A current-turbidity monitoring system (CTMS) was deployed on the intertidal flat at Wanggang, northern Jiangsu during October 16-17, 2000, to measure the tidal current speeds and seawater turbidities at 5 levels above...A current-turbidity monitoring system (CTMS) was deployed on the intertidal flat at Wanggang, northern Jiangsu during October 16-17, 2000, to measure the tidal current speeds and seawater turbidities at 5 levels above the seabed. Based upon the logarithmic-profile equation, the boundary layer parameters, i.e., u, z0 and C60, were obtained for 247 tidal flow velocity profiles. Around 90% of the profiles were logarithmic according to the critical correlation coefficient. Internal consistency analysis shows that these parameters derived by different methods are consistent with each other. In addition, the height of the bedforms observed is close to the seabed roughness lengths calculated from the velocity profiles, indicating that the boundary layer parameters obtained can reveal the conditions at the sediment-water interface on the intertidal flats. Suspended sediment concentrations were obtained from the 5 CTMS turbidity meters using laboratory and in-situ calibrations. The results show that the in-situ calibrated SSCs have a much higher accuracy than the laboratory calibrated ones. Calculation of suspended sediment fluxes on the intertidal flats, with a magnitude of 104 kg/m per spring tidal cycle, indicates that suspended sediment moves towards the northwest, which is reversal to the transport pattern controlled by the southward Northern Jiangsu Coastal Current in the sub-tidal zone and adjacent shallow waters.展开更多
Paleoclimate modeling has become an impor- tant tool to detect the future climate of the global warming that is difficult to be validated. The paleoclimate modeling has to be evaluated by regionally geological data in...Paleoclimate modeling has become an impor- tant tool to detect the future climate of the global warming that is difficult to be validated. The paleoclimate modeling has to be evaluated by regionally geological data in order to determine if it is able to reproduce a reality of climate states. Geological evidence shows that there was a warm-wet inter- stadial at 35000±3000 a BP in China, which provides an im- portant climate period to be historical analogue for the fu- ture climate changes induced by greenhouse gas emissions. Integrated geological records of later phase of the MSI3 from China also provide basements for evaluation of 35 ka BP climate modeling. This paper reports the paleoclimate ex- periments applied by various forces, and validates the out- puts by geological data, consequently improving the bound- ary conditions in the experiments and making the paleocli- mates more approach the reality. The simulations show an increased temperature in the mid-low latitudes and an ex- tended rain-belt northwards in East Asia, while a decreased temperature in high latitudes and a strong exchange of the N-S atmospheric circulation. As there is only ca. 10—15 ka from 35 ka BP to the LGM (21 ka BP) during which climate rapidly changed from a warm-wet interstadial to a typical ice age, this simulation provides scientific basis to recognize the criteria of global warming and trends of natural climate de- velopment.展开更多
This paper describes valley bottom troughs of the Changjiang River and infers the geomorphologic development of troughs. Based on the morphology of the troughs, the following conclusions are drawn. (1) The deep trough...This paper describes valley bottom troughs of the Changjiang River and infers the geomorphologic development of troughs. Based on the morphology of the troughs, the following conclusions are drawn. (1) The deep troughs on the Three Gorges valley bottom are formed by river downcutting along the structural zones on the background of regional tectonic uplift at about 40-30 ka BP. (2) When river downcutting occurred in the river bed of Changjiang, the jets current (particularly eddy current) with a large number of pebbles ground and eroded the valley bottom, resulting in trough formation and deepening. Meanwhile, water currents with gravels and pebbles eroded the bank and the left wall of No.76 trough as well as the right wall of No.77 trough by striking, scouring, horizontal and vertical grinding. (3) The depth of the trough is mainly determined by the intensity of the water current and the consistency of bedrock against erosion, and is not controlled by the altitude of the sea level as the base level of erosion.展开更多
文摘A current-turbidity monitoring system (CTMS) was deployed on the intertidal flat at Wanggang, northern Jiangsu during October 16-17, 2000, to measure the tidal current speeds and seawater turbidities at 5 levels above the seabed. Based upon the logarithmic-profile equation, the boundary layer parameters, i.e., u, z0 and C60, were obtained for 247 tidal flow velocity profiles. Around 90% of the profiles were logarithmic according to the critical correlation coefficient. Internal consistency analysis shows that these parameters derived by different methods are consistent with each other. In addition, the height of the bedforms observed is close to the seabed roughness lengths calculated from the velocity profiles, indicating that the boundary layer parameters obtained can reveal the conditions at the sediment-water interface on the intertidal flats. Suspended sediment concentrations were obtained from the 5 CTMS turbidity meters using laboratory and in-situ calibrations. The results show that the in-situ calibrated SSCs have a much higher accuracy than the laboratory calibrated ones. Calculation of suspended sediment fluxes on the intertidal flats, with a magnitude of 104 kg/m per spring tidal cycle, indicates that suspended sediment moves towards the northwest, which is reversal to the transport pattern controlled by the southward Northern Jiangsu Coastal Current in the sub-tidal zone and adjacent shallow waters.
基金the Intelligence Innovation Projects of the Chinese Academy of Sciences(KZCX2-SW-118)the National Basic Research Program of China(2002CB412301-1) the Key Project of the Chinese Academy of Sciences(KZCX1-SW-12-1).
文摘Paleoclimate modeling has become an impor- tant tool to detect the future climate of the global warming that is difficult to be validated. The paleoclimate modeling has to be evaluated by regionally geological data in order to determine if it is able to reproduce a reality of climate states. Geological evidence shows that there was a warm-wet inter- stadial at 35000±3000 a BP in China, which provides an im- portant climate period to be historical analogue for the fu- ture climate changes induced by greenhouse gas emissions. Integrated geological records of later phase of the MSI3 from China also provide basements for evaluation of 35 ka BP climate modeling. This paper reports the paleoclimate ex- periments applied by various forces, and validates the out- puts by geological data, consequently improving the bound- ary conditions in the experiments and making the paleocli- mates more approach the reality. The simulations show an increased temperature in the mid-low latitudes and an ex- tended rain-belt northwards in East Asia, while a decreased temperature in high latitudes and a strong exchange of the N-S atmospheric circulation. As there is only ca. 10—15 ka from 35 ka BP to the LGM (21 ka BP) during which climate rapidly changed from a warm-wet interstadial to a typical ice age, this simulation provides scientific basis to recognize the criteria of global warming and trends of natural climate de- velopment.
基金Exploration Corporation of the Three Gorges Project The"985 project"construction project of physical geography for Nanjing University
文摘This paper describes valley bottom troughs of the Changjiang River and infers the geomorphologic development of troughs. Based on the morphology of the troughs, the following conclusions are drawn. (1) The deep troughs on the Three Gorges valley bottom are formed by river downcutting along the structural zones on the background of regional tectonic uplift at about 40-30 ka BP. (2) When river downcutting occurred in the river bed of Changjiang, the jets current (particularly eddy current) with a large number of pebbles ground and eroded the valley bottom, resulting in trough formation and deepening. Meanwhile, water currents with gravels and pebbles eroded the bank and the left wall of No.76 trough as well as the right wall of No.77 trough by striking, scouring, horizontal and vertical grinding. (3) The depth of the trough is mainly determined by the intensity of the water current and the consistency of bedrock against erosion, and is not controlled by the altitude of the sea level as the base level of erosion.
