Surface Circulation off California: a Decade of HF Radar Observations.

High-frequency and spatially extensive observation of surface circulation with HF Radar has come of age in recent decades. This is nowhere more obvious than in California, where the State funded a statewide array that was completed in 2006 (now maintained through IOOS). While longer records off Monterey Bay, Santa Barbara, Bodega Bay and San Diego preceded this continuous long-range network, and higher resolution clusters are nested within the long-range array, a decade of statewide coverage has provided an unprecedented view of coastal circulation in a region characterized by upwelling oceanography. This adds additional value to the evident benefits already derived from real-time data that have been used in search and rescue, oil spill response, wastewater operations and more.

The spatio-temporal extent of the data combined with high-resolution in both time and space can be used to explore mean fields, seasonal/interannual/tidal variability, spatial features, temporal events, and propagating waves. In this paper, we describe the large-scale circulation off California, resolving a seasonal climatology and regional flow patterns. In turn this allows us to identify anomalies in space and time. Attention is given to mesoscale eddies, jets and meanders as well as to seasonal anomalies, and short-lived events. In conclusion, we comment on the challenges of collating and QC/QA of such a large data set – as well as on the past/future use of these data in numerical modeling and in addressing key ecological and environmental questions.