Development of the SMARTS Climatology for Upper Ocean Thermal Structure Estimation

A new oceanic climatology to estimate upper ocean thermal structure was developed for application year-round in the North Atlantic Ocean basin. The Systematically Merged Atlantic Regional Temperature and Salinity (SMARTS) Climatology blends temperature and salinity fields from the World Ocean Atlas 2001 and Generalized Digital Environmental Model v.3.0 at 1/4º resolution for use in a two-layer model to project sea surface height anomalies (SSHA) into the vertical. This higher resolution better resolves features in the Gulf of Mexico (GOM), including the Loop Current (LC) and eddy shedding field, than the previous coarser 1/2º products of previous studies. Daily mean isotherm depths of the 20ºC (D20) and 26ºC (D26), reduced gravity, and mixed layer depth (MLD) were extracted from the climatology and provide the physical parameters needed for the projection of SSHAs into the vertical. The algorithm for estimation of ocean temperature structure was advanced by an improved characterization of the reduced gravity term and an updated objective analysis scheme.

Using SMARTS with satellite-derived SSHA and SST fields, daily values of D20, D26, MLD, and Ocean Heat Content (OHC) were calculated from 1998 to 2010 using a two-layer model approach. OHC is an import scalar when determining the ocean's impact on tropical cyclone intensification, as OHC is an important predictor of sea surface temperature cooling during hurricane passage, controlling the magnitude of air-sea enthalpy fluxes. Airborne and ship-deployed eXpendable BathyThermographs (XBT), long-term moorings, and Argo profiling floats provided the in-situ data necessary to assess SMARTS estimates of isotherm depths and OHC. Based on over 45,000 temperature profiles of in-situ data from 1998 to 2010, a clear, direct relationship emerged from the detailed analysis between satellite-derived and in-situ measurements of isotherm depths and OHC. The SMARTS Climatology significantly improved upper ocean estimates of temperature structure and minimized a large positive OHC bias in the GOM.