Academic literature on the topic 'Rail surface temperatures'
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Journal articles on the topic "Rail surface temperatures"
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Chapman, L., J. E. Thornes, Y. Huang, X. Cai, V. L. Sanderson, and S. P. White. "Modelling of rail surface temperatures: a preliminary study." Theoretical and Applied Climatology 92, no. 1-2 (June 27, 2007): 121–31. http://dx.doi.org/10.1007/s00704-007-0313-5.
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Alizadeh Otorabad, Hossein, Parisa Hosseini Tehrani, Davood Younesian, Jilt Sietsma, and Roumen Petrov. "Analytical Formulation for Temperature Evolution in Flat Wheel-Rail Sliding Surfaces." Mathematical Problems in Engineering 2018 (November 12, 2018): 1–7. http://dx.doi.org/10.1155/2018/4239658.
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Studying the temperature evolution of the thermally affected zone (TAZ) of sliding surfaces is crucial because of its influence on microstructural evolution, wear, and fatigue. Due to the complexity of thermal analysis of sliding bodies, relationships that predict their surface temperature evolution are very helpful because they can be used as time-dependent boundary conditions; this makes the thermal analysis of sliding bodies independent. In this paper, by assuming thermal contact conductance (TCC) at the sliding common surface, the differential equation governing the thermal analysis of the wheel-rail sliding is solved throughout a wheel flat. The temperature evolution of wheel and rail surfaces and the heat partitioning factor are among the main results. Finally, the equations obtained for wheel and rail surface temperatures are applied to a freight wagon and a passenger car as two real cases. The results are discussed and compared to existing data in the literature and a solid agreement is achieved.
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Mirković, Nikola, Ljiljana Brajović, Zdenka Popović, Goran Todorović, Luka Lazarević, and Miloš Petrović. "Determination of temperature stresses in CWR based on measured rail surface temperatures." Construction and Building Materials 284 (May 2021): 122713. http://dx.doi.org/10.1016/j.conbuildmat.2021.122713.
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Hsu, Li-Shan, Pao-Chang Huang, Chih-Cheng Chou, Kung-Hsu Hou, Ming-Der Ger, and Gao-Liang Wang. "Effect of Nickel–Phosphorus and Nickel–Molybdenum Coatings on Electrical Ablation of Small Electromagnetic Rails." Coatings 10, no. 11 (November 10, 2020): 1082. http://dx.doi.org/10.3390/coatings10111082.
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The electromagnetic rail catapult is a device that converts electrical energy into kinetic energy, which means that the strength of electrical energy directly affects the muzzle speed of armature. In addition, the electrical conductivity, electromagnetic rails and armature surface roughness, and the holding force of the rail are influencing factors that cannot be ignored. However, the electric ablation on the surface of the electromagnetic rails caused by high temperatures seriously affects the service life performance of the electromagnetic catapult system. In this study, electrochemically deposited nickel-phosphorus and nickel-molybdenum alloy coatings are plated on the surface of electromagnetic iron rails and their effects on the reduction of ablation are investigated. SEM (scanning electron microscopy) with EDS (energy dispersive spectroscopy) detector, XRD (X-ray diffraction), 3D optical profiler, and Vickers microhardness tester are used. Our results show that the sliding velocity of the armature decreases slightly with the increased roughness of the rail coating surface. On the other hand, the area of electric ablation on the rail surface is inversely related to the hardness of the rail material. The electrically ablated surface areas of the rails are in: annealed nickel–molybdenum < nickel–molybdenum < annealed nickel–phosphorus < nickel–phosphorus < iron material. Heat treatment at 400 and 500 °C, respectively for Ni–P and Ni–Mo alloys, significantly increases hardness due to the precipitation of intermetallic compounds such as Ni3P and Ni4Mo phases. Comprehensive data analysis shows that the annealed nickel–molybdenum coating has the best electrical ablation wear resistance. The possible reason for that might be attributed to the high hardness of the heat-treated nickel–molybdenum coating. In addition, the thermal resistance capability of molybdenum is better than that of phosphorus, which might also contribute to the high wear resistance to electric ablation.
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Mazov, Yuriy Nikolaevich, Aleksey Alekseevich Loktev, and Vyacheslav Petrovich Sychev. "Assessing the influence of wheel defects of a rolling stockon railway tracks." Vestnik MGSU, no. 5 (May 2015): 61–72. http://dx.doi.org/10.22227/1997-0935.2015.5.61-72.
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Transfer of the load from the wheels on the rail occurs at a very small area compared with the size of the wheels and rails. The materials near this site have a very large voltage. Determination of contact stresses is complicated by the fact that the magnitude of these stresses in the rails under actually revolving wheel load exceeds the yield and compressive strength of modern rail steel. We should note that the metal of the rail head, experiencing contact stresses, especially when the location of the pads is closer to the middle of the rail head, works in the conditions close to the compression conditions, and therefore can withstand higher voltage without plastic deformation than the standard compressible sample. But, as a rule, the observed hardening of the metal in the zone of contact stresses and lapping at the edges of the rail head indicates the presence of plastic deformation and, consequently, higher stresses in the wheel-rail contact zone than the yield strength of the metal rail even in the conditions of its operation in the rail head.The use of the design equations derived on the basis of the Hertz theory for metal behavior in elastic stage, is valid. The reason is that each individual dynamic application of wheel loads on the rail is very short, and the residual plastic deformation from the individual loads of the pair of wheels on the rail is actually small. This elastic-plastic deformation of the rail becomes visible as a result of gradual gaining of a missed tonnage of rails and wheels respectively. Irregularities on the running surface of the wheels are of two types. The most common are the so-called continuous bumps on the wheel, when due to the uneven wear of rail the original shape of the wheel across the tread surface distorts. But nowadays, more and more often there occur isolated smooth irregularities of the wheel pairs, due to the increased wear of the wheel because of the stopping and blocking of wheels of the vehicles - slides (potholes), etc.The motion of the wheels with irregularities on the surface of the rail leads to vertical oscillation of the wheel, resulting in the forces of inertia, which is an additional load on the rail. In case of movement of the wheel with isolated roughness on the tread surface of the slide there is a strike, having a very large additional impact on the rail. Such attacks can cause kinked rails, especially in the winter months when there is increased fragility of rail steel, because of lowered temperatures. This is an abnormal phenomenon and occurs relatively rarely, at a small number of isolated irregularities on a wheel of the rolling stock. As correlations connecting the contact force and local deformation in the interaction of the wheel-rail system, we use the quasi-static Hertz’s model, linear-elastic model and two elastoplastic contact models: Alexandrov-Kadomtsev and Kil’chevsky. According to the results of Loktev’s studies ratios of the contact Hertz’s theory are quite suitable for modeling the dynamic effects of wheel and rail for speeds up to 90 km/h for engineering calculations. Since the contact surface is homogeneous and isotropic, the friction forces in the contact zone are not taken into account, the size of the pad is small compared to the dimensions of the contacting bodies and characteristic radii of curvature of the undeformed surfaces, the contacting surfaces are smooth.When train is driving, the position of the wheelset in relation to the rails varies con- siderably, giving rise to different combinations of the contact areas of the wheel and rail. Even assuming constant axial load the normal voltage will vary considerably because of the differences in the radii of curvature of the contacting surfaces of these zones. Thus, the proposed method allows evaluating the influence of several types of wheel defects on the condition of the rail and the prospects of its use in the upper structure of a railway track on plots with different speed and traffic volumes. Also the results can be used to solve the inverse of the considered problems, for example, when designing high-speed highways, when setting the vehicle speed and axle load, and the solution results are the parameters of the defects, both wheelsets and the rails, in case of which higher require- ments for the safe operation of railways are observed.
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Szychta, Elzbieta, and Leszek Szychta. "Comparative Analysis of Effectiveness of Resistance and Induction Turnout Heating." Energies 13, no. 20 (October 10, 2020): 5262. http://dx.doi.org/10.3390/en13205262.
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Turnouts are key parts of rail roads and are exposed to adverse weather conditions such as snowfall, snow drifts, low temperatures, or sleet. Effective protection assures good turnout function and contributes to rail traffic efficiency and safety. Presently, resistance heating (RH) is the most common system of turnout heating in Europe. In this study, we attempted to implement energy-saving induction heating (IH) in order to cut costs of operation and electricity. A turnout heating test stand, including a stock-rail and a switch-rail, was executed in a climatic chamber. Air temperature was constant at the time of heating. Active power received by both the systems was identical for any measurement (450 W). Test results enabled an assessment of switch-rail position and variations of climatic chamber air temperature on growth of turnout temperatures. Effects of heating type on correct lubrication of the slide plate surface were compared. Dynamics of heating variations and their impact on effectiveness of snow or ice removal were defined for both heating systems. Turnout’s readiness for switch-rail shifting and lubrication conditions of turnout’s moving parts were compared. An in-depth comparative analysis of efficiency of RH and IH turnout heating was undertaken in the conclusion.
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Galay, Marina, and Eduard Sidorov. "Increasing the operational stability of running surfaces of aluminothermiс welded rail joints by hot grinding." MATEC Web of Conferences 216 (2018): 01004. http://dx.doi.org/10.1051/matecconf/201821601004.
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Welded joints have traditionally been a weak point in a design of continuous welded rail (CWR) tracks. Grinding can be used as a resource-saving technology. The purpose of this paper is to study the grinding technology for welded rail joints at different temperatures. The temperature in the weld grinding zone varied from 560 to 850 °С. Using methods of microstructural analysis and hardness measurement, it has been established that different temperature conditions for weld grinding lead to the creation of non-identical mechanical properties of metal and a surface structure of the rail head in the weld zone. As a result of the research, an optimum temperature range, 600 ... 560 °C, was determined. This range is recommended for grinding aluminothermic welded joints.
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Tarabrin, V. F. "COMPARISON OF CHARACTERISTICS OF SEARCHING SYSTEMS OF MOBILE MEANS OF RAILS OF RAIL DEFECTOSCOPY." Kontrol'. Diagnostika, no. 268 (October 2020): 40–48. http://dx.doi.org/10.14489/td.2020.10.pp.040-048.
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The characteristics of wheel-type search systems and sliding systems used for ultrasonic rail monitoring are considered, and their comparison is performed. It is shown that the use of a wheel-type system, the acoustic path of which contains a liquid medium with an increased propagation time of ultrasonic vibrations, limits the control speed to 60 km/h. It is noted that when passing a wheel-type search system of curved sections of track and rails with lateral wear, a change in the direction of propagation of the ultrasonic beam is observed due to a change in the tilt of the wheel relative to the rolling surface of the rail head, which reduces the reliability of detection of rail defects. The disadvantages of the wheel system also include a complex design, low maintainability, poor protection when operating at low temperatures and mechanical stresses, limitations on the ability to operate at high speeds, complicated alignment and, in general, the complexity of maintenance. The characteristics of the retrieval sliding system developed by the specialists of JSC Firma TVEMA are given that provide detection of rail defects with high reliability, operate at low temperatures, and realize a control speed of up to 140 km/h, including in curved sections of the track. The advantages of the proposed non-contact magnetic centering system of the search system, excluding mechanical contact with the rail and the dependence of the centering accuracy on the state of the working face of the rail head, providing unhindered passage of turnouts, including without reducing the speed of control, are presented.
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Tarabrin, V. F. "COMPARISON OF CHARACTERISTICS OF SEARCHING SYSTEMS OF MOBILE MEANS OF RAILS OF RAIL DEFECTOSCOPY." Kontrol'. Diagnostika, no. 268 (October 2020): 40–48. http://dx.doi.org/10.14489/td.2020.10.pp.040-048.
Full textAbstract:
The characteristics of wheel-type search systems and sliding systems used for ultrasonic rail monitoring are considered, and their comparison is performed. It is shown that the use of a wheel-type system, the acoustic path of which contains a liquid medium with an increased propagation time of ultrasonic vibrations, limits the control speed to 60 km/h. It is noted that when passing a wheel-type search system of curved sections of track and rails with lateral wear, a change in the direction of propagation of the ultrasonic beam is observed due to a change in the tilt of the wheel relative to the rolling surface of the rail head, which reduces the reliability of detection of rail defects. The disadvantages of the wheel system also include a complex design, low maintainability, poor protection when operating at low temperatures and mechanical stresses, limitations on the ability to operate at high speeds, complicated alignment and, in general, the complexity of maintenance. The characteristics of the retrieval sliding system developed by the specialists of JSC Firma TVEMA are given that provide detection of rail defects with high reliability, operate at low temperatures, and realize a control speed of up to 140 km/h, including in curved sections of the track. The advantages of the proposed non-contact magnetic centering system of the search system, excluding mechanical contact with the rail and the dependence of the centering accuracy on the state of the working face of the rail head, providing unhindered passage of turnouts, including without reducing the speed of control, are presented.
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Moon, Abhijeet, and R. Balasubramaniam. "Determination of Hydrogen Diffusivity in Rail Steels by Sub-Scale Microhardness Profiling Technique." Defect and Diffusion Forum 293 (August 2009): 41–45. http://dx.doi.org/10.4028/www.scientific.net/ddf.293.41.
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Hydrogen diffusivity was estimated in three different eutectoid rail steels (C-Mn, Cu-Mo and Ni-Cu-Cr) at ambient temperatures using the technique of sub-surface microhardness profiling after cathodic hydrogen charging in 0.5mol/l sulphuric acid at a current density of 0.1A/cm2 for 24 hours. The increase in the concentration of hydrogen at a certain depth below the surface was related to the microhardness increase at this location as compared to the bulk value. The procedure used to obtain the diffusion coefficient of hydrogen from the microhardness profiles is discussed. The hydrogen diffusivity values in all of the rail steels were found to be similar (of the order of 10-13m2/sec). The estimated hydrogen diffusivity in the rail steel was lower than in pure iron (10-8m2/sec). Possible reasons for the difference are discussed.
Dissertations / Theses on the topic "Rail surface temperatures"
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Salahuddin, Ahmed. "The Relationship between Sea Surface Temperature in the Bay of Bengal and Monsoon Rainfall in Bangladesh, 1912-2001." Ohio University / OhioLINK, 2004. http://www.ohiolink.edu/etd/view.cgi?ohiou1090943747.
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Nel, Werner. "On the climate of the Drakensberg rainfall and surface-temperature attributes, and associated geomorphic effects /." Thesis, Pretoria : [S.n.], 2007. http://upetd.up.ac.za/thesis/available/etd-01252008-164156/.
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(13966684), Ying M. Wu. "Development of rail temperature prediction model and software." Thesis, 2011. https://figshare.com/articles/thesis/Development_of_rail_temperature_prediction_model_and_software/21344169.
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The railway track buckling occurs all over the world due to inadequate rail stress adjustment, which is greatly influenced by the variation in weather induced rail temperature and the rigidity of the track structure. Climate change and the ever increase in extreme changes in temperatures have made buckling an ever more prevalent problem in the railway industry. The ultimate goal of any research in the area of track stability management is to comprehensively manage rail buckling and the subsequent procedures that follow after buckling. The first step to have a clear understanding of how the temperature change of the rail track is influenced by the environmental conditions. The second step is to have an accurate prediction of what the environmental conditions will be in the next day so that management procedure can be put into place.
This study aims to develop a model and software that is capable of predicting rail temperature 24 hours in advance that is as accurate for use in the rail buckling management. Two distinct and separate mathematical manipulations are performed to achieve this goal.
One method used weather forecasts from the Australian Bureau of Meteorology (BoM) and forecasts the weather for the location that the rail is situated. This involves using 3-dimensional cubic interpolation that is the weather parameters are interpolated in 2-dimensions geographically and then 1-dimensionally through time. An interactive software is written in MATLAB to convert the BoM raw data into a rail temperature forecast for this study. The result is a 15 -minute forecast for every 3.06 km. The second method used multivariate linear regression, to predict the rail temperatures 24 to 48 hours in advance.
To validate the rail temperature predications, 3 months field test spanning June, July and August 2010, is conducted on Queensland Rail's (QR) coal network, this involved erecting an automated weather station (AWS) and adhering temperature sensors on to a section of track. The guidelines of World Meteorological Organization's (WMO) were followed for implementation of the AWS on site (WMO 2008). The AWS model WXT520 , produced by Vaisala (Vaisala 2009) was used in this study which an off the shelf product that is similar to what some rail compaies are already using for continues monitoring of critical sites.
The temperature sensors (surface thermocouples) and an off the shelf product Salient system's rail -stress modules are used to measure rail surface temperatures on both rails of the track (Salient Systems Inc 2009). The sensors were attached to the surface of the rail track to directly measure temperature change of the rail profile throughout the diurnal cycle. Statistical correlations between the different measured points of the rail profile are evaluated in relation to the diurnal cycle to assess the accuracy of current rail temperature measuring practices.
Statistical evaluation of how well the BoM predictions compare with weather parameters at the field experimentation site are performed, so too is a statistical evaluation of the accuracy of the rail temperature model developed. The prediction model is compared with the existing empirical methods as found in the literature review and an assessment of track conditions. This is a flag ship study in Australia; the main purpose of this study is to prove in a test case scenario that a rail temperature forecast without use of weather instrumentation is possible and the accuracy of the prediction is as good if not better than the instrumentation calculation.
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Tonin, Hemerson Everaldo. "Atmospheric freshwater sources for eastern Pacific surface salinity." 2006. http://catalogue.flinders.edu.au/local/adt/public/adt-SFU20061031.080144/index.html.
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Lo, Yu-Ting, and 羅玉婷. "Effects of Temperature and Acid Rain on Nutrients of Litter and Surface Soil in Natural Hardwoods." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/64670516482137488491.
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碩士國立中興大學
森林學系所
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The purposes of this study was to investigate the effects of temperature and acid rain on litter decomposition from natural hardwoods. Sample litter layer and surface soil from natural hardwoods. Control temperature by air- conditioned at 22 ℃, then were sprayed artificial acid rain, adjust the pH value caused by 2 , 4 and pH 6 . Spray once a week, spraying 200 ml of each sample and collect percolates back for analysis. Another group dealing in the same but the sample placed in air with an average temperature of shade at 29℃. The litter layer’s nutrient release content of the cations Ca, Mg, K and Na were significantly impact by acid rain. The temperature has no effect for Ca in litter layer and no interaction between temperature and acid rain. Temperature and acid rain also have no traction with each other in the surface soil’s K. The Ca, Mg and K content have the extremely remarkable difference in the forest litter layer and the surface soil .
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Bahr, Frederick L. "The effects of rainfall on temperature and salinity in the surface layer of the equatorial Pacific." Thesis, 1991. http://hdl.handle.net/1957/27797.
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Measurements of temperature and salinity in the upper 5 m of the ocean
along the equator showed cool fresh anomalies due to rain showers. The
measurements were made between 140 W and 110 W during April 1987, an
El Nino year. The eastern equatorial Pacific was characterized by weak winds
(3 m/s average), high rainfall (1.6 cm/day), and warm surface temperatures
(28.4 C). Measurements of temperature were made from a catamaran float
at 0.5 and 1 m depth and at 5 m depth from the ship. Salinity was measured
at a depth of 1 m from the float and 5 m from the ship. The float was towed
off of the port side of the ship outside of the bow wake. Near-surface low
temperature and low salinity anomalies due to cool rainfall were encountered.
These anomalies were on average cool and fresh by 0.02 C and 0.2 PSTJ
with maximum values of 0.5 C and 1.6 PSU. The horizontal extent of the
anomalies ranged from less than 10 to more than 100 km. Rainfall depths
estimated from salt conservation agreed roughly with shipboard rain-gauge
measurements. The characteristic lifetime of the anomalies, estimated from
the ratio of the average rain depth to average rain rate, was about 10 hrs.
Rainfall temperatures were computed from the T-S mixing curves for three
large, newly-formed anomalies. The average rainfall temperature was 21 C.
Ocean buoyancy fluxes estimated for intense rain showers were an order of
magnitude larger than the fluxes in the absence of rain.Graduation date: 1992
Best scan available for p.15-16, 35. Original is a black and white photocopy.
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Crimp, Steven Jeffrey. "Simulating sea-surface temperature effects on Southern African rainfall using a mesoscale numerical model." Thesis, 1996. https://hdl.handle.net/10539/24293.
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Dissertation submitted to the Faculty of Science, University of the Witwatersrand, for
completion of the Degree of' Master of ScienceThe atmospheric response of the Colorado State University Regional Atmospheric Modelling System (RAMS) to sea-surface temperature anomaliesis investigated. A period of four days was chosen from 21 to 24 January 1981, where focus was placed on the development and dissipation of a tropical-temperate trough across Southern Africa. Previous experimenting this mesoscalenumerical model have detemined the kinematic, moisture, and thermodynamic nature of these synoptic features. The research in this dissertation focuses specifically on the sensitivity of the numerical model's simulated responses to positive sea-surface temperature anomalies. Three separate experiments were devised, in which positive anomalous temperatures were added to the ocean surface north of Madagascar (in the tropical Indian Ocean), at the region of the Agulhas Current retroflection, and along the tropical African west coast (in the Northern Benguela and Angola currents). The circulation aspects of each sensitivity test were investigated through the comparison of simulated variables such as vapour and cloud mixing ratios, temperature, streamlines and vertical velocity, with the same variables created by a control simulation. The results indicate that for the first sensitivity test, (the Madagascar anomaly), cyclogenesis was initiated over the area of modified sea temperatures which resulted in a marginal decrease in continental precipitation. The second sensitivity test (over the Agulhas retroflection) produced a much smaller simulated response to the addition of anomalously warm sea temperatures than the tropical Indian Ocean anomaly. Instability and precipitation values increased over the anomalously warm retroflection region, and were slowly transferred along the westerly wave perturbation and the South African east coast. The third sensitivity experiment showed a predominantly localised simulated increase in precipitation over Gabon and the Congo, with the slow southward progression of other simulated circulation differences taking place. The small perturbations in each of the simulated meteorological responses are consistent with the expected climate response to anomalously warm sea-surface temperatures in those areas.
AC 2018
Books on the topic "Rail surface temperatures"
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Carlson, Toby N. A remotely sensed index of deforestation/urbanization for use in climate models: Annual performance report for the period 1 January 1995 - 31 December 1995. University Park, PA: Pennsylvania State University, 1995.
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Carlson, Toby N. A remotely sensed index of deforestation/urbanization for use in climate models: Annual performance report for the period 1 January 1995 - 31 December 1995. University Park, PA: Pennsylvania State University, 1995.
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Bahr, Frederick L. The effects of rainfall on temperature and salinity in the surface layer of the equatorial Pacific. 1991.
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Goswami, B. N., and Soumi Chakravorty. Dynamics of the Indian Summer Monsoon Climate. Oxford University Press, 2017. http://dx.doi.org/10.1093/acrefore/9780190228620.013.613.
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Lifeline for about one-sixth of the world’s population in the subcontinent, the Indian summer monsoon (ISM) is an integral part of the annual cycle of the winds (reversal of winds with seasons), coupled with a strong annual cycle of precipitation (wet summer and dry winter). For over a century, high socioeconomic impacts of ISM rainfall (ISMR) in the region have driven scientists to attempt to predict the year-to-year variations of ISM rainfall. A remarkably stable phenomenon, making its appearance every year without fail, the ISM climate exhibits a rather small year-to-year variation (the standard deviation of the seasonal mean being 10% of the long-term mean), but it has proven to be an extremely challenging system to predict. Even the most skillful, sophisticated models are barely useful with skill significantly below the potential limit on predictability. Understanding what drives the mean ISM climate and its variability on different timescales is, therefore, critical to advancing skills in predicting the monsoon. A conceptual ISM model helps explain what maintains not only the mean ISM but also its variability on interannual and longer timescales.The annual ISM precipitation cycle can be described as a manifestation of the seasonal migration of the intertropical convergence zone (ITCZ) or the zonally oriented cloud (rain) band characterized by a sudden “onset.” The other important feature of ISM is the deep overturning meridional (regional Hadley circulation) that is associated with it, driven primarily by the latent heat release associated with the ISM (ITCZ) precipitation. The dynamics of the monsoon climate, therefore, is an extension of the dynamics of the ITCZ. The classical land–sea surface temperature gradient model of ISM may explain the seasonal reversal of the surface winds, but it fails to explain the onset and the deep vertical structure of the ISM circulation. While the surface temperature over land cools after the onset, reversing the north–south surface temperature gradient and making it inadequate to sustain the monsoon after onset, it is the tropospheric temperature gradient that becomes positive at the time of onset and remains strongly positive thereafter, maintaining the monsoon. The change in sign of the tropospheric temperature (TT) gradient is dynamically responsible for a symmetric instability, leading to the onset and subsequent northward progression of the ITCZ. The unified ISM model in terms of the TT gradient provides a platform to understand the drivers of ISM variability by identifying processes that affect TT in the north and the south and influence the gradient.The predictability of the seasonal mean ISM is limited by interactions of the annual cycle and higher frequency monsoon variability within the season. The monsoon intraseasonal oscillation (MISO) has a seminal role in influencing the seasonal mean and its interannual variability. While ISM climate on long timescales (e.g., multimillennium) largely follows the solar forcing, on shorter timescales the ISM variability is governed by the internal dynamics arising from ocean–atmosphere–land interactions, regional as well as remote, together with teleconnections with other climate modes. Also important is the role of anthropogenic forcing, such as the greenhouse gases and aerosols versus the natural multidecadal variability in the context of the recent six-decade long decreasing trend of ISM rainfall.
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Cook, Kerry H. Climate Change Scenarios and African Climate Change. Oxford University Press, 2018. http://dx.doi.org/10.1093/acrefore/9780190228620.013.545.
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Accurate projections of climate change under increasing atmospheric greenhouse gas levels are needed to evaluate the environmental cost of anthropogenic emissions, and to guide mitigation efforts. These projections are nowhere more important than Africa, with its high dependence on rain-fed agriculture and, in many regions, limited resources for adaptation. Climate models provide our best method for climate prediction but there are uncertainties in projections, especially on regional space scale. In Africa, limitations of observational networks add to this uncertainty since a crucial step in improving model projections is comparisons with observations. Exceeding uncertainties associated with climate model simulation are uncertainties due to projections of future emissions of CO2 and other greenhouse gases. Humanity’s choices in emissions pathways will have profound effects on climate, especially after the mid-century.The African Sahel is a transition zone characterized by strong meridional precipitation and temperature gradients. Over West Africa, the Sahel marks the northernmost extent of the West African monsoon system. The region’s climate is known to be sensitive to sea surface temperatures, both regional and global, as well as to land surface conditions. Increasing atmospheric greenhouse gases are already causing amplified warming over the Sahara Desert and, consequently, increased rainfall in parts of the Sahel. Climate model projections indicate that much of this increased rainfall will be delivered in the form of more intense storm systems.The complicated and highly regional precipitation regimes of East Africa present a challenge for climate modeling. Within roughly 5º of latitude of the equator, rainfall is delivered in two seasons—the long rains in the spring, and the short rains in the fall. Regional climate model projections suggest that the long rains will weaken under greenhouse gas forcing, and the short rains season will extend farther into the winter months. Observations indicate that the long rains are already weakening.Changes in seasonal rainfall over parts of subtropical southern Africa are observed, with repercussions and challenges for agriculture and water availability. Some elements of these observed changes are captured in model simulations of greenhouse gas-induced climate change, especially an early demise of the rainy season. The projected changes are quite regional, however, and more high-resolution study is needed. In addition, there has been very limited study of climate change in the Congo Basin and across northern Africa. Continued efforts to understand and predict climate using higher-resolution simulation must be sustained to better understand observed and projected changes in the physical processes that support African precipitation systems as well as the teleconnections that communicate remote forcings into the continent.
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Remotely sensed index of deforestation/urbanization for use in climate models: Annual performance report for the period 1 January 1996 - 31 December 1996 for NASA grant no. NAGW-4250. University Park, PA: Pennsylvania State University, Office of Sponsored Programs, 1996.
Find full textBook chapters on the topic "Rail surface temperatures"
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Maley, Jean. "Late Quaternary Climatic Changes in the African Rain Forest : Forest Refugia and the Major Role of Sea Surface Temperature Variations." In Paleoclimatology and Paleometeorology: Modern and Past Patterns of Global Atmospheric Transport, 585–616. Dordrecht: Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-009-0995-3_25.
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Hansen, Gail, and Joseli Macedo. "Urban Climate." In Urban Ecology for Citizens and Planners, 62–73. University Press of Florida, 2021. http://dx.doi.org/10.5744/florida/9781683402527.003.0007.
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Cities often experience a climate phenomenon known as the urban heat island, where the built form, building materials, and lack of vegetation modify temperature, wind, rain, and humidity. Radiating heat from building materials, roads, and utilities form a dome of warm air where the transfer of heated air to and from building surfaces doesn’t allow for a temperature decrease at night to cool the air, creating the heat island. The dynamics of this urban heat budget involves several heat fluxes, including sensible, latent, and storage fluxes. A major health impact is heat stress in the summer and cities are employing several technologies to lower temperatures, such as heat mapping, solar micro-grids to power cooling centers, light-colored reflective pavements, and water retentive porous pavement for evaporative cooling.
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Wan, Xinyuan, Xiaojian Xia, Yiyang Chen, Deyuan Lin, Jiceng Han, Yinghao Ye, and Wenzhe Zhang. "The Performances of RTV Coated Surfaces and Their Services in Transmission Lines." In Advances in Energy Research and Development. IOS Press, 2022. http://dx.doi.org/10.3233/aerd220033.
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With climate change and global warming, there are extreme weather phenomena in some places. Excessive temperature can adversely affect room temperature vulcanized silicone rubber (RTV) insulators. Other factors such as air pollution, dust, fog, rain, ice and snow, and ultraviolet rays can cause damage to the surface hydrophobicity of the RTV surface and reduce its service life. Contamination from the above factors increases the risk of flashover and corona discharge, which can lead to accidents in the transmission system, resulting in economic loss or personal injury. In recent decades, scientists have investigated a variety of materials that can be compounded with RTV to improve their chemical and physical properties in order to extend the service life of RTV insulators. In this review, we conduct an extensive literature survey and summary on the development and application of RTV coated insulators.
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Swarbrooke, Professor John. "The Marine Environment." In The Impact of Tourism on the Marine Environment. Goodfellow Publishers, 2020. http://dx.doi.org/10.23912/9781911635574-4454.
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The fact that open ocean covers two-thirds of the surface of our planet dramati- cally illustrates the importance of the marine environment to life on Earth. But the importance of the oceans goes far beyond their sheer size for it is the oceans that largely determine our climate for the weather around the world is heavily influenced by what happens in our seas. ‘Weather patterns are primarily controlled by ocean currents which are influenced by surface winds, temperature, salinity, the Earth’s rotation and ocean tides....Ocean currents bring warm water and rain from the equator to the poles and cold water from the poles towards the equator’ (www.greentumble.com, 2016). Every schoolchild knows that the sun evaporates water from the sea which then become clouds that then produces almost all of the rain and snow which falls on every land mass in the world. The oceans also absorb heat from the sun and from human activities; this heat is then carried to the land in those places where the prevailing winds blow from the sea to the land. At the same time, the oceans play a vital role in the carbon cycle by absorbing carbon dioxide that is in the air.
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Hoyt, Douglas V., and Kenneth H. Shatten. "Rainfall." In The Role of the Sun in Climate Change. Oxford University Press, 1997. http://dx.doi.org/10.1093/oso/9780195094138.003.0010.
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This chapter examines rainfall and associated phenomena and their possible relationship to solar activity. Rainfall can be measured directly using rain gauges or estimated by monitoring lake levels and river flows. Satellite and radar rainfall measurements have become increasingly important. Historical documentation on drought, or the absence of rain, also reveals empirical relationships. Both rainfall and evaporation show marked variations with latitude and geography. First, we examine these rainfall-associated variations and estimate how they might change with solar activity. Second, we cover empirical studies of rainfall, lake levels, river flows, and droughts. The sun bathes the Earth’s equator with enormous amounts of surface energy. Much of this absorbed radiant energy evaporates water, causes atmospheric convection, and is later released to space as thermal radiation. Steady-state energy escapes, so tropical temperatures do not rise without limit. Some absorbed energy is transported poleward by winds from the point of absorption. Intense convection near the equator leads to a large updraft known as the intratropical convergence zone (ITCZ), a band of lofty, high-precipitation clouds producing the largest rainfall of any region on Earth. Solar energy in the ITCZ is carried to high elevations where it diverges and moves poleward. It is unable to travel all the way to the poles, so instead creates a large atmospheric circulation cell known as the Hadley cell. The Hadley cell has an upward motion near the equator and downward motions at about 30° north and south latitude. These downflow regions produce clear air with few clouds and create areas of minimum rainfall called deserts. These regions of upflow and downflow are connected by poleward flows in the upper atmosphere and equatorward flows in the lower atmosphere, forming a complete circulation pattern. Outside the Hadley cell are temperate and polar regions. The temperate regions have more rainfall than the deserts, while the cold polar regions have even less precipitation. Figure 6.1 shows the three regions with relative maximum rainfall. The mean evaporation has a much simpler latitudinal variation that tends to follow the surface temperature. Figure 6.1 shows this variation as a parabolicshaped dotted line.
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Brock, Fred V., and Scott J. Richardson. "Precipitation Rate." In Meteorological Measurement Systems. Oxford University Press, 2001. http://dx.doi.org/10.1093/oso/9780195134513.003.0011.
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Accurate rainfall measurements are required, usually over broad areas because of the natural variability of rain. Coverage of a large area can be achieved using many distributed point measurement instruments or a remote sensor with large areal coverage, such as radar, or both. This chapter describes several methods for measuring precipitation, both liquid and frozen types. Point measurements, e.g., rain gauges, are emphasized although a section on weather radar is included because this is a very important method of estimating precipitation. Precipitation rate could be specified as the mass flow rate of liquid or solid water across a horizontal plane per unit time: Mw in kg m-2 s-1. Water density is a function of temperature but that can be ignored in this context; then the volume flow rate, or precipitation rate, becomes R = Mw/pw in m s-1 or, more conveniently, in units of mm hr-1 or mm day-1. Precipitation rate is the depth to which a flat horizontal surface would have been covered per unit time if no water were lost by run-off, evaporation, or percolation. Precipitation rate is the quantity used in all applications but, in many cases, the unit of time is not specified, being understood for the application, commonly per day or per storm period. Some gauges measure precipitation, rain, snow and other frozen particles, while others measure only rain. Rainfall can be measured using point measurement techniques which involve measuring a collected sample of rain or measuring some property of the falling rain such as its optical effects. The other general technique is to use remote sensing, usually radar, to estimate rainfall over a large area. Both ground-based and space-based radars are used for rain measurement. A precipitation gage (US) or gauge (elsewhere) could be a simple open container on the ground to collect rain, snow, and hail. However, this is not a practical method for estimating the amount of precipitation because of the need to avoid wind effects, enhance accuracy and resolution, and make a measurement representative of a large area. These issues will be discussed in sect. 9.2.1.6.
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Wu, Zhiyuan, and Mack Conde. "Response of the Coastal Ocean to Tropical Cyclones." In Current Topics in Tropical Cyclone Research. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.90620.
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The Northwest Pacific and the South China Sea region are the birthplaces of most monsoon disturbances and tropical cyclones and are an important channel for the generation and transmission of water vapor. The Northwest Pacific plays a major role in regulating interdecadal and long-term changes in climate. China experiences the largest number of typhoon landfalls and the most destructive power affected by typhoons in the world. The hidden dangers of typhoon disasters are accelerating with the acceleration of urbanization, the rapid development of economic construction and global warming. The coastal cities are the most dynamic and affluent areas of China’s economic development. They are the strong magnetic field that attracts international capital in China, and are also the most densely populated areas and important port groups in China. Although these regions are highly developed, they are vulnerable to disasters. When typhoons hit, the economic losses and casualties caused by gale, heavy rain and storm surges were particularly serious. This chapter reviews the response of coastal ocean to tropical cyclones, included sea surface temperature, sea surface salinity, storm surge simulation and extreme rainfall under the influence of tropical cyclones.
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Ingersoll, Andrew P. "Saturn." In Planetary Climates. Princeton University Press, 2013. http://dx.doi.org/10.23943/princeton/9780691145044.003.0009.
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This chapter compares the climate of Saturn with that of Jupiter. Both Jupiter and Saturn have no oceans and no solid surfaces, but they have lightning storms and rain clouds that dwarf the largest thunderstorms on Earth. Saturn's weather is normally very calm, but every 20–30 years a giant storm erupts. These storms last for a few months and then disappear. In contrast, Jupiter's giant storms endure without change for decades or centuries. Saturn's winds are stronger than Jupiter's. The chapter first reviews the variables that might control the planets' climates before discussing how the climates actually differ. It examines Saturn's rotation, giant storms, effective radiating temperature, electrostatic discharges and lightning, enrichment relative to solar composition, helium raindrops, moist convection and conditional instability, and ortho-para instability.
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Benaradj, Abdelkrim, Hafidha Boucherit, Abdelkader Bouderbala, and Okkacha Hasnaoui. "Biophysical Effects of Evapotranspiration on Steppe Areas: A Case Study in Naâma Region (Algeria)." In Climate Issues in Asia and Africa - Examining Climate, Its Flux, the Consequences, and Society's Responses [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.97614.
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The Algerian steppe is of great interest in terms of vegetation, mainly in the Naâma region. This steppe vegetation is generally composed of annual and perennial grasses and other herbaceous plants, as well as, bushes and small trees. It is characterized by an arid Mediterranean climate where the average annual precipitation (100 to 250 mm) is insufficient to ensure the maintenance of the vegetation, in which the potential evaporation always exceeds the precipitations. This aridity has strong hydrological effect and edaphic implications from which it is inseparable. Water losses are great than gains due to the evaporation and transpiration from plants (evapotranspiration). The wind moves soils for one location to another, and causes a strong evapotranspiration of the plants, which is explained by a strong chronic water deficit of climatic origin of these compared to the potential evapotranspiration, opposed to a humid climate. Evapotranspiration is certainly closely linked to climate factors (solar radiation, temperature, wind, etc.), but it also depends on the natural environment of the studied region. Potential evapotranspiration (PET) data estimated from Thornthwaite’s method for the three stations (Mécheria, Naâma and Ainsefra). The average annual value of potential evapotranspiration is of the order of 807 mm in Mécheria, of 795 mm in Naâma de and in Ainsefra of 847 mm. It is more than 3 times greater than the value of the rainfall received. This propels it globally in the aridity of the region and from which the water balance of plants is in deficit. The potential evapotranspiration of vegetation in arid areas is very important due to high temperature and sunshine. During the cold season, precipitation covers the needs of the potential evapotranspiration and allows the formation of the useful reserve from which the emergence of vegetation. From the month of April there is an exhaustion of the useful reserve which results of progressive deficit of vegetation. Faced with this phenomenon of evatranspiration, the steppe vegetation of the region then invests in “survival” by reducing the phenomena of evapotranspiration, photosynthetic leaf surfaces, in times of drought. These ecophysiological relationships can largely explain the adaptation of steppe species (low woody and herbaceous plants) to the arid Mediterranean climate. Mechanisms and diverse modalities were allowing them to effectively resist for this phenomenon. The adaptation of the steppe vegetation by the presence of a root system with vertical or horizontal growth or both and seems to depend on the environmental conditions, and by the reduction of the surface of transpiration, and by the fall or the rolling up of the leaves, and by a seasonal reduction of transpiration surface of the plant to reduce water losses during the dry season (more than 6 months) of the year.. Some xerophytes produce “rain roots” below the soil surface, following light precipitation or during dew formation. Other persistent sclerophyllous species by which decreases transpiration by the hardness of the leaves often coated with a thick layer of wax or cutin.
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Bianchi, Thomas S. "Hydrodynamics." In Biogeochemistry of Estuaries. Oxford University Press, 2006. http://dx.doi.org/10.1093/oso/9780195160826.003.0009.
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The hydrologic cycle has received considerable attention in recent years with particular interest in the dynamics of land–atmosphere exchanges as it relates to global climate change and the need for more accurate numbers in global circulation models (GCMs). Recent advance in remote sensing and operational weather forecasts have significantly improved the ability to monitor the hydrologic cycle over broad regions (Vörösmarty and Peterson, 2000). The application of hydrologic models in understanding interactions between the watersheds and estuaries is critical when examining seasonal changes in the biogeochemical cycles of estuaries. Water is the most abundant substance on the Earth’s surface with liquid water covering approximately 70% of the Earth. Most of the water (96%) in the reservoir on the Earth’s surface is in the global ocean. The remaining water, predominantly stored in the form of ice in polar regions, is distributed throughout the continents and atmosphere—estuaries represent a very small fraction of this total reservoir as a subcomponent of rivers. Water is moving continuously through these reservoirs. For example, there is a greater amount of evaporation than precipitation over the oceans; this imbalance is compensated by inputs from continental runoff. The most prolific surface runoff to the oceans is from rivers which discharge approximately 37,500 km3 y−1 (Shiklomanov and Sokolov, 1983). The 10 most significant rivers, in rank of water discharge, account for approximately 30% of the total discharge to the oceans (Milliman and Meade, 1983; Meade, 1996). The most significant source of evaporation to the global hydrologic cycle occurs over the oceans; this occurs nonuniformly and is well correlated with latitudinal gradients of incident radiation and temperature. The flow of water from the atmosphere to the ocean and continents occurs in the form of rain, snow, and ice. Average turnover times of water in these reservoirs can range from 2640 y in the oceans to 8.2 d (days) in the atmosphere (Henshaw et al., 2000; table 3.1). The aqueous constituents of organic materials, such as overall biomass, have an even shorter turnover time (5.3 d). These differences in turnover rate are critical in controlling rates of biogeochemical processes in aquatic systems.
Conference papers on the topic "Rail surface temperatures"
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Stone, Daniel H., and Scott M. Cummings. "Effect of Residual Stress, Temperature and Adhesion on Wheel Surface Fatigue Cracking." In ASME 2008 Rail Transportation Division Fall Technical Conference. ASMEDC, 2008. http://dx.doi.org/10.1115/rtdf2008-74029.
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The Wheel Defect Prevention Research Consortium (WDPRC) conducted an analysis pertaining to the fatigue cracking of wheel treads by incorporating the effects of residual stresses, temperature, and wheel/rail contact stress. Laboratory fatigue tests were conducted on specimens of wheel tread material under a variety of conditions allowing the analysis to properly account for the residual stresses accumulated in normal operating conditions. Existing literature was used in the analysis in consideration of the effects of contact stress and residual stress relief. This project was performed to define a temperature range in which the life of an AAR Class C wheel is not shortened by premature fatigue and shelling. Wayside wheel thermal detectors are becoming more prevalent on North American railroads as a means of identifying trains, cars, and wheels with braking issues. Yet, from a wheel fatigue perspective, the acceptable maximum operating temperature remains loosely defined for AAR Class C wheels. It was found that residual compressive circumferential stresses play a key role in protecting a wheel tread from fatigue damage. Therefore, temperatures sufficient to relieve residual stresses are a potential problem from a wheel fatigue standpoint. Only the most rigorous braking scenarios can produce expected train average wheel temperatures approaching the level of concern for reduced fatigue life. However, the variation in wheel temperatures within individual cars and between cars can result in temperatures high enough to cause a reduction in wheel fatigue life.
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Wang, Hao, Jiaqi Chen, P. N. Balaguru, and Leith Al-Nazer. "Low Solar Absorption Coating for Reducing Rail Temperature." In 2014 Joint Rail Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/jrc2014-3819.
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The feasibility of using low-solar-absorption coatings to reduce the temperature rise of rails in summer is investigated in this paper using numerical analysis. Finite element (FE) models were developed based on the theory of heat transfer for predicting temperature fields in the rail track structure. Field measurements of air temperature and rail temperature were used to verify the modeled temperatures. Analysis results show that the developed FE models provide reasonable predictions of rail temperature. The 3-D rail temperature field shows that rail temperature differs spatially in the natural environment, which indicates that the current average temperature models may not provide accurate prediction of peak rail temperature. The peak temperature was observed at the top of rail seated on the wood ties. The developed FE models were further used to analyze the influence of solar absorptivity and emissivity of coating materials on rail temperature. Decreasing the absorptivity and increasing the emissivity of rail surface may decrease the peak rail temperature at different levels. The effect of decreased absorptivity was found to be more significant. This indicates that when an engineered coating material is applied on rail side surfaces, the peak rail temperature can be decreased significantly, which provides an alternative solution to reduce rail buckling risk without decreasing train speed or increasing the laydown temperature of rail. The experimental investigation of the effect of low solar absorption coating on rail temperature is ongoing.
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Li, Dingqing, and Monique Stewart. "Thermal Effects on Wheel Performance Based on Twin Disc Testing." In 2020 Joint Rail Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/jrc2020-8083.
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Abstract This paper presents the results and findings from a testing program conducted to investigate how temperature at the wheel-rail interface may affect wheel surface performance; i.e., development of rolling contact fatigue (RCF) and wear. Under this testing program, a twin disc test machine was used to test two different types of wheel specimens (cast and forged) under a range of temperatures (ambient to 800° F) and slip ratios from 0 to 0.75 percent. This testing program included a total of 32 tests, covering two wheel materials, four different temperatures, four slip ratios, and various traction coefficients as a ratio of longitudinal and vertical wheel/rail contact forces.
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Wang, Hao, Jiaqi Chen, P. N. Balaguru, and Leith Al-Nazer. "Thermal Benefits of Low Solar Absorption Coating for Preventing Rail Buckling." In 2015 Joint Rail Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/jrc2015-5669.
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A low solar absorption coating for rail application is developed to reduce the peak rail temperature and buckling risk in summer months. The proposed coating system provides a highly reflective surface through white or off-white color and has constituents to provide high abrasion resistance and self-cleaning properties. The zero volatile organic content (VOC) and one hundred percent inorganic coating system has excellent adhesion to steel surfaces with minimal surface preparation. This paper presented the outdoor temperature monitoring results of the coated rail segments under hot weather. The results show that the application of coating could significantly reduce the peak rail temperature up to 10.5°C. Three-dimensional finite element (FE) models were developed to predict temperature distributions and thermal stresses in the rail. The thermal stress simulation shows that, when the rail neutral temperature (RNT) is relatively low, rail coating decreases the compressive stress in the rail up to about 50% during the hottest hours. Although increasing the RNT decreases compressive thermal stresses in the rail, it could increase the risk of rail break due to the increased tensile stresses in the rail. The coating application could reduce the high RNT requirement during rail placement and prevent rail buckling as the effective RNT decreases after traffic and maintenance. Therefore, the low solar absorption coating could serve as a proactive way to control peak temperatures and thermal stresses in the rail.
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Dedmon, Steven L. "The Role of Oxidation in Railroad Wheels." In 2012 Joint Rail Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/jrc2012-74124.
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On-tread braking generates high heat and often results in temperatures on the tread surface in excess of 400C (750F). Temperatures this high result in rapid oxidation of the tread surface. High temperature oxidation for steel generally follows a parabolic rate law: the time to generate a given weight or thickness of an oxide layer increases proportionately to the square of the weight or thickness of that oxide layer. The decrease in the rate of generation of new scale thickness results from the longer time it takes for oxygen to diffuse through an increasingly thicker layer of oxide. However, wheel/rail contact and abrasive action from the brake pad often erodes the oxide layer as it forms, accelerating the rate of formation of the oxide. Further, as the oxide forms, cold worked tread material from rolling contact forces is removed thereby reducing the beneficial residual stresses and higher hardness layer that may have protected the tread surface from further plastic deformation. Environmental factors may also aggravate oxidation losses sufficiently to make it a primary rather than a secondary cause of wear. High temperature oxidation can contribute to an accelerated rate of shelling, which can result from oxide forming within tread cracks. Tensile stresses at the crack tip are caused by expansion when the oxide forms. Compressive stresses in the oxide are usually minimal, as expansion is not constrained in the scale growth direction. Volume constraints within a crack when the oxide forms generates compressive stresses in the newly formed oxide, which results in wedging forces at the crack tip. Oxidation of the tread surface may permit debris to adhere to the tread surface creating a defect called “built-up tread”. Although built-up tread defects require other factors in order to become a problem, oxidation of the tread surface appears to be an initiating mechanism. Results from experimentation and Finite Element Analyses are used to support this work.
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Dedmon, Steven, Takanori Kato, and James Pilch. "Effect of Temperature on Hardening and Residual Stress Development During Wheel/Rail Rolling Contact." In 2016 Joint Rail Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/jrc2016-5815.
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Brake heating of Railroad Wheels has been known to accelerate shelling, soften the wheel tread and contribute to stress reversal which is a requisite for generating thermal cracks. The effect brake heating has on shakedown has been investigated to a lesser extent, yet even here brake heating can be very important. This research combines field investigations and laboratory work in an attempt to quantify the thermal effects on wheel performance, especially as it relates to sub-surface shelling, microstructural changes and hardening mechanisms. Cyclic tensile tests were conducted at three temperatures to show the relationship between deformation at elevated temperatures and hardening response. Ductility measurements from both monotonic and cyclic tests were used to estimate residual stresses.
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Tarawneh, Constantine, James A. Aranda, Veronica V. Hernandez, and Claudia J. Ramirez. "An Analysis of the Efficacy of Wayside Hot-Box Detector Data." In 2018 Joint Rail Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/jrc2018-6218.
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Wayside hot-box detectors (HBDs) are devices that are currently used to monitor bearing, axle, and brake temperatures as a way of assessing railcar component health and to indicate any possible overheating or abnormal operating conditions. Conventional hot-box detectors are set to alarm whenever a bearing is operating at a temperature that is 94.4°C (170°F) above ambient, or when there is a 52.8°C (95°F) temperature difference between two bearings that share an axle. These detectors are placed adjacent to the railway and utilize an infrared sensor in order to obtain temperature measurements. Bearings that trigger HBDs or display temperature trending behavior are removed from service for disassembly and inspection. Upon teardown, bearings that do not exhibit any discernible defects are labeled as “non-verified”. The latter may be due to the many factors that can affect the measurement of HBDs such as location of the infrared sensor and the class of the bearing among other environmental factors. A field test was performed along a route that is more than 483 km (300 mi) of track containing 21 wayside hot-box detectors. Two freight cars, one fully-loaded and one empty, and one instrumentation car pulled by a locomotive were used in this field test. A total of 16 bearings (14 Class F and 2 Class K) were instrumented with K-type bayonet thermocouples to provide continuous temperature measurement. The data collected from this field test were used to perform a systematic study in which the HBD IR sensor data were compared directly to the onboard thermocouple data. The analyses determined that, in general, HBDs tend to overestimate Class K bearing temperatures more frequently than Class F bearing temperatures. Additionally, the temperatures of some bearings were underestimated by as much as 47°C (85°F). Furthermore, the HBD data exhibited some false trending events that were not seen in temperature histories recorded by the bayonet thermocouples. The findings from the field test suggest that HBDs may inaccurately report bearing temperatures, which may contribute to the increased percentage of non-verified bearing removals. To further investigate the accuracy of the wayside detection systems, a dynamic test rig was designed and fabricated by the University Transportation Center for Railway Safety (UTCRS) research team at the University of Texas Rio Grande Valley (UTRGV). A mobile infrared sensor was developed and installed on the dynamic tester in order to mimic the measurement behavior of a HBD. The infrared temperature measurements were compared to contact thermocouple and bayonet temperature measurements taken on the bearing cup surface. The laboratory-acquired data were compared to actual field test data, and the analysis reveals that the trends are in close agreement. The large majority of temperature measurements taken using the IR sensor have been underestimated with a similar distribution to that of the data collected by the HBDs in field service.
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Brimhall, Thomas, and Hasetetsion G. Mariam. "Dynamic Crush Test of Subcomponent Composite Front Frame Rails." In ASME 2001 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/imece2001/amd-25426.
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Abstract Testing of components is a usual method to evaluate structures, joining methods, and materials prior to full scale testing. Ambient temperature dynamic crush testing was performed on steel and composite sub-component front frame rails to compare the energy absorption and evaluate crush behavior. The sub-component composite frame rails were fabricated from two parts, an upper and lower, and bonded using three adhesives: Ashland polyurethane, Lord epoxy, and 3M epoxy. Prior to the dynamic test of the rails, single lap shear coupon tests were performed at ambient temperature and elevated temperature, 135°C, to evaluate relative bond strength of these adhesives. Testing was performed at elevated temperature because adhesives used for structural bonding in automotive, specifically under-hood, applications can be subjected to elevated temperatures. All three adhesives tested showed reduced bond strength at elevated temperatures. At room temperature, the Ashland urethane and Lord epoxy adhesives were observed to have comparable higher bond strength with the composite-to-composite lap shear coupons compared to the 3M epoxy. However, the crush failure mode for the composite tubes was confined to the substrate and the mean crush load was independent of the adhesive used for fabrication. Progressive crushing of the rail specimens was observed for all specimens tested. The amount of energy absorbed and crush mode for each rail design depended on its structural and material characteristics. The steel specimen absorbed energy by localized buckling in an accordion crush mode. The composite specimens absorbed energy by fracturing the composite matrix, delamination, fracture of the reinforcement fibers, and friction between the fracture and crushing surfaces. The crushing process of the steel rail was initiated by fabricated corrugations in the rail comers at the front, or impact, end of the rail. The composite rail crush event was initiated with an aluminum plug trigger designed to cause the composite rail to split at the comers with fracture of the composite matrix and delamination of the composite plies. Glass fibers were observed to fracture primarily at the tube corners. Fiber fracture elsewhere was infrequent. Close examination of the bonded joint fracture surface showed extensive fiber tear-out indicating that the failure was in the composite, not the adhesive. Mean crush load for the steel rail was 60% higher than the average mean load for the composite rails. The peak load for the steel rail was 71% higher than the average peak load for the composite rails. Specific energy absorption (SEA) of the steel rail was calculated to be 6.34 kJ/kgm compared with an average of 10.5 kJ/kgm for the composite rails.
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Mealer, Arthur, Constantine Tarawneh, and Stephen Crown. "Radiative Heat Transfer Analysis of Railroad Bearings for Wayside Hot-Box Detector Optimization." In 2017 Joint Rail Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/jrc2017-2260.
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The railroad industry utilizes wayside detection systems to monitor the temperature of freight railcar bearings in service. The wayside hot-box detector (HBD) is a device that sits on the side of the tracks and uses a non-contact infrared sensor to determine the temperature of the train bearings as they roll over the detector. Various factors can affect the temperature measurements of these wayside detection systems. The class of the railroad bearing and its position on the axle relative to the position of the wayside detector can affect the temperature measurement. That is, the location on the bearing cup where the wayside infrared sensor reads the temperature varies depending on the bearing class (e.g., class K, F, G, E). Furthermore, environmental factors can also affect these temperature readings. The abovementioned factors can lead to measured temperatures that are significantly different than the actual operating temperatures of the bearings. In some cases, temperature readings collected by wayside detection systems did not indicate potential problems with some bearings, which led to costly derailments. Attempts by certain railroads to optimize the use of the temperature data acquired by these wayside detection systems has led to removal of bearings that were not problematic (about 40% of bearings removed were non-verified), resulting in costly delays and inefficiencies. To this end, the study presented here aims to investigate the efficacy of the wayside detection systems in measuring the railroad bearing operating temperature in order to optimize the use of these detection systems. A specialized single bearing dynamic test rig with a configuration that closely simulates the operating conditions of railroad bearings in service was designed and built by the University Transportation Center for Railway Safety (UTCRS) research team at the University of Texas Rio Grande Valley (UTRGV) for the purpose of this study. The test rig is equipped with a system that closely mimics the wayside detection system functionality and compares the infrared sensor temperature reading to contact thermocouple and bayonet temperature sensors fixed to the outside surface of the bearing cup. This direct comparison of the temperature data will provide a better understanding of the correlation between these temperatures under various loading levels, operating speeds, and bearing conditions (i.e. healthy versus defective), which will allow for an optimization of the wayside detectors. The impact on railway safety will be realized through optimized usage of current wayside detection systems and fewer nonverified bearings removed from service, which translates into fewer costly train stoppages and delays.
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Ghodrati, Mohamad, Mehdi Ahmadian, and Reza Mirzaeifar. "Investigating the Rolling Contact Fatigue in Rails Using Finite Element Method and Cohesive Zone Approach." In 2018 Joint Rail Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/jrc2018-6183.
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A micromechanical-based 2D framework is presented to study the rolling contact fatigue (RCF) in rail steels using finite element method. In this framework, the contact patch of rail and wheel is studied by explicitly modeling the grains and grain boundaries, to investigate the potential origin of RCF at the microstructural level. The framework incorporates Voronoi tessellation algorithm to create the microstructure geometry of rail material, and uses cohesive zone approach to simulate the behavior of grain boundaries. To study the fatigue damage caused by cyclic moving of wheels on rail, Abaqus subroutines are employed to degrade the material by increasing the number of cycles, and Jiang-Sehitoglu fatigue damage law is employed as evolution law. By applying Hertzian moving cyclic load, instead of wheel load, the effect of traction ratio and temperature change on RCF initiation and growth are studied. By considering different traction ratios (0.0 to 0.5), it is shown that increasing traction ratio significantly increases the fatigue damage. Also by increasing traction ratio, crack initiation migrates from the rail subsurface to surface. The results also show that there are no significant changes in the growth of RCF at higher temperatures, but at lower temperatures there is a measurable increase in RCF growth. This finding correlates with anecdotal information available in the rail industry about the seasonality of RCF, in which some railroads report noticing more RCF damage during the colder months.
Reports on the topic "Rail surface temperatures"
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Brewer, K. D. Water level data from the Bells Corners Borehole Calibration Facility (2019-2021), Ottawa, Ontario. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/330087.
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The Geological Survey of Canada's deep borehole test site at the Bells Corners Borehole Calibration Facility in Ottawa, Ontario, has been in use since the 1980's for the development and calibration of geophysical logging instrumentation. In more recent times, the need for monitored deep borehole sites in Canada is increasingly important for long-term research into groundwater flow through fractured bedrock, and surface to groundwater interaction. In 2019, the facility underwent repairs to reopen deep boreholes, replace surface casings, and install atmospheric monitoring equipment. This report documents new groundwater level datasets in three of the six boreholes in the well cluster from March 2019 to October 2021. The compilation also integrates rainfall and air temperature data from a rain gauge installed on the site which provides insight into the rapid response times of this fractured bedrock system. This new water level information augments the growing number of datasets supporting the ongoing study of hydrogeological conditions at the calibration facility.
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Raymond, Kara, Laura Palacios, Cheryl McIntyre, and Evan Gwilliam. Status of climate and water resources at Chiricahua National Monument, Coronado National Memorial, and Fort Bowie National Historic Site: Water year 2019. National Park Service, May 2022. http://dx.doi.org/10.36967/nrr-2293370.
Full textAbstract:
Climate and hydrology are major drivers of ecosystems. They dramatically shape ecosystem structure and function, particularly in arid and semi-arid ecosystems. Understanding changes in climate, groundwater, and water quality and quantity is central to assessing the condition of park biota and key cultural resources. The Sonoran Desert Network collects data on climate, groundwater, and surface water at 11 National Park Service units in southern Arizona and New Mexico. This report provides an integrated look at climate, groundwater, and springs conditions at Chiricahua National Monument (NM), Coronado National Memorial (NMem), and Fort Bowie National Historic Site (NHS) during water year (WY) 2019 (October 2018–September 2019). Overall annual precipitation at Chiricahua NM and Coronado NMem in WY2019 was approximately the same as the normals for 1981–2010. (The weather station at Fort Bowie NHS had missing values on 275 days, so data were not presented for that park.) Fall and winter rains were greater than normal. The monsoon season was generally weaker than normal, but storm events related to Hurricane Lorena led to increased late-season rain in September. Mean monthly maximum temperatures were generally cooler than normal at Chiricahua, whereas mean monthly minimum temperatures were warmer than normal. Temperatures at Coronado were more variable relative to normal. The reconnaissance drought index (RDI) indicated that Chiricahua NM was slightly wetter than normal. (The WY2019 RDI could not be calculated for Coronado NMem due to missing data.) The five-year moving mean of annual precipitation showed both park units were experiencing a minor multi-year precipitation deficit relative to the 39-year average. Mean groundwater levels in WY2019 increased at Fort Bowie NHS, and at two of three wells monitored at Chiricahua NM, compared to WY2018. Levels in the third well at Chiricahua slightly decreased. By contrast, water levels declined in five of six wells at Coronado NMem over the same period, with the sixth well showing a slight increase over WY2018. Over the monitoring record (2007–present), groundwater levels at Chiricahua have been fairly stable, with seasonal variability likely caused by transpiration losses and recharge from runoff events in Bonita Creek. At Fort Bowie’s WSW-2, mean groundwater level was also relatively stable from 2004 to 2019, excluding temporary drops due to routine pumping. At Coronado, four of the six wells demonstrated increases (+0.30 to 11.65 ft) in water level compared to the earliest available measurements. Only WSW-2 and Baumkirchner #3 have shown net declines (-17.31 and -3.80 feet, respectively) at that park. Springs were monitored at nine sites in WY2019 (four sites at Chiricahua NM; three at Coronado NMem, and two at Fort Bowie NHS). Most springs had relatively few indications of anthropogenic or natural disturbance. Anthropogenic disturbance included modifications to flow, such as dams, berms, or spring boxes. Examples of natural disturbance included game trails, scat, or evidence of flooding. Crews observed 0–6 facultative/obligate wetland plant taxa and 0–3 invasive non-native species at each spring. Across the springs, crews observed six non-native plant species: common mullein (Verbascum thapsus), spiny sowthistle (Sonchus asper), common sowthistle (Sonchus oleraceus), Lehmann lovegrass (Eragrostis lehmanniana), rabbitsfoot grass (Polypogon monspeliensis), and red brome (Bromus rubens). Baseline data on water quality and water chemistry were collected at all nine sites. It is likely that that all nine springs had surface water for at least some part of WY2019, though temperature sensors failed at two sites. The seven sites with continuous sensor data had water present for most of the year. Discharge was measured at eight sites and ranged from < 1 L/minute to 16.5 L/minute.
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Raymond, Kara, Laura Palacios, Cheryl McIntyre, and Evan Gwilliam. Status of climate and water resources at Saguaro National Park: Water year 2019. Edited by Alice Wondrak Biel. National Park Service, December 2021. http://dx.doi.org/10.36967/nrr-2288717.
Full textAbstract:
Climate and hydrology are major drivers of ecosystems. They dramatically shape ecosystem structure and function, particularly in arid and semi-arid ecosystems. Understanding changes in climate, groundwater, and water quality and quantity is central to assessing the condition of park biota and key cultural resources. The Sonoran Desert Network collects data on climate, groundwater, and surface water at 11 National Park Service units in south-ern Arizona and New Mexico. This report provides an integrated look at climate, groundwater, and springs conditions at Saguaro National Park (NP) during water year 2019 (October 2018–September 2019). Annual rainfall in the Rincon Mountain District was 27.36" (69.49 cm) at the Mica Mountain RAWS station and 12.89" (32.74 cm) at the Desert Research Learning Center Davis station. February was the wettest month, accounting for nearly one-quarter of the annual rainfall at both stations. Each station recorded extreme precipitation events (>1") on three days. Mean monthly maximum and minimum air temperatures were 25.6°F (-3.6°C) and 78.1°F (25.6°C), respectively, at the Mica Mountain station, and 37.7°F (3.2°C) and 102.3°F (39.1°C), respectively, at the Desert Research Learning Center station. Overall temperatures in WY2019 were cooler than the mean for the entire record. The reconnaissance drought index for the Mica Mountain station indicated wetter conditions than average in WY2019. Both of the park’s NOAA COOP stations (one in each district) had large data gaps, partially due to the 35-day federal government shutdown in December and January. For this reason, climate conditions for the Tucson Mountain District are not reported. The mean groundwater level at well WSW-1 in WY2019 was higher than the mean for WY2018. The water level has generally been increasing since 2005, reflecting the continued aquifer recovery since the Central Avra Valley Storage and Recovery Project came online, recharging Central Arizona Project water. Water levels at the Red Hills well generally de-clined starting in fall WY2019, continuing through spring. Monsoon storms led to rapid water level increases. Peak water level occurred on September 18. The Madrona Pack Base well water level in WY2019 remained above 10 feet (3.05 m) below measuring point (bmp) in the fall and winter, followed by a steep decline starting in May and continuing until the end of September, when the water level rebounded following a three-day rain event. The high-est water level was recorded on February 15. Median water levels in the wells in the middle reach of Rincon Creek in WY2019 were higher than the medians for WY2018 (+0.18–0.68 ft/0.05–0.21 m), but still generally lower than 6.6 feet (2 m) bgs, the mean depth-to-water required to sustain juvenile cottonwood and willow trees. RC-7 was dry in June–September, and RC-4 was dry in only September. RC-5, RC-6 and Well 633106 did not go dry, and varied approximately 3–4 feet (1 m). Eleven springs were monitored in the Rincon Mountain District in WY2019. Most springs had relatively few indications of anthropogenic or natural disturbance. Anthropogenic disturbance included spring boxes or other modifications to flow. Examples of natural disturbance included game trails and scat. In addition, several sites exhibited slight disturbance from fires (e.g., burned woody debris and adjacent fire-scarred trees) and evidence of high-flow events. Crews observed 1–7 taxa of facultative/obligate wetland plants and 0–3 invasive non-native species at each spring. Across the springs, crews observed four non-native plant species: rose natal grass (Melinis repens), Kentucky bluegrass (Poa pratensis), crimson fountaingrass (Cenchrus setaceus), and red brome (Bromus rubens). Baseline data on water quality and chemistry were collected at all springs. It is likely that that all springs had surface water for at least some part of WY2019. However, temperature sensors to estimate surface water persistence failed...