Roll Vortices and Boundary-Layer Development during a Cold Air Outbreak

The development of the boundary layer during a cold air outbreak in the FramStrait is documented by aircraft measurements. The convection was organisedinto roll vortices with aspect ratios increasing from 2.9 near the ice edgeto more than 6 at 100 km further downstream. This increase coincides with anincrease of the latent heat release in the cloud layer. The stability parameter-zi/L varies from about zero at the ice edge to 30 at a distance of 200 kmdownstream over open water where the satellite picture still shows cloudstreets. The increase is mainly due to the deepening of the boundary layer.The turbulent vertical sensible and latent heat fluxes near the surface amountto 400 W m^-2 within a 300 km off-ice zone. 25% of the upward heat fluxin the subcloud layer is carried out by organised roll motions. Experimentswith a 2-dimensional non-hydrostatic model show a similar roll aspect ratio inthe first 50 km, but further downstream where condensational heating is moreimportant the modelled roll wavelengths are distinctly smaller than the observedones.     

Why GPS makes distances bigger than they are

Global navigation satellite systems such as the Global Positioning System (GPS) is one of the most important sensors for movement analysis. GPS is widely used to record the trajectories of vehicles, animals and human beings. However, all GPS movement data are affected by both measurement and interpolation errors. In this article we show that measurement error causes a systematic bias in distances recorded with a GPS; the distance between two points recorded with a GPS is – on average – bigger than the true distance between these points. This systematic ‘overestimation of distance’ becomes relevant if the influence of interpolation error can be neglected, which in practice is the case for movement sampled at high frequencies. We provide a mathematical explanation of this phenomenon and illustrate that it functionally depends on the autocorrelation of GPS measurement error (C). We argue that C can be interpreted as a quality measure for movement data recorded with a GPS. If there is a strong autocorrelation between any two consecutive position estimates, they have very similar error. This error cancels out when average speed, distance or direction is calculated along the trajectory. Based on our theoretical findings we introduce a novel approach to determine C in real-world GPS movement data sampled at high frequencies. We apply our approach to pedestrian trajectories and car trajectories. We found that the measurement error in the data was strongly spatially and temporally autocorrelated and give a quality estimate of the data. Most importantly, our findings are not limited to GPS alone. The systematic bias and its implications are bound to occur in any movement data collected with absolute positioning if interpolation error can be neglected.     

Ascending droplets in the earth's core

This paper is concerned with some new problems of the dynamics and energetics of the Earth's core. The model of the so-called gravitationally-powered dynamo is investigated under the assumption of liquid immiscibility in the FeS system as a possible core material. In this way the growing inner core causes nucleation of small FeS-droplets that ascend under the release of gravitational potential energy. This energy is enough to drive a dynamo with a toroidal magnetic field of mean size.     

Mineralogical,geochemical and microfabric evidences of gypsum crusts: a case study from Budapest

High levels of SO₂ and particulate pollution enable the rapid development of gypsum-rich weathering crusts in Budapest. Two types of white crusts, thin and thick ones, and two forms of black crusts, laminar and framboidal ones, were studied in limestone buildings of the parliament and Citadella. The percentage of crust cover and damage categories were documented on selected walls. Petrographic, XRD, XRF and sulphur isotope analyses were performed under laboratory conditions to understand the mechanism of crust formation. White crusts found both on exposed and sheltered walls display a calcite-rich layer with gypsum, while black crusts are enriched with gypsum. The sulphur isotopic composition of white and black crusts overlaps, but the crusts are slightly enriched in heavy isotopes compared to rainwater. S content, Si/Al ratios and particulates in black crusts suggest that air pollution (SO₂, dust) contributes to black crust formation. The accumulation of sulphur and Zn enrichment of white crusts were also documented indicating that under high pollution levels, even these compound can accumulate on exposed facades.     

Der Original-Beerbachit im Odenwald,ein Amphibolit-Hornfels in Pyroxen-Hornfelsfazies

With this petrographic re-investigation of the beerbachite (Chelius, 1892) from Odenwald/Germany geochemical and phase-petrological data are given for the first time.By petrofabric relics (Fig. 7) and geochemical characteristics (Figs. 8–11) is shown that the beerbachite-xenoliths are due to blocks broken down from the surrounding amphibolite series. They are present high grade hornfelses.Beerbachite, porphyroblastic by plagioclase (here porphyroblastic beerbachite, Bbp) (Chelius' Gabbroporphyrit) (Fig. 6) frequently forms marginal zones of beerbachite blocks and is explained as beerbachite-metablastite.Phase relation (Fig. 13) and mineral reactions with increasing metamorphic grade from amphibolite to amphibolite-hornfels (containing hornblende) finally to beerbachite are demonstrated and discussed.The first step may be the mineral reaction: plag_I(An 35–40)+hbl_I+sphene= plag_II(An 50–60)+hbl_II+cpx+opx+magnetite/ilmenite+H₂O. The pyroxene-hornfels facies respectively the orthopyroxene subfacies of the K-feldspar-cordierite-hornfels facies (Winkler, 1967) is only reached with the typical assemblage: plag(An 55–70)-cpx-opx-mt/ilm±(quartz) of beerbachite.On condition that the load correspondends to 3–4 km the maximum temperatures may not have exceeded 720–750° C. This valuation would result from experimental data of Choudhuri and Winkler (1967) of the model reaction: hbl=en+di+an+H₂O, if . The natural conditions will differ from this experimental model because of resp. P _load (p. 81)The very probably required temperature for the mineral assemblage of beerbachite would still be within sub-solidus temperatures of the corresponding model system, according to Fig. 13d. Therefore, the coarse grained plagioclases of Bbp (p. 69) could not be formed from cotectic pockets, too.Finally, convergences and divergences to the beerbachite concept are discussed out of the recent literature.

---

---

Herrn Dr. E. Knauer vom hiesigen Institut danken wir sehr für die Bestimmung des Chemismus zweier Pyroxen-Paare aus Beerbachit bzw. Hornfels mit der Mikrosonde (CAMEGA MS 46), Leihgabe der Deutschen Forschungsgemeinschaft. Den Herren Prof. E. Nickel und Dr. M. Maggetti vom Mineralogischen Institut der Universität Fribourg (Schweiz) und Dr. H. D. Trochim, Mineralogisches Institut der Universität Bochum, verdanken wir Vergleichsproben oder Einsichtnahme in vorhandene Dünnschliffe.     

Post-collisional transition from calc-alkaline to alkaline magmatism during transcurrent deformation in the southernmost Dom Feliciano Belt (Braziliano–Pan-African, Uruguay)

In the southernmost Dom Feliciano Belt of Uruguay, highly fractionated calc-alkaline granites, mildly alkaline granites, shoshonitic volcanics, and peralkaline intrusions and volcanics are spatially and temporal associated with the evolution of shear zones. Four representative magmatic unites of this diverse association were petrographic and geochemically investigated: the Solís de Mataojo Complex, a medium to high K2O calc-alkaline granite with signature typical of mature continental arcs and post-collisional settings; the Maldonado granite, highly fractionated calc-alkaline to alkaline, with characteristics that are transitional between both types of series; the Pan de Azúcar Pluton, with characteristics typical of post-collisional alkaline granites and the Las Flores shoshonitic basalts.

Geochemistry and geotectonic setting point out that slab breakoff was most likely the mechanism associated with the generation of high-K calc-alkaline magmas (Solís de Mataojo and Maldonado) shortly after collision. Extension associated to the formation of molassic basins and emplacement of dolerites and basalt flows with shoshonitic affinity (Las Flores) 15and finally a shift to magmas with alkaline signatures (Pan de Azúcar) simultaneous with a second transpressional phase were probably linked with lithospheric thinning through delamination. This evolution took place between 615 and 575 Ma, according to available data. Contrary to previous proposals, which considered this magmatism to represent the root of a continental magmatic arc, a post-collisional environment, transitional from orogenic to anorogenic, during transcurrent deformation is proposed.     

Noble gases in mineral separates from three shergottites: Shergotty,Zagami, and EETA79001

Abstract— This study provides a complete data set of all five noble gases for bulk samples and mineral separates from three Martian shergottites: Shergotty (bulk, pyroxene, maskelynite), Zagami (bulk, pyroxene, maskelynite), and Elephant Moraine (EET) A79001, lithology A (bulk, pyroxene). We also give a compilation of all noble gas and nitrogen studies performed on these meteorites. Our mean values for cosmic‐ray exposure ages from ³He, ²¹Ne, and ³⁸Ar are 2.48 Myr for Shergotty, 2.73 Myr for Zagami, and 0.65 Myr for EETA79001 lith. A. Serious loss of radiogenic ⁴He due to shock is observed. Cosmogenic neon results for bulk samples from 13 Martian meteorites (new data and literature data) are used in addition to the mineral separates of this study in a new approach to explore evidence of solar cosmic‐ray effects. While a contribution of this low‐energy irradiation is strongly indicated for all of the shergottites, spallation Ne in Chassigny, Allan Hills (ALH) 84001, and the nakhlites is fully explained by galactic cosmic‐ray spallation. Implanted Martian atmospheric gases are present in all mineral separates and the thermal release indicates a near‐surface siting. We derive an estimate for the ⁴⁰Ar/³⁶Ar ratio of the Martian interior component by subtracting from measured Ar in the (K‐poor) pyroxenes the (small) radiogenic component as well as the implanted atmospheric component as indicated from ¹²⁹Xe, * excesses. Unless compromised by the presence of additional components, a high ratio of ～2000 is indicated for Martian interior argon, similar to that in the Martian atmosphere. Since much lower ratios have been inferred for Chassigny and ALH 84001, the result may indicate spatial and/or temporal variations of ⁴⁰Ar/³⁶Ar in the Martian mantle.