The upper ocean environment responses to typhoon Prapiroon (2012)

摘要

Satellite-observed daily sea level anomaly (SLA), sea surface temperature (SST) and sea surface salinity (SSS) are used to determine the impact of the typhoon Prapiroon (2012) on the sea surface. The typhoon, Prapiroon, has a unique track when it went through the area (126°E-133°E, 17°N-25.5°N), where it influenced the sea greatly. For example, the lowest SST in this area was 25.2℃ on October 8 before it entered, while the SST dropped to 20.7 ℃ on October 15. On the other hand, the lowest SLA dropped from -20 cm (on October 8) to -53 cm (on October 29). Accompanied with this, the SSS increased about 0.8-0.9 psu in some region. This is qualitative but quantitative agree with the Argo data of 0.2 psu SSS increase. One possible reason is the precipitation of typhoon, as the SSS data by Aquarius are easily affected by precipitation. And such significant SST cooling and SSS increasing were mainly due to vertical mixing, caused by long-term strong wind stirring brought by Parpiroon. We find that both the cold patch and eddies were transported westward. The horizontal advection took the cold water to 100 km away, this non-local effect could have notable impact on ocean dynamics and bio-physical processes. In addition we analyzed the possible factors of the temperature and salinity decreasing below the thermocline by calculating the Ekman pumping velocity due to the typhoon. It reveals that this is caused by Ekman pumping and upwelling in the cyclonic eddy, and Ekman pumping is the main factor.