Abstract
Two remote sensing methods, satellite altimetry and 4D-Var assimilation of satellite imagery, are used to compute surface velocity fields in the Black Sea region. Surface currents derived from the two methods are compared for several cases with intense mesoscale and large-scale dynamics during low wind conditions. Comparison shows that the obtained results coincide well quantitatively and qualitatively. However, satellite imagery provides more reasonable results on the spatial variability of coastal dynamics than altimetry data. In particular, this is related to the reconstruction of eddy coastal dynamics, such as Black Sea near-shore anticyclones. Current streamlines in these eddies are not closed near the coast in altimetry data, which we relate to the extrapolation during mapping procedure in the absence of coastal along-track measurements. On the other hand, in offshore areas, imagery-derived currents can be underestimated due to the absence of thermal contrasts and smoothing during the procedure of the 4D-Var assimilation. Wind drift currents are another source of inconsistency, as their impact is directly observed in satellite imagery but absent in altimetry data. The advantage of the 4D-Var method for reconstructing coastal dynamics is used to compute surface currents in the Marmara Sea on the base of 250 m resolution Modis optical data. The results reveal the very complex dynamics of the basin, with a large number of mesoscale and sub-mesoscale eddies. 4D-Var assimilation of Modis imagery is used to obtain information about dynamic characteristics of these small eddies with radiuses of 4–10 km.
Highlights
Current velocity is an essential parameter for studying large-scale and mesoscale ocean dynamics, estimating heat and salt transport, and other important oceanographic tasks
Six cases were chosen for the comparison of current velocity reconstructed from satellite imagery and altimetry measurements: two with mesoscale eddies; two with complex mesoscale dynamics; and two basin-scale examples
Two different methods based on spaceborne measurements, satellite altimetry sea level measurements and 4D-Var analysis of IR image series, were used for surface current computation in the Black Sea basin
Summary
Current velocity is an essential parameter for studying large-scale and mesoscale ocean dynamics, estimating heat and salt transport, and other important oceanographic tasks. Altimetry measurements by satellites have allowed, for the first time in the history of oceanography, to determine the geostrophic circulation of the world ocean, almost in real time [1,2]. These data are widely used in different oceanographic studies, which provide a lot of new insights about large and mesoscale ocean dynamics all over the world [3,4,5].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
