A refined model for the influence of ocean tides on UT1 and polar motion

Periodic changes in Universal Time and polar motion have been derived from a numerical ocean model for a number of small partial tides. Combined with the results reported earlier our model now includes the 34 most important constituents of degree 2 (measured by the amplitude of the tidal potential). The results show that the terms neglected in all existing models amount to 80 μs in UT1 and to 0.3 mas in polar motion.     

An assessment of the Cenozoic avifauna of Switzerland, with a description of two fossil owls (Aves, Strigiformes)

The fossil skeletal record of birds from the Cenozoic of Switzerland is rather poor, despite the fact that avian tracks have been described from twenty tracksites. We review the Swiss fossil skeletal avifauna with emphasis put on new material discovered in the collection of the Natural History Museum Basel. This material includes two new owls (Strigiformes), one from a Late Eocene fissure filling from the Gösgen canal, and another from the Late Oligocene of Mümliswil. The Eocene owl specimen consists of a partial, distal tarsometatarsus, and is therefore too incompletely preserved to allow for reliable hypotheses concerning its taxonomic affinities. It does, however, display features resembling members of the extinct family Palaeoglaucidae. The Oligocene specimen is tentatively attributed to the genus Oligostrix, and it is the youngest representative of the extinct family Protostrigidae. Based on the first complete tarsometatarsus for this family, we erect a new species, ?Oligostrix bergeri. These two specimens represent the first record of fossil owls from Switzerland.     

Measurements of Trace Substances in the Arctic Troposphere as Potential Precursors and Constituents of Arctic Haze

During two measuring campaigns in early spring 1994 and 1995 (March/April) and one campaign in summer 1994, measurements of ozone, PAN, sulfur dioxide, nitric acid, and particulate nitrate, sulfate, and ammonium (only 1995) were recorded in the Arctic. Observations were made by aircraft at various sites in the eastern and western Arctic. Ozone concentrations showed a steady increase with altitude both in spring and summer. During five flights in springtime, low ozone events (LOEs) could be observed near the surface and up to altitudes of 2000 m. SO₂ background concentrations, ranging from detection limit (0.5 nmol/m³) to 5 nmol/m³, were observed during both spring and summer. Distinct maxima up to 55 nmol/m³ in lower altitudes were only obtained in springtime. Concentrations of the organic nitrate PAN were within a similar range as those of the inorganic nitrate HNO₃ during spring campaigns. In contrast, concentrations of particulate nitrate were one half an order of magnitude lower. HNO₃ concentrations increased significantly with altitude. Evidently, HNO₃ was intruded from the stratosphere into the troposphere. Sulfate concentrations ranged between 5 and 30 nmol/m³; ammonium concentrations were obtained within a range from 10 to 50 nmol/m³.     

Chemical composition of aerosols in the atmosphere of Mongolia

Presented are the results of studies of the component composition of atmospheric aerosols in Mongolia for the period of 2005?C2010. It is demonstrated that the local emissions mostly affect the composition of aerosols in industrial cities (Ulan Bator and Sükhbaatar), whereas the distant transport of pollutants and the wind regime of the area, in particular, the dust storms affect in small towns with the undeveloped industry (Baruun-Urt and Sainshand). Revealed is the dependence of the composition and concentration of suspended particles on the meteorological conditions in the research area. High concentrations of aerosols were observed on the days with strong winds and air masses transport from the deserts and industrial areas of China. Low concentrations of ions were observed during periods of calm weather and in case of the air masses transport from the territories of Russia and Kazakhstan.     

Influence of natural and anthropogenic activities on UV Index variations – a study over tropical urban region using ground based observations and satellite data

Measurements of total ozone column and solar UV radiation under different atmospheric conditions are needed to define variations of both UV and ozone and to study the impact of ozone depletion at the Earth’s surface. In this study, spectral and broadband measurements of UV-B irradiance were obtained along with total ozone observations and aerosol optical depth measurements in the tropical urban region of Hyderabad, south India. We specifically used an Ultra-Violet Multifilter Rotating Shadow band Radiometer (UVMFR-SR), to measure UV irradiance in time and space. To assess the aerosol and O₃ effects on ground-reaching UV irradiance, we used measurements from a Microtops II sun photometer in addition to the Tropospheric Ultraviolet Visible radiation (TUV) model. We also assessed the Defense Meteorological Satellite Program – Operational Line Scanner (DMSP-OLS) night time satellite data for inferring biomass burning fires during the study period. Results clearly suggested a negative correlation between the DMSP-OLS satellite derived fire count data and UVMFR-SR data suggesting that aerosols from biomass burning are directly attenuating UV irradiance in the study region. Also, correlation analysis between UV index and ozone measurements from sun photometer and TOMS-Ozone Mapping Instrument (OMI) indicated a clear decrease in ground reaching UV-B irradiance during higher ozone conditions. The higher levels are attributed to photochemical production of O₃ during the oxidation of trace gases emitted from biomass burning. Results also suggested a relatively high attenuation in UV irradiance (~6% higher) from smoke particles than dust. We also found a relatively good agreement between the modeled (TUV) and measured UV irradiance spectra for different atmospheric conditions. Our results highlight the factors affecting UV irradiance in a tropical urban environment, south India.     

The Alpine geodynamic evolution of Penninic nappes in the eastern Central Alps

The eastern Central Alps consist of several Pennine nappes with different tectonometamorphic histories. The tectonically uppermost units (oceanic Avers Bündnerschiefer, continental Suretta and Tambo nappes, oceanic Vals Bündnerschiefer) show Cretaceous/early Tertiary W-directed thrusting with associated blueschist facies metamorphism related to subduction of the Pennine units beneath the Austroalpine continental crust. This event caused eclogite facies metamorphism in the underlying continental Adula nappe. The gross effect was crustal thickening. The tectonically lower, continental Simano nappe is devoid of any imprint from this event. In the course of continent-continent collision, high- T metamorphism and N-directed movements occurred. Both affected the whole nappe pile more or less continuously from amphibolite to greenschist facies conditions. Crustal thinning commenced during the regional temperature peak. A final phase is related to differential uplift under retrograde P–T conditions. Further thinning of the crust was accommodated by E- to NE-directed extensional deformation.     

Estimation of instantaneous peak flows from maximum mean daily flows using the HBV hydrological model

The record length and quality of instantaneous peak flows (IPFs) have a great influence on flood design, but these high resolution flow data are not always available. The primary aim of this study is to compare different strategies to derive frequency distributions of IPFs using the Hydrologiska Byråns Vattenbalansavdelning (HBV) hydrologic model. The model is operated on a daily and an hourly time step for 18 catchments in the Aller‐Leine basin, Germany. Subsequently, general extreme value (GEV) distributions are fitted to the simulated annual series of daily and hourly extreme flows. The resulting maximum mean daily flow (MDF) quantiles from daily simulations are transferred into IPF quantiles using a multiple regression model, which enables a direct comparison with the simulated hourly quantiles. As long climate records with a high temporal resolution are not available, the hourly simulations require a disaggregation of the daily rainfall. Additionally, two calibrations strategies are applied: (1) a calibration on flow statistics; (2) a calibration on hydrographs. The results show that: (1) the multiple regression model is capable of predicting IPFs with the simulated MDFs; (2) both daily simulations with post‐correction of flows and hourly simulations with pre‐processing of precipitation enable a reasonable estimation of IPFs; (3) the best results are achieved using disaggregated rainfall for hourly modelling with calibration on flow statistics; and (4) if the IPF observations are not sufficient for model calibration on flow statistics, the transfer of MDFs via multiple regressions is a good alternative for estimating IPFs. Copyright © 2015 John Wiley & Sons, Ltd.     

Monitoring Koyulhisar landslide using rapid static GPS: a strategy to remove biases from vertical velocities

GPS is frequently used in the monitoring of natural hazards and other geophysical phenomena. Landslide monitoring is one such area in which various GPS methods are tested and various systematic error sources are introduced. In previous studies, one error source introduced on rapid static GPS was the effect of large height differences in GPS positions. In this study, we further investigate how GPS velocities/slip rates are affected by large station height differences when rapid static surveying is used. In order to demonstrate the influences, we used static GPS measurements from the Koyulhisar landslide in central Turkey. Comparison of rapid static GPS solutions with static GPS solutions using BERNESE 5.0 indicates that systematic biases occur in the estimated rapid static GPS deformation rates when the station height difference is large between baseline points. The effect is more significant on the vertical component, whereas it is negligible on the horizontal components. When reducing the height difference between the reference station and the rover stations, rapid static solutions from 15-min sessions show high correlation and similar deformation rates with static positioning solutions.     

Dawn Mission to Vesta and Ceres

The initial exploration of any planetary object requires a careful mission design guided by our knowledge of that object as gained by terrestrial observers. This process is very evident in the development of the Dawn mission to the minor planets 1 Ceres and 4 Vesta. This mission was designed to verify the basaltic nature of Vesta inferred both from its reflectance spectrum and from the composition of the howardite, eucrite and diogenite meteorites believed to have originated on Vesta. Hubble Space Telescope observations have determined Vesta’s size and shape, which, together with masses inferred from gravitational perturbations, have provided estimates of its density. These investigations have enabled the Dawn team to choose the appropriate instrumentation and to design its orbital operations at Vesta. Until recently Ceres has remained more of an enigma. Adaptive-optics and HST observations now have provided data from which we can begin to confidently plan the mission. These observations reveal a rotationally symmetric body with little surface relief, an ultraviolet bright point that can be used as a control point for determining the pole and anchoring a geographic coordinate system. They also reveal albedo and color variations that provide tantalizing hints of surface processes.