data assimilation system such as the localization radius is discussed. Guidelines extracted from this study for enhancing tropical cyclone prediction include a combination of seasonal glider deployments and pre-storm airborne surveys.