The Sea Surface Height Anomaly (SSHA) from the TOPEX/Poseidon altimeter data in 1994 is assimilated into a high-resolution model of the South China Sea (SCS) with nudging method. The model results can reveal the seaso...The Sea Surface Height Anomaly (SSHA) from the TOPEX/Poseidon altimeter data in 1994 is assimilated into a high-resolution model of the South China Sea (SCS) with nudging method. The model results can reveal the seasonal variations of SSHA and its time-space migration characters,at the same time,verify the effect of assimilation.Compared with non-assimilation results,assimilation results can show the seasonal variations of SSHA better,particularly in winter.Futhermore,it can distinguish temporal-spatial migration characters of SSHA clearly,i.e. cold signal of SSHA in northern SCS propagating westward and warm signal of SSHA in central SCS propagating eastward.It shows that as an easy and effective method,data assimilation of the SSHA with nudging method could make the simulated results closer to the available observations.展开更多
Previous study comes to the conclusion: based on the anomalies of the South Asian high (SAH), 100-hPa geopotential height, and 100-hPa circulation over tropical and subtropical regions, we can predict precipitation...Previous study comes to the conclusion: based on the anomalies of the South Asian high (SAH), 100-hPa geopotential height, and 100-hPa circulation over tropical and subtropical regions, we can predict precipitation anomaly in the Yangtze River Valley and North China. To test its validity, a series of experiments have been designed and operated, which include controlled experiment, sensitivity experiment (which has added anomalies into 100-hPa geopotential height and wind field), and four-composite experiments. Experiments based on the composed initial field such as EPR-CF, EPR-CD, EPR-HF, and EPR-HD, can reproduce the floods or droughts in the Yangtze River Valley and North China. It suggests that anomalies of the SAH, 100- hPa geopotential height, and circulation over tropical and subtropical regions may probably imply summer precipitation anomalies in the two regions. Sensitivity experiment results show that anomalies of the SAH, 100-hPa geopotential height, and southwest flow in the previous period is a signal of droughts or floods for the following summer in the Yangtze River Valley and North China. And it is also one of the factors that have impact on summer precipitation anomaly in the two regions. Positive anomaly of 100-hPa geopotential height and the anomalous intensifying of the SAH and southwest flow will induce floods in the Yangtze River Valley and droughts in North China; while negative anomaly of 100-hPa geopotential height and anomalous weakening of the SAH and southwest flow will induce droughts in the Yangtze River Valley and floods in North China.展开更多
Category 5 typhoon Megi was the most intense typhoon in 2010 of the world. It lingered in the South China Sea (SCS) for 5 d and caused a significant phytoplankton bloom detected by the satellite image. In this study...Category 5 typhoon Megi was the most intense typhoon in 2010 of the world. It lingered in the South China Sea (SCS) for 5 d and caused a significant phytoplankton bloom detected by the satellite image. In this study, the authors investigated the ocean biological and physical responses to typhoon Megi by using chlorophyll-a (chl-a) concentration, sea surface temperature (SST), sea surface height anomaly (SSHA), sea surface wind measurements derived from different satellites and in situ data. The chl-a concentration (〉3 mg/m3) increased thirty times in the SCS after the typhoon passage in comparison with the mean level of October averaged from 2002 to 2009. With the relationship of wind stress curl and upwelling, the authors found that the speed of upwelling was over ten times during typhoon than pre-typhoon period. Moreover, the mixed layer deepened about 20 m. These reveal that the enhancement of chl-a concentration was triggered by strong vertical mixing and upwelling. Along the track of typhoon, the maximum sea surface cooling (6-8~C) took place in the SCS where the moving speed of typhoon was only 1.4-2.8 m/s and the mixed layer depth was about 20 m in pre-typhoon period. However, the SST drop at the east of the Philippines is only 1-2~C where the translation speed of typhoon was 5.5-6.9 m/s and the mixed layer depth was about 40 m in pre-typhoon period. So the extent of the SST drop was probably due to the moving speed of typhoon and the depth of the mixed layer. In addition, the region with the largest decline of the sea surface height anomaly can indicate the location where the maximum cooling occurs.展开更多
Satellite-tracked drifting buoy data and altimetry data are used to study the active vortex field to the west of Big Island. A pair of vortexes were observed at the trajectory of buoy in 1995. The westward propagation...Satellite-tracked drifting buoy data and altimetry data are used to study the active vortex field to the west of Big Island. A pair of vortexes were observed at the trajectory of buoy in 1995. The westward propagation of the vortex pair is studied in detail by reproducing the loops of each vortex. The orbital period and radius of the pair of vortex are determined to be 10-11 d and 58-68 km. Two arrays of contra-rotating vortices are displayed in the average sea surface height anomaly (SSHA) field to the west of Big Island. Based on the calculation of the fluid dynamical parameter, the 'von Karman vortex street' is proved to be generated to the west of Big Island as the North Equatorial Current impinges upon Big Island from the east. Finally, the analysis of the buoy trajectories in a decade contributes to the conclusion of the pattern of VKVS in a statistical view.展开更多
基金the South China Sea Monsoon Experiment,the State Key Basic Research Program (G1999043806)the CAS Knowledge Innovation Project (KZCX2-202)the National Natural Science Foundation of China (400076007)
文摘The Sea Surface Height Anomaly (SSHA) from the TOPEX/Poseidon altimeter data in 1994 is assimilated into a high-resolution model of the South China Sea (SCS) with nudging method. The model results can reveal the seasonal variations of SSHA and its time-space migration characters,at the same time,verify the effect of assimilation.Compared with non-assimilation results,assimilation results can show the seasonal variations of SSHA better,particularly in winter.Futhermore,it can distinguish temporal-spatial migration characters of SSHA clearly,i.e. cold signal of SSHA in northern SCS propagating westward and warm signal of SSHA in central SCS propagating eastward.It shows that as an easy and effective method,data assimilation of the SSHA with nudging method could make the simulated results closer to the available observations.
基金Supported by the National Key Developing Programme for Basic Science Project under No.1998040900 amd the Key Project of National Natural Science Foundation of China under No.40175021.
文摘Previous study comes to the conclusion: based on the anomalies of the South Asian high (SAH), 100-hPa geopotential height, and 100-hPa circulation over tropical and subtropical regions, we can predict precipitation anomaly in the Yangtze River Valley and North China. To test its validity, a series of experiments have been designed and operated, which include controlled experiment, sensitivity experiment (which has added anomalies into 100-hPa geopotential height and wind field), and four-composite experiments. Experiments based on the composed initial field such as EPR-CF, EPR-CD, EPR-HF, and EPR-HD, can reproduce the floods or droughts in the Yangtze River Valley and North China. It suggests that anomalies of the SAH, 100- hPa geopotential height, and circulation over tropical and subtropical regions may probably imply summer precipitation anomalies in the two regions. Sensitivity experiment results show that anomalies of the SAH, 100-hPa geopotential height, and southwest flow in the previous period is a signal of droughts or floods for the following summer in the Yangtze River Valley and North China. And it is also one of the factors that have impact on summer precipitation anomaly in the two regions. Positive anomaly of 100-hPa geopotential height and the anomalous intensifying of the SAH and southwest flow will induce floods in the Yangtze River Valley and droughts in North China; while negative anomaly of 100-hPa geopotential height and anomalous weakening of the SAH and southwest flow will induce droughts in the Yangtze River Valley and floods in North China.
基金The National Basic Research Program "973" Program of China under contract No.2009CB421202the National Natural Science Foundation of China under contract Nos 40976110 and 40706061+1 种基金the Public Science and Technology Research Funds Projects of Ocean under contract No.200905012the Zhejiang Provincial Natural Science Foundation of China under contract No.Y5090381
文摘Category 5 typhoon Megi was the most intense typhoon in 2010 of the world. It lingered in the South China Sea (SCS) for 5 d and caused a significant phytoplankton bloom detected by the satellite image. In this study, the authors investigated the ocean biological and physical responses to typhoon Megi by using chlorophyll-a (chl-a) concentration, sea surface temperature (SST), sea surface height anomaly (SSHA), sea surface wind measurements derived from different satellites and in situ data. The chl-a concentration (〉3 mg/m3) increased thirty times in the SCS after the typhoon passage in comparison with the mean level of October averaged from 2002 to 2009. With the relationship of wind stress curl and upwelling, the authors found that the speed of upwelling was over ten times during typhoon than pre-typhoon period. Moreover, the mixed layer deepened about 20 m. These reveal that the enhancement of chl-a concentration was triggered by strong vertical mixing and upwelling. Along the track of typhoon, the maximum sea surface cooling (6-8~C) took place in the SCS where the moving speed of typhoon was only 1.4-2.8 m/s and the mixed layer depth was about 20 m in pre-typhoon period. However, the SST drop at the east of the Philippines is only 1-2~C where the translation speed of typhoon was 5.5-6.9 m/s and the mixed layer depth was about 40 m in pre-typhoon period. So the extent of the SST drop was probably due to the moving speed of typhoon and the depth of the mixed layer. In addition, the region with the largest decline of the sea surface height anomaly can indicate the location where the maximum cooling occurs.
文摘Satellite-tracked drifting buoy data and altimetry data are used to study the active vortex field to the west of Big Island. A pair of vortexes were observed at the trajectory of buoy in 1995. The westward propagation of the vortex pair is studied in detail by reproducing the loops of each vortex. The orbital period and radius of the pair of vortex are determined to be 10-11 d and 58-68 km. Two arrays of contra-rotating vortices are displayed in the average sea surface height anomaly (SSHA) field to the west of Big Island. Based on the calculation of the fluid dynamical parameter, the 'von Karman vortex street' is proved to be generated to the west of Big Island as the North Equatorial Current impinges upon Big Island from the east. Finally, the analysis of the buoy trajectories in a decade contributes to the conclusion of the pattern of VKVS in a statistical view.