Light, Temperature, and Oxygen Regimes of Selected Lakes in the Experimental Lakes Area, Northwestern Ontario

1971 ◽  
Vol 28 (2) ◽  
pp. 157-169 ◽  
Author(s):  
D. W. Schindler
Keyword(s):  
Standard Procedure ◽  
Heat Content ◽  
Oxygen Depletion ◽  
Secchi Disc ◽  
Experimental Lakes Area ◽  
Maximum Heat ◽  
Summer Heat ◽  
Visible Wavelengths ◽  
Heat Budgets ◽  
Subsurface Light

Light was measured in several Experimental Lakes Area (ELA) lakes in 1968 and 1969, using a Secchi disc, a standard photometer (cadmium sulfide cell), and a 16-channel spectroradiometer. The results of some checks upon the standard procedure usually used for making subsurface light measurements are presented. Light penetration at several wavelengths and total energy flux at several depths are given for a number of lakes. Oxygen and temperature isopleths, winter rates of oxygen depletion, annual heat budgets, and data on work of the wind are also presented. Vertical extinction coefficients (average of all visible wavelengths) ranged from 0.285 for lake 161 to 1.732 for lake 227, and Secchi disc visibility from 1.2 to 10.1 m. The wavelength of maximum transmittance shifted toward long wavelengths, as expected, when transmission coefficients and Secchi disc visibility decreased.Annual heat budgets ranged from 8400 to 24,200 cal/cm2. From 3700 to 16,000 cal/cm2 of this were summer heat income. Summer and annual heat budgets were larger for larger lakes. Annual and summer heat incomes were related to mean depth, surface area, and volume of the lakes by simple linear regression equations.The work of the wind and its efficiency in distributing summer heat income are discussed. The depth of the thermocline in ELA lakes was set early in the year, and did not change during the summer until well after the lake had reached maximum heat content. The temperature of the epilimnion followed the mean daily air temperature closely during the summer though remaining several degrees higher, probably as the result of radiant heating. It is concluded that wind work calculated by Birge's method (Trans. Wis. Acad. Sci. Arts Lett. 18: 341–391, 1916) is of little value, unless corrections for back-radiation and evaporation can be made.Rates of oxygen depletion under ice were compared in several lakes. Values ranged from 15.0 to 73.8 mg O2/m3∙day and from 36 to 253 mg O2/m2∙day.

Factors Controlling Oxygen Depletion in Ice-Covered Lakes

1980 ◽  
Vol 37 (2) ◽  
pp. 185-194 ◽  
Author(s):  
Jack A. Mathias ◽  
Jan Barica
Keyword(s):  
Volume Ratio ◽  
Lake Management ◽  
Eddy Diffusion ◽  
Oxygen Depletion ◽  
Eutrophic Lakes ◽  
Experimental Lakes Area ◽  
Lake Volume ◽  
Basin Morphometry ◽  
Depletion Rate ◽  
Prairie Lakes

Winter oxygen depletion rates from four sets of Canadian lakes (prairie, southeastern Ontario, Arctic, and Experimental Lakes Area) differing in morphometry and trophic state, were analyzed. An inverse relationship was found between oxygen depletion rate and mean depth. The effect of lake trophic status on oxygen depletion rate was demonstrable after the influence of basin morphometry was removed by regression of oxygen depletion rate against the sediment area: lake volume ratio. The sediments of eutrophic lakes consumed oxygen about 3 times faster (0.23 g∙m−2∙d−1) than those of oligotrophic lakes (0.08 g∙m−2∙d−1), but water column respiration was about the same (0.01 g∙m−3∙d−1) for both groups of lakes. Data from prairie lakes showed that the winter oxygen consumption was limited by oxygen supply below an average whole-lake oxygen concentration of 3.8 mg∙L−1. The rate of eddy diffusion near the sediments in ice-covered prairie lakes was 3.72 ± 1.41 × 10−3 cm2∙s−1. Implications for lake management during the winter are discussed.Key words: oxygen, depletion, respiration, lakes, ice-covered, winter, sediments, model, consumption

Summerkill Risk in Prairie Ponds and Possibilities of its Prediction

1975 ◽  
Vol 32 (8) ◽  
pp. 1283-1288 ◽  
Author(s):  
Jan Barica
Keyword(s):  
Chlorophyll A ◽  
Algal Blooms ◽  
Oxygen Depletion ◽  
Ammonia Nitrogen ◽  
Specific Conductance ◽  
Rating System ◽  
Late Winter ◽  
Fish Kills ◽  
Secchi Disc ◽  
Prediction Systems

Summer fish kills in shallow, landlocked ponds of the Erickson–Elphinstone area, southwestern Manitoba, were caused by collapses of heavy algal blooms, mostly Alphanizomenon flos-aquae, and subsequent oxygen depletion. Kills occurred only in ponds that were in the specific conductance range of 800–2000 μmho/cm and where chlorophyll a concentrations exceeded 100 μg/liter. A practical rating system for assessment of summerkill risk was suggested. Correlations between various parameters from 51 ponds were computed; the best correlation (r = 0.866; P = >0.99) was found between the late-winter concentration of ammonia nitrogen and the maximum concentration of chlorophyll a in the following summer. Two summerkill prediction systems were proposed, based on ammonia, dissolved oxygen, and Secchi disc transparency, enabling the prediction of summerkill risk 9 or 3 mo prior to stocking of the fish.

Some Comparisons in the Thermal Structure of Lakes Wood, Kalamalka, Okanagan, Skaha, and Osoyoos, British Columbia

1973 ◽  
Vol 30 (7) ◽  
pp. 917-925 ◽  
Author(s):  
J. O. Blanton
Keyword(s):  
Thermal Structure ◽  
Heat Content ◽  
Late Summer ◽  
Static Stability ◽  
Rate Of Change ◽  
Direct Relation ◽  
Maximum Heat ◽  
The North ◽  
Relative Ability ◽  
External Cooling

The rate of change of heat contents in the lakes and the relative ability of each lake to transfer heat vertically to warm its hypolimnion was investigated. Rates of warming of hypolimnion water ranged from 0.06 C/month in Okanagan to 0.54 C/month in the north basin of Osoyoos. All lakes reached maximum static stability through the thermocline in late August except for Osoyoos (N), which reached its maximum somewhat earlier. Maximum heat content ranged from 18,100 cal/cm2 in Wood Lake to 33,300 cal/cm2 in Lake Okanagan. Maximum values of heat content were observed in late August in all lakes.There is a direct relation between the hypolimnetic warming rates and the maximum observed stability in the thermocline regions of all the lakes. However, the relatively low rate of Lake Wood indicates that there is an external cooling source such as groundwater influx. The late summer increase in volume of the epilimnion in Wood and the corresponding entrainment of nutrients from the hypolimnion to the epilimnion appear to control the amount of production observed at that time.

Heat uptake and resistance to mixing in small humic forest lakes in Southern Finland

1990 ◽  
Vol 41 (6) ◽  
pp. 747 ◽  
Author(s):  
LC Bowling ◽  
K Salonen
Keyword(s):  
Thermal Stratification ◽  
Heat Of Fusion ◽  
Short Term ◽  
Thermal Stabilities ◽  
Maximum Heat ◽  
Lake Volume ◽  
Heat Uptake ◽  
Forest Lakes ◽  
Heat Budgets ◽  
Term Fluctuation

The annual heat budgets and maximum thermal stabilities achieved by small Finnish forest lakes are considerable for lakes of their size. Heat uptake is rapid during the brief period of vernal circulation, with the latent heat of fusion of ice contributing substantially to this. Heating then slows, with maximum heat contents and thermal stabilities occurring around early August. Absorption of solar radiation by the dystrophic waters, effective shelter from wind-induced turbulence, and considerable relative depths all combine to prevent mixing of heat much below the surface 2 m of most study lakes. Birgean wind-work values therefore remain low, and cold hypolimnetic waters occupy much of the lake volume. The lakes also respond quickly to meteorological change, which causes considerable year-to-year variation, and some short-term fluctuation, in their heat budgets and maximum stabilities. The lakes' small size and shallow thermal stratification may contribute to this.

Simulation of Power Efficient Cooling Technology for Continuously Cast Bars

2017 ◽  
Vol 265 ◽  
pp. 1086-1091 ◽  
Author(s):  
L.L. Demidenko
Keyword(s):  
Heat Insulation ◽  
Continuous Casting Machine ◽  
Casting Machine ◽  
Heat Content ◽  
Air Cooling ◽  
Cooling Zone ◽  
Maximum Heat ◽  
Power Efficient ◽  
Cooling Schedules ◽  
Continuously Cast

The article describes a power efficient technology, allowing to preserve and maintain the heat content in a continuously cast bar at the production line “Continuous Casting Machine – Rolling Mill”. It considers a possibility of obtaining the maximum heat content in the continuously cast bar by means of rational cooling schedules in the secondary cooling zone. In order to maintain the achieved heat content in the bar, it is proposed to utilize heat insulation of the bar in the air cooling zone prior to its cutting-to-length. The article describes the design of the heat insulating shell in the CCM process scheme and the materials to be used for it. To analyze the interaction of heat flows between the bar and the shell in the heat insulation zone, the author has made a thermal balance of this zone. A mathematical model of the concast bar cooling with due consideration of the heat insulation zone and its implementation by means of numerical methods is described here. The application of numerical simulation has allowed to predict rational cooling schedules for the continuously cast bar and to determine the heat content of the bar at the exit from the continuous casting machine with respect to the heat insulation. According to the results of the simulation, there have been plotted the charts of temperature distribution along the CCM length, comparing the air cooling of the bar and its thermal conditioning in the heat insulation zone. These results confirm the effectiveness of utilizing heat insulation for maintaining the maximum heat content of the bar, which makes it possible to reduce the power costs for its heating prior to the rolling.

Combustion in heat exchangers

1978 ◽  
Vol 360 (1700) ◽  
pp. 97-115 ◽  
Keyword(s):  
Heat Release ◽  
Heat Content ◽  
Release Rates ◽  
Flammability Limits ◽  
Maximum Heat ◽  
Theoretical Maximum ◽  
Heat Recirculation ◽  
Spiral Geometry ◽  
Double Spiral ◽  
Maximum Heat Release

The ranges of flow for which flames can stably be burnt in combustors based on extensive heat recirculation between products and reactants are examined in terms of the heat exchanger characteristics. This is important because, no matter how desirable it may be to burn poor fuels and mixtures of very low heat content efficiently, there are many applications for which the scheme would be attractive only for reasonably large throughputs and rates of energy release. A simple general theory based on the observed constant reaction temperature is shown to predict correctly the shape of the empirical curves for mixtures outside the flammability limits. Numerical correlations are obtained for a more detailed analysis of the very efficient double-spiral geometry. The results are compared with the theoretical maximum heat release rates per unit volume of flames in normally flammable mixtures. It is shown that mixtures containing only one fifth of the heat content at the normal limit of flammability in practice yield heat release rates comparable to the theoretical maximum for normal flames within the flammable range; the theoretical maximum for stoichiometric methane-air mixture should be attainable at little more than half the limit of flammability.

scholarly journals Empirical correction of XBT fall rate and its impact on heat content analysis

2011 ◽  
Vol 8 (1) ◽  
pp. 291-320 ◽  
Author(s):  
M. Hamon ◽  
P. Y. Le Traon ◽  
G. Reverdin
Keyword(s):  
Content Analysis ◽  
Collocation Method ◽  
Measurement Errors ◽  
Heat Content ◽  
Calibration Error ◽  
Fall Rate ◽  
Maximum Heat ◽  
Thermal Correction ◽  
Empirical Correction ◽  
Probe Calibration

Abstract. We used a collocation method between XBT and CTD/OSD (Ocean Station Data including bottle cast and low resolution CTD) from WOD05 (1°×2°×15 days) to statistically correct the XBT fall rate. An analysis of the annual median bias on depth showed that it is necessary to apply a thermal correction linked to probe calibration error, a second order correction on the depth as well as a depth offset representing measurement errors during XBT deployment. We had to separate data in several categories: shallow and deep XBT and deployment sea temperatures (below or above 10 °C). We also processed separately XBT measurements close to Japan between 1968 and 1985 due to large regional biases. Once the corrections have been applied, the analysis of heat content signal is derived from corrected XBT. From this analysis, we confirm that the maximum heat content in the top 700 m found during the 70's in early papers can be explained by the XBT biases. In addition, a trend of 0.32.1022 J/year is observed between the period 1970 and 2008.

Influence of Strain Reversals during High Pressure Torsion Process on Strengthening in Al-Cu-Mg(-Li) Alloy

2010 ◽  
Vol 667-669 ◽  
pp. 809-814 ◽  
Author(s):  
Jiu Wen Zhang ◽  
Marco J. Starink ◽  
Nong Gao ◽  
Wen Long Zhou
Keyword(s):  
Differential Scanning Calorimetry ◽  
High Pressure ◽  
High Pressure Torsion ◽  
Heat Content ◽  
S Phase ◽  
Phase Precipitation ◽  
Scanning Calorimetry ◽  
Maximum Heat ◽  
Strain Reversal ◽  
S Peak

The strengthening of AlCuMg(Li) alloys subjected to high pressure torsion (HPT) deformation with strain reversals was studied by microhardness (Hv) tests and differential scanning calorimetry (DSC). It was found that the strengthening is lower for both cyclic HPT (c-HPT) and single reversal HPT (sr-HPT) as compared to monotonic HPT (m-HPT). The DSC results demonstrate that |HPT influences S phase precipitation. With increasing strain, the maximum heat flow (height of the S peak) and the heat content of S formation peaks increases. There is a larger S heat content reaction in the periphery of HPT processed disks compared with those in the centre. Strain reversal also has a significant influence on the S precipitation. The strengthening during HPT deformation is discussed in terms of the density of statistically stored and geometrically necessary dislocations.

Heat contents, thermal stabilities and Birgean wind work in Dystrophic Tasmanian Lakes and Reservoirs

1990 ◽  
Vol 41 (3) ◽  
pp. 429 ◽  
Author(s):  
LC Bowling
Keyword(s):  
Work Values ◽  
Heat Content ◽  
Thermal Stabilities ◽  
Energy Parameters ◽  
Lakes And Reservoirs ◽  
Short And Long Term ◽  
Heat Budgets ◽  
Standing Waters ◽  
Standard Energy

Values of whole-lake standard energy parameters (heat content, thermal stability and Birge's work of the wind) for ten dystrophic standing waters from western Tasmania were lower than expected for lakes of their depth and area. Although controlled principally by morphometric factors, the degree of shelter from wind and the extent of each lake's dystrophy also had considerable effects. These factors allowed only surface waters to contribute to the annual heat exchange cycle, thereby reducing the magnitude of each lake's heat budgets and influencing stability and wind work values. The lakes show considerable short- and long-term fluctuations in heat content, stability and wind work values in response to the capricious maritime meteorological conditions of the area. However, long periods between successive samplings may have caused some underestimation of the ranges of these three parameters. Despite this, the study reveals that these standard energy parameters are effective in describing the annual energy input and resistance to wind-induced mixing of these dystrophic Tasmanian lakes.

Detection and Characterization of earth-like Planets

1997 ◽  
Vol 161 ◽  
pp. 299-311 ◽  
Author(s):  
Jean Marie Mariotti ◽  
Alain Léger ◽  
Bertrand Mennesson ◽  
Marc Ollivier
Keyword(s):  
Direct Detection ◽  
Contrast Ratio ◽  
Angular Size ◽  
Physical Nature ◽  
Major Axis ◽  
Infrared Emission ◽  
Space Technology ◽  
Semi Major Axis ◽  
Earth Like Planets ◽  
Visible Wavelengths

AbstractIndirect methods of detection of exo-planets (by radial velocity, astrometry, occultations,...) have revealed recently the first cases of exo-planets, and will in the near future expand our knowledge of these systems. They will provide statistical informations on the dynamical parameters: semi-major axis, eccentricities, inclinations,... But the physical nature of these planets will remain mostly unknown. Only for the larger ones (exo-Jupiters), an estimate of the mass will be accessible. To characterize in more details Earth-like exo-planets, direct detection (i.e., direct observation of photons from the planet) is required. This is a much more challenging observational program. The exo-planets are extremely faint with respect to their star: the contrast ratio is about 10−10at visible wavelengths. Also the angular size of the apparent orbit is small, typically 0.1 second of arc. While the first point calls for observations in the infrared (where the contrast goes up to 10−7) and with a coronograph, the latter implies using an interferometer. Several space projects combining these techniques have been recently proposed. They aim at surveying a few hundreds of nearby single solar-like stars in search for Earth-like planets, and at performing a low resolution spectroscopic analysis of their infrared emission in order to reveal the presence in the atmosphere of the planet of CO H2O and O3. The latter is a good tracer of the presence of oxygen which could be, like on our Earth, released by biological activity. Although extremely ambitious, these projects could be realized using space technology either already available or in development for others missions. They could be built and launched during the first decades on the next century.

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