Malaysian Airlines Flight MH370 disappeared on 8 March 2014, while flying from Kuala Lumpur to Beijing. A flaperon from the flight was found on Reunion Island in July 2015. Two more confirmed pieces of debris were fou...Malaysian Airlines Flight MH370 disappeared on 8 March 2014, while flying from Kuala Lumpur to Beijing. A flaperon from the flight was found on Reunion Island in July 2015. Two more confirmed pieces of debris were found in Mauritius and Tanzania, and 19 unconfirmed items were found off Mozambique, South Africa, and Madagascar. Drift buoys originating from the designated underwater search area arrived in Reunion Island, Mauritius, and Tanzania. Some of these buoys took a similarly long time as did real debris to reach these destinations, following a heading northeast and then west. For the present study, a maritime object drift prediction model was developed. ＂High resolution surface currents, Stokes drift, and winds＂ were processed, and a series of model experiments were constructed. The predicted trajectories of the modeled objects were similar to the observed trajectories of the drift buoys. Many modeled objects drifted northward then westward, ending up in Reunion Island, Mauritius, and Tanzania with probabilities of 5%0, 5%0, and 19%o, respectively. At the end of the simulation, most objects were located near 10~S in the western Indian Ocean. There were significant differences between experiments with different leeway factors, possibly because of the influence of southeast trade winds. The north part of the underwater search area is most likely to be the crash site, because the predicted trajectories of objects originating here are consistent with the many pieces of debris found along the east coast of Africa and the absence of such findings on the west coast of Australia.展开更多
Surface currents measured by high frequency （HF） radar arrays are assimilated into a regional ocean model over Qingdao coastal waters based on Kalman filter method. A series of numerical experiments are per- formed ...Surface currents measured by high frequency （HF） radar arrays are assimilated into a regional ocean model over Qingdao coastal waters based on Kalman filter method. A series of numerical experiments are per- formed to evaluate the performance of the data assimilation schemes. In order to optimize the analysis pro- cedure in the traditional ensemble Kalman filter （ENKF）, a different analysis scheme called quasiensemble Kaman filter （QENKF） is proposed. The comparisons between the ENKF and the QENKF suggest that both them can improve the simulated error and the spatial structure. The estimations of the background error covariance （BEC） are also assessed by comparing three different methods： Monte Carlo method; Canadian quick covariance （CQC） method and data uncertainty engine （DUE） method. A significant reduction of the root-mean-square （RMS） errors between model results and the observations shows that the CQC method is able to better reproduce the error statistics for this coastal ocean model and the corresponding external forcing. In addition, the sensibility of the data assimilation system to the ensemble size is also analyzed by means of different scales of the ensemble size used in the experiments. It is found that given the balance of the computational cost and the forecasting accuracy, the ensemble size of 50 will be an appropriate choice in the Qingdao coastal waters.展开更多
Seasonal and interannual variations of surface currents in the southern Taiwan Strait to the west of Taiwan Shoals were investigated by using measurements of high frequency(HF)ground wave radars from January 2006 to A...Seasonal and interannual variations of surface currents in the southern Taiwan Strait to the west of Taiwan Shoals were investigated by using measurements of high frequency(HF)ground wave radars from January 2006 to April 2009.The results demonstrate that surface currents in the water channel to the west of Taiwan Shoals are composed of a significant,seasonally fluctuating component and a relatively stable northward component.Forced by the East Asia monsoon,the annual variation of the surface longshore current is linearly correlated with the longshore wind.Behind the seasonal signal is a stable northward flow with speeds of O(10 cm/s).The observations also show that surface currents in the area are subject to distinct interannual variation,and the southward surface flow was more profound in winter 2007/2008 than in other winters.Observations from bottom-mounted ADCP also indicated that,in that winter,longshore currents in the west side of the Taiwan Strait are very different from the previous winter.The northward flow appeared much weaker,the currents were southward in most layers,and the interannual differences were observed throughout the water column.Hydrographic observations in the same period suggest that the large-scale southward intrusion of the Zhe-Min coastal water is the direct cause of the interannual difference.The enhancement of the East Asian monsoon during the 2007/2008 La Ni a event is considered as the main reason for the winter current anomalies in the study area.展开更多
基金Acknowledgements This work is supported by the National Key Research and Development Program of China （No. 2017YFC1404700） the National Natural Science Foundation of China （Grant Nos. 41430963 and 41606005） the Fundamental Research Funds for the Central Universities （No. 201713023）. Surface drifter data were provided by the Global Drifter Program. Surface currents data were from Hybrid Coordinate Ocean Model developed by Florida State University （HYCOM）. Wave data were provided by the European Centre for Medium-Range Weather Forecasts （ECMWF）. Wind data were provided by NOAA＇s National Centers for Environmental Prediction （NCEP）.
文摘Malaysian Airlines Flight MH370 disappeared on 8 March 2014, while flying from Kuala Lumpur to Beijing. A flaperon from the flight was found on Reunion Island in July 2015. Two more confirmed pieces of debris were found in Mauritius and Tanzania, and 19 unconfirmed items were found off Mozambique, South Africa, and Madagascar. Drift buoys originating from the designated underwater search area arrived in Reunion Island, Mauritius, and Tanzania. Some of these buoys took a similarly long time as did real debris to reach these destinations, following a heading northeast and then west. For the present study, a maritime object drift prediction model was developed. ＂High resolution surface currents, Stokes drift, and winds＂ were processed, and a series of model experiments were constructed. The predicted trajectories of the modeled objects were similar to the observed trajectories of the drift buoys. Many modeled objects drifted northward then westward, ending up in Reunion Island, Mauritius, and Tanzania with probabilities of 5%0, 5%0, and 19%o, respectively. At the end of the simulation, most objects were located near 10~S in the western Indian Ocean. There were significant differences between experiments with different leeway factors, possibly because of the influence of southeast trade winds. The north part of the underwater search area is most likely to be the crash site, because the predicted trajectories of objects originating here are consistent with the many pieces of debris found along the east coast of Africa and the absence of such findings on the west coast of Australia.
基金The National High Technology Research and Development Program of China under contract No.2007AA09Z117the Science and Technology Project of the North China Sea Brach of SOA under contract No.2012A01the Joint BMBF-WTZ Project of China under contract No. CHN 09/031
文摘Surface currents measured by high frequency （HF） radar arrays are assimilated into a regional ocean model over Qingdao coastal waters based on Kalman filter method. A series of numerical experiments are per- formed to evaluate the performance of the data assimilation schemes. In order to optimize the analysis pro- cedure in the traditional ensemble Kalman filter （ENKF）, a different analysis scheme called quasiensemble Kaman filter （QENKF） is proposed. The comparisons between the ENKF and the QENKF suggest that both them can improve the simulated error and the spatial structure. The estimations of the background error covariance （BEC） are also assessed by comparing three different methods： Monte Carlo method; Canadian quick covariance （CQC） method and data uncertainty engine （DUE） method. A significant reduction of the root-mean-square （RMS） errors between model results and the observations shows that the CQC method is able to better reproduce the error statistics for this coastal ocean model and the corresponding external forcing. In addition, the sensibility of the data assimilation system to the ensemble size is also analyzed by means of different scales of the ensemble size used in the experiments. It is found that given the balance of the computational cost and the forecasting accuracy, the ensemble size of 50 will be an appropriate choice in the Qingdao coastal waters.
基金supported by the National Natural Science Foundation of China (40906052)Chinese Ministry of Science and Technology through the National Basic Research Program (2009CB421205)the Scientific Research Foundation of Third Institute of Oceanography, State Oceanic Administration (2009009 and 2009066)
文摘Seasonal and interannual variations of surface currents in the southern Taiwan Strait to the west of Taiwan Shoals were investigated by using measurements of high frequency(HF)ground wave radars from January 2006 to April 2009.The results demonstrate that surface currents in the water channel to the west of Taiwan Shoals are composed of a significant,seasonally fluctuating component and a relatively stable northward component.Forced by the East Asia monsoon,the annual variation of the surface longshore current is linearly correlated with the longshore wind.Behind the seasonal signal is a stable northward flow with speeds of O(10 cm/s).The observations also show that surface currents in the area are subject to distinct interannual variation,and the southward surface flow was more profound in winter 2007/2008 than in other winters.Observations from bottom-mounted ADCP also indicated that,in that winter,longshore currents in the west side of the Taiwan Strait are very different from the previous winter.The northward flow appeared much weaker,the currents were southward in most layers,and the interannual differences were observed throughout the water column.Hydrographic observations in the same period suggest that the large-scale southward intrusion of the Zhe-Min coastal water is the direct cause of the interannual difference.The enhancement of the East Asian monsoon during the 2007/2008 La Ni a event is considered as the main reason for the winter current anomalies in the study area.
