A regional characterization of the GlobCurrent ocean surface current analysis

Observations of extreme conditions, characterized by high heat flux, rapidly changing surface salinity, or strong ocean current, are rare. Although analyses provide estimates of these conditions, because there are few observations to begin with, it is difficult to separately characterize (in terms of calibration and validation) extreme and typical conditions using independent observations. This requirement of independence may not be so dire, however, if we acknowledge that the impact of observations on an analysis is generally local, as is the propagation of errors in space and time. We propose that temporal extrapolation from outside a typical analysis window permits a calibration and validation by triple collocation (e.g., using only an analysis and available in situ observations; cf. Stoffelen 1998). We seek evidence of analysis performance improvement (as expected) using the calibrations that can be derived. We also seek to validate the GlobCurrent ocean current analysis across an entire current speed range, including at both the low (0.1ms-1) and high (1ms-1) ends.