American horseshoe crabs Limulus polyphemus were tracked using acoustic telemetry and traditional tagging in asemi-enclosed bay on Cape Cod (Pleasant Bay),Massachusetts,USA,to determine seasonal movement patterns.Fift...American horseshoe crabs Limulus polyphemus were tracked using acoustic telemetry and traditional tagging in asemi-enclosed bay on Cape Cod (Pleasant Bay),Massachusetts,USA,to determine seasonal movement patterns.Fifty-five activelyspawning females were fitted with transmitters in 2008 and 2009 and were tracked using acoustic telemetry from May 2008through July 2010.Fifteen crabs with transmitters also had archive depth-temperature tags attached.In addition,over 2000spawning crabs (males and females) were tagged with US Fish and Wildlife (USFWS) button tags over the same period.Ninety-one percent of the crabs with transmitters were detected during this study.In the spring,crabs were primarily located inthe northern section of the bay near spawning beaches,whereas in the fall crabs moved towards the deeper portions of the bay,and some may have overwintered in the bay.There was evidence that a majority (58%-71%) of the females with transmittersspawned in two sequential seasons.One archive tag was recovered resulting in a year-long continuous record of depth and temperaturedata that,when integrated with telemetry data,indicated that the crab overwintered in the bay.The live recapture rate ofcrabs with USFWS button tags was 11%,with all re-sighted crabs except one observed inside Pleasant Bay.Eighty-three percentof recaptures were found within 2.5km of the tagging location,and 51% were observed at the same beach where they were tagged.This study provides further evidence that horseshoe crabs in Pleasant Bay may be philopatric to this展开更多
In this study, we construct one 2-dimensional tidal simulation, using an unstructured Finite Volume Coastal Ocean Model （FVCOM）. In the 2-D model, we simulated the tidal turbines through adding additional bottom dra...In this study, we construct one 2-dimensional tidal simulation, using an unstructured Finite Volume Coastal Ocean Model （FVCOM）. In the 2-D model, we simulated the tidal turbines through adding additional bottom drag in the element where the tidal turbines reside. The additional bottom drag was calculated from the relationship of the bottom friction dissipation and the rated rotor efficiency of the tidal energy turbine. This study analyzed the effect of the tidal energy turbine to the hydrodynamic environment, and calculated the amount of the extractable tidal energy resource at the Guishan Hangmen Channel, considering the rotor wake effect.展开更多
With dense seismic arrays and advanced imaging methods, regional three-dimensional （3D） Earth models have become more accurate. It is now increasingly feasible and advantageous to use a 3D Earth model to better loca...With dense seismic arrays and advanced imaging methods, regional three-dimensional （3D） Earth models have become more accurate. It is now increasingly feasible and advantageous to use a 3D Earth model to better locate earthquakes and invert their source mechanisms by fitting synthetics to observed waveforms. In this study, we develop an approach to determine both the earthquake location and source mechanism from waveform information. The observed waveforms are filtered in different frequency bands and separated into windows for the individual phases. Instead of picking the arrival times, the traveltime differences are measured by cross-correlation between synthetic waveforms based on the 3D Earth model and observed waveforms. The earthquake location is determined by minimizing the cross-correlation traveltime differences. We then fix the horizontal location of the earthquake and perform a grid search in depth to determine the source mechanism at each point by fitting the synthetic and observed waveforms. This new method is verified by a synthetic test with noise added to the synthetic waveforms and a realistic station distribution. We apply this method to a series of Mw3.4-5.6 earthquakes in the Longmenshan fault （LMSF） zone, a region with rugged topography between the eastern margin of the Tibetan plateau and the western part of the Sichuan basin. The results show that our solutions result in improved waveform fits compared to the source parameters from the catalogs we used and the location can be better constrained than the amplitude-only approach. Furthermore, the source solutions with realistic topography provide a better fit to the observed waveforms than those without the topography, indicating the need to take the topography into account in regions with rugged topography.展开更多
Release of dissolved volatiles during submarine fire fountaining eruptions can profoundly influence the buoyancy flux at the vent. Theoretical considerations indicate that in some cases buoyant magma can be erupted pr...Release of dissolved volatiles during submarine fire fountaining eruptions can profoundly influence the buoyancy flux at the vent. Theoretical considerations indicate that in some cases buoyant magma can be erupted prior to fragmentation (~75% vesicle volume threshold). Laboratory simulations using immiscible fluids of contrasting density indicate that the structure of the source flow at the vent depends critically on the relative magnitudes of buoyancy and momentum fluxes as reflected in the Richardson number (Ri). Analogue laboratory experiments of buoyant discharges demonstrate a variety of complex flow structures with the potential for greatly enhanced entrainment of surrounding seawater. Such conditions are likely to favor a positive feedback between phreatomagmatic explosions and volatile degassing that will contribute to explosive volcanism. The value of the Richardson number for any set of eruption parameters (magma discharge rate and volatile content) will depend on water depth as a result of the extent to which the exsolved volatile components can expand.展开更多
For selected locations in the Atlantic and Pacific Ocean, we compared surface ocean chlorophyll time series extracted from SeaWiFS imagery from 1997-2004 with the results of an ocean coupled circulation and biogeochem...For selected locations in the Atlantic and Pacific Ocean, we compared surface ocean chlorophyll time series extracted from SeaWiFS imagery from 1997-2004 with the results of an ocean coupled circulation and biogeochemical model covering the period 1958-2004. During the 1997-2004 time period, linear trends in model and satellite time series were significantly correlated at most of the 44 sites we studied. Eleven sites were selected for further study, and we used the longer time series of the model to assess whether trends observed during the SeaWiFS period at these 11 sites were unusual in relation to those observed over the longer historical period covered by the model. The results show that the trends observed during the SeaWiFS period were not unusual and fell well within the range in magnitude of linear trends observed in other 8-year periods of model output. This result implies that the SeaWiFS satellite ocean color time series is not yet sufficiently long, on its own, to directly observe any long term changes in phytoplankton chlorophyll that may be occurring in the surface waters of the open ocean as a result of increased ocean stratification linked to global climate changed.展开更多
The Wenchuan earthquake of 12 May 2008 is the most destructive earthquake in China in the past 30 years in terms of property damage and human losses. In order to understand the earthquake process and the geo-morpholog...The Wenchuan earthquake of 12 May 2008 is the most destructive earthquake in China in the past 30 years in terms of property damage and human losses. In order to understand the earthquake process and the geo-morphological factors affecting the seismic hazard, we simulated the strong ground mo-tion caused by the earthquake, incorporating three-dimensional (3D) earth structure, finite-fault rupture, and realistic surface topography. The simulated ground motions reveal that the fault rupture and basin structure control the overall pattern of the peak ground shaking. Large peak ground velocity (PGV) is distributed in two narrow areas: one with the largest PGV values is above the hanging wall of the fault and attributed to the locations of fault asperities and rupture directivity; the other is along the north-western margin of the Sichuan Basin and caused by both the directivity of fault rupture and the ampli-fication in the thick sediment basin. Rough topography above the rupture fault causes wave scattering, resulting in significantly larger peak ground motion on the apex of topographic relief than in the valley. Topography and scattering also reduce the wave energy in the forward direction of fault rupture but increase the PGV in other parts of the basin. These results suggest the need for a localized hazard as-sessment in places of rough topography that takes the topographic effects into account. Finally, had the earthquake started at the northeast end of the fault zone and ruptured to the southwest, Chengdu would have suffered a much stronger shaking than it experienced on 12 May, 2008.展开更多
It has long been known that human activities such as waste fluid disposal and reservoir impoundment may cause earthquakes. Recently, anthropogenic activities to tackle the increasing energy demand and to address clima...It has long been known that human activities such as waste fluid disposal and reservoir impoundment may cause earthquakes. Recently, anthropogenic activities to tackle the increasing energy demand and to address climate change issues are also reported to induce earthquakes. These activities have a common attribute in that fluids are injected and extracted underground and induce spatiotemporal changes of pore pressure and stress, which may cause slip on faults. Induced earthquakes not only pose significant impacts on seismic hazard assessment and preparation, but also raise the question to the society as how to balance the economic needs of resources development and the public's concerns about potential environmental impacts. Here we review the observations of fluid-injection/extraction induced earthquakes, ground deformation associated with these activities, and their physical mechanisms. Furthermore, we discuss the influences of induced earthquakes on seismic hazard models, regulatory policies on these anthropogenic activities, and current development of academic, industrial and government initiatives and collaborations in order to understand this intriguing phenomenon and address associated challenges.展开更多
Ⅰ. METHODSAll of the aerosol samples were collected in the spring of 1990 during and after three dust storms. The first was on April 6 in Xi’an (34.3°N, 108.9°E)(dust storm Ⅰ); the second was in Shapuotou...Ⅰ. METHODSAll of the aerosol samples were collected in the spring of 1990 during and after three dust storms. The first was on April 6 in Xi’an (34.3°N, 108.9°E)(dust storm Ⅰ); the second was in Shapuotou (37.5°N, 105°E) and Beijing (39.9°N, 116.4°E) on April 10 and in Xi’an on April 11 (dust storm Ⅱ); and the third on April 25 in Beijing (dust storm Ⅲ).展开更多
In the region southeast of Okinawa, during May to July 2001, a cyclonic and an anticyclonic eddy were observed from combined measurements of hydrocasts, an upward-looking moored acoustic Doppler current profiler (MADC...In the region southeast of Okinawa, during May to July 2001, a cyclonic and an anticyclonic eddy were observed from combined measurements of hydrocasts, an upward-looking moored acoustic Doppler current profiler (MADCP), pressure-recording inverted echo sounders (PIESs), satellite altimetry, and a coastal tide gauge. The hydrographic data showed that the lowest/highest temperature (T) and salinity (S) anomalies from a 13-year mean for the same season were respectively -3.0/+2.5℃ and -0.20/+0.15 psu at 380/500 dbar for the cyclonic/anticyclonic eddies. From the PIES data, using a gravest empirical mode method, we estimated time-varying surface dynamic height (D) anomaly referred to 2000 dbar changing from -20 to 30 cm, and time-varying T and S anomalies at 500 dbar ranging through about ±2 ℃ and ±0.2 psu, respectively. The passage of the eddies caused variations of both satellite-measured sea surface height anomaly (SSHA) and tide-gauge-measured sea level anomaly to change from about –20 to 30 cm, consistent with the D anomaly from the PIESs. Bottom pressure sensors measured no variation related to these eddy activities, which indicated that the two eddies were dominated by baro-clinicity. Time series of SSHA map confirmed that the two eddies, originating from the North Pacific Subtropical Countercurrent region near 20°―30°N and 150°―160°E, traveled about 3000 km for about 18 months with mean westward propagation speed of about 6 cm/s, before arriving at the region southeast of Okinawa Island.展开更多
In spite of increasing attention on Chinese aerosol, there has never been a country-wide survey of its general characteristics. This paper presents elemental data for aerosol at 23 sites in and around China, mostly dr...In spite of increasing attention on Chinese aerosol, there has never been a country-wide survey of its general characteristics. This paper presents elemental data for aerosol at 23 sites in and around China, mostly drawn from the literature, and shows some of the large-scale patterns. Al, Na, and Se are used to represent the crustal, marine, and pollution components, respectively. Most of the patterns are aligned in SW-NE. Al and Na are highest to the NW and the SE, respectively, and their ratio changes rapidly near the coast. Se has a broad maximum over Central China, and the Se/Al ratio （an indicator of pollution vs. crustal aerosol） increases progressively from the NW to the SE. A simple index for simulating pollution aerosol, which uses population density, annual precipitation, and mean wind speed, adequately reproduces the large-scale pattern of pollution aerosol and shows how crustal Al in the NW gradually gives way to flyash Al toward the SE.展开更多
We present numerical computations of a new wind-wave coupling theory that is governed by a system of nonlinear advance-delay differential equations (NLADDE). NLADDE are functional differential equations for which the ...We present numerical computations of a new wind-wave coupling theory that is governed by a system of nonlinear advance-delay differential equations (NLADDE). NLADDE are functional differential equations for which the derivative of an unknown function depends nonlinearly on the past (delayed), present, and future (advanced) values of the unknown function (if time is the independent variable). A practical numerical method for solving NLADDE is implemented, based on a collocation method. The method is tested for two problems with known analytic solutions and is shown to be numerically convergent. Numerical solutions to the coupled wind and wave problem reveal estimates of the wave height spectrum, the distribution of breaking waves (both depend on wave scale), as well as the vertical air-side profiles of turbulent stress and wind speed.展开更多
2001年5～7月,在冲绳岛以东海区,我们通过CTD(conductivity temperature and depth)、锚系海流剖面、PIES(pressure-recording inverted echo sounders)、卫星海面高度计和沿岸潮位仪的组合观测到一个气旋涡和一个反气旋涡.CTD断面数据...2001年5～7月,在冲绳岛以东海区,我们通过CTD(conductivity temperature and depth)、锚系海流剖面、PIES(pressure-recording inverted echo sounders)、卫星海面高度计和沿岸潮位仪的组合观测到一个气旋涡和一个反气旋涡.CTD断面数据显示,气旋涡和反气旋涡中心位于380/500dbar水深,对应的温度(T)和盐度(S)距平分别为-3.0/+2.5℃和-0.20/+0.15.从PIES数据,我们估算了气旋涡和反气旋涡经过时,相对于2000dbar深基准的动力高度(D)的时间变化为-20～30cm,500dbar深的T和S距平的变化范围约±2℃和±0.2.同时,由卫星海面高度计和潮位仪观测得到的海面高度距平变化范围约为-20至30cm,与PIES观测到的D的变化基本一致.由于两个涡经过时,PIES的压力传感器没有显示出相应的变化,反映出这两个涡具有较强的斜压特性.从卫星海面高度距平时间序列图追溯确认,这两个涡起源于北太平洋副热带逆流区附近,即20°～30°N,150°～160°E海区.它们以6cm·s-1的平均速度向西传播了约3000km,历时约18个月,然后抵达冲绳岛以东海区.展开更多
基金supported by the National Park Service under Cooperative Agreement Number CA452099007 with the University of Rhode Island
文摘American horseshoe crabs Limulus polyphemus were tracked using acoustic telemetry and traditional tagging in asemi-enclosed bay on Cape Cod (Pleasant Bay),Massachusetts,USA,to determine seasonal movement patterns.Fifty-five activelyspawning females were fitted with transmitters in 2008 and 2009 and were tracked using acoustic telemetry from May 2008through July 2010.Fifteen crabs with transmitters also had archive depth-temperature tags attached.In addition,over 2000spawning crabs (males and females) were tagged with US Fish and Wildlife (USFWS) button tags over the same period.Ninety-one percent of the crabs with transmitters were detected during this study.In the spring,crabs were primarily located inthe northern section of the bay near spawning beaches,whereas in the fall crabs moved towards the deeper portions of the bay,and some may have overwintered in the bay.There was evidence that a majority (58%-71%) of the females with transmittersspawned in two sequential seasons.One archive tag was recovered resulting in a year-long continuous record of depth and temperaturedata that,when integrated with telemetry data,indicated that the crab overwintered in the bay.The live recapture rate ofcrabs with USFWS button tags was 11%,with all re-sighted crabs except one observed inside Pleasant Bay.Eighty-three percentof recaptures were found within 2.5km of the tagging location,and 51% were observed at the same beach where they were tagged.This study provides further evidence that horseshoe crabs in Pleasant Bay may be philopatric to this
基金The Public Science and Technology Research Funds Projects of Ocean under contract No.201305031
文摘In this study, we construct one 2-dimensional tidal simulation, using an unstructured Finite Volume Coastal Ocean Model （FVCOM）. In the 2-D model, we simulated the tidal turbines through adding additional bottom drag in the element where the tidal turbines reside. The additional bottom drag was calculated from the relationship of the bottom friction dissipation and the rated rotor efficiency of the tidal energy turbine. This study analyzed the effect of the tidal energy turbine to the hydrodynamic environment, and calculated the amount of the extractable tidal energy resource at the Guishan Hangmen Channel, considering the rotor wake effect.
基金supported by National Natural Science Foundation of China (Grants No.41374056)the Fundamental Research Funds for the Central Universities (WK2080000053)
文摘With dense seismic arrays and advanced imaging methods, regional three-dimensional （3D） Earth models have become more accurate. It is now increasingly feasible and advantageous to use a 3D Earth model to better locate earthquakes and invert their source mechanisms by fitting synthetics to observed waveforms. In this study, we develop an approach to determine both the earthquake location and source mechanism from waveform information. The observed waveforms are filtered in different frequency bands and separated into windows for the individual phases. Instead of picking the arrival times, the traveltime differences are measured by cross-correlation between synthetic waveforms based on the 3D Earth model and observed waveforms. The earthquake location is determined by minimizing the cross-correlation traveltime differences. We then fix the horizontal location of the earthquake and perform a grid search in depth to determine the source mechanism at each point by fitting the synthetic and observed waveforms. This new method is verified by a synthetic test with noise added to the synthetic waveforms and a realistic station distribution. We apply this method to a series of Mw3.4-5.6 earthquakes in the Longmenshan fault （LMSF） zone, a region with rugged topography between the eastern margin of the Tibetan plateau and the western part of the Sichuan basin. The results show that our solutions result in improved waveform fits compared to the source parameters from the catalogs we used and the location can be better constrained than the amplitude-only approach. Furthermore, the source solutions with realistic topography provide a better fit to the observed waveforms than those without the topography, indicating the need to take the topography into account in regions with rugged topography.
文摘Release of dissolved volatiles during submarine fire fountaining eruptions can profoundly influence the buoyancy flux at the vent. Theoretical considerations indicate that in some cases buoyant magma can be erupted prior to fragmentation (~75% vesicle volume threshold). Laboratory simulations using immiscible fluids of contrasting density indicate that the structure of the source flow at the vent depends critically on the relative magnitudes of buoyancy and momentum fluxes as reflected in the Richardson number (Ri). Analogue laboratory experiments of buoyant discharges demonstrate a variety of complex flow structures with the potential for greatly enhanced entrainment of surrounding seawater. Such conditions are likely to favor a positive feedback between phreatomagmatic explosions and volatile degassing that will contribute to explosive volcanism. The value of the Richardson number for any set of eruption parameters (magma discharge rate and volatile content) will depend on water depth as a result of the extent to which the exsolved volatile components can expand.
文摘For selected locations in the Atlantic and Pacific Ocean, we compared surface ocean chlorophyll time series extracted from SeaWiFS imagery from 1997-2004 with the results of an ocean coupled circulation and biogeochemical model covering the period 1958-2004. During the 1997-2004 time period, linear trends in model and satellite time series were significantly correlated at most of the 44 sites we studied. Eleven sites were selected for further study, and we used the longer time series of the model to assess whether trends observed during the SeaWiFS period at these 11 sites were unusual in relation to those observed over the longer historical period covered by the model. The results show that the trends observed during the SeaWiFS period were not unusual and fell well within the range in magnitude of linear trends observed in other 8-year periods of model output. This result implies that the SeaWiFS satellite ocean color time series is not yet sufficiently long, on its own, to directly observe any long term changes in phytoplankton chlorophyll that may be occurring in the surface waters of the open ocean as a result of increased ocean stratification linked to global climate changed.
基金the U.S. National Science Foundation (Grant Nos. EAR 0738779 and OCE 0727919)the National Basic Research Program of China (Grant No. 2004CB418404)partially by the National Nature Science Foundation of China (Grant No. 40521002)
文摘The Wenchuan earthquake of 12 May 2008 is the most destructive earthquake in China in the past 30 years in terms of property damage and human losses. In order to understand the earthquake process and the geo-morphological factors affecting the seismic hazard, we simulated the strong ground mo-tion caused by the earthquake, incorporating three-dimensional (3D) earth structure, finite-fault rupture, and realistic surface topography. The simulated ground motions reveal that the fault rupture and basin structure control the overall pattern of the peak ground shaking. Large peak ground velocity (PGV) is distributed in two narrow areas: one with the largest PGV values is above the hanging wall of the fault and attributed to the locations of fault asperities and rupture directivity; the other is along the north-western margin of the Sichuan Basin and caused by both the directivity of fault rupture and the ampli-fication in the thick sediment basin. Rough topography above the rupture fault causes wave scattering, resulting in significantly larger peak ground motion on the apex of topographic relief than in the valley. Topography and scattering also reduce the wave energy in the forward direction of fault rupture but increase the PGV in other parts of the basin. These results suggest the need for a localized hazard as-sessment in places of rough topography that takes the topographic effects into account. Finally, had the earthquake started at the northeast end of the fault zone and ruptured to the southwest, Chengdu would have suffered a much stronger shaking than it experienced on 12 May, 2008.
基金supported by the NSFC/RGC Joint Research Scheme sponsored by the Research Grants Council of the Hong Kong Special Administrative Region, China (Grant Nos. N_CUHK418/15, N_CUHK430/16)CUHK-University of Manchester Research Fund (Grant No. 4930227)+4 种基金United States National Science Foundation (Grant No. OCE-1357433)Natural Sciences and Engineering Research Council of Canada (Grant No. STPGP 494141-16)Japan Society for the Promotion of Science (Grant Nos. KAKENHI 2624004, 26280006)National Natural Science Foundation of China (Grant No. 41474033)the Summer School Program of Peking University
文摘It has long been known that human activities such as waste fluid disposal and reservoir impoundment may cause earthquakes. Recently, anthropogenic activities to tackle the increasing energy demand and to address climate change issues are also reported to induce earthquakes. These activities have a common attribute in that fluids are injected and extracted underground and induce spatiotemporal changes of pore pressure and stress, which may cause slip on faults. Induced earthquakes not only pose significant impacts on seismic hazard assessment and preparation, but also raise the question to the society as how to balance the economic needs of resources development and the public's concerns about potential environmental impacts. Here we review the observations of fluid-injection/extraction induced earthquakes, ground deformation associated with these activities, and their physical mechanisms. Furthermore, we discuss the influences of induced earthquakes on seismic hazard models, regulatory policies on these anthropogenic activities, and current development of academic, industrial and government initiatives and collaborations in order to understand this intriguing phenomenon and address associated challenges.
基金Project supported by the National Natural Science Foundation of China and the National Science Foundation of the United States
文摘Ⅰ. METHODSAll of the aerosol samples were collected in the spring of 1990 during and after three dust storms. The first was on April 6 in Xi’an (34.3°N, 108.9°E)(dust storm Ⅰ); the second was in Shapuotou (37.5°N, 105°E) and Beijing (39.9°N, 116.4°E) on April 10 and in Xi’an on April 11 (dust storm Ⅱ); and the third on April 25 in Beijing (dust storm Ⅲ).
基金the National Natural Science Foundation of China (Grant No. 40776021)the National Basic Research Program of China (Grant No. 2006CB400603)+1 种基金the National High Technology Research and Development Program of China (Grant No.2006AA09Z102)the Office of Naval Research (Grant No. N000140210271)
文摘In the region southeast of Okinawa, during May to July 2001, a cyclonic and an anticyclonic eddy were observed from combined measurements of hydrocasts, an upward-looking moored acoustic Doppler current profiler (MADCP), pressure-recording inverted echo sounders (PIESs), satellite altimetry, and a coastal tide gauge. The hydrographic data showed that the lowest/highest temperature (T) and salinity (S) anomalies from a 13-year mean for the same season were respectively -3.0/+2.5℃ and -0.20/+0.15 psu at 380/500 dbar for the cyclonic/anticyclonic eddies. From the PIES data, using a gravest empirical mode method, we estimated time-varying surface dynamic height (D) anomaly referred to 2000 dbar changing from -20 to 30 cm, and time-varying T and S anomalies at 500 dbar ranging through about ±2 ℃ and ±0.2 psu, respectively. The passage of the eddies caused variations of both satellite-measured sea surface height anomaly (SSHA) and tide-gauge-measured sea level anomaly to change from about –20 to 30 cm, consistent with the D anomaly from the PIESs. Bottom pressure sensors measured no variation related to these eddy activities, which indicated that the two eddies were dominated by baro-clinicity. Time series of SSHA map confirmed that the two eddies, originating from the North Pacific Subtropical Countercurrent region near 20°―30°N and 150°―160°E, traveled about 3000 km for about 18 months with mean westward propagation speed of about 6 cm/s, before arriving at the region southeast of Okinawa Island.
基金the National Natural Science Foundation of China （Grant Nos. 29837190, 20077004, and 30230310）.
文摘In spite of increasing attention on Chinese aerosol, there has never been a country-wide survey of its general characteristics. This paper presents elemental data for aerosol at 23 sites in and around China, mostly drawn from the literature, and shows some of the large-scale patterns. Al, Na, and Se are used to represent the crustal, marine, and pollution components, respectively. Most of the patterns are aligned in SW-NE. Al and Na are highest to the NW and the SE, respectively, and their ratio changes rapidly near the coast. Se has a broad maximum over Central China, and the Se/Al ratio （an indicator of pollution vs. crustal aerosol） increases progressively from the NW to the SE. A simple index for simulating pollution aerosol, which uses population density, annual precipitation, and mean wind speed, adequately reproduces the large-scale pattern of pollution aerosol and shows how crustal Al in the NW gradually gives way to flyash Al toward the SE.
基金supported by the U.S. National Science Foundation (Grant OCE- 0526177)the U.S. Office of Naval Research (Grant N00014-06-10729)supported by a WHOI/NOAA Cooperative Institute for Climate and Ocean Research Postdoctoral Scholarship
文摘We present numerical computations of a new wind-wave coupling theory that is governed by a system of nonlinear advance-delay differential equations (NLADDE). NLADDE are functional differential equations for which the derivative of an unknown function depends nonlinearly on the past (delayed), present, and future (advanced) values of the unknown function (if time is the independent variable). A practical numerical method for solving NLADDE is implemented, based on a collocation method. The method is tested for two problems with known analytic solutions and is shown to be numerically convergent. Numerical solutions to the coupled wind and wave problem reveal estimates of the wave height spectrum, the distribution of breaking waves (both depend on wave scale), as well as the vertical air-side profiles of turbulent stress and wind speed.
文摘2001年5～7月,在冲绳岛以东海区,我们通过CTD(conductivity temperature and depth)、锚系海流剖面、PIES(pressure-recording inverted echo sounders)、卫星海面高度计和沿岸潮位仪的组合观测到一个气旋涡和一个反气旋涡.CTD断面数据显示,气旋涡和反气旋涡中心位于380/500dbar水深,对应的温度(T)和盐度(S)距平分别为-3.0/+2.5℃和-0.20/+0.15.从PIES数据,我们估算了气旋涡和反气旋涡经过时,相对于2000dbar深基准的动力高度(D)的时间变化为-20～30cm,500dbar深的T和S距平的变化范围约±2℃和±0.2.同时,由卫星海面高度计和潮位仪观测得到的海面高度距平变化范围约为-20至30cm,与PIES观测到的D的变化基本一致.由于两个涡经过时,PIES的压力传感器没有显示出相应的变化,反映出这两个涡具有较强的斜压特性.从卫星海面高度距平时间序列图追溯确认,这两个涡起源于北太平洋副热带逆流区附近,即20°～30°N,150°～160°E海区.它们以6cm·s-1的平均速度向西传播了约3000km,历时约18个月,然后抵达冲绳岛以东海区.
