Solar limb darkening 1986–1990 (λλ303 to 1099 nm)     

Heinz Neckel  Dietrich Labs 《Solar physics》1994,153(1-2):91-114

The Sun's limb darkening was observed repeatedly between the 1986 minimum and the 1990 maximum of solar activity.Systematic variations, which could depend either on the momentary activity and/or the phase in the solar cycle, werenot detectable, either at continuum wavelengths or in two broad-band spectral intervals. Completelyirregular variations, which concern not only individual, successive scans (due to granulation, etc.), but also thedaily andseasonal averages, are usually less than 1%, but can reach occasionally 2% or even more. Minoreast-west asymmetries even in the seasonal means seem to be well established, mainly for < 400 nm. Thefinal, mean limb-darkening coefficients agree basically with those published by Pierce and Slaughter (1977) and Pierce, Slaughter, and Weinberger (1977), but show a much lower scatter when plotted against wavelength.  相似文献   

Towards an integration of process measurements, archive analysis and modelling in geomorphology — the Kärkevagge experimental site, Abisko area, northern Sweden     

Martin Gude  Gerhard Daut  Susanne Dietrich  Roland Mäusbacher  Christer Jonasson  Annett Bartsch  & Dieter Scherer 《Geografiska Annaler: Series A, Physical Geography》2002,84(3-4):205-212

The analysis of Holocene geomorphic process activity demands long–term data sets, which are available for the Kärkevagge catchment due to 50 years of intensive geomorphologic field studies. This data set is used in combination with additional field measurements, remote sensing and digital elevation model (DEM) analysis to provide input data for modelling Holocene valley development. On the basis of this information, geomorphic process units (GPUs) are defined by means of GIS modelling. These units represent areas of homogeneous process composition that transfer sediments. Since the data base enables the quantification of single processes, the interaction of processes within the units can also be quantified. Applying this concept permits calculation of recent sediment transfer rates and hence leads to a better understanding of actual geomorphic landscape development activity. To extrapolate these data in time and space the process–related sediments in the valley are analysed for depth and total volume, primarily using geophysical methods. In this fashion the validity of measured process rates is evaluated for the Holocene time scale. Results from this analysis are exemplified in a cross–profile showing some of the principal sediment units in the valley. For example, the measured modern rates on a slush torrent debris fan seem to represent the Holocene mean rate. This approach should also be suitable for revealing Holocene geomorphic landscape development in terms of climate change.  相似文献   

A site effect study in the Verchiano valley during the 1997 Umbria-Marche (Central Italy) earthquakes     

Stéphane Gaffet  Giovanna Cultrera  Michel Dietrich  Françoise Courboulex  Fabrizio Marra  Michel Bouchon  Arrigo Caserta  Cécile Cornou  Anne Deschamps  Jean-Paul Glot  Robert Guiguet 《Journal of Seismology》2000,4(4):525-541

Strong site effects were observed during the two M _W 5.7 and M _W 6.0 main shocks of the Colfiorito seismic crisis which occured on September 26, 1997 in Umbria-Marche (Central Italy).The most obvious indications of these effects are the dramatic differences in damage shown by buildings of similar construction in neighboring villages.Such observations were specifically made in the Verchiano valley in the fault area, 15 km south of Colfiorito where the Verchiano village and the Colle and Camino hamlets were heavily damaged (MCS intensity IX-X) since the first main shock of 1997/09/26,while in contrast, the Curasci village located 2 km eastwards remains almost intact.In order to study the anomalous ground motion amplifications in this area, an array of 11, 3-components seismo- and accelero-meters was set up during the 1997/10/20-24 period, extending from the western side of the valley, up to the top of Mount San Salvatore, going accross the Colle and Curasci hamlets.During the experiment, 67 aftershocks enlightened the valley from the Colfiorito (10 km north) and the Sellano (6 km south) active swarms.Seismic refraction experiments were conducted at the same time in the 500 m wide, 1500 m long Verchiano valley in order to determine the thickness and main characteristics of the alluvial infilling.The main results are: (i) compared to the valley side ground motion, and for all the events, recordings in the central part of the valley (piana di Verchiano) show relative amplification of 10 with a clear lengthening of the seismogram duration by a factor of 2 – (ii) broad band relative amplification of 6–8 is also clearly identified at the top of the Mount San Salvatore overhanging the valley – (iii) any of the site effect measurements done explains by itself the strongly contrasted damage observed at Colle and Curasci: i.e. the modification of the near-field radiation pattern by interaction with the free heterogeneous surface may have induced local shadow zones that saved Curasci.  相似文献   

Anchored locally – Linked globally. Transnational social movement organizations in a (seemingly) borderless world*     

Dietrich Soyez 《GeoJournal》2000,52(1):7-16

Dial locally -act globally: this slogan seems to appropriately reflect, under prevailing conditions of globalization and disembeddedness, the seemingly unrestrained possibilities of a variety of actors to influence events - without being present - anywhere on the planet. While focusing on a broadly conceived group of transnational social movement organizations - from non-governmental organizations to loosely linked transnational advocacy networks - the aim of this paper is to give evidence of the fact that geography - and all manner of borders - still matters even for these actors. Despite being linked with the world, they continue to act from deeply embedded local contexts, very often not triggering true transnational interaction but much more limited translocal encounters. In doing so, however, they literally cause collisions between different worlds while not only modifying existing but also constructing new spaces.September 1984 – first week of my field-work on Cape Breton Island, Nova Scotia, eastern Canada. A teacher at the local high school had agreed to make the first contacts with environmental groups, who were opposed to the use of pesticides by a Swedish forest products company. In return, he asked me to give two geography lessons on Germany to his class.After the lessons the 15-year-old pupils asked questions. One of the first of these was what I did with my family on a free weekend. Without long consideration, I answered: ``We often go for a walk in the forest with our children'. The pupils doubled up laughing in response, and the geography teacher was obviously also amused.A few days later I understood the reason for this reaction, when I saw typical forest land in Nova Scotia for the first time. Forests of an age which in Germany would be airy timber forests, which could be walked through even away from paths, were here largely inpenetrable thickets with numerous trunks per square meter not much thicker than an arm. Nobody could `go for a walk' here...This episode serves as a background to the issues that will be discussed, and I will return to it in my conclusion. It supports a central aspect, which is often neglected in many discussions about globalization: geography matters.  相似文献   

Högbomite in migmatitic paragneiss in the Betroka shear belt, Vohidava area, Precambrian of southern Madagascar     

T. Razakamanana  D. Ackermand  B. F. Windley 《Mineralogy and Petrology》2000,68(4):257-269

Summary ?The Betroka sinistral shear belt is a major geotectonic unit in the Precambrian of southern Madagascar. It consists of migmatitic paragneiss commonly interlayered with phlogopite-bearing diopsidite, phlogopite-humite-diopside-spinel marble, sillimanite-garnet quartzite and syn-tectonic S-type leucogranite. H?gbomite occurs sporadically in the migmatitic paragneiss in patches of magnetite with hercynite, and at the border of magnetite where it is in contact with hercynite, rare ilmenite, rutile and cordierite, which contains a network of chlorite, pyrophyllite and rare corundum/diaspore. X_Mg = Mg/(Mg + Fe) decreases as follows: Crd > Bt > Chl > H?g > Hc. The textural relations suggest the following h?gbomite-participating reactions: Ti-bearing hercynite ↠ hercynite + h?gbomite (intergrown/exsolution lamellae) ilmenite + cordierite ↠ hercynite + h?gbomite + rutile + chlorite/pyrophyllite   h?gbomite ↠ hercynite + ilmenite + corundum The chemical composition of h?gbomite varies substantially from grain to grain in individual samples and from sample to sample, this variation being highly dependent on the associated minerals. There is a weak zoning from core to rim in individual grains intergrown with hercynite and also in grains at the margin of hercynite, but this zoning is overprinted by zones formed at grain rims depending on the surrounding phases. In contact with hercynite, h?gbomite has FeO (total Fe as FeO) 27.1–28.5 wt.%, and MgO 4.5–5.8 wt.%, and in contact with magnetite FeO 24.9–26.5 wt.%, and MgO 6.0–8.5 wt.% and the core contents are within these values. TiO₂7.5–4.0 wt.% and Al₂O₃62.0–59.0 wt.% show zonations with increase from core to rim. Estimated P-T conditions are 6.0 ± 1.0 kbar and 700 ± 100 °C reached during a peak metamorphic stage of the Pan-African orogeny. However, the presence of diaspore with exsolved hercynite-magnetite indicates extreme retrograde metamorphism in the decompressional central part of this shear belt of southern Madagascar.

---

Zusammenfassung ?H?gbomit in migmatitischem Paragneis von Vohidava in der Betroka Scherzone im südlichen Pr?kambrium von Madagaskar Die sinistrale Betroka Scherzone ist eine ausgepr?gte tektonische Einheit des Pr?kambriums in Süd Madagaskar. Sie besteht aus migmatitischem Paragneis, in dem Phlogopit-führender Diopsidit, Phlogopit-Humit-Diopsid-Spinell-Marmor, Sillimanit-Granat-Quarzit und syntektonischer S-Typ Granit eingelagert sind. Im migmatitischen Paragneis kommen sporadisch H?gbomit/Hercynit Nester im Magnetit vor und am Magnetitrand findet sich H?gbomit im Kontakt mit Hercynit und Cordierit, der mit einem Netzwerk aus Chlorit/Pyrophyllit gefüllt ist, sowie sporadisch mit Korund/Diaspor, Ilmenit und Rutil. X_Mg = Mg/(Mg + Fe) nimmt in folgender Reihung ab: Crd > Bt > Chl > H?g > Hc. Aus den texturellen Beziehungen werden folgende H?gbomit-partizipierende Reaktionen abgeleitet: Ti-führender Hercynit ↠ Hercynit + H?gbomit (verwachsen/Entmischungslamellen)   H?gbomit ↠ Hercynit + Ilmenit + Korund Die chemische Zusammensetzung von H?gbomit variiert betr?chtlich von Korn zu Korn in einer Probe und von Probe zu Probe; wobei die Variation von den Kontaktmineralen abh?ngt. H?gbomit im Hercynit hat eine schwache Zonierung von Kern zum Rand. Im H?gbomit am Hercynitrand ist die Kern-Rand-Zonierung durch die von den Kontaktmineralen abh?ngige Randzusammensetzung überpr?gt. Im Kontakt zum Hercynit hat H?gbomit 27,1–28,5 Gew.% FeO (total Fe als FeO) und 4,5–5,8 Gew.% MgO und im Kontakt zu Magnetit 24,9–26,5 Gew.% FeO und 6,0–8,5 Gew.% MgO, die Kernzusammensetzung liegt zwischen den beiden Randwerten. TiO₂nimmt vom Kern zu den R?ndern von 7,5 bis 4,0 Gew.% ab und Al₂O₃von 62,0 bis 59,0 Gew.%. Die P-T Bedingungen des Metamorphose-Peaks w?hrend der Pan-Afrikanischen Orogenese erreichten 6,0 ± 1,0 Kbar und 700 ± 100 °C. Die sp?te Bildung von Diaspor und die Hercynit-Magnetit-Entmischung weisen auf eine tiefgreifende retrograde Metamorphose im Dekompressions-Zentralbereich der Betroka-Scherzone im südlichen Madagaskar hin.

---

---

Received January 15, 1999;/revised version accepted July 6, 1999  相似文献   

Using Lightning Data to Better Understand and Predict Flash Floods in the Mediterranean     

C. Price  Y. Yair  A. Mugnai  K. Lagouvardos  M. C. Llasat  S. Michaelides  U. Dayan  S. Dietrich  F. Di Paola  E. Galanti  L. Garrote  N. Harats  D. Katsanos  M. Kohn  V. Kotroni  M. Llasat-Botija  B. Lynn  L. Mediero  E. Morin  K. Nicolaides  S. Rozalis  K. Savvidou  B. Ziv 《Surveys in Geophysics》2011,32(6):733-751

One of the costliest natural hazards around the globe is flash floods, resulting from localized intense convective precipitation over short periods of time. Since intense convective rainfall (especially over the continents) is well correlated with lightning activity in these storms, a European Union FP6 FLASH project was realized from 2006 to 2010, focusing on using lightning observations to better understand and predict convective storms that result in flash floods. As part of the project, 23 case studies of flash floods in the Mediterranean region were examined. For the analysis of these storms, lightning data were used together with rainfall estimates in order to understand the storms?? development and electrification processes. In addition, these case studies were simulated using mesoscale meteorological models to better understand the local and synoptic conditions leading to such intense and damaging storms. As part of this project, tools for short-term predictions (nowcasts) of intense convection across the Mediterranean and Europe, and long-term forecasts (a few days) of the likelihood of intense convection, were developed and employed. The project also focused on educational outreach through a special Web site http://flashproject.org supplying real-time lightning observations, real-time experimental nowcasts, medium-range weather forecasts and educational materials. While flash floods and intense thunderstorms cannot be prevented, long-range regional lightning networks can supply valuable data, in real time, for warning the public, end-users and stakeholders of imminent intense rainfall and possible flash floods.  相似文献   

On modelling geophysical flows having low rossby numbers     

David E. Dietrich 《大气与海洋》2013,51(1):57-71

Abstract

New, fourth‐order “c” grid Coriolis term treatments are compared with widely used second‐order treatments. Their improved accuracy is demonstrated by a grid convergence study for a relevant linear problem. Such an accuracy improvement is relatively easy and costs little for low Rossby number flows compared with high Rossby number flows, because one must consider only the Coriolis and pressure gradient terms in low Rossby number flows. The “c” grid is favourable for the latter, but the Coriolis terms benefit greatly by the higher order treatments analysed herein.  相似文献   

Perturbation of the Plane-Wave Reflectivity of A Depth-Dependent Elastic Medium By Weak Inhomogeneities     

M. Dietrich  F. Kormendi 《Geophysical Journal International》1990,100(2):203-214

  相似文献   

OBSERVATION OF THE UV SOLAR SPECTRAL IRRADIANCE BETWEEN 200 AND 350 nm DURING THE ATLAS I MISSION BY THE SOLSPEC SPECTROMETER     

Thuillier  Gérard  Hersé  Michel  Simon  Paul C.  Labs  Dietrich  Mandel  Holger  Gillotay  Didier 《Solar physics》1997,171(2):283-302

The SOLSPEC instrument has been built to carry out solar spectral irradiance measurements from space. It consists of three spectrometers designed to measure the solar spectral irradiance from 180 to 3000 nm. It flew for the first time in December 1983 with the SpaceLab 1 mission (SL1) and later with the ATLAS missions after significant improvement of the instrument optics and calibration procedures. For the ATLAS 1 mission in March 1992, the thermal conditions encountered during the measurements were better than those of SL1, leading to better data quality. Furthermore, other Sun spectrometers, two on the same platform and two others on board the Upper Atmosphere Research Satellite, have also carried out UV absolute spectral measurements at the same time. These opportunities allowed comparisons of solar irradiance determinations. The UV part of the measurements made during that mission is presented here as well as its calibration and accuracy analysis.  相似文献   

Remarks on the convergency of photospheric model conceptions and the solar quasi continuum     

Dietrich Labs  Heinz Neckel 《Solar physics》1972,22(1):64-69

A comparison is made of the observed intensity in the solar continuous spectrum with those predicted by some models. Arguments are given that the bend-off observed for < 0.6 is a real phenomenon, and due to a veiled line haze.  相似文献