Daily Coastal Upwelling Index Derived from Modis Sst Data and Surf Zone Thermistors

Upwelling indices are commonly calculated using wind stress measurements [1]. They describe the physical process which causes upwelling but may not accurately predict the presence or absence of cold, nutrient rich, upwelled water reaching the surf zone. Cold, nutrient-rich, upwelled water plays an important role in surf zone ecosystems and therefore needs to be quantified. Here a daily coastal upwelling index is defined and calculated for 5 years of data from 8 sites along the west coast of South Africa. The indices of 2 sites are additionally compared to offshore temperature moorings to study stratification changes during upwelling and relaxation.