The C-band wind speed retrieval models, CMOD4, CMOD - IFR2, and CMOD5 were applied to retrieval of sea surface wind speeds from ENVISAT （European environmental satellite） ASAR （advanced synthetic aperture radar） d...The C-band wind speed retrieval models, CMOD4, CMOD - IFR2, and CMOD5 were applied to retrieval of sea surface wind speeds from ENVISAT （European environmental satellite） ASAR （advanced synthetic aperture radar） data in the coastal waters near Hong Kong during a period from October 2005 to July 2007. The retrieved wind speeds are evaluated by comparing with buoy measurements and the QuikSCAT （quick scatterometer） wind products. The results show that the CMOD4 model gives the best performance at wind speeds lower than 15 m/s. The correlation coefficients with buoy and QuikSCAT winds are 0.781 and 0.896, respectively. The root mean square errors are the same 1.74 m/s. Namely, the CMOD4 model is the best one for sea surface wind speed retrieval from ASAR data in the coastal waters near Hong Kong.展开更多
This study aims to explore generation mechanisms of the ocean internal wave using the dynamical analysis methods based on linear theories. Historical cruise measurements and recent synthetic aperture radar （SAR） obs...This study aims to explore generation mechanisms of the ocean internal wave using the dynamical analysis methods based on linear theories. Historical cruise measurements and recent synthetic aperture radar （SAR） observations of mesoscale eddies with diameter of several tens of kilometers to hundreds of kilometers show that the internal wave packets with wavelength of hundreds of meters to kilometer exist inside the mesoscale eddies. This coexistence phenomenon and inherent links between the two different scale processes are revealed in the solutions of governing equations and boundary conditions for the internal wave disturbance with a horizontally slowly variable amplitude in a cylindrical coordinate system. The theoretical solutions indicate that the instability of eddy current field provides the dynamical mechanism to internal wave generation. The derived dispersion relation indicates that the internal wave propagation is modified by the eddy current field structure. The energy equation of the internal waves clearly shows the internal wave energy increment comes from the eddy. The theoretical models are used to explain the observation of the mesoscale eddy-induced internal waves off the Norwegian coast. The two-dimensional waveform solution of the anticyclonic eddy-induced internal wave packet appears as ring-shaped curves, which contains the typical features of eddy stream lines. The comparison of theoretical solutions to the structure of the internal wave packets on SAR image shows a good agreement on the major features.展开更多
Sea level observed by altimeter during the 1993–2007 period and the thermosteric sea level from 1945 through 2005 obtained by using the global ocean temperature data sets recently published are used to investigate th...Sea level observed by altimeter during the 1993–2007 period and the thermosteric sea level from 1945 through 2005 obtained by using the global ocean temperature data sets recently published are used to investigate the interannual and decadal variability of the sea level in the Japan/East Sea (JES) and its response to El Nio and Southern Oscillation (ENSO). Both the interannual variations of the sea level observed by altimeter and those of the thermosteric sea level obtained from reanalyzed data in the JES are closely related to ENSO. As a result, one important consequence is that the sea level trends are mainly caused by the thermal expansion in the JES. An ‘enigma’ is revealed that the correlation between the thermosteric sea level and ENSO during the PDO (Pacific Decadal Oscillation) warm phase (post mid-1970s) is inconsistent with that during the cold phase (pre mid-1970s) in the JES. The thermosteric sea level trends and the Southern Oscillation Index (SOI) suggest a strong negative correlation during the period 1977–1998, whereas there appears a relatively weak positive correlation during the period 1945–1976 in the JES. Based on the SODA (Simple Oceanographic Data Assimilation) datasets, possible mechanisms of the interannual and decadal variability of the sea level in the JES are discussed. Comprehensive analysis reveals that the negative anomalies of SOI correspond to the positive anomalies of the southeast wind stress, the net advective heat flux and the sea level in the JES during the PDO warm phase. During the PDO cold phase, the negative anomalies of SOI correspond to the positive anomalies of the southwest wind stress, the negative anomalies of the net advective heat flux and the sea level in the JES.展开更多
Time series of sea surface temperature (SST),wind speed and significant wave height (SWH) from meteorological buoys of the National Data Buoy Center (NDBC) are useful for studying the interannual variability and trend...Time series of sea surface temperature (SST),wind speed and significant wave height (SWH) from meteorological buoys of the National Data Buoy Center (NDBC) are useful for studying the interannual variability and trend of these quantities at the buoy areas. The measurements from 4 buoys (B51001,B51002,B51003 and B51004) in the Hawaii area are used to study the responses of the quantities to EI Ni?o and Southern Oscillation (ENSO). Long-term averages of these data reflect precise seasonal and climatological characteristics of SST,wind speed and SWH around the Hawaii area. Buoy observations from B51001 suggest a significant warming trend which is,however,not very clear from the other three buoys. Compared with the variability of SST and SWH,the wind speeds from the buoy observations show an increasing trend. The impacts of EI Nio on SST and wind waves are also shown. Sea level data observed by altimeter during October 1992 to September 2006 are analyzed to investigate the variability of sea level in the Hawaii area. The results also show an increasing trend in sea level anomaly (SLA). The low-passed SLA in the Hawaii area is consistent with the inverse phase of the low-passed SOI (Southern Oscillation Index). Compared with the low-passed SOI and PDO (Pacific Decadal Oscillation),the low-passed PNA (Pacific-North America Index) has a better correlation with the low-passed SLA in the Hawaii area.展开更多
基金Research Grant Council under contract No.461907Innovation and Technology Commission under contract No.GHP/026/06+1 种基金partly by China Postdoctoral Science Foundation under contract No.2008041345 for ChengONR under contract NosN00014-05-1-0328 and N00014-05-1-0606 for Zheng
文摘The C-band wind speed retrieval models, CMOD4, CMOD - IFR2, and CMOD5 were applied to retrieval of sea surface wind speeds from ENVISAT （European environmental satellite） ASAR （advanced synthetic aperture radar） data in the coastal waters near Hong Kong during a period from October 2005 to July 2007. The retrieved wind speeds are evaluated by comparing with buoy measurements and the QuikSCAT （quick scatterometer） wind products. The results show that the CMOD4 model gives the best performance at wind speeds lower than 15 m/s. The correlation coefficients with buoy and QuikSCAT winds are 0.781 and 0.896, respectively. The root mean square errors are the same 1.74 m/s. Namely, the CMOD4 model is the best one for sea surface wind speed retrieval from ASAR data in the coastal waters near Hong Kong.
基金The RGC under contract No.461907the ONR under contract Nos N00014-05-1-0328and N00014-05-1-0606+1 种基金the SFMSBRP under contract No.973-2007CB411807the NASA JPL under contract No.NMO710968
文摘This study aims to explore generation mechanisms of the ocean internal wave using the dynamical analysis methods based on linear theories. Historical cruise measurements and recent synthetic aperture radar （SAR） observations of mesoscale eddies with diameter of several tens of kilometers to hundreds of kilometers show that the internal wave packets with wavelength of hundreds of meters to kilometer exist inside the mesoscale eddies. This coexistence phenomenon and inherent links between the two different scale processes are revealed in the solutions of governing equations and boundary conditions for the internal wave disturbance with a horizontally slowly variable amplitude in a cylindrical coordinate system. The theoretical solutions indicate that the instability of eddy current field provides the dynamical mechanism to internal wave generation. The derived dispersion relation indicates that the internal wave propagation is modified by the eddy current field structure. The energy equation of the internal waves clearly shows the internal wave energy increment comes from the eddy. The theoretical models are used to explain the observation of the mesoscale eddy-induced internal waves off the Norwegian coast. The two-dimensional waveform solution of the anticyclonic eddy-induced internal wave packet appears as ring-shaped curves, which contains the typical features of eddy stream lines. The comparison of theoretical solutions to the structure of the internal wave packets on SAR image shows a good agreement on the major features.
基金supported by the National Basic Research Program of China under Grant No. 973-2007CB- 411807
文摘Sea level observed by altimeter during the 1993–2007 period and the thermosteric sea level from 1945 through 2005 obtained by using the global ocean temperature data sets recently published are used to investigate the interannual and decadal variability of the sea level in the Japan/East Sea (JES) and its response to El Nio and Southern Oscillation (ENSO). Both the interannual variations of the sea level observed by altimeter and those of the thermosteric sea level obtained from reanalyzed data in the JES are closely related to ENSO. As a result, one important consequence is that the sea level trends are mainly caused by the thermal expansion in the JES. An ‘enigma’ is revealed that the correlation between the thermosteric sea level and ENSO during the PDO (Pacific Decadal Oscillation) warm phase (post mid-1970s) is inconsistent with that during the cold phase (pre mid-1970s) in the JES. The thermosteric sea level trends and the Southern Oscillation Index (SOI) suggest a strong negative correlation during the period 1977–1998, whereas there appears a relatively weak positive correlation during the period 1945–1976 in the JES. Based on the SODA (Simple Oceanographic Data Assimilation) datasets, possible mechanisms of the interannual and decadal variability of the sea level in the JES are discussed. Comprehensive analysis reveals that the negative anomalies of SOI correspond to the positive anomalies of the southeast wind stress, the net advective heat flux and the sea level in the JES during the PDO warm phase. During the PDO cold phase, the negative anomalies of SOI correspond to the positive anomalies of the southwest wind stress, the negative anomalies of the net advective heat flux and the sea level in the JES.
基金the National Basic Research Program of China under Grant No 973-2007CB411807National High Technology Development Project under Grant No 863-2006AA09Z140+1 种基金China Postdoctoral Science Foundation funded project under Grant No 2008041345the Scientific Research Starting Foundation for Doctoral of Institute of Meteorology,PLA University of Science and Technology
文摘Time series of sea surface temperature (SST),wind speed and significant wave height (SWH) from meteorological buoys of the National Data Buoy Center (NDBC) are useful for studying the interannual variability and trend of these quantities at the buoy areas. The measurements from 4 buoys (B51001,B51002,B51003 and B51004) in the Hawaii area are used to study the responses of the quantities to EI Ni?o and Southern Oscillation (ENSO). Long-term averages of these data reflect precise seasonal and climatological characteristics of SST,wind speed and SWH around the Hawaii area. Buoy observations from B51001 suggest a significant warming trend which is,however,not very clear from the other three buoys. Compared with the variability of SST and SWH,the wind speeds from the buoy observations show an increasing trend. The impacts of EI Nio on SST and wind waves are also shown. Sea level data observed by altimeter during October 1992 to September 2006 are analyzed to investigate the variability of sea level in the Hawaii area. The results also show an increasing trend in sea level anomaly (SLA). The low-passed SLA in the Hawaii area is consistent with the inverse phase of the low-passed SOI (Southern Oscillation Index). Compared with the low-passed SOI and PDO (Pacific Decadal Oscillation),the low-passed PNA (Pacific-North America Index) has a better correlation with the low-passed SLA in the Hawaii area.
