RECOVERING SPATIAL FEATURES IN THE OCEAN - PERFORMANCE OF ISOPYCNIC VS. ISOBARIC ANALYSIS

This study compares the properties of isopycnal and isobaric coordinat e systems as a basis for spatial interpolation of oceanographic observ ations. The effect of 2D interpolation between observations sampled on either isobaric or isopycnal surfaces is investigated using both real and simulated vertical soundings whose locations correspond to CTD ca sts carried out during an intensive survey in the Alboran Sea (western Mediterranean). In the case of hydrographic data, a spatial analysis of 3D features via interpolation on regularly spaced isopycnal surface s is clearly superior to one based on isobaric interpolation within a stably stratified ocean. The isopycnal distribution of geostrophic vel ocity can be derived via interpolation of a Montgomery potential funct ion, sample values of which are easily obtained from hydrographic data . The advantage of isopycnal interpolation of current data appears to be significant only within frontal regions characterized by a pycnocli ne of high static stability separating water masses of relatively low static stability. In regions of more uniform stratification, isobaric spatial interpolation is equally effective in resolving baroclinic fea tures sampled by observed current profile data. (C) 1997 Elsevier Scie nce B.V.