Extreme and non-tidal events in the Chesapeake Bay high frequency radar surface currents record

Abstract

The lower Chesapeake Bay high frequency radar (HFR) surface currents record now spans more than eight years from April 2007 to present day. In that time, the surface circulation has been observed during the passage of severe storms and other significant non-tidal events including those associated with periods of sustained high winds, high volume river discharge and complete reversals of tidal current direction. Tides are the dominant forcing mechanism for currents in the area; however, this paper focuses on the frequency and characterization of events representing the largest deviations from tidal flow. The data record is scrutinized during the passage of significant named storms including Ida (2009), Earl (2010), Irene (2011), Sandy (2012) and Arthur (2014). Storm events can disrupt data flow in observational networks for various reasons. Equipment may suffer damage and the power supply to equipment may be interrupted. Radar station outages and surface current map data quality are evaluated when storms passed through the area. For completely different reasons related to the complexity of the physical forcings, extreme events often present challenges for numerical modeling. An anticipated benefit of this study is that insights gained by describing the important non-tidal episodes may serve as a starting point for future work in analyzing the performance of numerical models and improving predictive capabilities for these events.