Applicability of T-S algorithms to the Canary Islands region

A Marrero-Díaz,P Sangrà,J L Pelegrí,A Rodríguez-Santana

doi:10.3989/scimar.2001.65s1195

Abstract

The high cost of oceanographic cruises often makes it advisable to use opportunity vessels for simple measurements, such as determining the temperature of the water column with expandable bathythermographs (XBT). In this work we examine the goodness and reliability of a method aimed at obtaining the maximum possible information from XBT data, and we apply it to the Canary Islands region. It consists in calculating analytic relations between temperature and salinity from historical conductivity-temperature-depth (CTD) data for the region, which are then used to hindcast/forecast the salinity and density distribution, as well as the distribution of other inferred quantities such as velocity. A hindcasting is carried out using direct independent temperature measurements obtained from a hydrographic cruise south of the island of Gran Canaria. At depths greater than 100-150 m the results show good agreement with the calculations obtained from CTD in situ data.

Highlights

When designing a hydrographic cruise we must take into account different logistic aspects, such as the cost of ship operation and the necessity of fast measurements in regions where the oceanographic structures change rapidly in time
These fast measurements at a relatively low cost can usually be done from opportunity vessels
In this work we further examine MarreroDíaz et al.’s (1997) method in order to asses its applicability for calculating density as well as other derived quantities such as dynamic height and geostrophic velocity, and to provide estimates for the relative errors involved in the calculations

Summary

Introduction

When designing a hydrographic cruise we must take into account different logistic aspects, such as the cost of ship operation and the necessity of fast measurements in regions where the oceanographic structures change rapidly in time. These fast measurements at a relatively low cost can usually be done from opportunity vessels. The sort of instrumentation used from this type of ship, is usually very limited because it cannot be expensive and its operation must be either automatic or fairly simple. The development of new techniques and instruments must come together with the advance of methodologies for checking the reliability and usefulness of these measurements.

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Methods

Results