Remote sensing of river and ocean surface currents

Vast amounts of energy (heat and momentum) and chemical constituents are moved about within ocean and river currents. In the case of deep ocean currents, some reasonable estimates of this transport can be derived from models and sea surface altimetry data. River flows can be estimated from river channel models and indirectly from stage/discharge relationships. However, much of what we know with some measure of accuracy about river and ocean currents is derived from in situ measurements. Current meters are the usual choice for obtaining direct observations of the current profiles with depth. Obtaining such profiles using some form of remote sensing is a technological challenge. Surface currents, on the other hand, are more attractive targets for non-contact monitoring. However, useful relationships between the surface motion and the deeper motions are problematic with confounders including wind stress and/or density stratification. In spite of these impediments, there may indeed be some useful information derivable from observations limited to the surface motions of the oceans or rivers, particularly if observations can be obtained with high spatial and temporal density. This paper looks at the possibility of measuring surface currents using airborne and space-based Doppler lidars.