Satellite-derived Ocean Thermal Structure for the North Atlantic Hurricane Season
Iam-Fei Pun, National Central University, Graduate Institute of Hydrological and Oceanic Sciences, Taoyuan, Taiwan, James Price, Woods Hole Oceanographic Inst, Woods Hole, MA, United States and Steven R Jayne, Woods Hole Oceanographic Institution, Physical Oceanography, Woods Hole, MA, United States
Abstract:
This paper describes a new model (method) called SNAP (Satellite-derived North Atlantic Profiles) that seeks to provide a high resolution, near real-time ocean thermal field to aid TC forecasting. The heart of the method is a regression of sea surface height anomaly upon the depth of ocean isotherms. Using about 139000 profiles from Argo floats and historical in situ observations, a spatially-dependent regression model is developed for the North Atlantic Ocean during the hurricane season, June to November. A new step introduced in this work is that the daily mixed layer depth (MLD) is derived from the output of a one-dimensional Price-Weller-Pinkel ocean mixed layer model with time-dependent wind and radiation forcing. The surface layer temperature and thickness of a SNAP temperature profile is a satellite-observed sea surface temperature and this model-computed MLD.
The accuracy of SNAP is assessed by comparison to 10761 independent Argo profiles from the hurricane seasons of 2011 and 2012. The root-mean-squared differences (RMSDs) of the SNAP-estimated isotherm depths are found to be 10-20 m for upper thermocline isotherms (29°C to 20°C), 35-55 m for middle isotherms (18°C to 11°C), and 60-90 m for lower isotherms (6°C to 4°C). The primary error sources for SNAP-derived isotherm depths include SSHA uncertainty, high frequency fluctuations of isotherm depths, salinity effects and the barotropic component of SSHA. These account for roughly ~29%, ~25%, ~19% and ~10% of the overall estimated isotherm depth errors, respectively. The RMSDs of TC-related ocean parameters, upper ocean heat content and averaged temperature of the upper 100 m, are ~10 kJ cm-2 and ~0.82°C, respectively.
