Growth of homogeneously nucleated water droplets: a quantitative comparison of experiment and theory

The formation of aerosols proceeds through nucleation, growth and aging stages. The understanding of nucleation and droplet growth is essential for handling the more complex atmospheric condensation processes. To achieve this goal, measurements of the nucleation rate of various systems are performed in an expansion chamber. In this manner nucleation and growth are decoupled by applying a short nucleation pulse of about 1 ms during which the nuclei are formed. The subsequent droplet growth is quantitatively monitored by Mie-scattering. To this end, the Mie-maxima and -minima are detected as a function of time and compared to theoretical Mie-scattering calculations for increasing radii. In this fashion, a wealth of growth curves for pure water depending on supersaturations, number densities of droplets, and temperatures were obtained. Following the approach of Fuchs and Sutugin [Fuchs, N.A., Sutugin, A.G., 1970. Highly Dispersed Aerosols. Ann Arbor Science Publishers, Ann Arbor; Fuchs, N.A., Sutugin, A.G., 1971. In: Hidy, G.M., Brock, J.R. (Eds.), International Reviews in Aerosol Physics and Chemistry: Topics in Current Aerosol Research (Part 2), Pergamon, New York, p. 1], we calculated theoretical growth curves taking into account the depletion of water vapor, the increase of droplet- and system-temperature, temperature-dependent functions of the diffusion coefficient, surface tension, liquid density and latent heat of condensation. The calculated growth curves and experimental data for 230, 240 and 250 K with number densities of droplets between 5×10² and 2×10⁶ droplets/cm³ yield quantitative agreement between theory and experiment. This is remarkable in so far as the theory contains no adjustable parameters and assumes the sticking probability of the vapor molecules to be unity. Using a sticking probability smaller than 0.8 in the calculation leads to growth functions already outside the experimental error.     

Basin formation during the post-collisional evolution of the Eastern Alps: the example of the Lavanttal Basin

The Miocene Lavanttal Basin formed in the Eastern Alps during extrusion of crustal blocks towards the east. In contrast to basins, which formed contemporaneously along the strike-slip faults of the Noric Depression and on top of the moving blocks (Styrian Basin), little is known about the Lavanttal Basin. In this paper geophysical, sedimentological, and structural data are used to study structure and evolution of the Lavanttal Basin. The eastern margin of the 2-km-deep basin is formed by the WNW trending Koralm Fault. The geometry of the gently dipping western basin flank shows that the present-day basin is only a remnant of a former significantly larger basin. Late Early (Karpatian) and early Middle Miocene (Badenian) pull-apart phases initiated basin formation and deposition of thick fluvial (Granitztal Beds), lacustrine, and marine (Mühldorf Fm.) sediments. The Mühldorf Fm. represents the Lower Badenian cycle TB2.4. Another flooding event caused brackish environments in late Middle Miocene (Early Sarmatian) time, whereas freshwater environments existed in Late Sarmatian time. The coal-bearing Sarmatian succession is subdivided into four fourth-order sequences. The number of sequences suggests that the effect of tectonic subsidence was overruled by sea-level fluctuations during Sarmatian time. Increased relief energy caused by Early Pannonian pull-apart activity initiated deposition of thick fluvial sediments. The present-day shape of the basin is a result of young (Plio-/Pleistocene) basin inversion. In contrast to the multi-stage Lavanttal Basin, basins along the Noric Depression show a single-stage history. Similarities between the Lavanttal and Styrian basins exist in Early Badenian and Early Sarmatian times.     

Combined use of field observations and SAR interferometry to study ice dynamics and mass balance in Dronning Maud Land, Antarctica

In the region of the Schirmacheroase (71 °S, 12°E) various geodetic and glaciological research activities have been carried out in the last decade. Several times three geodetic-glaciological traverses were undertaken to study ice velocity, accumulation and ablation, and ice surface height changes. Repeated ground surveys show a significant decrease in surface heights by about 15 cm/y for a large blue-ice area. This paper presents the first interferometrically derived ice velocity field of the inland ice close to the Schirmacheroase. The interferometric analysis of the synthetic aperture radar (SAR) data is performed in combination with ground-based information. Since only ERS-1&2 tandem mission image couples are available for this region a digital elevation model (DEM) is used to remove the effect of topography. Ice velocities up to 100 m/y are proved interferometrically for this part of the inland ice.     

The ALICE instrument and the measured cosmic ray elemental abundances

A Large Isotopic Composition Experiment (ALICE) is a balloon-borne spectrometer which can determine the elemental and isotopic composition of galactic cosmic rays with energies near 1 GeV/nucleon. ALICE was flown from Prince Albert, Canada in August 1987, and remained at float altitude (120000 feet) for 14.7 hours. In this paper, we describe the experimental methods and analysis which will be used for subsequent isotopic analysis. We obtained very precise charge resolution over the entire designed range: 0.10 and 0.16 charge units at neon and iron, respectively. Results on the galactic cosmic ray abundances and absolute fluxes of the elements from neon through nickel are reported.     

Stellarv sini and optical emission line widths in Be stars

I re-investigate empirical correlations between line widths of photospheric absorption lines — as a measure of the stellar projected rotational velocityv sini- and of circumstellar emission lines in Be stars. The degree of this correlation is a measure for the kinematic, i.e., rotational, contribution to the total emission line broadening.From the literature and from additional data, I have collected a sample of photoelectric measurements of Balmer and Feii emission lines of the 115 brightest Be stars in the sky, most of them observed several times during the past decade. I investigate the following emission line widths parameters: full width at half maximum, total width at the base, and double-peak separation. I find from the FWHM that the basic origin of emission line broadening in Be stars is undoubtedly rotational, the correlations withv sini being best for weaker emission lines while H shows considerable scatter. Total width at the base is uncorrelated withv sini except for the Feii lines. Peak separation is found to be a function both ofv sini and of equivalent width. The latter dependence can straightforwardly be understood by the fact that within Huang's disk model peak separation, normalized tov sini, is governed by the outer envelope radius.I conclude that observational evidence leaves no doubt that Be star envelopes as visible in optical emission lines are rotationally supported and have axisymmetric geometry.Partly based on observations obtained at the European Southern Observatory, La Silla, Chile.     

Using remote sensing to quantify aeolian transport and estimate the age of the terminal dune field Dunas Pampa Blanca in southern Peru

Aeolian dunes are widely used to reconstruct paleoenvironmental conditions. However, terminal dune fields (ergs) in the coastal desert of southern Peru – where information regarding Quaternary paleoenvironmental conditions is very limited – have until now not been used for paleoenvironmental reconstructions and the time depth of their accumulation is unknown. Here, different estimates are derived to constrain the time depth recorded in the Dunas Pampa Blanca, a terminal dune field in coastal southern Peru. Dune field age is calculated using the volume of the Dunas Pampa Blanca and (i) recent aeolian transport rate in migrating transverse dunes feeding the Dunas Pampa Blanca (derived from digital processing of sequential Landsat and Quickbird images) and (ii) limitations posed by recent fluvial sediment supply to the source of aeolian transport. The resulting maximum age estimate of 70 ± 8 ka (from aeolian transport) compares with a minimum age estimate of 4–75 ka (from sediment supply). However, a minimum age estimate of 110–450 ka is deduced from the tectonic and topographic evolution of the region. This discrepancy contradicts the hypothesis of late Quaternary stability in the Peruvian coastal desert and indicates that recent conditions of aeolian sediment supply and transport are not representative for the late Quaternary.     

Regional geoid determination in Antarctica utilizing airborne gravity and topography data

Antarctica is the only continent that suffers major gaps in terrestrial gravity data coverage. To overcome this problem and to close these gaps as well as to densify the global satellite gravity field solutions, the International Association of Geodesy (IAG) Commission Project 2.4 “Antarctic Geoid” was set into action. This paper reviews the current situation concerning the gravity field in Antarctica. It is shown that airborne geophysical surveys are the most promising tools to gain new gravity data in Antarctica. In this context, a number of projects to be carried out during the International Polar Year 2007/2008 will contribute to this goal. To demonstrate the feasibility of the regional geoid improvement in Antarctica, we present a case study using gravity and topography data of the southern Prince Charles Mountains, East Antarctica. During the processing, the remove–compute– restore (RCR) technique and least-squares collocation (LSC) were applied. Adding signal parts of up to 6 m to the global gravity field model that was used as a basis, the calculated regional quasigeoid reveals the dominant features of bedrock topography in that region, namely the graben structure of the Lambert glacier system. The accuracy of the improved regional quasigeoid is estimated to be at the level of 15 cm.     

Different Asian Monsoon Rainfall Responses to Idealized Orography Sensitivity Experiments in the HadGEM3-GA6 and FGOALS-FAMIL Global Climate Models

Recent work has shown the dominance of the Himalaya in supporting the Indian summer monsoon(ISM),perhaps by surface sensible heating along its southern slope and by mechanical blocking acting to separate moist tropical flow from drier midlatitude air.Previous studies have also shown that Indian summer rainfall is largely unaffected in sensitivity experiments that remove only the Tibetan Plateau.However,given the large biases in simulating the monsoon in CMIP5 models,such results may be model dependent.This study investigates the impact of orographic forcing from the Tibetan Plateau,Himalaya and Iranian Plateau on the ISM and East Asian summer monsoon(EASM) in the UK Met Office's Had GEM3-GA6 and China's Institute of Atmospheric Physics FGOALS-FAMIL global climate models.The models chosen feature oppositesigned biases in their simulation of the ISM rainfall and circulation climatology.The changes to ISM and EASM circulation across the sensitivity experiments are similar in both models and consistent with previous studies.However,considerable differences exist in the rainfall responses over India and China,and in the detailed aspects such as onset and retreat dates.In particular,the models show opposing changes in Indian monsoon rainfall when the Himalaya and Tibetan Plateau orography are removed.Our results show that a multi-model approach,as suggested in the forthcoming Global Monsoon Model Intercomparison Project(GMMIP) associated with CMIP6,is needed to clarify the impact of orographic forcing on the Asian monsoon and to fully understand the implications of model systematic error.