NOAA Operational Satellite Derived Oceanic Heat Content Products

In September 2012, the National Oceanic and Atmospheric Administration (NOAA) and the National Environmental Satellite, Data, and Information Service (NESDIS) began providing a suite of operational satellite derived ocean heat content (OHC) measurements. The satellite derived OHC is a measure of the integrated vertical temperature from the sea surface to the depth of the 26°C isotherm including the surface mixed layer.  The product is computed from altimeter-derived isotherm depths in the upper ocean relative to 20°C based on a daily climatology from the World Ocean Atlas (WOA) and Global Digital Elevation Model (GDEM) cast within a 2.5 layer ocean model. Product generation requires data from at least two satellite altimeters and the daily Sea Surface Height Anomaly updates from the U.S. Navy Altimeter Processing System.

In the present model, the OHC estimates are calculated from 5 km resolution sea surface temperatures (SST) obtained from NESDIS GEO-POLAR Blended SST Analyses (Harris and Maturi, 2012) combined with Jason-2, SARAL and Cyrosat-2 altimeter estimates of the 20°C and 26°C isotherm depths; the altimeter estimates are derived from a scheme using a daily ocean climatology of mean isotherm depths and reduced gravities. Based on a mean ratio between the 20°C and 26°C isotherm depths, the depth of the 26°C isotherm and the ocean mixed layer depth are inferred. By integrating the 26°C isotherm depth to the surface (where SST is the surface boundary condition) an OHC is calculated. The product fields are evaluated monthly when thermal structure data from various ocean data collection platforms become available (e.g.  Argo floats, XBT transects, mooring measurements, and airborne profiling from NOAA research aircraft).

Satellite derived OHC is currently produced operationally for the North Atlantic, North Pacific, and South Pacific. A suite of Ocean Heat Content Products are planned for the North and South Indian Oceans.

As new altimeters are available, they will be incorporated into the Oceanic Heat Content algorithm for product generation.