2. Ocean initialization in the GFDL/URI coupled hurricane prediction system
a. Overview of the feature-based modeling procedure
The feature-based modeling procedure used as part of the GFDL model ocean initialization is described in detail by Falkovich et al. (2005) and references therein. Therefore, only a brief summary of the procedure is presented here, with new improvements described in more detail in the next section. The basic premise of the procedure is that major oceanic fronts in the Atlantic basin, namely the Gulf Stream (GS) and LC, are poorly represented by the GDEM climatology’s temperature and salinity fields. By defining the spatial structure of these fronts using historical observations gathered from various field experiments, as discussed in section 3 of Falkovich et al. (2005), cross-frontal “sharpening” of the GDEM temperature and salinity fields can be performed to obtain more realistic fields. In addition, an algorithm was developed to initialize the GS and LC with prescribed paths (see their section 4), which may be derived from real-time observations. In the GoM, once the LC path is defined, the GDEM temperature profiles along the center line between the two LC branches are replaced with a more accurate temperature profile (hereafter LCPROFILE); by default, the GDEM temperature profile near 21°N, 83°W in the Caribbean Sea is used to define LCPROFILE because the LC water originates from the Caribbean. Cross-frontal sharpening is then performed between these center-line profiles and the surrounding Gulf of Mexico temperature profiles. This version of the LC initialization procedure provides the basis for the new improvements that are described in the next section.