In this study, a sea fog event which occurred on 27 March 2005 over the Yellow and Bohai Seas was investigated observationally and numerically. Almost all available observational data were used, including satellite im...In this study, a sea fog event which occurred on 27 March 2005 over the Yellow and Bohai Seas was investigated observationally and numerically. Almost all available observational data were used, including satellite imagery of Geostationary Operational Environmental Satellite （GOES）-9, three data sets from station observations at Dandong, Dalian and Qingdao, objectively reanalyzed data of final run analysis （FNL） issued by the National Center for Environmental Prediction （NCEP） and Regional Atmospheric Modeling System （RANIS） results. Synoptic conditions and fog characteristics were analyzed. The fog formed when warm, moist air was advected northwards over the cool water of the Yellow and Bohai Seas, and dissipated when a cold front brought northerly winds and cool, dry air. In order to better understand the fog formation mechanism, a high-resolution RAMS modeling with a 6km×6km grid, initialized and validated by FNL data, was designed. A 48h modeling that started from 12 UTC 26 March 2005 reproduced the main characteristics of this sea fog event. The simulated lower visibility area agreed reasonably well with the sea fog region identified from the satellite imagery. Advection cooling effect seemed to play a significant role in the fog formation.展开更多
Tidal waves in the East China Sea are simulated numerically with POM(Princeton Ocean Model) model for normal mean sea level, 30 cm higher, 60 cm higher, and 100 cm higher, respectively, and the simulated result is com...Tidal waves in the East China Sea are simulated numerically with POM(Princeton Ocean Model) model for normal mean sea level, 30 cm higher, 60 cm higher, and 100 cm higher, respectively, and the simulated result is compared with the harmonic analysis result of hourly sea level data from 19 tide gauges for more than 19 years. It is indicated that the long-term mean sea level variation affects notably tidal waves in this region. Generally, the tidal amplitude increases when the mean sea level rises, but this relationship may be inverse for some sea areas. The maximal variation of tidal amplitude takes place in the zones near the Fujian coast and the Zhejiang coast, rather than the shallowest Bohai Sea. The maximum increase of M2 amplitude can exceed about 15 cm corresponding to the 60 cm rise of the mean sea level along the Fujian coast. The other regions with large variations of tidal amplitude are those along the Jiangsu coast, the south-east coast of Shandong, and the south-east coast of Dalian. The propagation of tidal waves is also related to mean sea level variation, and the tidal phase-lag decreases generally when the mean sea level rises. Almost all the regions where the tidal phase-lag increases with rising mean sea level are close to amphidromic points, meanwhile the spatial area of such regions is very small. Because the influence of mean sea level variation upon tidal waves is spatially marked, such spatial effect should be considered in calculation of the tidal characteristic value and engineering water level. In the region where the amplitudes of the major tidal constituents increase, the probable maximum high water level becomes higher, the probable maximum low water level becomes lower, and both design water level andcheck water level increase obviously. For example, the design water level at Xiamen increases by 13.5 cm due to the variation of tidal waves when the mean sea level rises 60 cm, the total increase of design water level being 73.5 cm.展开更多
This study on the distribution features of petroleum hydrocarbon in water and sediment off the Fujian shore using data obtained from the baseline research on oceanic contamination in Fujian showed that: during the res...This study on the distribution features of petroleum hydrocarbon in water and sediment off the Fujian shore using data obtained from the baseline research on oceanic contamination in Fujian showed that: during the research period, petroleum hydrocarbon concentrations in water varied from 5.77 μg/L to 37.28 μg/L, averaged 14.48 μg/L; was lower in the wet season than in the dry season; and was highest in the Minjiang Estuary and Jiulong Estuary in both seasons. The petroleum hydrocarbon concentrations in shore sediment varied from 14.48 mg/kg to 784.36 mg/kg, averaged 133.3 mg/kg, and was closely related to sediment types (granularity).展开更多
In this paper, a heavy sea fog event occurring over the Yellow Sea on 11 April 2004 was investigated based upon observational and modeling analyses. From the observational analyses, this sea fog event is a typical adv...In this paper, a heavy sea fog event occurring over the Yellow Sea on 11 April 2004 was investigated based upon observational and modeling analyses. From the observational analyses, this sea fog event is a typical advection cooling case. Sea surface temperature(SST) and specific humidity(SH) show strong gradients from south to north, in which warm water is located in the south and consequently, moisture is larger in the south than in the north due to evaporation processes. After fog formation, evaporation process provides more moisture into the air and further contributes to fog evolution. The sea fog event was reproduced by the Regional Atmospheric Modeling System(RAMS) reasonably. The roles of important physical processes such as radiation, turbulence as well as atmospheric stratification in sea fog's structure and its formation mechanisms were analyzed using the model results. The roles of long wave radiation cooling, turbulence as well as atmospheric stratification were analyzed based on the modeling results. It is found that the long wave radiative cooling at the fog top plays an important role in cooling down the fog layer through turbulence mixing. The fog top cooling can overpower warming from the surface. Sea fog develops upward with the aid of turbulence. The buoyancy term, i.e., the unstable layer, contributes to the generation of TKE in the fog region. However, the temperature inversion layer prevents fog from growing upward.展开更多
Finescale spiral rainbands associated with Typhoon Rananim （2004） with the band length ranging from 10 to nearly 100 km and band width varying from 5 to 15 km are simulated using the Fifth-Generation NCAR/Penn State...Finescale spiral rainbands associated with Typhoon Rananim （2004） with the band length ranging from 10 to nearly 100 km and band width varying from 5 to 15 km are simulated using the Fifth-Generation NCAR/Penn State Mesoscale Model （MM5）. The finescale rainbands have two types： one intersecting the eyewall and causing damaging wind streaks, and the other distributed azimuthally along the inner edge of the eyewall with a relatively short lifetime. The formation of the high-velocity wind streaks results from the interaction of the azimuthal flow with the banded vertical vorticity structure triggered by tilting of the horizontal vorticity. The vertical advection of azimuthal momentum also leads to acceleration of tangential flow at a relatively high Mtitude. The evolution and structures of the bands are also examined in this study. Further investigation suggests that the boundary inflection points are related tightly to the development of the finescale rainbands, consistent with previous findings using simple symmetric models. In particular; the presence of the level of inflow reversal in the boundary layer is a crucial factor controlling the formation of these bands. The near-surface wavy peaks of vertical vorticity always follow the inflection points in radial flow. The mesoscale vortices and associated convective updrafts in the eyewall are considered to strengthen the activity of finescale bands, and the updrafts can trigger the formation of the bands as they reside in the environment with inflow reversal in the boundary layer.展开更多
Arctic Intermediate Water （AIW）, advected from the North Atlantic Ocean, has a potential influence on climate in the Arctic region, but is poorly simulated in coarse resolution models. In this study, a coupled ice-o...Arctic Intermediate Water （AIW）, advected from the North Atlantic Ocean, has a potential influence on climate in the Arctic region, but is poorly simulated in coarse resolution models. In this study, a coupled ice-ocean model is used to investigate features of AIW by conducting two sensitivity experiments based on Neptune parameterization and horizontal resolution. The re- suits show that both experiments improve the modeling of temperature profiles in the western Eurasian Basin, mainly as a result of more realistic volume and heat transport through the Fram Strait. Topographical flows are well reproduced using Neptune parame- terization or a finer horizontal resolution. In the eddy-permitting model with relatively higher resolution, the velocity field is more realistic than in the Neptune parameterization model, and complex inflow and outflow belts of barotropic structure are well repro- duced. The findings of this study suggest that increased model resolution, as provided by an eddy-resolving model, is needed to reproduce realistic circulation and thermohaline structure in the Arctic, since the Rossby radius of deformation is only several kilometers in the Arctic Ocean. This paper focuses on the external heat input rather than internal mixing process, and obtains a conclusion that the heat input from the Fram Strait is a main factor to reproduce AIW in the Eurasian Basin successfully, at least for the western part.展开更多
A protected semi-enclosed embayment,the Eastern Harbor(EH),is situated in the central sector of the Mediterranean coast of Alexandria,Egypt.It is a famous fishing dock and water-sport center and its importance arose a...A protected semi-enclosed embayment,the Eastern Harbor(EH),is situated in the central sector of the Mediterranean coast of Alexandria,Egypt.It is a famous fishing dock and water-sport center and its importance arose after the discovery of the Ptolemaic royal quarter of ancient Alexandria.To protect this national treasure and improve its environmental health,the untreated anthropogenic effluents,which continued for decades into the EH since 1992,must be totally stopped.Accordingly,it is an important issue to continually monitor and asses the environmental status of the EH.The sediment texture,total organic carbon,and the accumulation,distribution,and ecological risks of Cd,Cr,Pb,As,Hg and A1 were determined with a total of 14 surficial sediments samples collected in the EH during 2010.Metal contents were compared to the literature data to assess the pollution status of sediments.Enrichment factors,Degree of contamination(mCd)and potential ecological risk were calculated as a criterion of possible contamination.Since mCd calculation produces an overall average value for a range of pollutants,in the present study the contamination factor that provides a measure of the degree of overall contamination in the surface layers in a particular sampling site may provide a better indication of the state of pollution in the EH sediments than other indicators.展开更多
Based on a ship survey during January 1998, the characteristics of the flow, the thermohaline properties and the volume transport of the Arabian Sea are discussed. A strong westward flow exists between 10.5?N and 11?N...Based on a ship survey during January 1998, the characteristics of the flow, the thermohaline properties and the volume transport of the Arabian Sea are discussed. A strong westward flow exists between 10.5?N and 11?N, part of which turns to the south as the Somali current near the coast at about 10?N and the rest turns north. At the passage between the African continent and the So- cotra Island, the northern branch separates into two flows: the left one enters the passage and the right one flows eastward along the southern slope of the island. Off the island the flow separates once more, most of it meandering northeast and a small fraction flow- ing southeast. Volume transport calculation suggests that the tidal transport is one or two orders of magnitude smaller than the total transport in this region and it becomes more important near the coast. The average velocity of the flow in the upper layer (0-150 m) is about 20 cm s-1, with a maximum of 53 cm s-1 appearing east of the Socotra Island, and the subsurface layer (200-800 m) has an aver- age velocity of 8.6 cm s-1; the velocity becomes smaller at greater depths. The depth of the seasonal thermocline is about 100 m, above which there is a layer with well mixed temperature and dissolved oxygen. High-salinity and oxygen-rich water appears near the surface of the northern Arabian Sea; a salinity maximum and oxygen minimum at 100 m depth along 8?N testifies the subduction of surface water from the northern Arabian Sea. Waters from the Red Sea and the Persian Gulf also influence the salinity of the area.展开更多
Makran zone is one of the largest accretionary wedges in the world. This research had used methods such as studies of Office and library, field observation and surveying that several field visits, sampling, registered...Makran zone is one of the largest accretionary wedges in the world. This research had used methods such as studies of Office and library, field observation and surveying that several field visits, sampling, registered structural evidence, Laboratory studies, Data analysis, interpretation and conclusions. The most important objective of this study is assessment of Tectonics and hazard Potential in Coasts the Oman Sea based on tectonics and sedimentology. The northward movement and subduction of Oman oceanic lithosphere beneath Iranian micro-plate at a very shallow angle and at high rate is responsible for active orogenesis and uplift. Detailed seismological and geological information in planning is extremely essential to avoid any disaster. It is to be remembered that seismicity does not remain fixed in an area but migrates slowly with time. Thus, the planners are expected to be more concerned with the building code and prevention strategies. It is also important to mention that the Coastal zones are always vulnerable to natural hazards and liquefaction. The geomorphology of an area is the first indicator of on-going tectonic activity. In order to measure the amount of deformation due to tectonic processes, the initial geometry of the geomorphic markers is reconstructed accurately. Study of sediments shows that abundant shell fragments organized in laminae also favor a storm origin. Storm deposits contain no internal mud layers and rarely contain pieces of mud. Maximum deposit thickness is near the shore, and landward thinning of the deposit is commonly abrupt. Storm deposits fill in topographic lows, and the upper surface is relatively uniform in elevation alongshore. Finally, landforms of tectonically active regions and sediments are controlling factors interactions between tectonic, sedimentary, climatic, and surficial processes.展开更多
The sea ice community plays an important role in the Arctic marine ecosystem. Because of the predicted environmental changes in the Arctic environment and specifically related to sea ice, the Arctic pack ice biota has...The sea ice community plays an important role in the Arctic marine ecosystem. Because of the predicted environmental changes in the Arctic environment and specifically related to sea ice, the Arctic pack ice biota has received more attention in recent years using modern ice-breaking research vessels. Studies show that the Arctic pack ice contains a diverse biota and besides ice algae, the bacterial and protozoan biomasses can be high. Surprisingly high primary production values were observed in the pack ice of the central Arctic Ocean. Occasionally biomass maximum were discovered in the interior of the ice floes, a habitat that had been ignored in most Arctic studies. Many scientific questions, which deserve special attention, remained unsolved due to logistic limitations and the sea ice characteristics. Little is know about the pack ice community in the central Arctic Ocean. Almost no data exists from the pack ice zone for the winter season. Concerning the abundance of bacteria and protozoa, more studies are needed to understand the microbial network within the ice and its role in material and energy flows. The response of the sea ice biota to global change will impact the entire Arctic marine ecosystem and a long-term monitoring program is needed. The techniques, that are applied to study the sea ice biota and the sea ice ecology, should be improved.展开更多
In continental shelf areas works where the focus is Geochemistry are widely relevant, due to the vast complexity and uses of these relief features (social, environmental and economic). On the Brazilian Northeast tropi...In continental shelf areas works where the focus is Geochemistry are widely relevant, due to the vast complexity and uses of these relief features (social, environmental and economic). On the Brazilian Northeast tropical shelves, with emphasis on the Pernambuco Continental Shelf (PCS), the published studies are limited and have aimed at portions closer to the coastline. The objective of the present work is the description of the characteristics and origin of sedimentary organic matter (SOM) in the inner and middle Pernambuco shelf, defining and classifying the local geochemical sedimentary facies. The sampling stations (136) were collected in the study area, and the grain-size, contents of total organic matter (TOM), calcium carbonate (CaCO<sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;">) were analyzed. The samples were processed in an elemental analyzer coupled with a mass spectrometer after the elimination of calcium carbonate. The obtained data were the grain-size, TOM, CaCO</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;">, elemental (C, N) and the stable isotopic ratios of </span><i><span style="font-family:Verdana;">δ</span></i><sup><span style="font-family:Verdana;">13</span></sup><span style="font-family:Verdana;">C e </span><i><span style="font-family:Verdana;">δ</span></i><sup><span style="font-family:Verdana;">15</span></sup><span style="font-family:Verdana;">N of SOM. Based on the measured values of carbon and nitrogen, the C/N ratio, associated to </span><i><span style="font-family:Verdana;">δ</span></i><sup><span style="font-family:Verdana;">13</span></sup><span style="font-family:Verdana;">C e </span><i><span style="font-family:Verdana;">δ</span></i><sup><span style="font-family:Verdana;">15</span></sup><span style="font-family:Verdana;">N, is observed that in the PCS predominates an organic matter of marine origin along its entire length: C < 1%, N < 1%, C/N < 5, </span><i><span style="font-family:Verdana;">δ</span></i><sup><span style="font-family:Verdana;">13</span></sup><span style="font-family:Verdana;">C > -21</span><span><span><span> </span></span></span><span><span><span><span style="font-family:Verdana;">PDB e </span><i><span style="font-family:Verdana;">δ</span></i><sup><span style="font-family:Verdana;">15</span></sup><span style="font-family:Verdana;">N > 8</span><sub><span style="font-family:Verdana;">Ar</span></sub><span style="font-family:Verdana;">. The PCS presents patches of continental origin SOM, associated to the coastal zones adjacent to estuarine systems mouths and covering the paleochannels, which may indicate that this material was carried from the coastal rivers to the offshore areas, possibly by the paleo-valleys that also act as traps of fine sediments and SOM. The statistical analysis indicates the existence of 6 different sedimentary facies and a prevalence of one of them, characterized by poorly-sorted bioclastic sandy-gravel, with low to medium organic contents of marine origin. This indicates that the coastal sedimentary material contributions are low and the local cover is autochthonous of biogenic origin, and deposited according to the surficial topography, morphosedimentary processes and meteoceanographycal conditionings of the study area, typical of moderate hydrodynamic energy environments.</span></span></span></span>展开更多
This paper presents a study of physical and biogeochemical variables using numerical model and mixed layer oceanographic data from a 2 - 3 year?in situmeasurements in the Northwestern and Northeastern sites of the Atl...This paper presents a study of physical and biogeochemical variables using numerical model and mixed layer oceanographic data from a 2 - 3 year?in situmeasurements in the Northwestern and Northeastern sites of the Atlantic Ocean. Model outputs are presented and indicated that very good estimates may be obtained. The outputs showed considerable agreement in reproducing seasonal distributions of?pCO2,?pCO2-T,?pCO2-nonT, mixed layer temperature, and chlorophyll-a?in both winter and summer, and therefore provide useful physical and theoretical understanding of their biogeochemistry. The model?pCO2indicated a distinct temporal variability with seasonal changes coinciding with the change in sea surface temperature. It also provides an agreement that there is a strong seasonal cycle of mixed layer parameters filliped by nonthermal and physical factors. As an outgrowth of this work, the?pCO2?model outputs affirm the North Atlantic Ocean capacity as an important oceanographic sink for anthropogenic carbon dioxide.展开更多
The aim of the current study was to evaluate the productive capacity of the phytoplankton community and other environmental variables in the estuarine area of Suape;while considering the constant morphological, sedime...The aim of the current study was to evaluate the productive capacity of the phytoplankton community and other environmental variables in the estuarine area of Suape;while considering the constant morphological, sedimentological and hydrological changes, the site has been facing due to the implementation and expansion of an industrial and port complex. The study comprised 6 campaigns: 3 in the dry season and 3 in the rainy season. Water samples were collected from the surface layer of the internal and external portions of the estuarine bay during low spring tides. The salinity ranged from 32.20 to 37.10, the water temperature ranged from 26.60°C to 29.40°C, and the oxygen saturation rate ranged from 58.5% to 114.5%. There was significant seasonal variation. The nitrite concentration was higher during the rainy season, whereas the ammonia concentration was higher during the dry season;the higher ammonia concentration helped increase chlorophyll-a levels and rates of primary productivity, which ranged from 0.02 - 2.45 mg·m−3 and from 0.34 to 4.32 mg·C·m−3·h−1, respectively. Chlorophyll-a a-containing biomass, and this reflected the low nutrient content in the water and indicated that the area was free from eutrophication processes. The decrease of rainfall during the sampling months and the anthropogenic changes in the environment led to reduced continental contributions, increased marine interference, nutrient dilution and loss of phytoplankton production capacity in Suape Bay, which severely damaged other trophic links in the ecosystem.展开更多
Two additional features are particularly useful in pixelwise satellite data segmentation using neural networks: one results from local window averaging around each pixel (MWA) and another uses a standard deviation est...Two additional features are particularly useful in pixelwise satellite data segmentation using neural networks: one results from local window averaging around each pixel (MWA) and another uses a standard deviation estimator (MWSD) instead of the average. While the former’s complexity has already been solved to a satisfying minimum, the latter did not. This article proposes a new algorithm that can substitute a <i><span style="font-family:Verdana;">naive</span></i><span style="font-family:Verdana;"> MWSD, by making the complexi</span><span><span style="font-family:Verdana;">ty of the computational process fall from </span><i><span style="font-family:Verdana;">O</span></i><span style="font-family:Verdana;">(</span><i><span style="font-family:Verdana;">N</span></i><sup><span style="font-family:Verdana;">2</span></sup><i><span style="font-family:Verdana;">n</span></i><sup><span style="font-family:Verdana;">2</span></sup><span style="font-family:Verdana;">) to </span><i><span style="font-family:Verdana;">O</span></i><span><span style="font-family:Verdana;">(</span><i><span style="font-family:Verdana;">N</span></i></span><sup><span style="font-family:Verdana;">2</span></sup><i><span style="font-family:Verdana;">n</span></i><span style="font-family:Verdana;">)</span><span style="font-family:Verdana;">, where </span><i><span style="font-family:Verdana;">N</span></i><span style="font-family:Verdana;"> is a square</span></span><span style="font-family:Verdana;"> input array side, and </span><i><span style="font-family:Verdana;">n</span></i><span style="font-family:Verdana;"> is the moving window’s side length. The Num</span><span style="font-family:Verdana;">ba python compiler was used to make python a competitive high-performance</span> <span style="font-family:Verdana;">computing language in our optimizations. Our results show efficiency benchmars</span>展开更多
Objective:To identify the potentially harmful epiphytic Oscillatoriales species and follow up their distribution along Alexandria coast.Methods:Samples were collected bimonthly from April 2009 to February 2010 at thre...Objective:To identify the potentially harmful epiphytic Oscillatoriales species and follow up their distribution along Alexandria coast.Methods:Samples were collected bimonthly from April 2009 to February 2010 at three sites along Alexandria coast.Both morphological and molecular analyses were used for identifying the dominant species.Results:Five species belonging to two families were identified;Oscillatoria acutissima,Oscillatoria nigroviridis,Oscillatoria sp.,Lyngbya majuscule and Phormidium formosum.Their cell density ranged from 10^(3)to 126×10^(3)filament g^(-1)fresh weight macroalgae.The morphological study of the dominant species,Oscillatoria sp.(Oscillatoria sp.W1)showed much similarity with Planktothrix agardhii with no heterocysts and akinetes,while molecular ananlysis(16S rDNA)clustered the species in the same group with Anabaena sp.Conclusions:The 16S rDNA genes are not suitable for identifying Oscillatoriales during the present study and another molecular method should be used instead.展开更多
Objective:To evaluate the stock of Alepes djedaba(A.djedaba)by describing the length composition,growth parameters,mortality rates of A.djedaba captured in Arabian Gulf off Saudi Arabia and adopting yield per recruit ...Objective:To evaluate the stock of Alepes djedaba(A.djedaba)by describing the length composition,growth parameters,mortality rates of A.djedaba captured in Arabian Gulf off Saudi Arabia and adopting yield per recruit and biomass per recruit models.Methods:A random sample of 490 fish representing a moderate range of total lengths(16.5-32.4cm)and weights(60-410 g)were sampled in Arabian Gulf off Dammam,Saudi Arabia during the period from August 2008 to July 2009.LFD5 software was used for estimation of growth parameters.Total mortality was calculated using the length converted catch curve.Natural mortality was estimated using Pauly and David's formula.Fishing mortality was computed by subtracting natural mortality from total mortality.Per recruit analysis was made using Beverton and Holt model.Results:Length-frequency analysis revealed four peaks and the length range from 22 cm to 27 cm dominated the catch,constituting about 71%of the catch.Values of the von Bertalanffy growth parameters were computed using LFD5 software as follows:the asymptotic length(L_(∞))=41.71 cm,curvature parameter(K)=0.36 year^(-1),and hypothetic age at zero length(t_(0))=-0.76 year.The total mortality(Z)was estimated as 2.07 year^(-1),and natural mortality was 0.8 year^(-1).Fishing mortality F=1.27 year^(-1),which was higher than F_(0.1)(0.3 year^(-1)),F_(SB(50))(0.59 year^(-1))and FS_(B(40))(0.86 year^(-1)).Atthe current levels of fishing and natural mortality,the biomass per recruit is 34%of the virgin biomass.Conclusions:These may indicate an overexploitation state of the fisheries of A.djedaba in Arabian Gulf.展开更多
Digital information on sea ice extent,thickness,volume,and distribution is crucial for understanding Earth's climate system.The Snow and Ice Mass Balance Apparatus(SIMBA)is used to determine snow and ice temperatu...Digital information on sea ice extent,thickness,volume,and distribution is crucial for understanding Earth's climate system.The Snow and Ice Mass Balance Apparatus(SIMBA)is used to determine snow and ice temperatures in Arctic,Antarctic,ice-covered seas,and boreal lakes.Snow depth and ice thickness are derived from SIMBA temperature regimes(SIMBA_ET and SIMBA_HT).In warm conditions,SiMBA_ET temperature-based ice thickness may have errors due to the isothermal vertical profile.SIMBA_HT provides a visible ice-bottom interface for manual quantification.We propose an unmanned approach,combining neural networks,wavelet analysis,and Kalman filtering(NWK),to mathematically establish NwK and retrieve ice bottoms from various SIMBA_HT datasets.In the Arctic,NWK-derived total thickness showed a bias range of-5.64 cm to 4.01 cm and a correlation coefficient of 95%-99%.For Baltic Sea ice,values ranged from 1.31 cm to 2.41 cm(88%-98%correlation),and for boreal lake ice,-0.7 cm to 2.6 cm(75%-83%correlation).During ice growth,thermal equilibrium,and melting,the bias varied from-3.93 cm to 2.37 cm,-1.92 cm to 0.04 cm,and-4.90 cm to 3.96 cm,with correlation coefficients of 76%-99%.These results demonstrate NWK's robustness in retrieving ice bottom evolution in different water environments.展开更多
During the 7-9th century,the Tibetan Empire constituted a superpower between the Tang Empire and Abbasid Caliphate:one that played significant roles in geopolitics in Asia during the Early Medieval Period.The factors ...During the 7-9th century,the Tibetan Empire constituted a superpower between the Tang Empire and Abbasid Caliphate:one that played significant roles in geopolitics in Asia during the Early Medieval Period.The factors which led to the rise and rapid decline of this powerful Empire,the only united historical regime on the Tibetan Plateau(TP),remain unclear.Sub-annual scale precipitation and decadalscale temperature records of the central TP are presented,indicating that the height of this Empire coincided with a two-century long interval of uncharacteristically warm and humid climate.The ameliorated climate enabled the expansion of arable land and increased agricultural production.The close relationship between the precipitation records and historical events implied that the Empire implemented flexible strategies to tackle the effects of climate changes.This has implications for agricultural production in alpine regions including the TP,in the context of current global warming.展开更多
基金supported by the National Natural Science Foundation of China under the grant number 40675060the Chinese Ministry of Science and Technology under the 863 Project grant number 2006AA09Z151+2 种基金supported by the State Oceanic Administration under the grant 908-02-03-10the Chinese Meteorological Administration under the grant CMATG 2006M32supported by the National Science Foundation under grant number OISE-0229657.
文摘In this study, a sea fog event which occurred on 27 March 2005 over the Yellow and Bohai Seas was investigated observationally and numerically. Almost all available observational data were used, including satellite imagery of Geostationary Operational Environmental Satellite （GOES）-9, three data sets from station observations at Dandong, Dalian and Qingdao, objectively reanalyzed data of final run analysis （FNL） issued by the National Center for Environmental Prediction （NCEP） and Regional Atmospheric Modeling System （RANIS） results. Synoptic conditions and fog characteristics were analyzed. The fog formed when warm, moist air was advected northwards over the cool water of the Yellow and Bohai Seas, and dissipated when a cold front brought northerly winds and cool, dry air. In order to better understand the fog formation mechanism, a high-resolution RAMS modeling with a 6km×6km grid, initialized and validated by FNL data, was designed. A 48h modeling that started from 12 UTC 26 March 2005 reproduced the main characteristics of this sea fog event. The simulated lower visibility area agreed reasonably well with the sea fog region identified from the satellite imagery. Advection cooling effect seemed to play a significant role in the fog formation.
文摘Tidal waves in the East China Sea are simulated numerically with POM(Princeton Ocean Model) model for normal mean sea level, 30 cm higher, 60 cm higher, and 100 cm higher, respectively, and the simulated result is compared with the harmonic analysis result of hourly sea level data from 19 tide gauges for more than 19 years. It is indicated that the long-term mean sea level variation affects notably tidal waves in this region. Generally, the tidal amplitude increases when the mean sea level rises, but this relationship may be inverse for some sea areas. The maximal variation of tidal amplitude takes place in the zones near the Fujian coast and the Zhejiang coast, rather than the shallowest Bohai Sea. The maximum increase of M2 amplitude can exceed about 15 cm corresponding to the 60 cm rise of the mean sea level along the Fujian coast. The other regions with large variations of tidal amplitude are those along the Jiangsu coast, the south-east coast of Shandong, and the south-east coast of Dalian. The propagation of tidal waves is also related to mean sea level variation, and the tidal phase-lag decreases generally when the mean sea level rises. Almost all the regions where the tidal phase-lag increases with rising mean sea level are close to amphidromic points, meanwhile the spatial area of such regions is very small. Because the influence of mean sea level variation upon tidal waves is spatially marked, such spatial effect should be considered in calculation of the tidal characteristic value and engineering water level. In the region where the amplitudes of the major tidal constituents increase, the probable maximum high water level becomes higher, the probable maximum low water level becomes lower, and both design water level andcheck water level increase obviously. For example, the design water level at Xiamen increases by 13.5 cm due to the variation of tidal waves when the mean sea level rises 60 cm, the total increase of design water level being 73.5 cm.
文摘This study on the distribution features of petroleum hydrocarbon in water and sediment off the Fujian shore using data obtained from the baseline research on oceanic contamination in Fujian showed that: during the research period, petroleum hydrocarbon concentrations in water varied from 5.77 μg/L to 37.28 μg/L, averaged 14.48 μg/L; was lower in the wet season than in the dry season; and was highest in the Minjiang Estuary and Jiulong Estuary in both seasons. The petroleum hydrocarbon concentrations in shore sediment varied from 14.48 mg/kg to 784.36 mg/kg, averaged 133.3 mg/kg, and was closely related to sediment types (granularity).
基金supported by the 201205010-5 program of the State Oceanic Administration of China and the Natural Science Foundation of China under the grant 41306028partly supported by the National Natural Science Foundation of China under the grant number, 406750060 and 41275049+5 种基金the Chinese Ministry of Science and Technology under the 863 Project grant number 2006 AA09Z151the Chinese Meteorological Administration under the grant number GYHY(QX)200706031the China Scholarship Council for the financial support to his study in NOAA from 2008 to 2010, which enables him to participate in the present worksupported by China postdoctoral funding under the grant 2012M511545the Natural Science Foundation of China under the grant 41305086supported by the open project of the Lab. of Physical Oceanography, Ocean University of China
文摘In this paper, a heavy sea fog event occurring over the Yellow Sea on 11 April 2004 was investigated based upon observational and modeling analyses. From the observational analyses, this sea fog event is a typical advection cooling case. Sea surface temperature(SST) and specific humidity(SH) show strong gradients from south to north, in which warm water is located in the south and consequently, moisture is larger in the south than in the north due to evaporation processes. After fog formation, evaporation process provides more moisture into the air and further contributes to fog evolution. The sea fog event was reproduced by the Regional Atmospheric Modeling System(RAMS) reasonably. The roles of important physical processes such as radiation, turbulence as well as atmospheric stratification in sea fog's structure and its formation mechanisms were analyzed using the model results. The roles of long wave radiation cooling, turbulence as well as atmospheric stratification were analyzed based on the modeling results. It is found that the long wave radiative cooling at the fog top plays an important role in cooling down the fog layer through turbulence mixing. The fog top cooling can overpower warming from the surface. Sea fog develops upward with the aid of turbulence. The buoyancy term, i.e., the unstable layer, contributes to the generation of TKE in the fog region. However, the temperature inversion layer prevents fog from growing upward.
基金supported by the National Basic Research Program of China (2009CB421505)the National Natural Science Foundation of China under Grants Nos.40730948+5 种基金the National Natural Science Foundation of China under Grants Nos.40575030the National Natural Science Foundation of China under Grants Nos.40705024the Shanghai Typhoon Foundation (2009ST09)supported by the National Nature Science Foundation of China under the Grant No.40675060the program of the Ministry of Science and Technology of the People's Republic of China (2006AA09Z151)the program of China Meteorological Administration(GYHY200706031)
文摘Finescale spiral rainbands associated with Typhoon Rananim （2004） with the band length ranging from 10 to nearly 100 km and band width varying from 5 to 15 km are simulated using the Fifth-Generation NCAR/Penn State Mesoscale Model （MM5）. The finescale rainbands have two types： one intersecting the eyewall and causing damaging wind streaks, and the other distributed azimuthally along the inner edge of the eyewall with a relatively short lifetime. The formation of the high-velocity wind streaks results from the interaction of the azimuthal flow with the banded vertical vorticity structure triggered by tilting of the horizontal vorticity. The vertical advection of azimuthal momentum also leads to acceleration of tangential flow at a relatively high Mtitude. The evolution and structures of the bands are also examined in this study. Further investigation suggests that the boundary inflection points are related tightly to the development of the finescale rainbands, consistent with previous findings using simple symmetric models. In particular; the presence of the level of inflow reversal in the boundary layer is a crucial factor controlling the formation of these bands. The near-surface wavy peaks of vertical vorticity always follow the inflection points in radial flow. The mesoscale vortices and associated convective updrafts in the eyewall are considered to strengthen the activity of finescale bands, and the updrafts can trigger the formation of the bands as they reside in the environment with inflow reversal in the boundary layer.
基金supported by the "Plan 111"(Grant no.B07036)the National Natural Science Foundation of China (NNSFC) (Grant no.40631006)the International Cooperate Fund of NNSFC (Grant no.40810104046)
文摘Arctic Intermediate Water （AIW）, advected from the North Atlantic Ocean, has a potential influence on climate in the Arctic region, but is poorly simulated in coarse resolution models. In this study, a coupled ice-ocean model is used to investigate features of AIW by conducting two sensitivity experiments based on Neptune parameterization and horizontal resolution. The re- suits show that both experiments improve the modeling of temperature profiles in the western Eurasian Basin, mainly as a result of more realistic volume and heat transport through the Fram Strait. Topographical flows are well reproduced using Neptune parame- terization or a finer horizontal resolution. In the eddy-permitting model with relatively higher resolution, the velocity field is more realistic than in the Neptune parameterization model, and complex inflow and outflow belts of barotropic structure are well repro- duced. The findings of this study suggest that increased model resolution, as provided by an eddy-resolving model, is needed to reproduce realistic circulation and thermohaline structure in the Arctic, since the Rossby radius of deformation is only several kilometers in the Arctic Ocean. This paper focuses on the external heat input rather than internal mixing process, and obtains a conclusion that the heat input from the Fram Strait is a main factor to reproduce AIW in the Eurasian Basin successfully, at least for the western part.
文摘A protected semi-enclosed embayment,the Eastern Harbor(EH),is situated in the central sector of the Mediterranean coast of Alexandria,Egypt.It is a famous fishing dock and water-sport center and its importance arose after the discovery of the Ptolemaic royal quarter of ancient Alexandria.To protect this national treasure and improve its environmental health,the untreated anthropogenic effluents,which continued for decades into the EH since 1992,must be totally stopped.Accordingly,it is an important issue to continually monitor and asses the environmental status of the EH.The sediment texture,total organic carbon,and the accumulation,distribution,and ecological risks of Cd,Cr,Pb,As,Hg and A1 were determined with a total of 14 surficial sediments samples collected in the EH during 2010.Metal contents were compared to the literature data to assess the pollution status of sediments.Enrichment factors,Degree of contamination(mCd)and potential ecological risk were calculated as a criterion of possible contamination.Since mCd calculation produces an overall average value for a range of pollutants,in the present study the contamination factor that provides a measure of the degree of overall contamination in the surface layers in a particular sampling site may provide a better indication of the state of pollution in the EH sediments than other indicators.
基金supported by NSFC project of Nos.40376005,40506006,40676015,NCET-04-0646 and SRFDP project of No.20060423014The NCEP reanalysis wind data are provided by the NOA A/OAR/ESRL PSD,Boulder,Colorado,USA,from their Web site(http://www.cdc.noaa.gov/).The gnidded monthly mean anomaly of sea level height data of TOPEX/Poscidon are provided by The Center for Space Research/The Univer sity ofTexas at Austin
文摘Based on a ship survey during January 1998, the characteristics of the flow, the thermohaline properties and the volume transport of the Arabian Sea are discussed. A strong westward flow exists between 10.5?N and 11?N, part of which turns to the south as the Somali current near the coast at about 10?N and the rest turns north. At the passage between the African continent and the So- cotra Island, the northern branch separates into two flows: the left one enters the passage and the right one flows eastward along the southern slope of the island. Off the island the flow separates once more, most of it meandering northeast and a small fraction flow- ing southeast. Volume transport calculation suggests that the tidal transport is one or two orders of magnitude smaller than the total transport in this region and it becomes more important near the coast. The average velocity of the flow in the upper layer (0-150 m) is about 20 cm s-1, with a maximum of 53 cm s-1 appearing east of the Socotra Island, and the subsurface layer (200-800 m) has an aver- age velocity of 8.6 cm s-1; the velocity becomes smaller at greater depths. The depth of the seasonal thermocline is about 100 m, above which there is a layer with well mixed temperature and dissolved oxygen. High-salinity and oxygen-rich water appears near the surface of the northern Arabian Sea; a salinity maximum and oxygen minimum at 100 m depth along 8?N testifies the subduction of surface water from the northern Arabian Sea. Waters from the Red Sea and the Persian Gulf also influence the salinity of the area.
文摘Makran zone is one of the largest accretionary wedges in the world. This research had used methods such as studies of Office and library, field observation and surveying that several field visits, sampling, registered structural evidence, Laboratory studies, Data analysis, interpretation and conclusions. The most important objective of this study is assessment of Tectonics and hazard Potential in Coasts the Oman Sea based on tectonics and sedimentology. The northward movement and subduction of Oman oceanic lithosphere beneath Iranian micro-plate at a very shallow angle and at high rate is responsible for active orogenesis and uplift. Detailed seismological and geological information in planning is extremely essential to avoid any disaster. It is to be remembered that seismicity does not remain fixed in an area but migrates slowly with time. Thus, the planners are expected to be more concerned with the building code and prevention strategies. It is also important to mention that the Coastal zones are always vulnerable to natural hazards and liquefaction. The geomorphology of an area is the first indicator of on-going tectonic activity. In order to measure the amount of deformation due to tectonic processes, the initial geometry of the geomorphic markers is reconstructed accurately. Study of sediments shows that abundant shell fragments organized in laminae also favor a storm origin. Storm deposits contain no internal mud layers and rarely contain pieces of mud. Maximum deposit thickness is near the shore, and landward thinning of the deposit is commonly abrupt. Storm deposits fill in topographic lows, and the upper surface is relatively uniform in elevation alongshore. Finally, landforms of tectonically active regions and sediments are controlling factors interactions between tectonic, sedimentary, climatic, and surficial processes.
基金supported by the National Natural Science Foundation of China(No.40006010,30270112)National Basic Science and Technology Programme(2003DEB5J057).
文摘The sea ice community plays an important role in the Arctic marine ecosystem. Because of the predicted environmental changes in the Arctic environment and specifically related to sea ice, the Arctic pack ice biota has received more attention in recent years using modern ice-breaking research vessels. Studies show that the Arctic pack ice contains a diverse biota and besides ice algae, the bacterial and protozoan biomasses can be high. Surprisingly high primary production values were observed in the pack ice of the central Arctic Ocean. Occasionally biomass maximum were discovered in the interior of the ice floes, a habitat that had been ignored in most Arctic studies. Many scientific questions, which deserve special attention, remained unsolved due to logistic limitations and the sea ice characteristics. Little is know about the pack ice community in the central Arctic Ocean. Almost no data exists from the pack ice zone for the winter season. Concerning the abundance of bacteria and protozoa, more studies are needed to understand the microbial network within the ice and its role in material and energy flows. The response of the sea ice biota to global change will impact the entire Arctic marine ecosystem and a long-term monitoring program is needed. The techniques, that are applied to study the sea ice biota and the sea ice ecology, should be improved.
文摘In continental shelf areas works where the focus is Geochemistry are widely relevant, due to the vast complexity and uses of these relief features (social, environmental and economic). On the Brazilian Northeast tropical shelves, with emphasis on the Pernambuco Continental Shelf (PCS), the published studies are limited and have aimed at portions closer to the coastline. The objective of the present work is the description of the characteristics and origin of sedimentary organic matter (SOM) in the inner and middle Pernambuco shelf, defining and classifying the local geochemical sedimentary facies. The sampling stations (136) were collected in the study area, and the grain-size, contents of total organic matter (TOM), calcium carbonate (CaCO<sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;">) were analyzed. The samples were processed in an elemental analyzer coupled with a mass spectrometer after the elimination of calcium carbonate. The obtained data were the grain-size, TOM, CaCO</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;">, elemental (C, N) and the stable isotopic ratios of </span><i><span style="font-family:Verdana;">δ</span></i><sup><span style="font-family:Verdana;">13</span></sup><span style="font-family:Verdana;">C e </span><i><span style="font-family:Verdana;">δ</span></i><sup><span style="font-family:Verdana;">15</span></sup><span style="font-family:Verdana;">N of SOM. Based on the measured values of carbon and nitrogen, the C/N ratio, associated to </span><i><span style="font-family:Verdana;">δ</span></i><sup><span style="font-family:Verdana;">13</span></sup><span style="font-family:Verdana;">C e </span><i><span style="font-family:Verdana;">δ</span></i><sup><span style="font-family:Verdana;">15</span></sup><span style="font-family:Verdana;">N, is observed that in the PCS predominates an organic matter of marine origin along its entire length: C < 1%, N < 1%, C/N < 5, </span><i><span style="font-family:Verdana;">δ</span></i><sup><span style="font-family:Verdana;">13</span></sup><span style="font-family:Verdana;">C > -21</span><span><span><span> </span></span></span><span><span><span><span style="font-family:Verdana;">PDB e </span><i><span style="font-family:Verdana;">δ</span></i><sup><span style="font-family:Verdana;">15</span></sup><span style="font-family:Verdana;">N > 8</span><sub><span style="font-family:Verdana;">Ar</span></sub><span style="font-family:Verdana;">. The PCS presents patches of continental origin SOM, associated to the coastal zones adjacent to estuarine systems mouths and covering the paleochannels, which may indicate that this material was carried from the coastal rivers to the offshore areas, possibly by the paleo-valleys that also act as traps of fine sediments and SOM. The statistical analysis indicates the existence of 6 different sedimentary facies and a prevalence of one of them, characterized by poorly-sorted bioclastic sandy-gravel, with low to medium organic contents of marine origin. This indicates that the coastal sedimentary material contributions are low and the local cover is autochthonous of biogenic origin, and deposited according to the surficial topography, morphosedimentary processes and meteoceanographycal conditionings of the study area, typical of moderate hydrodynamic energy environments.</span></span></span></span>
文摘This paper presents a study of physical and biogeochemical variables using numerical model and mixed layer oceanographic data from a 2 - 3 year?in situmeasurements in the Northwestern and Northeastern sites of the Atlantic Ocean. Model outputs are presented and indicated that very good estimates may be obtained. The outputs showed considerable agreement in reproducing seasonal distributions of?pCO2,?pCO2-T,?pCO2-nonT, mixed layer temperature, and chlorophyll-a?in both winter and summer, and therefore provide useful physical and theoretical understanding of their biogeochemistry. The model?pCO2indicated a distinct temporal variability with seasonal changes coinciding with the change in sea surface temperature. It also provides an agreement that there is a strong seasonal cycle of mixed layer parameters filliped by nonthermal and physical factors. As an outgrowth of this work, the?pCO2?model outputs affirm the North Atlantic Ocean capacity as an important oceanographic sink for anthropogenic carbon dioxide.
基金the National Council for Scientific and Technological Development(CNPq)for financial support for the project(No.465634/2014-1,INCT-AmbiTropic,Process No.370821/2019-0)part of a larger project entitled“Studies on Dissolved Inorganic Carbon Cycle in Northeastern and Coastal Areas in Brazil and its Relation to Ocean Acidification Processes(DICAM)”funded by the Coordination for the Improvement of Higher Education Personnel(CAPES).
文摘The aim of the current study was to evaluate the productive capacity of the phytoplankton community and other environmental variables in the estuarine area of Suape;while considering the constant morphological, sedimentological and hydrological changes, the site has been facing due to the implementation and expansion of an industrial and port complex. The study comprised 6 campaigns: 3 in the dry season and 3 in the rainy season. Water samples were collected from the surface layer of the internal and external portions of the estuarine bay during low spring tides. The salinity ranged from 32.20 to 37.10, the water temperature ranged from 26.60°C to 29.40°C, and the oxygen saturation rate ranged from 58.5% to 114.5%. There was significant seasonal variation. The nitrite concentration was higher during the rainy season, whereas the ammonia concentration was higher during the dry season;the higher ammonia concentration helped increase chlorophyll-a levels and rates of primary productivity, which ranged from 0.02 - 2.45 mg·m−3 and from 0.34 to 4.32 mg·C·m−3·h−1, respectively. Chlorophyll-a a-containing biomass, and this reflected the low nutrient content in the water and indicated that the area was free from eutrophication processes. The decrease of rainfall during the sampling months and the anthropogenic changes in the environment led to reduced continental contributions, increased marine interference, nutrient dilution and loss of phytoplankton production capacity in Suape Bay, which severely damaged other trophic links in the ecosystem.
文摘Two additional features are particularly useful in pixelwise satellite data segmentation using neural networks: one results from local window averaging around each pixel (MWA) and another uses a standard deviation estimator (MWSD) instead of the average. While the former’s complexity has already been solved to a satisfying minimum, the latter did not. This article proposes a new algorithm that can substitute a <i><span style="font-family:Verdana;">naive</span></i><span style="font-family:Verdana;"> MWSD, by making the complexi</span><span><span style="font-family:Verdana;">ty of the computational process fall from </span><i><span style="font-family:Verdana;">O</span></i><span style="font-family:Verdana;">(</span><i><span style="font-family:Verdana;">N</span></i><sup><span style="font-family:Verdana;">2</span></sup><i><span style="font-family:Verdana;">n</span></i><sup><span style="font-family:Verdana;">2</span></sup><span style="font-family:Verdana;">) to </span><i><span style="font-family:Verdana;">O</span></i><span><span style="font-family:Verdana;">(</span><i><span style="font-family:Verdana;">N</span></i></span><sup><span style="font-family:Verdana;">2</span></sup><i><span style="font-family:Verdana;">n</span></i><span style="font-family:Verdana;">)</span><span style="font-family:Verdana;">, where </span><i><span style="font-family:Verdana;">N</span></i><span style="font-family:Verdana;"> is a square</span></span><span style="font-family:Verdana;"> input array side, and </span><i><span style="font-family:Verdana;">n</span></i><span style="font-family:Verdana;"> is the moving window’s side length. The Num</span><span style="font-family:Verdana;">ba python compiler was used to make python a competitive high-performance</span> <span style="font-family:Verdana;">computing language in our optimizations. Our results show efficiency benchmars</span>
基金Supported by University of Tanta(Grant No.2009/2013).
文摘Objective:To identify the potentially harmful epiphytic Oscillatoriales species and follow up their distribution along Alexandria coast.Methods:Samples were collected bimonthly from April 2009 to February 2010 at three sites along Alexandria coast.Both morphological and molecular analyses were used for identifying the dominant species.Results:Five species belonging to two families were identified;Oscillatoria acutissima,Oscillatoria nigroviridis,Oscillatoria sp.,Lyngbya majuscule and Phormidium formosum.Their cell density ranged from 10^(3)to 126×10^(3)filament g^(-1)fresh weight macroalgae.The morphological study of the dominant species,Oscillatoria sp.(Oscillatoria sp.W1)showed much similarity with Planktothrix agardhii with no heterocysts and akinetes,while molecular ananlysis(16S rDNA)clustered the species in the same group with Anabaena sp.Conclusions:The 16S rDNA genes are not suitable for identifying Oscillatoriales during the present study and another molecular method should be used instead.
文摘Objective:To evaluate the stock of Alepes djedaba(A.djedaba)by describing the length composition,growth parameters,mortality rates of A.djedaba captured in Arabian Gulf off Saudi Arabia and adopting yield per recruit and biomass per recruit models.Methods:A random sample of 490 fish representing a moderate range of total lengths(16.5-32.4cm)and weights(60-410 g)were sampled in Arabian Gulf off Dammam,Saudi Arabia during the period from August 2008 to July 2009.LFD5 software was used for estimation of growth parameters.Total mortality was calculated using the length converted catch curve.Natural mortality was estimated using Pauly and David's formula.Fishing mortality was computed by subtracting natural mortality from total mortality.Per recruit analysis was made using Beverton and Holt model.Results:Length-frequency analysis revealed four peaks and the length range from 22 cm to 27 cm dominated the catch,constituting about 71%of the catch.Values of the von Bertalanffy growth parameters were computed using LFD5 software as follows:the asymptotic length(L_(∞))=41.71 cm,curvature parameter(K)=0.36 year^(-1),and hypothetic age at zero length(t_(0))=-0.76 year.The total mortality(Z)was estimated as 2.07 year^(-1),and natural mortality was 0.8 year^(-1).Fishing mortality F=1.27 year^(-1),which was higher than F_(0.1)(0.3 year^(-1)),F_(SB(50))(0.59 year^(-1))and FS_(B(40))(0.86 year^(-1)).Atthe current levels of fishing and natural mortality,the biomass per recruit is 34%of the virgin biomass.Conclusions:These may indicate an overexploitation state of the fisheries of A.djedaba in Arabian Gulf.
基金supported by the Key-Area Research and Development Program of Guangdong Province,China(No.2021B0101190003)the Natural Science Foundation of Guangdong Province,China(No.2022A1515010831)BC was partly supported by the European Union’s Horizon 2020 research and innovation program(727890-INTAROS)in the early phase of SIMBA data analyzes and partly by Polar Regions in the Earth System project(PolarRES,grant 101003590)during the finalization stage of this work.
文摘Digital information on sea ice extent,thickness,volume,and distribution is crucial for understanding Earth's climate system.The Snow and Ice Mass Balance Apparatus(SIMBA)is used to determine snow and ice temperatures in Arctic,Antarctic,ice-covered seas,and boreal lakes.Snow depth and ice thickness are derived from SIMBA temperature regimes(SIMBA_ET and SIMBA_HT).In warm conditions,SiMBA_ET temperature-based ice thickness may have errors due to the isothermal vertical profile.SIMBA_HT provides a visible ice-bottom interface for manual quantification.We propose an unmanned approach,combining neural networks,wavelet analysis,and Kalman filtering(NWK),to mathematically establish NwK and retrieve ice bottoms from various SIMBA_HT datasets.In the Arctic,NWK-derived total thickness showed a bias range of-5.64 cm to 4.01 cm and a correlation coefficient of 95%-99%.For Baltic Sea ice,values ranged from 1.31 cm to 2.41 cm(88%-98%correlation),and for boreal lake ice,-0.7 cm to 2.6 cm(75%-83%correlation).During ice growth,thermal equilibrium,and melting,the bias varied from-3.93 cm to 2.37 cm,-1.92 cm to 0.04 cm,and-4.90 cm to 3.96 cm,with correlation coefficients of 76%-99%.These results demonstrate NWK's robustness in retrieving ice bottom evolution in different water environments.
基金supported by Pan-Third Pole Environment Study for a Green Silk Road of the Strategic Priority Research Program of Chinese Academy of Sciences(XDA20090000)the National Key Research and Development Program of China(2018YFA0606400)+1 种基金Part laboratory and fieldwork costs were supported by the National Natural Science Foundation of China(41772178,91747207,and 41620104007)Field expedition was supported by the Second Tibetan Plateau Scientific Expedition(2019QZKK0601)。
文摘During the 7-9th century,the Tibetan Empire constituted a superpower between the Tang Empire and Abbasid Caliphate:one that played significant roles in geopolitics in Asia during the Early Medieval Period.The factors which led to the rise and rapid decline of this powerful Empire,the only united historical regime on the Tibetan Plateau(TP),remain unclear.Sub-annual scale precipitation and decadalscale temperature records of the central TP are presented,indicating that the height of this Empire coincided with a two-century long interval of uncharacteristically warm and humid climate.The ameliorated climate enabled the expansion of arable land and increased agricultural production.The close relationship between the precipitation records and historical events implied that the Empire implemented flexible strategies to tackle the effects of climate changes.This has implications for agricultural production in alpine regions including the TP,in the context of current global warming.
