The Determination Of Ocean Correlation Scales Using Argo Float Data

Abstract

The scales over which ocean properties vary play a critical role in the assimilation of ocean data. Previous studies do not explore these scales in great detail and pre-Argo observations limited investigations to the upper ocean (<500m). In this study Argo data have been used to develop a method of estimating the correlation scales of salinity on depth and potential temperature surfaces to depths of 1600m. Zonal and meridional scales of mean field salinity and salinity anomalies are examined in the Pacific and Atlantic.

Correlation scales are calculated by the fitting of a Gaussian function to the differences in salinity between observation pairs that satisfy given spatial and temporal separation requirements. The intercept and scale that result in the best fit are taken to be the optimum values for the region. The significance of the correlation scale is tested by the calculation of the F-ratio.

Comparisons of the scales show mean field scales to be larger than anomaly field scales. Scales are found to be anisotropic in all cases but anomaly field scales differ in size and pattern between the Pacific and Atlantic. Correlation scales exhibit dependence on latitude and depth with longer scales observed in the tropics and in general, scales shorten with depth down to ?800m and then increase below this. Comparing scales of S(z ) with those of S(?) indicates there is no significant difference between z and ? scales in the Pacific. However, salinity differences on ?-surfaces are lower than on z, linked to the heaving of water masses and the vertical gradient of salinity. Atlantic scales of S(?)prove to be significantly larger than those of S(z ).

Recommendations are made for the use of these correlation scales in assimilation models

More information

Identifiers

Catalogue record

Export record