Impacts of distinct observations during the 2009 Prince William Sound field experiment: A data assimilation study

A set of data assimilation experiments, known as Observing System Experiments (OSEs) are performed to assess the relative impacts of different types of observations acquired during the 2009 Prince William Sound Field Experiment. The observations assimilated consist primarily of two types: High Frequency (HF) radar surface velocities and vertical profiles of temperature/salinity (T/S) measured by ships, moorings, an Autonomous Underwater Vehicle and a glider. The impact of all the observations, HF radar surface velocities, and T/S profiles is assessed. Without data assimilation, a frequently occurring cyclonic eddy in the central Sound is overly persistent and intense. The assimilation of the HF radar velocities effectively reduces these biases and improves the representation of the velocities as well as the T/S fields in the Sound. The assimilation of the T/S profiles improves the large scale representation of the temperature/salinity and also the velocity field in the central Sound. The combination of the HF radar surface velocities and sparse T/S profiles results in an observing system capable of representing the circulation in the Sound reliably and thus producing analyses and forecasts with useful skill.

► Observing System Experiments (OSEs) performed using a multi-scale three-dimensional variational data assimilation scheme.
► Impact of High Frequency (HF) radar surface velocities and sparse temperature/salinity profiles is demonstrated.
► Assimilation of HF radar velocities alongside sparse temperature/salinity profiles resulting in skillful forecasts.