Estimation of effective roughness length for heat and momentum from FIFE data

Using aircraft and surface data from the 1987 FIFE experiment in Kansas, we estimate the roughness length for momentum to be 0.19 m (with an error range 0.10–0.35 m), and the ratio of roughness length for momentum to that for heat to be about 16 (with an error range of 7–35).     

The sensitivity of winter evaporation to the formulation of aerodynamic resistance in the ECMWF model

In atmospheric models, the roughness length for momentum, heat and moisture are often taken equal, and tuned to the momentum budget problem. In this paper, it is shown that the roughness lengths have considerable impact on the evaporation in winter. One-column simulations of the land-surface scheme are driven with a long time series of observations for Cabauw in The Netherlands. It is shown that with the operational roughness lengths for this location (as in use at ECMWF in May 1993), evaporation in January, February and March is overestimated by more than a factor 2. More realistic parameters, as documented for this site, virtually eliminate the error. This study shows the importance of the surface roughness lengths in determining evaporation from wet surfaces. It also illustrates the strength of long observational time series in identifying model deficiencies.     

Approximate solutions of the surface mass loading of a spherical Earth model

Summary Simple linear representation of the components of an approximate plane solution of point mass loading of the Earth's surface in a conveniently chosen coordinate system leads to selection of a 2nd-degree curve which is the best fit of the spherical solution for the given Earth model. The new approximate solution, which, analogously to the plane solution, can be called a parabolic solution, enables the simple input parameters of the plane solution to be used also for substantially larger angular distances. The comparison with the spherical solution is carried out by computing the effects of the M₂-wave of ocean tides. The results of the computations for the tidal station Brussels prove the two solutions to be in sufficient agreement for global problems as well.

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Pressure dependence of electrical conductivity of (Mg,Fe)SiO<Subscript>3</Subscript> ilmenite

The electrical conductivity of (Mg_0.93Fe_0.07)SiO₃ ilmenite was measured at temperatures of 500–1,200 K and pressures of 25–35 GPa in a Kawai-type multi-anvil apparatus equipped with sintered diamond anvils. In order to verify the reliability of this study, the electrical conductivity of (Mg_0.93Fe_0.07)SiO₃ perovskite was also measured at temperatures of 500–1,400 K and pressures of 30–35 GPa. The pressure calibration was carried out using in situ X-ray diffraction of MgO as pressure marker. The oxidation conditions of the samples were controlled by the Fe disk. The activation energy at zero pressure and activation volume for ilmenite are 0.82(6) eV and −1.5(2) cm³/mol, respectively. Those for perovskite were 0.5(1) eV and −0.4(4) cm³/mol, respectively, which are in agreement with the experimental results reported previously. It is concluded that ilmenite conductivity has a large pressure dependence in the investigated P–T range.     

Prehnit — ein neuer Schichtsilikattyp

Zusammenfassung Prehnitkristalle vom Radautal, Harzburg, besitzen die Gitterkonstanten a=4,62₇ Å, b=5,49₀ Å, c=18,48 Å, die Raumgruppe P2cm–C _2v ⁴ , Z=2 für die Formel Ca₂Al(OH)₂[Si₃AlO₁₀]. Es wird gezeigt, daß im Prehnit ein neuer Schichtsilikattyp verwirklicht ist, der einer Vierereinfachschicht [Si₃AlO₁₀] ² entspricht. Die Lage der Schicht, senkrecht zur c-Achse, spiegelt die Spaltbarkeit in dieser Ebene gut wider. Ferner wird ausgeführt, daß in der Struktur des Prehnits vom Radautal die Si/Al-Verteilung einen hohen Ordnungsgrad besitzt.

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Summary Prehnite crystals from Radautal, Harzburg, have the lattice parameters a=4.62₇ Å, b=5.49₀ Å, c=18,48 Å, the space group P2cm–C _2v ⁴ , Z=2 for the formula Ca₂Al(OH)₂[Si₃AlO₁₀]. It is proved that in prehnite a new type of layer silicate is realized, in this case a Vierer-single layer [Si₃AlO₁₀] ² . This layer which is perpenticular to the c-axis reflects the cleavage in this plane. It is shown further that in the prehnite structure from Radautal the Si/Al-distribution has a high degree of order.

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Mit 4 Textabbildungen     

The Shatter Belt and the European Core - A Geopolitical Discussion on the Untypical Case of Slovenia

Europe in general is in a great state of change. States uniting with difficulty, states collapsing in pain, newly freed states struggling for new political, economic, and social identities - it is a region in a true transition. The paper is focussing primarily on the European Shatter Belt, formerly known as Eastern Europe. This is in fact a subset of new and old nation-states in the region of Central and Eastern Europe or, to use an older, but increasingly popular term, Mitteleuropa (Ruppert, 1997). Mitteleuropa is reemerging from the commotion resulting from the collapse of the old political order - communism. Our focus in this presentation is on personal experiences and observations. We will note the progress and positive dimensions of the change (transition) in the light of Europe's and NATO expansion. We will address the issues at two scales- at the international/national level and then, at the level of a Slovenian case study. This will enable us to discuss the natural system of the process of enlargement and incorporate supporting material of geographical, historical and social nature as envisioned by Hartshorne. Since the collapse of communism, the region has experienced some serious traumas that vary in intensity across the region. Probably the greatest pain has been experienced in the former Yugoslavia - an estimated 150,000 have perished and about 2.5 millions have been displaced within and outside the country. Chaos still exists despite the protectorate arrangement in Bosnia. The hot spot Kosovo has yet to be calmed down. In parts of the region economic pain has been considerable. Every state of Mitteleuropa experienced absolute economic decline from 1990–1995; high inflation rates, increased economic inequality, high levels of poverty, increase of crime and more. Economic and psychological stress effect demographic processes. Things have partly changed to the better in the most recent years. The adoption of capitalism and a democratic political system has been painful, disorienting, and is still in progress. The democratization process varies considerably across the region and in some states is in jeopardy. Reformed communist parties had staged a restoration in nearly all of the states - in some winning the control of the government, in others gaining strong and influential positions, or both. But, two major processes promise future democracy, rule of law, wealth and stability in general. This is the decision of the member states of the European Union and NATO to incorporate some/several states of the Shatter Belt into their own zone of protection and/or federation. Nation-states of the region tend to follow the EU Agenda 2000 rules with Slovenia one of the first!