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Atmospheric boundary layer observations are conducted at a coastal site during a transition phase from winter to summer season over the Indian peninsula. Thermal Internal Boundary Layer (TIBL) characteristics in presence of an off-shore and a weakly influenced on-shore synoptic wind are examined with the help of measurements carried out with a mini-SODAR (SOund Detection And Ranging), tethered balloon, and tower-based micrometeorological measurements. Influence of the changing synoptic scale conditions on turbulent characteristics of TIBL is discussed.

It is usual to assume that the "velocity gradient" Lp associated with slip is KZ 1 a, 0 nK, where y, is the rate of shear of the Kth slip system defined by the slip direction so and the normal to the plane n,. The above expression, written directly as the linear superposition of instantaneous rates of shear over all the active slip systems, is motivated both by experiments and the single slip case. On the other hand, one might assume that the deformation gradient Fp has a multiplicative decomposition, but here the sequence of activation of the slip systems becomes important. These representations for Fp and Lp should be viewed as constraints, and they are consistent for linearized theories and proportional deformations but not for all deformations; that is, not all deformations for which LP has the above form can one express Fp as a product of deformation gradients associated with each of the slip systems. In this paper, we discuss sufficient conditions under which the two constraints are equivalent, and we also provide a sufficient condition that guarantees that the form for the plastic deformation gradient is independent of the sequence of activation.

We compare three different methods for determining an average ‘effective‧ UV albedo. These methods are applied to spectral irradiance data from a measurement campaign held in the German Alps during the spring of 1999. The first method is based on the comparison of measurements of absolute levels of UV irradiance with model calculations. The second method takes advantage of changes in the spectral slope of spectral UV irradiance, which is a function of the surface albedo. In the third method, the surrounding area is partitioned into snow-covered and snow-free regions, and the effective albedo estimated by applying a higher or lower reflectivity to each facet before integrating over the surroundings. We present the differences and the correlations between the various methods as well as the results for the different locations.

The broad focus of this paper is on developing continuum models of inelastic response of crystalline materials that include the influence of microstructure, material symmetry, and dissipation of energy accompanying the changes in the microstructure. A framework has been developed, built on the idea of natural configurations of a material, that has provisions for explicit treatment of material microstructure (slip planes, dislocations, interfaces, etc.). It is demonstrated that the developed framework is applicable to diverse phenomena such as plasticity due to slip and twinning, and martensitic phase transformations. The developed framework is used to study the inelastic behavior of crystalline silicon at elevated temperatures.

Seven spectroradiorneters measured simultaneous surface UV irradiances at six different sites in the vicinity of Garmisch-Partenkirchen, Germany, during spring 1999. The measured clear-sky irradiance variability between the sites was analyzed with respect to altitude, aerosol optical depth, solar zenith angle, effective albedo, and tropospheric ozone. For conditions of low aerosol loading the increase of irradiance per 1000 m altitude difference was 9% at 400 nm. 20% at 320 nm, and 30% at 300 nm in this season. Effective albedo differences of 0.15, 0.29, and 0.65 were found between the snow-covered stations and the snow-free ground station with the higher effective albedo values determined at the two mountain stations. Clean continental aerosols with a single-scatter albedo of 0.95 were observed during this campaign. The measurements and the observed variations between the sites should enable more accurate modeling studies to be performed for an Alpine environment.

Using two different kinds of many-body potentials as well as the Lennard-Jones potential for hexagonal close packed metals, we have found that c +a edge dislocations with dislocation lines along 1 00 can split onto the basal plane, forming a non-planar sessile structure. The `type I' undissociated dislocation core, observed in previous papers, is shown to be stable only for small simulations. The observed dissociated core structure has a large distorted region that we interpret as a (11 1) twin nucleus, which may help the formation of (11 1) tension twins. We also find that this core structure is lower in energy than the previously observed glissile `type II' configuration, dissociated on the (11 2) plane. The sessile splitting of the core gives rise to non-Schmid behaviour, with the twin nucleus expanding under c -axis tension, and contracting under compression.

In this work the influences of ozone, aerosols, and albedo on the clear sky UVA and UVB irradiance at a high-mountain station are investigated by using both routine spectral UV measurements from the high-mountain Sonnblick observatory in Austria (3106-m altitude) and theoretical simulations. The 501 single measurements and the model output show that calculations are on average higher than the measurements by 10%–12% at 305 nm, 8%–10% at 315 nm, and 5%–8% at 370 nm. The study of the fluctuations in UV irradiance constitutes the second part of this work. Columnar-ozone fluctuations lead to enhancements of UV irradiances of 560% at 305 nm and 69% at 315 nm as columnar ozone changes from 380 to 230 Dobson units. The radiative transfer model shows the same behavior with changes in columnar ozone and solar zenith angle as the measurements do. By using the measurement:model ratio, it therefore is possible to analyze the fluctuations in UV irradiance occurring at Sonnblick observatory that are not depend...

Vertical profiles of drainage winds were monitored continuously by a Doppler-Mini-Sodar during case studies in two valleys, on both sides of the U. S. Continental Divide. A tethered balloon provided additional information on the vertical temperature and wind structure up to the Divide level. Ambient wind data were collected by a radar wind profiler on the west side, and a tower on the crest of the Divide. The onset, evolution and breakup of the drainage flow were studied on two nights, when the ridge-top winds were westerly and skies were clear. To study the influence of the ambient flow on drainage winds, changes in drainage wind speed, direction and depth, along with the volume flux were examined. It was found that, on the leeward side, the drainage was strongly influenced by the ambient winds (King, 1995b), which led to interruption and erosion of the locally generated valley flow. The drainage on the windward side of the Divide was almost undisturbed. A comparison of balloon and sodar wind profiles showed very good agreement during steady drainage conditions.

Phenomenological models of shape memory behavior are based on either continuum hypothesis (macroscopic) or on volume averages over a representative volume element consisting of several grains. These constitutive models attempt to model the shape memory behavior using macro/micromechanics and thermodynamics. In general, these models share a common feature. They describe the martensitic phase transformation by a parameter representing the martensite volume fraction, and formulate an evolution law for the martensite volume fraction. Exploiting the similarity of these models to elastoplasticity, we describe a finite element formulation of a micromechanics based constitutive model. Several other models can be formulated in a similar way, and the present work can be seen as a testbed approach to study and evaluate the constitutive models on a common platform. We present numerical results for Au-47.5at%Cd and Ti-50.6at%Ni to validate the finite element formulation. ? 1998 Elsevier Science Ltd.

An instrument system to measure the UVA and visible albedo from the snow capped mountain ranges has been built. Albedo is the ratio between the incoming radiation and the reflected radiation for a given location. Measuring albedo of the UVA and the Photosynthetic Active Radiation (PAR) wavelength range involves measuring the global irradiance and the reflections from the slopes around the measuring location. This system can be installed in any mountain peak to measure the reflectivity around the snow covered slopes. Global irradiance is measured by a standard global sensor using a Gigahertz UVA head and a home built UVA head. The UVA reflection is measured by an 1° telescope fitted with a home built UVA head. The home built UVA detector systems have been built using Hamamatsu silicon UV diodes and temperature stabilized using Peltier elements driven by a closed loop feedback control system. Two such similar systems have been built and used for directional and global measurements for direct comparison. PAR reflection is measured by a standard area CCD camera fitted with a wide angle lens and an optical filter. Global PAR is measured by using LI-COR Quantum sensors. The telescope and the CCD camera have been mounted on an Alta-Azimuth mount for scanning the surface around the peak to measure the reflectivity. A set of reflection standards along with the global PAR sensor has been mounted on a boom and fixed with the azimuth table. These reflection standards are visible in the field of view of the CCD camera. This provides the reference pixels in every CCD image that can be used to calibrate the rest of the CCD pixels. This system has been used to make the albedo images at the Zugspitze for the CUVRA (Characteristic of Ultra Violet Radiation in the Alps) project. Preliminary results are shown here.

The reflectivity distribution of the surrounding area of Zugspitze (2964 m) was measured within the scope of the EU project CUVRA. The albedo measurements were performed in the UVA and visible range by using a CCD camera and a UVA sensor. First results of the albedo distribution in the visible wavelength range of the surrounding areas are shown. The reflectivity of snow, rocks and of vegetation and its dependence on illumination are studied. The albedo of snow surfaces ranges between 0.4 in the shade and values up to 2 when the orientation of the facet is favourable. Reflectivity of rocks and forests lies between 0.1 and 0.25. Further work on the albedo in the UV wavelength range will be carried out. First, a relationship between UV albedo and visible albedo will be established.

The reflectivity of the 22 km x 24 km region surrounding Sonnblick Observatory near Salzburg, Austria (3104-m altitude, 47.05 degrees N, 12.95 degrees E), was calculated with a three-dimensional albedo model. The average albedo of the region was calculated at 305 and 380 nm for different solar zenith angles, ground reflectances, and solar azimuth angles. To determine geometrical effects, we first carried out the simulations without taking account of the effects of the atmosphere. The ratio to the reflectivity of a corresponding flat surface area (area with the same ground characteristics) was always less than 1 and showed a decrease with increasing solar zenith angle and with diminishing ground reflectance. Even when the ground reflectance was 100%, the average albedo was less than 1. The effect of the atmosphere was then taken into consideration in these calculations and was found to diminish the reflected components. This diminishing effect was compensated for, however, by the scattered irradiance. Finally, simulations of real conditions (nonhomogeneous ground reflectivities) were performed for different snow lines in the Sonnblick region. The average albedos obtained when all the surroundings were covered with snow were 0.32-0.63 with low solar zenith angles and 0.38-0.77 with a 40 degrees solar zenith angle.

Albedo inversion techniques are investigated in this work. Several methods are applied to spectral irradiance data from a measurement campaign held in the German Alps during the spring of 1999. One first method is based on the comparison of measurements of absolute levels of UV irradiance with model calculations. The second method takes advantage of changes in the spectral slope of spectral UV irradiance, which is a function of the surface albedo. In the third method, the surrounding area is partitioned into snow- covered and snow-free regions, and the effective albedo estimated by applying a higher or lower reflectivity to each facet before integrating over the surroundings. We present sensitivity analysis, the differences and the correlations between the various methods as well as the results for the different locations.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

One aim of the project CUVRA was to improve the modeling of effects of inhomogeneous albedo fields on ground UV irradiance. For the determination of the effect of heterogeneous illumination (shading effects, inclination and orientation of the facet) on the reflectivity of a facet in a mountainous region more complex approaches (than for the calculation of the reflectivity of flat surfaces) have to be chosen. We determined the 'effective' albedo for the surroundings of the Observatory Sonnblick (3106 m) by using three different methods. The first method consisted of a combination of a 3D albedo model calculation and 1D radiative transfer calculation. By using this method and a digital elevation map, the reflectivity of the region surrounding Sonnblick Observatory was calculated. The second method was an inversion method using a 1D radiative transfer model. The routine spectral UV measurements performed at Sonnblick were used to calculate the average effective albedo. The third method was entirely experimental. An albedo measuring system was used to perform reflectivity measurements of the surrounding of Sonnblick. Overall, the results showed that the average albedo of a topographically structured surface is lower than the average albedo of a corresponding (surface with same ground characteristics) flat surface.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

There are three inherent length scales associated with the shape memory phenomena. At the continuum length scale, we can describe the global response of a shape memory material in a phenomenological sense. At the other end, in the atomic length scale, the motion of atoms (diffusionless, in this case) causing the phase change can be studied by experiments (both physical and numerical). In between the two length scales lies the mesoscopic length scale wherein the microstructure is the dominating material feature. In order to study the phase transformation and the associated microstructure at this scale, we adopt a recently proposed technique called the quasicontinuum method. This technique marries the continuum and atomic length scales.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Continuum constitutive models of shape memory behavior share a common feature. They describe the martensitic phase transformation by a parameter representing the martensite volume fraction, and formulate an evolution law in terms of the parameter. Exploiting the similarity of these models to elastoplasticity, a finite element formulation of a micromechanics based constitutive model is described. Several other models can be formulated in a similar way, and the present work can be seen as a testbed approach to study and evaluate the constitutive models on a common platform. Numerical results are presented for Au-47.5at%Cd to validate the finite element formulation.