Methodology
The close relationship that exists between the dynamic height and the mass field of the ocean allows these two parameters to be used within a two-layer reduced gravity ocean model to monitor the upper layer thickness (Goni et al., 1996), which is defined in this study to go from the sea surface to the depth of the 20.C isotherm. This isotherm is chosen because it lies within the center of the main thermocline and is often used as an indicator of the upper layer flow in the western tropical Atlantic and Gulf of Mexico waters. Although there are other factors controlling the sea height anomaly, it is assumed here that most of its variability is due to changes in the depth of the main thermocline and of barotropic origin. The tropical cyclone heat potential, is defined here as a measure of the integrated vertical temperature from the sea surface to the depth of the 26.C isotherm. This parameter is computed from the altimeter-derived vertical temperature profiles estimates in the upper ocean. The temperature profiles are estimated using four points: (a) the sea surface temperature obtained from the Tropical Rainfall Measuring Mission's (TRMM) Microwave Imager (TMI) fields, (b) the altimeter-estimates of the 20.C isotherm within a two-layer reduced gravity scheme (Goni et al, 1996), (c) the depth of the 26.C isotherm from a climatological relationship between the depths of the 20.C and 26.C isotherm.
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In this page, we present five daily maps: sea height anomalies, sea surface temperature, altimeter-estimate of the depth of the 26.C and 20.C isotherms and tropical cyclone heat potential.
The sea height anomaly represents the deviation of the sea height with respect to its mean. Sea height anomaly fields from three altimeters, JASON-1, ERS-2 and GFO, are used in this analysis. For analysis and corrections of altimeter data, please refer to: Cheney et al, TOPEX/POSEIDON:
The 2-cm Solution, J. Geophys. Res., 99, 24555-24564, 1994. The tropical cyclone heat potential, is a measure of the integrated vertical temperature between the sea surface temperature and the estimate of the depth of the 26.C isotherm (Shay et al., 2000).
These maps can be used to identify warm anticyclonic features, usually characterized by sea height anomalies and a depth of the 26.C isotherm larger than their surrounding waters; and to monitor regions of very high (usually larger than 90 kJ cm-2) tropical cyclone heat potential.
These regions have been associated with the sudden intensification of tropical cyclones.