Estimation of velocity elds at the estuary—coastal interface through statistical analysis of successive airborne remotely sensed images

Abstract. The study of surface water velocity elds through in situ sampling is intrinsically diYcult because they are highly variable in time and space. With airborne remote sensing, however, it is possible to determine changes in velocity elds because spatially and temporally comprehensivedata may be obtained. This letter shows how changes in the statistical properties of successive remotely sensed images may be used to estimate velocity vectors associated with chlorophyll-a and sea surface temperature (SST). The study area is Kirkcudbright Bay, a small estuary in south-west Scotland. Multi-temporal imagery of the study area were acquired by the NERC DaedalusADDS-1268Airborne ThematicMapper (ATM) and processed to show chlorophyll and thermal indices as substitutes for chloro-phyll-a and SST. Velocity elds were estimated by the Maximum Cross Correlation technique. Complex patterns were found, con rming that the com-prehensive coverage provided by airborne remote sensing is required for their analysis. The chlorophyll-a velocity eld diVered from the SST velocity eld, suggesting that these elds are relevant to the water quality variable in question, and not necessarily the water body itself. 1