Resonant Fly-by Missions to Near Earth Asteroids

The authors here propose a mission scenario, aimed at close exploration of a Near-Earth Asteroid, exploiting low-V resonant trajectories. These trajectories allow repeated fly-bys of a chosen target. A selection procedure, which has been used to find some interesting mission opportunities in the 2005-2015 time frame, is described and the corresponding detailed mission profiles are derived, using an indirect optimization method.     

Seismic risk assessment for the mega-city of Istanbul: Ductility, strength and maximum interstory drift demands

This study investigates the seismic demands due to the catastrophic 1999 M_w=7.4 Kocaeli and the M_w=7.1 Duzce earthquakes. The inelastic response spectra for the Kocaeli and Duzce earthquakes are investigated for systems with known strength and ductility. An analytical fiber element model is developed for a typical reinforced concrete building in Turkey. The interstory drifts are calculated from nonlinear dynamic analysis using 26 recorded strong-motion data from the 1999 Kocaeli and the Duzce earthquakes. In the dynamic analysis, the structural members are modeled by employing distributed plasticity fiber elements and both geometrical as well as material nonlinearities are taken into account. This study shows that the ductility and interstory drift demands due to the Kocaeli and the Duzce earthquakes were very severe (well above the code prescribed values) even for moderately inelastic structures. It is apparent from the results that the forward directivity effect is the most influential factor on the interstory drift demand. Both the distance to the fault rupture and the site conditions affect seismic demands, but the site conditions and the local topography are more influential than the distance from the fault rupture. This study shows that substantial damage should be expected in a future earthquake at all districts of Istanbul, but especially at Avcilar, Cekmece, Fatih, Bakirkoy and the Zeytinburnu districts. It is also shown that base isolation may substantially improve the performance of a structure in the inelastic domain and base isolated structures may be designed for lower minimum lateral strengths and higher strength reduction factors.     

Radiative-photochemical models of the primitive terrestrial atmosphere

The vertical thermal structure of a primitive terrestrial atmosphere is investigated with a radiative-convective-photochemical model. The radiative code includes the short wave contribution from water vapor and ozone, and long wave contribution from methane, carbon dioxide, water vapor and ozone. Calculations for an oxygen level of 10^?3 PAL and different CO₂ levels shows that the water vapor content, and consequently the odd hydrogen concentration, in the stratosphere is controlled by the temperature which is strongly reduced from present values due to the lower ozone content. As a result, depending on the assumed mechanism for controlling the H₂O mixing ratio, a considerable feedback is introduced on the ozone columnar density.The same model is used to parameterize the infrared outgoing flux as a function of surface temperature to be used in a two-mode energy balance climate model. This computation is addressed to the question of whether a large amount of carbon dioxide in the primitive atmosphere could be effective in producing a greenhouse effect able to compensate for the Sun's lower luminosity. It is found that with 25 times the present carbon dioxide mixing ratio, due to the ice-albedo feedback mechanism, a decrease of 9% in the solar constant could be enough to produce an ice-covered Earth.     

A geological transect from Kun Lun to Karakorum (Sinkiang, China): the western termination of the Tibetan Plateau. Preliminary note

A geological-geophysical expedition (Ev-K2–CNR 1988) visited the area from West Kun Lun to Karakorum (K2–Gasherbrum). Seven tectonic units including sedimentary, magmatic and metamorphic rocks were distinguished in this area; the northernmost are suggested to belong to the Kun Lun and Qiangtang Microplates. The sedimentary sequence of Shaksgam is proved to extend from the Permian to the Jurassic, with Carboniferous and Cretaceous ages more doubtful. This sequence shows intermediate affinities between the Karakorum and the Qiangtang. The two southernmost units belong to the Karakorum Microplate. The Karakorum Fault Zone comprises a complex pattern of faults and thrusts, with brittle deformation and uplifting of granitoid bodies.     

Impact of coupled perturbations of atmospheric trace gases on Earth's climate and ozone

We have studied the effects on the ozone concentration and surface temperature, of perturbations in the atmospheric content of nitrous oxide, methane, carbon dioxide and chlorofluorocarbons (CFC). The sensitivity study has been carried out with a radiative-convective-photochemical model. The doubling of carbon dioxide concentration has the effect of warming the troposphere and cooling the stratosphere. As a result of this cooling, the change of ozone columnar density produced by 10 ppb of chlorine amount to 9.3% as compared to –10.9% obtained without temperature feedback. Perturbation in nitrous oxide correspond to an increase in NO _x of the stratosphere with consequent ozone reduction while doubling the methane concentration correspond to a slight increase in columnar density. The effect of the increased methane concentration in the stratosphere contributes to reduce the effect of CFC due to the enhanced formation of HCl. The perturbation of these two minor constituents appreciably increase the greenhouse effect to 2.30 from 1.67°, obtained when carbon dioxide alone is considered.     

Stages in the development of the ports of Rotterdam and Antwerp1

Rotterdam and Antwerp, situated in close proximity to each other, have evolved over the past seven centuries to become the world's largest and Europe's second largest ports respectively. Mainly for political reasons, the stages of rise and decline occurred in complementary time periods, until freedom of inland shipping became international law on the Rhine and in the Rhine-Maas-Schelde delta region in the 19th century. Since then Antwerp's ascendancy has occurred without serious interruption, though areal expansion is now limited by the Belgian-Dutch boundary. Rotterdam, on the other hand, has faced two difficult periods involving ease and speed of access to the North Sea, and destruction during World War II.     

Investigating soil moisture feedbacks on precipitation with tests of Granger causality

Granger causality (GC) is used in the econometrics literature to identify the presence of one- and two-way coupling between terms in noisy multivariate dynamical systems. Here we test for the presence of GC to identify a soil moisture (S) feedback on precipitation (P) using data from Illinois. In this framework S is said to Granger cause P if F(P_t|Ω_t−Δt)≠F(P_t|Ω_t−Δt−S_t−Δt) where F denotes the conditional distribution of P, Ω_t−Δt represents the set of all knowledge available at time t−Δt, and Ω_t−Δt−S_t−Δt represents all knowledge except S. Critical for land–atmosphere interaction research is that Ω_t−Δt includes all past information on P as well as S. Therefore that part of the relation between past soil moisture and current precipitation which results from precipitation autocorrelation and soil water balance will be accounted for and not attributed to causality. Tests for GC usually specify all relevant variables in a coupled vector autoregressive (VAR) model and then calculate the significance level of decreased predictability as various coupling coefficients are omitted. But because the data (daily precipitation and soil moisture) are distinctly non-Gaussian, we avoid using a VAR and instead express the daily precipitation events as a Markov model. We then test whether the probability of storm occurrence, conditioned on past information on precipitation, changes with information on soil moisture. Past information on precipitation is expressed both as the occurrence of previous day precipitation (to account for storm-scale persistence) and as a simple soil moisture-like precipitation-wetness index derived solely from precipitation (to account for seasonal-scale persistence). In this way only those fluctuations in moisture not attributable to past fluctuations in precipitation (e.g., those due to temperature) can influence the outcome of the test. The null hypothesis (no moisture influence) is evaluated by comparing observed changes in storm probability to Monte-Carlo simulated differences generated with unconditional occurrence probabilities. The null hypothesis is not rejected (p>0.5) suggesting that contrary to recently published results, insufficient evidence exists to support an influence of soil moisture on precipitation in Illinois.     

The altitudinal temperature lapse rates applied to high elevation rockfalls studies in the Western European Alps

Theoretical and Applied Climatology - Temperature is one of the most important aspects of mountain climates. The relationships between air temperature and rockfalls at high-elevation sites are very...     

Characterizing and Predicting Traffic Accidents in Extreme Weather Environments

Motorists are vulnerable to extreme weather events, which are likely to be exacerbated by climate change throughout the world. Traffic accidents are conceptualized in this article as the result of a systemic failure that includes human, vehicular, and environmental factors. The snowstorm and concurrent accidents that occurred in the Northeastern United States on 26 January 2011 are used as a case study. Traffic accident data for Fairfax County, Virginia, are supplemented with Doppler radar and additional weather data to characterize the spatiotemporal patterns of the accidents resulting from this major snowstorm event. A kernel density smoothing method is implemented to identify and predict patterns of accident locations within this urban area over time. The predictive capability of this model increases over time with increasing accidents. Models such as these can be used by emergency responders to identify, plan for, and mitigate areas that are more susceptible to increased risk resulting from extreme weather events.