The impact of typhoon "Phanfone" on hydrological characteristics and ecological environment of the upper ocean in the South China Sea
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Abstract
Based on Hybrid Coordinate Ocean Model (HYCOM) data and Moderate Resolution Imaging Spectroradiometer (MODIS) sensor data, we studied the impact of typhoon Phanfone on local surface temperature, chlorophyll-a concentration, vertical thermohaline structure, and ocean current in the South China Sea. Results show that in the typhoon event, wave height increased to 9 m and the velocity of surface current increased from 0.3 to 0.7 m/s, and reached the maximum of 1.8 m/s. After the typhoon passage, the sea surface temperature (SST) decreased from 25.8 ℃ to 24.9 ℃. The mixed layer depth increased by 15 m from 23 m to 38 m. In the upper part of the mixed layer, temperature decreased and the salinity slightly increased, while in the lower part, the opposite. The flow velocity of vertical layer increased with the direction deflection of nearly 90°, and the variation range of the flow velocity decreased gradually from the surface to the bottom. The chlorophyll-a concentration did not increase timely after the typhoon passage. As temperature and light were decreased during the typhoon, nutrients added by enhanced vertical mixing were not fully utilized by phytoplankton, resulting in a slightly increase in chlorophyll-a concentration three days after the passage of the typhoon Phanfone.
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