Investigation of droplet dynamics in a convective cloud using a Lagrangian cloud model

A precipitating convective cloud is simulated successfully using the Lagrangian cloud model, in which the flow field is simulated by large eddy simulation and the droplets are treated as Lagrangian particles, and the results are analyzed to investigate precipitation initiation and to examine the parameterization of cloud microphysics. It is found that raindrops appear initially near the cloud top, in which strong turbulence and broadened droplet spectrum are induced by the entrainment of dry air, but high liquid–water mixing ratio is maintained within cloud parts because of insufficient mixing. Statistical analysis of the downward vertical velocity of a droplet W reveals that the transition from cloud droplets to raindrops occurs in the range 20 μm < r < 100 μm, while the variation of W depends on turbulence as well as the droplet radius r. The general pattern of the raindrop size distribution is found to be consistent with the Marshall–Palmer distribution. The precipitation flux can be underestimated substantially, if the terminal velocity $w_{\text{s}}$ is used instead of W, but it is not sensitive to the choice of the critical droplet radius dividing cloud drops and raindrops. It is also found that precipitation starts earlier and becomes stronger if the effect of turbulence is included in the collection kernel.     

An assessment of the ENSO forecast skill of GEOS-5 system

The seasonal forecast skill of the NASA Global Modeling and Assimilation Office atmosphere–ocean coupled global climate model (AOGCM) is evaluated based on an ensemble of 9-month lead forecasts for the period 1993 to 2010. The results from the current version (V2) of the AOGCM consisting of the GEOS-5 AGCM coupled to the MOM4 ocean model are compared with those from an earlier version (V1) in which the AGCM (the NSIPP model) was coupled to the Poseidon Ocean Model. It was found that the correlation skill of the Sea Surface Temperature (SST) forecasts is generally better in V2, especially over the sub-tropical and tropical central and eastern Pacific, Atlantic, and Indian Ocean. Furthermore, the improvement in skill in V2 mainly comes from better forecasts of the developing phase of ENSO from boreal spring to summer. The skill of ENSO forecasts initiated during the boreal winter season, however, shows no improvement in terms of correlation skill, and is in fact slightly worse in terms of root mean square error (RMSE). The degradation of skill is found to be due to an excessive ENSO amplitude. For V1, the ENSO amplitude is too strong in forecasts starting in boreal spring and summer, which causes large RMSE in the forecast. For V2, the ENSO amplitude is slightly stronger than that in observations and V1 for forecasts starting in boreal winter season. An analysis of the terms in the SST tendency equation, shows that this is mainly due to an excessive zonal advective feedback. In addition, V2 forecasts that are initiated during boreal winter season, exhibit a slower phase transition of El Nino, which is consistent with larger amplitude of ENSO after the ENSO peak season. It is found that this is due to weak discharge of equatorial Warm Water Volume (WWV). In both observations and V1, the discharge of equatorial WWV leads the equatorial geostrophic easterly current so as to damp the El Nino starting in January. This process is delayed by about 2 months in V2 due to the slower phase transition of the equatorial zonal current from westerly to easterly.     

Abtragung,Transport und Sedimentation in der östlichen Beltsee (Ostsee)

Ohne ZusammenfassungEine ausführliche Darstellung erscheint in Die Küste, Bd. 3, 1955.     

The North-Chilean Coast Range — an example for the development of an active continental margin

Analysis of extended plutons in the Coast Range of North Chile between 25°30′ and 26°35′ led to the recognition of a complex magmatic and structural evolution from the Upper Paleozoic to the Tertiary. The ascension of the intrusive bodies is dictated by deep-seated block tectonics. Generally the chemistry changes from S-type magmas in the Paleozoic to I-type magmas in the Mesozoic and Cainozoic. This is accompanied by a change in the structural geology of the continental margin which we present in six hypothetic phases (Devonian-Tertiary). We are only at the beginning of an encompassing synthesis of the genesis of the Andean orogen.     

Volcanic dykes in the north Chilean Coast Range

Dense swarms of predominantly mafic dykes outcrop in the north Chilean Coast Range. These rocks are not lamprophyres. They mark channelways used by Jurassic-to-Lower Cretaceous extrusives.The dykes can be divided into three groups according to their petrography, major and trace element compositions. Rocks of the oldest group (series I) are essentially andesitic with high Na, K, Fe, Ti, Mn, P, V and low Al and Sr values. The rocks of series II are normal calc-alkaline basalts and andesites, whereas the rocks of series III are rhyodacites with calc-alkaline affinities.It is proposed that the series I dykes are genetically related to a continental fault system, whereas the dykes of series II and III are directly related to the post-Triassic evolution of the Andean active continental margin.

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Zusammenfassung Die nordchilenische Küstenkordillere wird von einem dichten Netz vorwiegend mafischer Gänge durchzogen. Es sind dies keine Lamprophyre, sondern sie stellen Zufuhrsysteme effusiver Tätigkeit im Zeitraum Jura bis Unterkreide dar.Die Ganggesteine lassen sich petrographisch und aufgrund Haupt- und Spurenelementchemischer Charakteristika in drei Serien einteilen. Die ältere alkaline Serie I zeichnet sich durch erhöhte Na-, K-, Fe-, Ti-, Mn-, P-, V- sowie niedrige Al- und Sr-Gehalte aus. Die Basalte und Andesite der zweiten Serie hingegen zeigen eine normale kalkalkaline Entwicklung, die sich in den Rhyodaziten der dritten Serie fortsetzen dürfte.Während die Magmen der ersten Serie Affinitäten zu Basaltassoziationen kontinentaler Bruchsysteme aufzeigen, sind die kalkalkalinen Zusammensetzungen für die Magmenentwicklung des andinen, aktiven Kontinentalrandes seit dem Jura typisch.

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Resumen La Cordillera de la Costa en el Norte de Chile es atravesada por una densa red de filones principalmente máficos. No se trata de rocas lamprofidicas sino representan sistemas de conductión de un volcanismo Jurásico/Cretácico Inferior.Basandose en sus caracteristicas petrográficas y geoquímicas las rocas filonianas se pueden dividir en tres series. La serie I, la más antigua, demuestra altas concentraciones de los elementos Na, K, Fe, Ti, Mn, P y V así como bajos contenidos de Al y Sr. Al contrario, las rocas basálticas y andesíticas de la serie II son caracterizadas por un desarollo calco-alcalino normal, lo cual habrá continuado en las rocas riodacíticas de la serie III.Mientras los magmas de la primera serie se pueden comparar con asociaciones basálticas de sistemas de fallas continentales, las series calco-alcalinas, por el contrario, son tipicas para un magmatismo que actuó en el borde continental activo andino desde el Jurásico.

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- , , . , , . . . — 1 — Na, K, Fe, Mn, P, V . - ; . , - .

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Prof. Dr. W. Zeil zum 65. Geburtstag gewidmet     

Validation of daily increment deposition in the otoliths of spot (Leiostomus xanthurus)

The otoliths of 200 postlarval spot (Leiostomus xanthurus) were marked by immersing the fish for 24 hr in a solution of 0.4 g tetracycline HCl l^?1 of salt water (15 ‰). The resulting time-mark could later be identified under ultraviolet (UV) light with an epifluorescence microscope. Spot were held in the laboratory or in the field for up to 30 d. Two validation methods were employed to document daily increment formation. The total number of increments per otolith, or the number of increments formed after the time-mark, were regressed against days held in an experiment. The hypothesis of one increment per day would result in a regression coefficient not significantly different from 1.0. In the field both the total count method (b=1.05) and the time-mark method (b=0.90) supported a one-increment-per-day hypothesis and were not significantly different from each other (p>0.05). In the laboratory the total count method (b=0.56) and the time-mark method (b=0.36) were significantly different from 1.0 (p<0.05), and thus did not support the one-increment-per-day hypothesis. Failure to resolve a one-increment-per-day deposition rate in the laboratory was primarily attributed to food limitation in the experiments.     

Experimental and texture-derived P-wave anisotropy of principal rocks from the TRANSALP traverse: An aid for the interpretation of seismic field data

A representative suite of deformed, metamorphic rocks from the TRANSALP reflection seismic traverse in the Eastern Alps was studied in the laboratory with respect to elastic properties and whole-rock texture. Compressional wave (P-wave) velocities and their anisotropies were measured at various experimental conditions (dry, wet, confining pressure), and compared to the texture-related component of anisotropy. Here ‘texture’ refers to crystallographic preferred orientations (CPOs), which were determined by neutron texture goniometry. In gneisses and schists P-wave anisotropies are mainly controlled by the microcrack fabric. In marbles and amphibolites CPO contributes very significantly to anisotropy. At 200 MPa confining pressure the degree of anisotropy is between 5% and 15%, depending on rock composition and/or CPO intensity. Special emphasis was also put on discussing possible effects of fluids on seismic velocity and anisotropy. Distributions of water-filled microcracks and pores are distinctly anisotropic, with maximum contribution to bulk rock velocity mostly parallel to the foliation pole. Decreasing P-wave velocity and increasing anisotropy of immersed samples may be explained by crack-induced changes of the elastic moduli of bulk rock. The main conclusion regarding interpretation of TRANSALP data is that strong reflections in the deep Alpine crust are probably due to marble–gneiss and metabasite–gneiss contacts, although P-wave anisotropy and boundaries between zones of ‘dry’ or ‘wet’ series may contribute to reflectivity to some extent.     

Late Paleozoic deformation and exhumation in the Sierras Pampeanas (Argentina): 40Ar/39Ar-feldspar dating constraints

International Journal of Earth Sciences - Systematic 40Ar/39Ar feldspar data obtained from the Sierras Pampeanas are presented, filling the gap between available high-...