Finding a proxy for wind stress over the coastal ocean

Abstract

Wind stress forcing is a critical driver of oceanographic processes. In the absence of over-ocean wind measurements, re-analysis products and over-land measurements are often used. The present paper compares a unique wind-data series from an ocean mooring with two re-analysis products and data from six over-land sites in Sydney, Australia, to determine whether these data can infer over-ocean wind conditions. Four oceanographic moorings are located here; however, over-ocean meteorological observations are no longer available. Correlations between over-ocean and over-land sites wind stress were >0.8, whereas for re-analysis products, correlations ranged from 0.28 to 0.72. Re-analysis products were unable to resolve variability at the over-ocean site with periods shorter than 2 days, indicating that they are not appropriate wind proxies for the coastal ocean. Somewhat counter-intuitively, our results showed that proximity of over-land sites to the over-ocean site does not necessarily imply the highest correlation or the lowest error and careful site selection is required. An upwelling study showed that wind observations from selected over-land sites can accurately represent isotherm uplift in the coastal ocean. Threshold wind stress values that uplift isotherms at these over-land sites are provided, along with a recommendation for the use of the over-land site that best represents over-ocean wind conditions in this region.