Challenge Future – Technical Progress and Globalization

Central elements of the challenges of the future are the population, supply and disposal trap, the question of how the increasing world population will be supplied with long‐lasting and effective sources of energy, raw materials and food? How do we deal with the problems of greenhouse effect, ozone hole, forest dieback, ground erosion, desertification and other environmental threats? Driven by the dynamics of the technical progress the world is in the midst of experiencing the transition from an industrial to an information society. The process of globalization is intrinsically tied to the information society and plays a vital role in the path to a new, digital development of the world. Therefore, new challenges have been added to the traditional ecological challenges at the beginning of the 21^st century, which the world community must react swiftly to.     

Atmospheric temperature sounding with the Fourier spectrometer

Preliminary results of a space experiment using the IKFS-2 infrared sounder (Meteor-M2 satellite) showed high-quality of measurements of spectra of the outgoing thermal radiation of the atmosphere–surface system and the adequacy of developed IR radiation atmospheric models in the 15-μm carbon gas absorption band used to recover the vertical profiles of the atmospheric temperature. Outgoing radiation spectra measured by IKFS-2 instruments make it possible to restore vertical temperature profiles with errors close to 1K in most of the 0–30 km high-altitude region, except for the lower troposphere and altitudes above 30 km, where these errors are close to 2–3K.     

An Intercomparison of Large-Eddy Simulations of the Stable Boundary Layer

Results are presented from the first intercomparison of large-eddy simulation (LES) models for the stable boundary layer (SBL), as part of the Global Energy and Water Cycle Experiment Atmospheric Boundary Layer Study initiative. A moderately stable case is used, based on Arctic observations. All models produce successful simulations, in as much as they generate resolved turbulence and reflect many of the results from local scaling theory and observations. Simulations performed at 1-m and 2-m resolution show only small changes in the mean profiles compared to coarser resolutions. Also, sensitivity to subgrid models for individual models highlights their importance in SBL simulation at moderate resolution (6.25 m). Stability functions are derived from the LES using typical mixing lengths used in numerical weather prediction (NWP) and climate models. The functions have smaller values than those used in NWP. There is also support for the use of K-profile similarity in parametrizations. Thus, the results provide improved understanding and motivate future developments of the parametrization of the SBL.     

Analysis of the geomagnetic induction tensor

The geomagnetic induction tensor is a means of summarizing the response of the earth at a given observing site to a geomagnetic variation source field. In this paper the characteristics of the tensor elements are examined, both generally and for the special cases of one-dimensional and two-dimensional geologic structure. The first-order model is taken of uniform source fields originating external to a semi-infinite half-space. Graphical ways of presenting the information contained in an induction tensor are explored, including ellipses of rotation, polar diagrams, and diagrams analogous to the Mohr circles of elasticity theory. Criteria to distinguish “two-dimensional” data from “three-dimensional” data are established. The advantages of simultaneously recording “normal” and “anomalous” variations are demonstrated in terms of the extra tensor elements which may then be estimated. The most practical way of presenting information from many stations on a map may be by drawing, for each site, arrows which summarize the response in the vertical field and quadrics which summarize the response in the horizontal field.     

边坡开挖破坏过程的离心模型试验研究

边坡开挖是工程中经常遇到的问题。在清华大学土工离心机上,开发了一种离心机运转过程中的边坡开挖模拟技术。进行了土坡开挖的离心模型试验,测量了开挖过程中边坡的位移场变化。结果表明,边坡的破坏过程是从坡体下部开始的剪切带逐渐向上发展贯通的过程,并经历了滑裂面贯通前的平缓变形和贯通后变形迅速增大两个阶段。坡顶裂缝最初均是由受拉引起的,但随着剪切带的不断向上发展,裂缝的扩展是由拉伸和剪切两种作用综合引起的。     

Transmission electron microscope texture and crystal chemistry of coexisting ortho- and clinopyroxene in the Antarctic ureilite Frontier Mountain 90054: Implications for thermal history

Abstract— Frontier Mountain (FRO) 90054, from Antarctica, is a rare clino- and orthopyroxene-bearing ureilite with a coarse equigranular oriented texture (grains up to 3 mm); it is classified as a low-shock Ca-rich type. The crystal chemistry of its clinopyroxene (Wo_39.3En_54.6Fs_6.1), orthopyroxene (En_{84 2}Fs₁₁Wo_4.8) and olivine (Fa_12.6Fo_86.9) was investigated by single-crystal x-ray structural refinements and transmission electron microscope (TEM) observations to obtain data on the evolutionary history of the parent body. The M1 octahedron and unit cell volumes of the orthopyroxene and clinopyroxene are consistent with low-pressure crystallization. The closure temperatures for intracrystalline Mg-Fe²⁺ ordering yielded values of 674 °C and 804 °C for opx and 596 °C for cpx, which indicate high-temperature equilibration and fast cooling. Trasmission electron microscope investigations were performed on clinopyroxene, orthopyroxene and pigeonite. The (100) twin lamellae in the clinopyroxene and intergrowth of clino- and orthoenstatite lamellae in orthopyroxene most probably originated by deformation. Exsolution was not observed in any of the phases, which suggests rapid cooling. Analysis by TEM also revealed interstitial Na-rich glass and pigeonite with sharp h + k odd reflections and rare stacking faults parallel to (100). Textural and crystal chemical data, obtained by TEM, indicated rapid cooling that was probably due to fast radiative heat loss as a result of the disintegration of the parent body into small fragments, which subsequently reassembled into a larger body. One or more collisional events caused fine-scale stacking faults and partial melting.     

An algorithm for determination of aerosol opticalthickness from AVHRR imagery over oceans

Summary The uncertainty in aerosol size distributions is a main source of errors in aerosol optical thickness determined from satellite measurements. To reduce the errors resulting from the uncertainty in aerosol size distributions, we have performed sensitivity analyses. It is found the errors resulting from the uncertainty in aerosol size distribution can be considerably reduced by using the Junge power law to approximate the aerosol size distribution in an actual atmosphere, if the exponent value is determined at the same time. An iterative algorithm is then developed for the simultaneous determination of aerosol optical thickness and the exponent of the Junge power law over ocean areas from the upwelling radiances measured in AVHRR visible and near infrared channels. A number of numerical experiments are carried out to investigate the validity of the Junge power law approximation by assuming the aerosol size distributions in an actual atmosphere are bimodal with different mode parameters, and by using the actual aerosol size distributions determined at several places by Kaufman et al. (1994). The results show that the errors in determined aerosol optical thickness resulting from the Junge power law approach are significantly reduced. The iterative algorithm is investigated further by comparing the aerosol optical thickness deduced from satellite measurement with that observed by a sun photometer. Received October 10, 2001 Revised December 28, 2001