Effects of eddies on Bay of Bengal cyclone intensity

Abstract

Predicting cyclone intensities in the Indian Ocean has been a challenging problem. Because of the highly varying bathymetry of the Indian coast, even a slight error in the prediction of landfall point and intensity can lead to a totally different storm surge height. Though capabilities of cyclone track prediction have significantly improved during recent years, cyclone intensity forecasts still need improvement. Various dynamical and statistical models have different rates of success for cyclone intensity prediction. In addition to atmospheric parameters and sea surface temperature (SST), another important parameter that enhances the understanding of the intensification of the cyclones is the upper ocean heat storage that is generally reflected in the oceanic eddies and dynamic topography. Sea surface height anomalies (SSHAs) from radar altimeters can provide information on this parameter. The relationship between the SSHAs and the associated hydrographic structure, particularly of eddies, is discussed by Ali et al. [1998], Gopalan et al. [2000], Babu et al. [2003], and Gopalakrishna et al. [2003]. Because of these changes in hydrographic features caused by SSHAs, warm (cold) core oceanic eddies have more (less) heat content compared with their surroundings.

Multidecadal Variability of Tropical Cyclone Rapid Intensification in the Western North Pacific

“…Recently, tropical cyclone heat potential (TCHP), which represents ocean heat content in water warmer than 268C, has been shown to reduce the error in intensity forecasts of tropical Atlantic hurricanes when used as a predictor in statistical prediction methods (e.g., Mainelli et al 2008;Goni et al 2009). Most of the major category 4 or 5 TCs in various basins have been found to rapidly intensify over regions of high TCHP associated with warm eddies or the thick and warm mixed layer (e.g., Shay et al 2000;Lin et al 2005Lin et al , 2008Lin et al , 2009aAli et al 2007;Rozoff and Kossin 2011). In regions of high freshwater input where significant salinity stratification sets in within a deep isothermal layer, a barrier layer between the base of the isothermal layer and the base of the mixed layer can appears.…”

A GIS Study of the Influences of Warm Ocean Eddies on the Intensity Variations of Tropical Cyclones in the South China Sea

“…When a TC encounters a warm ocean eddy, the upper-ocean mixed layer of the warm ocean eddy tends to prevent the cold water beneath from upwelling; consequently, the sea surface temperature does not drop as significantly as in areas lacking warm ocean eddies. Such an effect has been identified from both observation data and from the results of numerical experiment [12,13,18,19,[22][23][24][25][26][27][28][29]. For example, as Hurricane Opal swept across the Gulf of Mexico, post-storm sea surface temperatures (SST) fell by approximately 0.5 • C and 2 • C in the areas with and without warm ocean eddies, respectively.…”

Importance of Ocean Heat Content for Cyclone Studies

“…Incidentally, there was a strong anticyclonic eddy in the western Arabian Sea, which has more heat content compared to the surroundings. Ali et al [9] examined the effect of this eddy on the unusual westward movement of this cyclone. They linearly converted the SSHA to SST and used these SST values in the Mesoscale Model (MM5).…”

“…Satellite altimeters can provide SSHA to a required accuracy. Ali et al [9] estimated sub-surface temperature profiles from dynamic height (considering as a proxy to SSHA) and other surface parameters. Recently Pun et al [10] used altimeter derived SSHA to estimate the subsurface thermal structure for cyclone studies.…”