This study deals with a unusual cooling event after Typhoon Mujigea passed over the northern South China Sea(SCS) in October 2015. We analyze the satellite sea surface temperature(SST) time series from October 3 to 18...This study deals with a unusual cooling event after Typhoon Mujigea passed over the northern South China Sea(SCS) in October 2015. We analyze the satellite sea surface temperature(SST) time series from October 3 to 18,2015 and find that the cooling process in the coastal ocean had two different stages. The first stage occurred immediately after typhoon passage on October 3, and reached a maximum SST drop of –2℃ on October 7 as the usual cold wake after typhoon. The second stage or the unusual extended cooling event occurred after 7d of the typhoon passage, and lasted for 5d from October 10 to 15. The maximum SST cooling was –4℃ and occurred after 12d of typhoon passage. The mechanism analysis results indicate that after landing and moving northwestward to the Yunnan-Guizhou Plateau(YGP), Typhoon Mujigea(2015) met the westerly wind front on October 5. The lowpressure and positive-vorticity disturbances to the front triggered meridional air flow and low-pressure trough,thus induced a katabatic cold jet downward from the Qinghai-Tibet Plateau(QTP) passing through the YGP to the northwestern SCS. The second cooling reached the maximum SST drop 4d later after the maximum air temperature drop of –9℃ on October 11. The simultaneous air temperature and SST observations at three coastal stations reveal that it is this katabatic cold jet intrusion to lead the unusual SST cooling event.展开更多
Daily and weekly sea surface temperature data of Tropical Rainfall Measuring Mission (TRMM) Microwave Imager and Advanced Microwave Scanning Radiometer-Earth Observing System sensors are used as forcing of the underly...Daily and weekly sea surface temperature data of Tropical Rainfall Measuring Mission (TRMM) Microwave Imager and Advanced Microwave Scanning Radiometer-Earth Observing System sensors are used as forcing of the underlying sea surface in the mesoscale numerical model to simulate Typhoon Dujuan that moved across the South China Sea in 2003. The numerical results show that different SSTs near the typhoon center result in differences in the atmospheric wind field, indicating that the model has a fast and obvious response to SSTs. Different SST influences the intensity and track of Dujuan to some degree and has significant impacts on its precipitation and latent heat flux near the eye. The SST influence on Dujuan is mainly fulfilled by changing the latent heat flux between the ocean surface and the atmosphere above.展开更多
The impact of typhoon Kujira(2015)on the ocean environment around Yongxing Island in the South China Sea was observed using multiple-satellite sensors and on-site data.A subsurface buoy and Agro float were located to ...The impact of typhoon Kujira(2015)on the ocean environment around Yongxing Island in the South China Sea was observed using multiple-satellite sensors and on-site data.A subsurface buoy and Agro float were located to the left and lower right of the track of the typhoon.Satellite observations revealed sea surface cooling of up to 2.5℃,a maximum decrease in sea surface salinity of 2 in the main study area because of heavy rain,and increases in the chlorophyll concentration induced by the slow-moving typhoon with a maximum observed instantaneous wind speed of 35.1 m/s.The sea surface temperature to the right of the typhoon track changed more than that on the left owing to a right bias of the typhoon associated with coupling of the typhoon with wind stress on the sea surface.In the ocean interior,there was obvious downwelling at 24.7 m and upwelling at a depth of 35.7 m with the vertical entrainment and agitation of the typhoon,and the ef fects extended to different depths of up to more than 1000 m.When the typhoon passed through the main study area,the maximum flow velocity change at depths of 51 and 660 m was about 0.44 and 0.04 m/s,respectively.The typhoon af fected the flow field to a depth of 660 m as it formed and decayed in 11 h,moved at an average speed of 60 m/h,and af fected the sea surface over a range exceeding 700 km as it moved slowly and stayed at sea for 2 d.Vertical entrainment and agitation generated by the typhoon,as well as rainfall,cooled the sea surface.This inhibited the strengthening of the typhoon,but the energy transmitted to the ocean led to divergence-convergence flow from a shallow to deep layer.展开更多
In this paper, the three-dimensional variational data assimilation scheme (3DVAR) in the mesoscale model version 5 (MM5) of the US Pennsylvania State University/National Center for Atmospheric Research is used to stud...In this paper, the three-dimensional variational data assimilation scheme (3DVAR) in the mesoscale model version 5 (MM5) of the US Pennsylvania State University/National Center for Atmospheric Research is used to study the effect of assimilating the sea-wind data from QuikSCAT on the prediction of typhoon track and intensity. The case of Typhoon Dujuan (2003) is first tested and the results show appreciable improvements. Twelve other cases in 2003 are then evaluated. The assimilation of the QuikSCAT data produces significant impacts on the structure of Dujuan in terms of the horizontal and vertical winds, sea-level pressure and temperature at the initial time. With the assimilation, the 24-h (48-h) track prediction of 11 (10) out of the 12 typhoons is improved. The 24-h (48-h) prediction of typhoon intensity is also improved in 10 (9) of the 12 cases. These experiments therefore demonstrate that assimilation of the QuikSCAT sea-wind data can increase the accuracy of typhoon track and intensity predictions through modification of the initial fields associated with the typhoon.展开更多
基金The National Natural Science Foundation of China under contract Nos 41776034,41476009 and41706025the GASI Project under contract Nos GASI-IPOVAI-01-02 and GASI-02-SCS-YGST2-02+1 种基金the Natural Key Research and Development Program of China under contract No 2016YFC1401403the Foundation of Guangdong Province for Outstanding Young Teachers in University under contract No.YQ201588
文摘This study deals with a unusual cooling event after Typhoon Mujigea passed over the northern South China Sea(SCS) in October 2015. We analyze the satellite sea surface temperature(SST) time series from October 3 to 18,2015 and find that the cooling process in the coastal ocean had two different stages. The first stage occurred immediately after typhoon passage on October 3, and reached a maximum SST drop of –2℃ on October 7 as the usual cold wake after typhoon. The second stage or the unusual extended cooling event occurred after 7d of the typhoon passage, and lasted for 5d from October 10 to 15. The maximum SST cooling was –4℃ and occurred after 12d of typhoon passage. The mechanism analysis results indicate that after landing and moving northwestward to the Yunnan-Guizhou Plateau(YGP), Typhoon Mujigea(2015) met the westerly wind front on October 5. The lowpressure and positive-vorticity disturbances to the front triggered meridional air flow and low-pressure trough,thus induced a katabatic cold jet downward from the Qinghai-Tibet Plateau(QTP) passing through the YGP to the northwestern SCS. The second cooling reached the maximum SST drop 4d later after the maximum air temperature drop of –9℃ on October 11. The simultaneous air temperature and SST observations at three coastal stations reveal that it is this katabatic cold jet intrusion to lead the unusual SST cooling event.
基金Natural Science Foundation of China (U0733002, 40876009)Natural Science Foundation of Guangdong Province (8351030101000002)+1 种基金Science and Technology Planning Project of Guangdong Province (2008B030303025)Tropical Marine Meteorology Science Research Project
文摘Daily and weekly sea surface temperature data of Tropical Rainfall Measuring Mission (TRMM) Microwave Imager and Advanced Microwave Scanning Radiometer-Earth Observing System sensors are used as forcing of the underlying sea surface in the mesoscale numerical model to simulate Typhoon Dujuan that moved across the South China Sea in 2003. The numerical results show that different SSTs near the typhoon center result in differences in the atmospheric wind field, indicating that the model has a fast and obvious response to SSTs. Different SST influences the intensity and track of Dujuan to some degree and has significant impacts on its precipitation and latent heat flux near the eye. The SST influence on Dujuan is mainly fulfilled by changing the latent heat flux between the ocean surface and the atmosphere above.
基金Supported by the National Natural Science Foundation of China(Nos.41576032,41176160)the International Cooperation,CAS,ChineseForeign Cooperation in Key Projects(No.133337KYSB20160002)the National Key R&D Program of China(No.2017YFC1405600)
文摘The impact of typhoon Kujira(2015)on the ocean environment around Yongxing Island in the South China Sea was observed using multiple-satellite sensors and on-site data.A subsurface buoy and Agro float were located to the left and lower right of the track of the typhoon.Satellite observations revealed sea surface cooling of up to 2.5℃,a maximum decrease in sea surface salinity of 2 in the main study area because of heavy rain,and increases in the chlorophyll concentration induced by the slow-moving typhoon with a maximum observed instantaneous wind speed of 35.1 m/s.The sea surface temperature to the right of the typhoon track changed more than that on the left owing to a right bias of the typhoon associated with coupling of the typhoon with wind stress on the sea surface.In the ocean interior,there was obvious downwelling at 24.7 m and upwelling at a depth of 35.7 m with the vertical entrainment and agitation of the typhoon,and the ef fects extended to different depths of up to more than 1000 m.When the typhoon passed through the main study area,the maximum flow velocity change at depths of 51 and 660 m was about 0.44 and 0.04 m/s,respectively.The typhoon af fected the flow field to a depth of 660 m as it formed and decayed in 11 h,moved at an average speed of 60 m/h,and af fected the sea surface over a range exceeding 700 km as it moved slowly and stayed at sea for 2 d.Vertical entrainment and agitation generated by the typhoon,as well as rainfall,cooled the sea surface.This inhibited the strengthening of the typhoon,but the energy transmitted to the ocean led to divergence-convergence flow from a shallow to deep layer.
基金This research was supported by the National Natural Science Foundation of China under Grant No.40333025.
文摘In this paper, the three-dimensional variational data assimilation scheme (3DVAR) in the mesoscale model version 5 (MM5) of the US Pennsylvania State University/National Center for Atmospheric Research is used to study the effect of assimilating the sea-wind data from QuikSCAT on the prediction of typhoon track and intensity. The case of Typhoon Dujuan (2003) is first tested and the results show appreciable improvements. Twelve other cases in 2003 are then evaluated. The assimilation of the QuikSCAT data produces significant impacts on the structure of Dujuan in terms of the horizontal and vertical winds, sea-level pressure and temperature at the initial time. With the assimilation, the 24-h (48-h) track prediction of 11 (10) out of the 12 typhoons is improved. The 24-h (48-h) prediction of typhoon intensity is also improved in 10 (9) of the 12 cases. These experiments therefore demonstrate that assimilation of the QuikSCAT sea-wind data can increase the accuracy of typhoon track and intensity predictions through modification of the initial fields associated with the typhoon.
