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Uncertainties in Climatological Seawater Density Calculations
Author(s) -
Dai Hao,
Zhang Xining
Publication year - 2018
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/2017jc013427
Subject(s) - seawater , anomaly (physics) , environmental science , salinity , temperature salinity diagrams , representative concentration pathways , correlation coefficient , work (physics) , measurement uncertainty , range (aeronautics) , meteorology , climatology , geology , climate change , climate model , physics , mathematics , thermodynamics , oceanography , materials science , statistics , composite material , condensed matter physics
In most applications, with seawater conductivity, temperature, and pressure data measured in situ by various observation instruments e.g., Conductivity‐Temperature‐Depth instruments (CTD), the density which has strong ties to ocean dynamics and so on is computed according to equations of state for seawater. This paper, based on density computational formulae in the Thermodynamic Equation of Seawater 2010 (TEOS‐10), follows the Guide of the expression of Uncertainty in Measurement (GUM) and assesses the main sources of uncertainties. By virtue of climatological decades‐average temperature/Practical Salinity/pressure data sets in the global ocean provided by the National Oceanic and Atmospheric Administration (NOAA), correlation coefficients between uncertainty sources are determined and the combined standard uncertaintiesu c ( ρ )in seawater density calculations are evaluated. For grid points in the world ocean with 0.25° resolution, the standard deviations ofu c ( ρ )in vertical profiles cover the magnitude order of 10 −4 kg m −3 . Theu c ( ρ )means in vertical profiles of the Baltic Sea are about 0.028kg m −3 due to the larger scatter of Absolute Salinity anomaly. The distribution of theu c ( ρ )means in vertical profiles of the world ocean except for the Baltic Sea, which covers the range of( 0.004 , 0.01 )kg m −3 , is related to the correlation coefficient r ( S A , p )between Absolute SalinityS Aand pressure p . The results in the paper are based on sensors' measuring uncertainties of high accuracy CTD. Larger uncertainties in density calculations may arise if connected with lower sensors' specifications. This work may provide valuable uncertainty information required for reliability considerations of ocean circulation and global climate models.