Prediction of Gas Exchange Rate Using Microwave Backscatter From the Ocean Surface

Radar backscatter from the surface of the ocean is proving to be useful in establishing a relationship between sea surface roughness and gas transfer velocity. This is possible because radar wavelengths fall in the same centimetric range as surface waves that promote near surface turbulence that drives gas exchange. We have established two algorithms that link a field-based relationship between gas transfer velocity and mean square slope of the capillary wave field to a relationship between mean square slope and radar backscatter. The first algorithm exploits specular scattering of altimeter microwave pulses by the sea surface. The second algorithm involves Bragg scattering of microwave signals from a scatterometer. We will briefly review these algorithms, their uses and drawbacks, and insights they provide about the global distribution of gas transfer velocity.