Home About us Contact
|
Home About us Contact | ||
|
|
||
Lake Surface (lake + surface)
Terms modified by Lake Surface Selected AbstractsModelling hydrodynamics in Yachiyo Lake using a non-hydrostatic general circulation model with spatially and temporally varying meteorological conditionsHYDROLOGICAL PROCESSES, Issue 14 2009Han Soo Lee Abstract In this study, a three-dimensional (3D) non-hydrostatic circulation model was applied to study the thermal structure, its evolution and water circulation of Yachiyo Lake in Hiroshima, Japan. The simulations were conducted for 1 month during July 2006. The meteorological forcing variables such as wind stress, surface atmospheric pressure and heat flux transfer through the lake surface were provided by an atmospheric mesoscale model run. The vertical mixing process of the lake was calculated using the Mellor-Yamada turbulence model. The 1-month numerical simulation revealed the wind-induced currents of the lake, two gyres in the mid-layer, and depth-averaged monthly mean currents. Further numerical experiments studying the mechanism of the two gyres in the lake showed the important role of topography in gyre formation. The thermal structure of the lake and its evolution both in space and in time as predicted by the model showed very good agreement with the observed values and characteristics of Yachiyo Lake. The internal gravity waves, which are crucial for mixing in the stratified lake, are depicted by the vertical fluctuation of isotherms. Using the non-dimensional gradient Richardson number, Yachiyo Lake was determined to be stable under strong stratification during the study period, and therefore very sensitive to wind stress. Copyright © 2009 John Wiley & Sons, Ltd. [source] Simulation of ice phenology on Great Slave Lake, Northwest Territories, CanadaHYDROLOGICAL PROCESSES, Issue 18 2002Patrick Ménard Abstract A one-dimensional thermodynamic lake ice model (Canadian Lake Ice Model or CLIMo) is used to simulate ice phenology on Great Slave Lake (GSL) in the Mackenzie River basin, Northwest Territories, Canada. Model simulations are validated against freeze-up and break-up dates, as well as ice thickness and on-ice snow depth measurements made in situ at three sites on GSL (Back Bay near Yellowknife, 1960,91; Hay River, 1965,91; Charlton Bay near Fort Reliance, 1977,90). Freeze-up and break-up dates from the lake ice model are also compared with those derived from SSM/I 85 GHz passive microwave imagery over the entire lake surface (1988,99). Results show a very good agreement between observed and simulated ice thickness and freeze-up/break-up dates over the 30,40 years of observations, particularly for the Back Bay and Hay River sites. CLIMo simulates the ice thickness and annual freeze-up/break-dates with a mean error of 7 cm and 4 days respectively. However, some limitations have been identified regarding the rather simplistic approach used to characterize the temporal evolution of snow cover on ice. Future model improvements will therefore focus on this particular aspect, through linkage or coupling to a snow model. Copyright © 2002 John Wiley & Sons, Ltd. [source] Feeding ecology of silverperch, Terapon plumbeus Kner, and the impact of fish-pens in Laguna de Bay, PhilippinesJOURNAL OF APPLIED ICHTHYOLOGY, Issue 6 2000M. Kock Summary Aquaculture is an important factor in the fishery of Laguna de Bay in the Philippines; fish-pens and net-cages covered ,10% of the lake surface in the late 1990s. The present study was carried out to assess the possible influences of aquaculture on a wild fish species, silverperch, Terapon plumbeus Kner, with a special emphasis on the feeding ecology of this fish. For the purposes of the investigation, 24-h samples were taken at 2-month intervals close to a fish-pen as well as in open water over a one-year period to acquire more information on this species. Significant differences in standard length and total weight were found between stations and sampling months. In open water, a mean standard length of 53.6 mm and a mean total weight of 4.2 g were found, whereas close to the fish-pen, the corresponding values were 57.6 mm and 5.4 g, respectively. The maximum mean standard length was attained around December 1996 and February 1997 (59.5 mm in open water; 66.1 mm close to the fish-pen), and the minimum was found in June 1996 (49.1 mm in open water; 46.2 mm close to the fish-pen). Noticeable differences were found in the food spectrum between the two sampling stations. Zooplankton, the major food source at both stations, was more important in the stomach content of fish in open water. The same was true for insects (i.e. chironomid larvae), although these did not make up such a large fraction of the diet. On the other hand, close to the fish-pen, aufwuchs- algae, phytoplankton and fish were more important. Generally, benthic organisms were consumed more frequently close to the fish-pen. Zooplankton was more important in the diet of smaller fish. In all size groups, the importance of zooplankton decreased during the rainy season. [source] Archaeabacterial lipids in drill core samples from the Bosumtwi impact structure, GhanaMETEORITICS & PLANETARY SCIENCE, Issue 11 2008Marina ESCALA The Bosumtwi crater in Ghana (West Africa) is a relatively young (1.07 Myr) structure with a rim-to-rim diameter of about 10.5 km. In a preliminary study targeting the subsurface microbial life in the impact structure, seven samples of the impact breccia from the central uplift of the Bosumtwi crater were analyzed for the presence of typical archaeal membrane-lipids (GDGTs). These have been detected in four of the samples, at a maximum depth of 382 m below the lake surface, which is equivalent to 309 m below the surface sediment. The concentration of the GDGTs does not show a trend with depth, and their distribution is dominated by GDGT-0. Possible origins of these lipids could be related to the soils or rocks predating the impact event, the hydrothermal system generated after the impact, or due to more recent underground water [source] Quaternary Lake Deposits of Nam Co, Tibet, with a Discussion of the Connection of Nam Co with Ring Co-Jiuru CoACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 3 2002ZHU Dagang Abstract Shorelines are widespread and lake deposits and lake geomorphology are well developed on the northern Tibetan Plateau. Through field observations of lacustrine deposits of Nam Co,the highest and largest Quaternary lake in Tibet, the authors found four-step shore terraces composed of sands and clays with well-developed horizontal bedding and 3,12 m, 15,22 m, 25,30 m and 35,45 m higher than the lake surface respectively, lacustrine deposits resting on the bedrocks and 60,150 m higher than the lake surface, and up to ,50 levees composed of oblate lakeshore gravels. Moreover they found lacustrine and lakeshore deposits making up the terraces and levees on the bottoms of wide dividing valleys connecting Nam Co with the Rencoyuema, Rencogongma and Jiuru Co northwest of Nam Co (the valley bottoms are 20 m, 90 m and 60 m higher than the above-mentioned three lakes) and on slopes north of it, i.e. terraces II and III of Nam Co. Thus they confirm that Nam Co and Ring Co-Jiuru Co had connected with each other several times, i.e. formed a unified large lake several times, rather than had been different lakes connected only by river channels. From indications such as the distribution of the highest shoreline and lake deposits and geomorphology, the authors conclude that the total area of the old large lakes on the northern Tibetan Plateau is a few times larger than that of the modern lakes and that the last-stage old large lakes formed in the interglacial interval of the last glaciation. [source] Paleoecology and geochronology of glacial Lake Hind during the Pleistocene,Holocene transition: A context for Folsom surface finds on the Canadian PrairiesGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 6 2003Matthew Boyd Stratigraphic and paleoecologic (palynomorph, macrobotanical) data obtained from a cutbank of the Souris River in southwestern Manitoba establish some fundamental parameters of Folsom land-use in association with a proglacial lake on the Canadian Prairies. By dating the regression of glacial Lake Hind, we observed that recorded Folsom sites are restricted to areas of the Hind basin drained shortly before 10,400 yr B.P. This pattern may therefore record the interception of seasonal resources on recently-drained proglacial lake surfaces. Based on paleovegetation reconstructions, we note that these surfaces were rapidly colonized by emergent and aquatic vegetation following regression, generating a viable resource base for Folsom hunter-gatherers. However, low plant productivity and diversity may have greatly limited the extent to which this locale was exploited, in contrast to nonperiglacial regions on the Plains. We also suggest that wetland plant succession during the Pleistocene-Holocene transition was due, at least locally, to climate-forced fluctuations in groundwater levels. © 2003 Wiley Periodicals, Inc. [source] Modelling lake stage and water balance of Lake Tana, EthiopiaHYDROLOGICAL PROCESSES, Issue 25 2009Yirgalem A. Chebud Abstract The level of Lake Tana, Ethiopia, fluctuates annually and seasonally following the patterns of changes in precipitation. In this study, a mass balance approach is used to estimate the hydrological balance of the lake. Water influx from four major rivers, subsurface inflow from the floodplains, precipitation, outflow from the lake constituting river discharge and evapotranspiration from the lake are analysed on monthly and annual bases. Spatial interpolation of precipitation using rain gauge data was conducted using kriging. Outflow from the lake was identified as the evaporation from the lake's surface as well as discharge at the outlet where the Blue Nile commences. Groundwater inflow is estimated using MODular three-dimensional finite-difference ground-water FLOW model software that showed an aligned flow pattern to the river channels. The groundwater outflow is considered negligible based on the secondary sources that confirmed the absence of lake water geochemical mixing outside of the basin. Evaporation is estimated using Penman's, Meyer's and Thornwaite's methods to compare the mass balance and energy balance approaches. Meteorological data, satellite images and temperature perturbation simulations from Global Historical Climate Network of National Oceanographic and Atmospheric Administration are employed for estimation of evaporation input parameters. The difference of the inflow and outflow was taken as storage in depth and compared with the measured water level fluctuations. The study has shown that the monthly and annually calculated lake level replicates the observed values with root mean square error value of 0·17 and 0·15 m, respectively. Copyright © 2009 John Wiley & Sons, Ltd. [source] | ||||||||||