Global Drag-Coefficient Estimates From Scatterometer Wind and Wave Steepness

A neural-network model was developed to retrieve the wave steepness (delta), which was used to represent the sea state (particularly wave state), from the European Remote Sensing (ERS) scatterometer onboard ERS-1/2. Using the retrieved delta and scatterometer wind speed, we calculated and examined the drag coefficient (C-D) over the global ocean. The results show that C-D changes significantly when wave steepness is included in the calculation. Combining wave steepness and wind speed increases C-D by nearly 14% on average. That change is spatially variable, ranging from -18.76% for the tropical Eastern Pacific Ocean to 104% for the Southern Ocean.A neural-network model was developed to retrieve the wave steepness (delta), which was used to represent the sea state (particularly wave state), from the European Remote Sensing (ERS) scatterometer onboard ERS-1/2. Using the retrieved delta and scatterometer wind speed, we calculated and examined the drag coefficient (C-D) over the global ocean. The results show that C-D changes significantly when wave steepness is included in the calculation. Combining wave steepness and wind speed increases C-D by nearly 14% on average. That change is spatially variable, ranging from -18.76% for the tropical Eastern Pacific Ocean to 104% for the Southern Ocean