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Surface Observations (surface + observation)
Selected AbstractsInfluence of a TiO2 surface treatment on the growth and adhesion of alumina scales on FeCrAl alloysMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 5 2008A. Galerie Abstract Deposits of TiO2 on FeCrAl alloys were obtained by surface TiO2 slurry application or by immersion of samples in tetraisopropylorthotitanate (TIPT) solution followed by air dry which gave the thinnest coatings. Isothermal oxidation of treated samples showed strong modification compared to non-treated ones, particularly in the temperature range of 850,925,°C where parabolic rate constants rapidly decreased when alloys were TiO2 treated. SEM surface observation, X-ray diffraction and ruby fluorescence showed that the presence of TiO2 promoted the formation of ,-Al2O3 whereas non-treated samples exhibited large amounts of transition aluminas. An interesting effect of the rapid change from metastable to stable ,-alumina was a strong increase of scale adhesion, determined by tensile testing, from 300,400 to 2000 J/m2 for scales grown at 850,°C on Aluchrom YHfAl. This was explained not only by the change from outward to mainly inward growth but also by the volume reduction at the transition to alpha transformation. [source] Downscaling daily maximum and minimum temperatures in the midwestern USA: a hybrid empirical approachINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 4 2007J. T. Schoof Abstract A new hybrid empirical downscaling technique is presented and applied to assess 21st century projections of maximum and minimum daily surface air temperatures (Tmax, Tmin) over the Midwestern USA. Our approach uses multiple linear regression to downscale the seasonal variations of the mean and standard deviation of daily Tmax and Tmin and the lag-0 and lag-1 correlations between daily Tmax and Tmin based on GCM simulation of the large-scale climate. These downscaled parameters are then used as inputs to a stochastic weather generator to produce time series of the daily Tmax and Tmin at 26 surface stations, in three time periods (1990,2001, 2020,2029, and 2050,2059) based on output from two coupled GCMs (HadCM3 and CGCM2). The new technique is demonstrated to exhibit better agreement with surface observations than a transfer-function approach, particularly with respect to temperature variability. Relative to 1990,2001 values, downscaled temperature projections for 2020,2029 indicate increases that range (across stations) from 0.0 K to 1.7 K (Tmax) and 0.0 K to 1.5 K (Tmin), while increases for 2050,2059 relative to 1990,2001 range from 1.4 K to 2.4 K (Tmax) and 0.8 to 2.2K (Tmin). Although the differences between GCMs demonstrate the continuing uncertainty of GCM-based regional climate downscaling, the inclusion of weather-generator parameters represents an advancement in downscaling methodology. Copyright © 2006 Royal Meteorological Society [source] A 10 year cloud climatology over Scandinavia derived from NOAA Advanced Very High Resolution Radiometer imageryINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 9 2003Karl-Göran Karlsson Abstract Results from a satellite-based method to compile regional cloud climatologies covering the Scandinavian region are presented. Systematic processing of multispectral image data from the NOAA Advanced Very High Resolution Radiometer (AVHRR) instrument has been utilized to provide monthly cloud climatologies covering the period 1991,2000. Considerable local-scale variation of cloud amounts was found in the region. The inland Baltic Sea and adjacent land areas exhibited a large-amplitude annual cycle in cloudiness (high cloud amounts in winter, low cloud amounts in summer) whereas a weak-amplitude reversed annual cycle (high cloud amounts with a weak maximum in summer) was found for the Scandinavian mountain range. As a contrast, conditions over the Norwegian Sea showed high and almost unchanged cloud amounts during the course of the year. Some interesting exceptions to these patterns were also seen locally. The quality of the satellite-derived cloud climatology was examined through comparisons with climatologies derived from surface cloud observations, from the International Satellite Cloud Climatology Project (ISCCP) and from the European Centre for Medium-range Weather Forecasts ERA-40 data set. In general, cloud amount deviations from surface observations were smaller than 10% except for some individual winter months, when the separability between clouds and snow-covered cold land surfaces is often poor. The ISCCP data set showed a weaker annual cycle in cloudiness, generally caused by higher summer-time cloud amounts in the region. Very good agreement was found with the ERA-40 data set, especially for the summer season. However, ERA-40 showed higher cloud amounts than SCANDIA and ISCCP during the winter season. The derived cloud climatology is affected by errors due to temporal AVHRR sensor degradation, but they appear to be small for this particular study. The data set is proposed as a valuable data set for validation of cloud description in numerical weather prediction and regional climate simulation models. Copyright © 2003 Royal Meteorological Society [source] Geophysical implications of Izu,Bonin mantle wedge hydration from chemical geodynamic modelingISLAND ARC, Issue 1 2010Laura B. Hebert Abstract Using two-dimensional dynamic models of the Northern Izu,Bonin (NIB) subduction zone, we show that a particular localized low-viscosity (,LV = 3.3 × 1019 , 4.0 × 1020 Pa s), low-density (,, , ,10 kg/m3 relative to ambient mantle) geometry within the wedge is required to match surface observations of topography, gravity, and geoid anomalies. The hydration structure resulting in this low-viscosity, low-density geometry develops due to fluid release into the wedge within a depth interval from 150 to 350 km and is consistent with results from coupled geochemical and geodynamic modeling of the NIB subduction system and from previous uncoupled models of the wedge beneath the Japan arcs. The source of the fluids can be either subducting lithospheric serpentinite or stable hydrous phases in the wedge such as serpentine or chlorite. On the basis of this modeling, predictions can be made as to the specific low-viscosity geometries associated with geophysical surface observables for other subduction zones based on regional subduction parameters such as subducting slab age. [source] Satellite Precipitation Measurements for Water Resource Monitoring,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 3 2009Chris Kidd Abstract:, Satellites offer an unrivaled vantage point to observe and measure Earth system processes and parameters. Observations of meteorological phenomena permit a more holistic view of the weather and climate that is not possible through conventional surface observations. Precipitation (rain and snow) in particular, benefit from such observations since precipitation is spatially and temporally highly variable: conventional gauge and radar measurements tend to be land-based with variable coverage. This paper provides an overview of the satellite systems that provide the observations, the techniques used to derive precipitation from the observations, and examples of the precipitation products available for users to access. [source] Molecular dynamics simulation of the contact process in AFM surface observationsLUBRICATION SCIENCE, Issue 2 2002J. Shimizu Abstract In the present work, several molecular dynamics simulations have been performed to clarify dynamically the contact mechanism between the specimen surface and probe tip in surface observations by an atomic force microscope (SFM) or friction force microscope (FFM). In the simulation, a three-dimensional model is proposed where the specimen and the probe are assumed to consist of monocrystalline copper and rigid diamond or a carbon atom, respectively. The effect of the cantilever stiffness of the AFM/FFM is also taken into consideration. The surface observation process is simulated on a well-defined Cu{100} surface. From the simulation results it has been verified that the surface images and the two-dimensional atomic-scale stick-slip phenomenon, just as is the case for real AFM/FFM surface observations, can be detected from the spring force acting on the cantilever. From the evaluation of the behaviour of specimen surface atoms, the importance of the specimen stiffness in deciding the cantilever properties can also be understood. The influence of the probe tip shape on the force images is also evaluated. From the results it can be verified that the behaviour of the specimen surface atoms as well as the solid surface images in AFM/FFM surface observations can be understood using the molecular dynamics simulation of the model presented. [source] | |||||||||||||