Reconciling aerosol light extinction measurements from spaceborne lidar observations and in situ measurements in the Arctic

© Author(s) 2014. This work is distributed under the Creative Commons Attribution 3.0 License.In this study we investigate to what degree it is possible to reconcile continuously recorded particle light extinction coefficients derived from dry in situ measurements at Zeppelin station (78.92° N, 11.85° E; 475 m above sea level), Ny-Ålesund, Svalbard, that are recalculated to ambient relative humidity, as well as simultaneous ambient observations with the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) aboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite. To our knowledge, this represents the first study that compares spaceborne lidar measurements to optical aerosol properties from short-term in situ observations (averaged over 5 h) on a case-by-case basis. Finding suitable comparison cases requires an elaborate screening and matching of the CALIOP data with respect to the location of Zeppelin station as well as the selection of temporal and spatial averaging intervals for both the ground-based and spaceborne observations. Reliable reconciliation of these data cannot be achieved with the closest-approach method, which is often used in matching CALIOP observations to those taken at ground sites. This is due to the transport pathways of the air parcels that were sampled. The use of trajectories allowed us to establish a connection between spaceborne and ground-based observations for 57 individual overpasses out of a total of 2018 that occurred in our region of interest around Svalbard (0 to 25° E, 75 to 82° N) in the considered year of 2008. Matches could only be established during winter and spring, since the low aerosol load during summer in connection with the strong solar background and the high occurrence rate of clouds strongly influences the performance and reliability of CALIOP observations. Extinction coefficients in the range of 2 to 130 Mmg-1 at 532 nm were found for successful matches with a difference of a factor of 1.47 (median value for a range from 0.26 to 11.2) between the findings of in situ and spaceborne observations (the latter being generally larger than the former). The remaining difference is likely to be due to the natural variability in aerosol concentration and ambient relative humidity, an insufficient representation of aerosol particle growth, or a misclassification of aerosol type (i.e., choice of lidar ratio) in the CALIPSO retrieval.Peer reviewe

Are violations to temporal Bell inequalities there when somebody looks?

The possibility of observing violations of temporal Bell inequalities, originally proposed by Leggett as a mean of testing the quantum mechanical delocalization of suitably chosen macroscopic bodies, is discussed by taking into account the effect of the measurement process. A general criterion quantifying this possibility is defined and shown not to be fulfilled by the various experimental configurations proposed so far to test inequalities of different forms.Comment: 7 pages, 1 eps figure, needs europhys.sty and euromacr.tex, enclosed in the .tar.gz file; accepted for publication in Europhysics Letter

Modeling and Simulation of a Microstrip-SQUID Amplifier

Using a simple lumped-circuit model, we numerically study the dependence of the voltage gain and noise on the amplifier's parameters. Linear, quasi-linear, and nonlinear regimes are studied. We have shown that the voltage gain of the amplifier cannot exceed a characteristic critical value, which decreases with the increase of the input power. We have also shown that the spectrum of the voltage gain depends significantly on the level of the Johnson noise generated by the SQUID resistors.Comment: 13 page

Voltage-current and voltage-flux characteristics of asymmetric high TC DC SQUIDs

We report measurements of transfer functions and flux shifts of 20 on-chip high T$_C$ DC SQUIDs half of which were made purposely geometrically asymmetric. All of these SQUIDs were fabricated using standard high T$_C$ thin film technology and they were single layer ones, having 140 nm thickness of YBa$_2$Cu$_3$O$_{7-x}$ film deposited by laser ablation onto MgO bicrystal substrates with 24$^0$ misorientation angle. For every SQUID the parameters of its intrinsic asymmetry, i. e., the density of critical current and resistivity of every junction, were measured directly and independently. We showed that the main reason for the on-chip spreading of SQUIDs' voltage-current and voltage-flux characteristics was the intrinsic asymmetry. We found that for SQUIDs with a relative large inductance ($L>120$ pH) both the voltage modulation and the transfer function were not very sensitive to the junctions asymmetry, whereas SQUIDs with smaller inductance ($L\simeq 65-75$ pH) were more sensitive. The results obtained in the paper are important for the implementation in the sensitive instruments based on high T$_C$ SQUID arrays and gratings.Comment: 11 pages, 4 tables, 17 figures This version is substantially modified. The Introduction and Section 2 are completely rewritten, while experimental part is mainly the same as in previous versio

Senderos interdisciplinarios hacia tres territorios poéticos sur patagónicos del Butahuillimapu

Este artículo propone la hipótesis de la construcción de identidad textual en tres territorios poéticos sur patagónicos del Butahuillimapu, a saber, Bernardo Colipán, Jaime Huenún y Clemente Riedemann. La geografía identitaria revela zonas negadas o clausuradas que proyectan un modo de existir. La presencia de estas zonas en el discurso poético interroga la representación de la geografía y la diferencia del territorio el que considera las relaciones sociales, culturales y políticas que confluyen en el proceso de construcción de identidades

Quantum effects after decoherence in a quenched phase transition

We study a quantum mechanical toy model that mimics some features of a quenched phase transition. Both by virtue of a time-dependent Hamiltonian or by changing the temperature of the bath we are able to show that even after classicalization has been reached, the system may display quantum behaviour again. We explain this behaviour in terms of simple non-linear analysis and estimate relevant time scales that match the results of numerical simulations of the master-equation. This opens new possibilities both in the study of quantum effects in non-equilibrium phase transitions and in general time-dependent problems where quantum effects may be relevant even after decoherence has been completed.Comment: 7 pages, 7 figures, revtex, important revisions made. To be published in Phys. Rev.

Self-aligned nanoscale SQUID on a tip

A nanometer-sized superconducting quantum interference device (nanoSQUID) is fabricated on the apex of a sharp quartz tip and integrated into a scanning SQUID microscope. A simple self-aligned fabrication method results in nanoSQUIDs with diameters down to 100 nm with no lithographic processing. An aluminum nanoSQUID with an effective area of 0.034 $\mu$m$^2$ displays flux sensitivity of 1.8$\cdot 10^{-6}$ $\Phi_0/\mathrm{Hz}^{1/2} and operates in fields as high as 0.6 T. With projected spin sensitivity of 65$\mu_B/\mathrm{Hz}^{1/2}$ and high bandwidth, the SQUID on a tip is a highly promising probe for nanoscale magnetic imaging and spectroscopy.Comment: 14 manuscript pages, 5 figure

Decoherence in rf SQUID Qubits

We report measurements of coherence times of an rf SQUID qubit using pulsed microwaves and rapid flux pulses. The modified rf SQUID, described by an double-well potential, has independent, in situ, controls for the tilt and barrier height of the potential. The decay of coherent oscillations is dominated by the lifetime of the excited state and low frequency flux noise and is consistent with independent measurement of these quantities obtained by microwave spectroscopy, resonant tunneling between fluxoid wells and decay of the excited state. The oscillation's waveform is compared to analytical results obtained for finite decay rates and detuning and averaged over low frequency flux noise.Comment: 24 pages, 13 figures, submitted to the journal Quantum Information Processin

Continuous weak measurement of quantum coherent oscillations

We consider the problem of continuous quantum measurement of coherent oscillations between two quantum states of an individual two-state system. It is shown that the interplay between the information acquisition and the backaction dephasing of the oscillations by the detector imposes a fundamental limit, equal to 4, on the signal-to-noise ratio of the measurement. The limit is universal, e.g., independent of the coupling strength between the detector and system, and results from the tendency of quantum measurement to localize the system in one of the measured eigenstates

Macroscopic quantum damping in SQUID rings

The measurement process is introduced in the dynamics of Josephson devices exhibiting quantum behaviour in a macroscopic degree of freedom. The measurement is shown to give rise to a dynamical damping mechanism whose experimental observability could be relevant to understand decoherence in macroscopic quantum systems.Comment: 7 Pages; Plain REVTeX; 3 Figures available upon request; to be published in Phys. Lett. A 229, 23 (1997