SEASONAL TEMPERATURE AND SALINITY FIELDS IN THE MEDITERRANEAN-SEA - CLIMATOLOGICAL ANALYSES OF A HISTORICAL DATA SET

Climatological analyses of a historical data base have been carried ou t with the aim of reconstructing the three-dimensional temperature and salinity fields in the Mediterranean Sea. Seasonal and monthly distri butions of hydrographic properties have been computed by a variational inverse method as an alternate to the standard Gandin (1969; Objectiv e analysis of meterological fields, Israeli Program for Scientific Tra nslation, Jerusalem) procedure. The spline solutions of the minimizati on problem are demonstrated to be numerically and theoretically equiva lent to field estimates obtained by conventional objective analysis. T he application of a finite-element technique allows analysis to be per formed in the model space rather than in the observational space, whic h substantially improves the numerical efficiency of the procedure. Th e parameters of the scheme are adjusted according to the statistics of the climatological data. The results,realized as gridded data sets (h orizontal resolution of 0.25 degrees), show some trends in seasonal va riability affecting the properties of water masses. As expected, the u pper layer is subject to a well-defined seasonal signal affecting both the temperature and salinity fields. Error maps, reflecting the degre e of uncertainty in the analyses, have been systematically produced. T he present work is conceived as a basic support to more advanced studi es such as diagnostic calculations, initialization of dynamical models , assimilation of hydrological data into primitive equation models, or planning of experimental surveys. New versions of the climatological fields will be released as data are added to the historical data base. Copyright (C) 1996 Elsevier Science Ltd.