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Shallow ocean response to tropical cyclones observed on the continental shelf of the northwestern S outh C hina S ea
Author(s) -
Yang Bing,
Hou Yijun,
Hu Po,
Liu Ze,
Liu Yahao
Publication year - 2015
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/2015jc010783
Subject(s) - thermocline , geology , stratification (seeds) , tropical cyclone , typhoon , mixed layer , climatology , potential vorticity , oceanography , inertial wave , sea surface temperature , atmospheric sciences , middle latitudes , ocean dynamics , rossby wave , ocean current , vorticity , vortex , meteorology , physics , seed dormancy , mechanical wave , longitudinal wave , botany , germination , quantum mechanics , dormancy , wave propagation , biology
Based on observed temperature and velocity in 2005 in northwestern South China Sea, the shallow ocean responses to three tropical cyclones were examined. The oceanic response to Washi was similar to common observations with 2°C cooling of the ocean surface and slight warming of the thermocline resulted from vertical entrainment. Moreover, the wavefield was dominated by first mode near‐inertial oscillations, which were red‐shifted and trapped by negative background vorticity leading to an e ‐folding timescale of 12 days. The repeated reflections by the surface and bottom boundaries were thought to yield the successive emergence of higher modes. The oceanic responses to Vicente appeared to be insignificant with cooling of the ocean surface by only 0.5°C and near‐inertial currents no larger than 0.10 m/s as a result of a deepened surface mixed layer. However, the oceanic responses to Typhoon Damrey were drastic with cooling of 4.5°C near the surface and successive barotropic‐like near‐inertial oscillations. During the forced stage, the upper ocean heat content decreased conspicuously by 11.65% and the stratification was thoroughly destroyed by vertical mixing. In the relaxation stage, the water particle had vertical displacement of 20–30 m generated by inertial pumping. The current response to Damrey was weaker than Washi due to the deepened mixed layer and the destroyed stratification. Our results suggested that the shallow water oceanic responses to tropical cyclones varied significantly with the intensity of tropical cyclones, and was affected by local stratification and background vorticity.