Abstract
The upper ocean thermodynamic and biological responses to two sequential tropical cyclones (TCs) over the Northwestern Pacific Ocean were investigated using multi-satellite datasets, in situ observations and numerical model outputs. During Kalmaegi and Fung-Wong, three distinct cold patches were observed at sea surface. The locations of these cold patches are highly correlated with relatively shallower depth of the 26 °C isotherm and mixed layer depth (MLD) and lower upper ocean heat content. The enhancement of surface chlorophyll a (chl-a) concentration was detected in these three regions as well, mainly due to the TC-induced mixing and upwelling as well as the terrestrial runoff. Moreover, the pre-existing ocean cyclonic eddy (CE) has been found to significantly modulate the magnitude of surface cooling and chl-a increase. With the deepening of the MLD on the right side of TCs, the temperature of the mixed layer decreased and the salinity increased. The sequential TCs had superimposed effects on the upper ocean response. The possible causes of sudden track change in sequential TCs scenario were also explored. Both atmospheric and oceanic conditions play noticeable roles in abrupt northward turning of the subsequent TC Fung-Wong.
Highlights
Tropical cyclones (TCs), which are among the most devastating natural disasters, pose significant threat on the lives and property of global coastal regions [1]
It is well recognized that the magnitude and spatial distribution of Sea surface temperature (SST) decrease and chl-a enhancement mainly depend on the intensity and translation speed of TCs and the background ocean environments, such as the mixed layer depth (MLD) and mesoscale eddies, as well as topography [2,13,14,15,16]
This study aims to explore the thermodynamic and biological responses of the upper ocean to two sequential TCs over the Northwestern Pacific Ocean (NWP) in 2014 and reveal the possible causes leading to the sudden track change of the subsequent TC in this scenario
Summary
Tropical cyclones (TCs), which are among the most devastating natural disasters, pose significant threat on the lives and property of global coastal regions [1]. When two or more TCs exist simultaneously in the same region, it becomes much more difficult to forecast their tracks [27,28] Previous studies suggested both atmospheric and oceanic factors could affect the forecast accuracy of the TC by influencing its motion and intensity, such as western North Pacific subtropical high (WNPSH), the environmental flow, SST and upper ocean heat content (UOHC) [29,30,31,32,33]. How these factors contribute to the sudden track change in sequential TCs scenario has been seldom systematically investigated.
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