jianlong feng - Academia.edu (original) (raw)

Papers by jianlong feng

Research paper thumbnail of Assessing changes in extreme sea levels along the coast of China

Journal of Geophysical Research: Oceans, 2015

Research paper thumbnail of Estimates of reynolds stress and TKE production in the seasonally stratified East China Sea

Journal of Ocean University of China, 2013

ABSTRACT During the two cruises in March and July of 2011, the tidal cycling of turbulent propert... more ABSTRACT During the two cruises in March and July of 2011, the tidal cycling of turbulent properties and the T/S profiles at the same location in seasonally stratified East China Sea (ECS) were measured synchronously by a bottom-mounted fast sampling ADCP (acoustic Doppler current profiler) and a RBR CTD (RBR-620) profiler. While focusing on the tide-induced and stratification’s impact on mixing, the Reynolds stress and the turbulent kinetic energy (TKE) production rate were calculated using the ‘variance method’. In spring, the features of mixing mainly induced by tides were clear when the water column was well-mixed. Velocity shear and turbulent parameters intensified towards the seabed due to the bottom friction. The components of the velocity shear and the Reynolds stress displayed a dominant semi-diurnal variation related to velocity changes caused by the flood and ebb of M2 tide. Stratification occurred in summer, and the water column showed a strongly stratified pycnocline with a characteristic squared buoyancy frequency of N2 ∼ (1–6) × 10−3 s−2. The components of the velocity shear and the Reynolds stress penetrated upwards very fast from the bottom boundary layer to the whole water column in spring, while in summer they only penetrated to the bottom of the pycnocline with a relatively slow propagation speed. In summer, the TKE production within the pycnocline was comparable with and sometimes larger than that in the well-mixed bottom layer under the pycnocline. Considering the associated high velocity shear, it is speculated that the mixing in the pycnocline is a result of the local velocity shear.

Research paper thumbnail of Extreme Water Level Analysis at three stations on the Northwestern Pacific Ocean Coast

In this study, the data from three long-term observation stations, Aburatsu, Xiamen and Hong Kong... more In this study, the data from three long-term observation stations, Aburatsu, Xiamen and Hong Kong, located on the northwest Pacific Ocean coast were analyzed to estimate the 100-year annual maximum water levels. The performances of four common frequency analysis methods, namely Gumbel, Weibull, GEV and GPD distributions, were evaluated. It is found that the GEV model performs best among these four distribution models in Hong Kong and Aburatsu, while at Xiamen station the Gumbel distribution is the best. It is also found that the GEV model generally performs better than the Gumbel model with regard to the mean high correlation coefficient and mean minimum root-mean-square error. Moreover, in this study the r-largest value model was used to study temporal trends in the annual maximum water levels on the northwest Pacific coast over the past fifty years, using the observation data of Hong Kong, Xiamen and Aburatsu. Results show that there are two temporal features in the 50-year return levels at all of the three stations, with the first being an overall increasing trend over the whole period, the other being an oscillatory trend over the period of observation. The relationships between the temporal trends and the Pacific Decadal Oscillation (PDO), sea level rise and change of typhoons were also analyzed in this paper. It is found that when the PDO index is shifted to be 4 years in advance, a significantly negative correlation will occur between the PDO index and the 50-year return levels. However, sea level rise and changes of typhoons cause the overall increase over the entire period.

Research paper thumbnail of Numerical prediction of storm surge in the Qingdao area under the impact of climate change

A typhoon-induced storm surge simulation system was developed for the Qingdao area, including a t... more A typhoon-induced storm surge simulation system was developed for the Qingdao area, including a typhoon diagnostic model for the generation of wind and pressure fields and a 2D Advanced Circulation (ADCIRC) model for simulating the associated storm surge with a 200 m resolution along the Qingdao coastline. The system was validated by an extreme surge event Typhoon Mamie (8509) and the parameters of Typhoon Mamie were used to investigate the sensitivity of typhoon paths to Qingdao storm surges with four selected paths: the paths of typhoons Mamie (8509), Opal, 3921 and 2413, the selection being made according to their relative position to Qingdao. Experiments based on the Typhoon Mamie (8509) storm surge were also conducted to study the possible influences of future climate changes, including the sea level rise and sea surface temperature (SST) rise, on storm surges along the Qingdao coast. Storm surge conditions under both present day and future (the end of the 21th century) climate scenarios associated with the four selected paths were simulated. The results show that with the same intensity, when typhoons follow the paths of 3921 and 2413, they would lead to the most serious disasters in different areas of Qingdao. Sea level and SST affect storm surges in different ways: sea level rise affects storm surge mainly through its influence on the tide amplitude, while the increased SST has direct impact on the intensity of the surges. The possible maximum risk of storm surges in 2100 in the Qingdao area caused by typhoons like Mamie (8509) was also estimated in this study.

Research paper thumbnail of Assessing changes in extreme sea levels along the coast of China

Journal of Geophysical Research: Oceans, 2015

Research paper thumbnail of Estimates of reynolds stress and TKE production in the seasonally stratified East China Sea

Journal of Ocean University of China, 2013

ABSTRACT During the two cruises in March and July of 2011, the tidal cycling of turbulent propert... more ABSTRACT During the two cruises in March and July of 2011, the tidal cycling of turbulent properties and the T/S profiles at the same location in seasonally stratified East China Sea (ECS) were measured synchronously by a bottom-mounted fast sampling ADCP (acoustic Doppler current profiler) and a RBR CTD (RBR-620) profiler. While focusing on the tide-induced and stratification’s impact on mixing, the Reynolds stress and the turbulent kinetic energy (TKE) production rate were calculated using the ‘variance method’. In spring, the features of mixing mainly induced by tides were clear when the water column was well-mixed. Velocity shear and turbulent parameters intensified towards the seabed due to the bottom friction. The components of the velocity shear and the Reynolds stress displayed a dominant semi-diurnal variation related to velocity changes caused by the flood and ebb of M2 tide. Stratification occurred in summer, and the water column showed a strongly stratified pycnocline with a characteristic squared buoyancy frequency of N2 ∼ (1–6) × 10−3 s−2. The components of the velocity shear and the Reynolds stress penetrated upwards very fast from the bottom boundary layer to the whole water column in spring, while in summer they only penetrated to the bottom of the pycnocline with a relatively slow propagation speed. In summer, the TKE production within the pycnocline was comparable with and sometimes larger than that in the well-mixed bottom layer under the pycnocline. Considering the associated high velocity shear, it is speculated that the mixing in the pycnocline is a result of the local velocity shear.

Research paper thumbnail of Extreme Water Level Analysis at three stations on the Northwestern Pacific Ocean Coast

In this study, the data from three long-term observation stations, Aburatsu, Xiamen and Hong Kong... more In this study, the data from three long-term observation stations, Aburatsu, Xiamen and Hong Kong, located on the northwest Pacific Ocean coast were analyzed to estimate the 100-year annual maximum water levels. The performances of four common frequency analysis methods, namely Gumbel, Weibull, GEV and GPD distributions, were evaluated. It is found that the GEV model performs best among these four distribution models in Hong Kong and Aburatsu, while at Xiamen station the Gumbel distribution is the best. It is also found that the GEV model generally performs better than the Gumbel model with regard to the mean high correlation coefficient and mean minimum root-mean-square error. Moreover, in this study the r-largest value model was used to study temporal trends in the annual maximum water levels on the northwest Pacific coast over the past fifty years, using the observation data of Hong Kong, Xiamen and Aburatsu. Results show that there are two temporal features in the 50-year return levels at all of the three stations, with the first being an overall increasing trend over the whole period, the other being an oscillatory trend over the period of observation. The relationships between the temporal trends and the Pacific Decadal Oscillation (PDO), sea level rise and change of typhoons were also analyzed in this paper. It is found that when the PDO index is shifted to be 4 years in advance, a significantly negative correlation will occur between the PDO index and the 50-year return levels. However, sea level rise and changes of typhoons cause the overall increase over the entire period.

Research paper thumbnail of Numerical prediction of storm surge in the Qingdao area under the impact of climate change

A typhoon-induced storm surge simulation system was developed for the Qingdao area, including a t... more A typhoon-induced storm surge simulation system was developed for the Qingdao area, including a typhoon diagnostic model for the generation of wind and pressure fields and a 2D Advanced Circulation (ADCIRC) model for simulating the associated storm surge with a 200 m resolution along the Qingdao coastline. The system was validated by an extreme surge event Typhoon Mamie (8509) and the parameters of Typhoon Mamie were used to investigate the sensitivity of typhoon paths to Qingdao storm surges with four selected paths: the paths of typhoons Mamie (8509), Opal, 3921 and 2413, the selection being made according to their relative position to Qingdao. Experiments based on the Typhoon Mamie (8509) storm surge were also conducted to study the possible influences of future climate changes, including the sea level rise and sea surface temperature (SST) rise, on storm surges along the Qingdao coast. Storm surge conditions under both present day and future (the end of the 21th century) climate scenarios associated with the four selected paths were simulated. The results show that with the same intensity, when typhoons follow the paths of 3921 and 2413, they would lead to the most serious disasters in different areas of Qingdao. Sea level and SST affect storm surges in different ways: sea level rise affects storm surge mainly through its influence on the tide amplitude, while the increased SST has direct impact on the intensity of the surges. The possible maximum risk of storm surges in 2100 in the Qingdao area caused by typhoons like Mamie (8509) was also estimated in this study.