Methodology

The real time ocean thermal structure (OTS or depth-temperature profiles) is derived based upon the satellite sea surface height anomaly (SSHA) and sea surface temperature (SST) observations as well as the mixed layer depth (MLD) from the 1D Price-Weller-Pinkel (PWP) mixed layer model.

The depths of 29°C isotherm (D29) to 4°C isotherm (D4), with a 1°C interval, are derived from the satellite altimetry SSHA with linear regressions. The top layer of the OTS is the mixed layer consisted of satellite SST and MLD estimated by PWP model. Here, SSHA used is the up-to-date series near real time daily 1/3° merged, gridded map from AVSIO (http://www.aviso.oceanobs.com). SST used is the real time fusion of the cloud penetrating microwave SST from Remote Sensing Systems (http://www.ssmi.com/).

Regression:

132,881 in situ temperature profiles during the hurricane season (Jun-Nov) collected from Argo (2000-2010), CTD (2000-2010) and XBT (1993-2010) are used to construct the linear regressions of SSHA onto isotherm depth variations.

Use the depth of 20°C isotherm (D20) as an example to demonstrate how the regression is developed. Firstly, in situ ΔD20 is obtained by subtracting the climatological D20 (black profile on the left) from Argo in situ D20 (blue profile on the left). Secondly, pair with collocated and coincident SSHA from altimetry (yellow bar on the left). With numerous pairs of ΔD20 and SSHA (red dots on the right) within the boxes of 10° longitudes by 5° latitudes, a linear regression is developed. In this method, the regression is calculated at each 0.25° grid point and for each isotherm depth (from D29 to D4) with 1°C interval.

MLD from PWP:

Real time daily MLD is generated by PWP model. Climatological temperature and salinity profiles from Generalized Digital Environmental Model (GDEM) are used as initial condition. Wind and heat fluxes from NOGAPS are used to force the PWP model for 15 days to obtain the MLD.