Complex empirical orthogonal functions analysis of ERS-1 and TOPEX/POSEIDON combined altimetric data in the region of the Algerian current

摘要: Maps of sea level anomalies (SLA) relative to the 1993 annual mean combine data from two altimetric missions, ERS-1 and TOPEX/POSEIDON, during overlap period (October 1992 December 1993). These regular maps in space time residual every 10 days on a 0.2° grid are used region Algerian current where mesoscale eddies primary importance circulation all Mediterranean water masses. They first compared with along-track scanning radiometer surface temperature images get information anticyclonic produced by instabilities visible both infrared sets. Then, an analysis complex empirical orthogonal functions (CEOFs) is performed SLA set see correlation different dynamic features observed variability. The CEOF applied series formed original their Hubert transforms separate variability into spatially coherent modes. correlated signal study area (0–15°E 35°–40°N) was found be dominated CEOFs. modes explain nearly 85% variability, 80% total variance for one 5% second one. temporal phase mode indicates that constant frequency cycle per year clearly dominant, corresponding seasonal signal. strongest amplitude obtained southern part channel Sardinia south Strait Sicily. show periodicity about 6 months which appears associated as isolines parallel path along coast. located near African coast at ∼4°E 8°E. points high could correspond eddy detachments main current.