An Automated Method for Tracking Clouds in Planetary Atmospheres

We present an automated method for cloud tracking which can be applied to planetary images. The method is based on a digital correlator which compares two or more consecutive images and identifies patterns by maximizing correlations between image blocks. This approach bypasses the problem of feature detection. Four variations of the algorithm are tested on real cloud images of Jupiter’s white ovals from the Galileo mission, previously analyzed in Vasavada et al. [Vasavada, A.R., Ingersoll, A.P., Banfield, D., Bell, M., Gierasch, P.J., Belton, M.J.S., Orton, G.S., Klaasen, K.P., Dejong, E., Breneman, H.H., Jones, T.J., Kaufman, J.M., Magee, K.P., Senske, D.A. 1998. Galileo imaging of Jupiter’s atmosphere: the great red spot, equatorial region, and white ovals. Icarus, 135, 265, doi:10.1006/icar.1998.5984]. Direct correlation, using the sum of squared differences between image radiances as a distance estimator (baseline case), yields displacement vectors very similar to this previous analysis. Combining this distance estimator with the method of order ranks results in a technique which is more robust in the presence of outliers and noise and of better quality. Finally, we introduce a distance metric which, combined with order ranks, provides results of similar quality to the baseline case and is faster. The new approach can be applied to data from a number of space-based imaging instruments with a non-negligible gain in computing time

Velocities of Venus clouds derived from VIRTIS observations

Retrograde superrotation is a well known feature of the atmosphere of Venus, with Venus’ cloud tops rotating in only 4.4 days, much faster than the 243-day rotation period of the solid globe. A good characterization of the circulation of the venusian atmosphere is essential in order to understand the mechanisms controlling superrota- tion. VIRTIS, onboard ESA’s Venus Express, is one of the most flexible instruments for such a characterization. The VIRTIS-M imaging spectrometer, operating in the range 0.25 to 5 micrometers, has acquired images of Venus’ clouds from the cloud tops, in visible wavelengths, to the lower cloud layer, close to 40 km, at infrared wavelengths. We present velocity determinations from automated cloud tracking in the night side at 1.74, 2.3 and 5 micrometers, from high to mid latitudes in the south- ern hemisphere. The method is based on a digital correlator which compares two or more consecutive images and identifies patterns by maximizing correlations between image blocks (Luz, Berry and Roos-Serote, 2008, New Ast. 13, 224). Notable features are the variability of the winds and the detection of a clear transition region between 75S and 80S. The meridional component is suggestive of a polar Hadley cell. Wave motions are detected at the transition latitudes with wavenumbers 3 and 8 for the zonal and meridional components. We estimate the contribution from the subsolar to antisolar-point wind component to be higher than 10 m/s

A Cloud Tracking Tool for Planetary Orbiter Images

During their operations phase, planetary missions continuously produce a wealth of data that tend to overwhelm research teams. Spectral imagers, in particular, produce data cubes in which the wavelength dimension adds to the two spatial dimensions. Tracking of atmospheric features in order to derive winds and the construction of global maps from such large data volumes becomes particularly time-consuming if done manually. This highlights the importance of automated procedures capable of analysing sequences of data cubes with minimal user interaction. A tool for cloud tracking for such a purpose is currently under development in our group. In its present state it is based on synthetic images and uses a simple method of multiple matrix comparison to derive wind components. Deriving winds from data from the Venus Express - Visible and InfraRed Thermal Imaging Spectrometer (VIRTIS) instrument will be a possible application. We shall present an overview of the method, its benchmarking and the current status and future development of the project

South polar dynamics of the Venusian atmosphere from VIRTIS/Venus Express mapping in the thermal range

We report on measurements of Venus cloud velocities from VIRTIS/Venus Express observations of the south polar region of Venus. Cloud tracking has been performed using a method of automated digital correlation. Tracking has been performed on pairs of monochromatic VIRTIS images selected mainly in the 5 μm window, but also at 1.74, 2.3, 3.93 micrometers. Wind measurements from vector retrievals based on automated feature tracking show high variability, indicating the presence of important transient motions. The time-averaged zonal winds indicate different day and night side regimes. On the day side both the zonal wind component (u) and the meridional one (v) are approximately uniform between 84S and 76S, with u ∼ −40 m/s and v ∼ −10 m/s. On the night side the zonal wind decreases poleward, from a maximum at 76S. The meridional wind is smaller than on the day side and appears to change sign from poleward to equatorward at 76S. The cold collar boundary appears to be a transition region not only for the temperature, but for the winds as well. In this region wave motions are also apparent, with amplitudes on the order of 40 m/s for u′ and 10 m/s for v′

Imaginary landscapes of the time Between moors and Andean towns of Venezuela

The present article approaches the topic of the social representation of the time. Their content constitutes the interpretation of the second moment of an investigation in the moor of Mucuchíes, municipality Rangel, of the state Merida, mountain range of Merida that in turn is articulated to the mountain range of The Andes. From conversations about the time with women and their world of life between the high moors and some villages and populated centers are obtained—starting from a cross-section analysis and plural in the method—los testimonials of women in their context moor. Using the theory of the representations, and having certain cautions regarding this, data of some dimensions are obtained: of knowledge, of affections and valuations, as well as of the practices. It is supposed that this “social representations” they have a psico-philosophical-social, but also symbolic-cultural content (myths, rites and customs) that eat expression of a matrix context and lateral routine daily acts it is they are able to configure “imaginary landscapes” in an architecture of the space-time from a philosophiaplebeia that he/she specifies to be recoveredPresente artículo aborda el tema de la representación social del tiempo. Su contenido constituye la interpretación del segundo momento de una investigación en el páramo de Mucuchíes, municipio Rangel, del estado Mérida, cordillera de Mérida, que a su vez se articula a la cordillera de Los Andes.Desde conversaciones sobre el tiempo con mujeres y su mundo de vida entre los altos páramos y algunas aldeas y centros poblados se obtienen —a partir de un análisis transversal y plural en el método— los testimonios de mujeres en su contexto páramo. Usando la teoría de las representaciones, y teniendo ciertas precauciones respecto a esta, se obtienen datos de algunas dimensiones: de conocimiento, de afectos y valoraciones, así como de las prácticas. Se supone que dichas “representaciones sociales” tienen un contenido psico-filosóficosocial, pero también simbólico-cultural (mitos, ritos y costumbres), que como expresión de un contexto matricial y actos cotidianos rutinarios laterales logran configurar “paisajes imaginarios” en una arquitectura del espaciotiempo desde una philosophiaplebeia que precisa ser recuperad

Ion backflow studies with a triple-GEM stack with increasing hole pitch

Gas Electron Multipliers have undergone a very consistent development since their invention in 1997. Their production procedures have been tuned in such a way that nowadays it is possible to produce foils with areas of the order of the square meter that can operate at a reasonable gain, uniform over large areas and with a good stability in what concerns electrical discharges. For the third run of LHC, they will be included in the CMS and ALICE experiments after significant upgrades of the detectors, confirming that these structures are suitable for very large experiments. In the special case of Time Projection Chambers, the ion backflow and the energy resolution are sensitive issues that must be addressed and the GEM has shown to be able to deal with both of them. In this work, a stack of three GEMs with different pitches has been studied as a possible future approach for ion-backflow suppression to be used in TPCs and other detection concepts. With this approach, an ion backflow of 1 % with an energy resolution of 12 % at 5.9 keV has been achieved with the detector operating in an Ar/CO2 (90/10) mixture at a gain of ~ 2000.Comment: 15 pages, 11 figure

Collective Action for Watershed Management: Field Experiments in Colombia and Kenya

The dilemma of collective action around water use and management involves solving both the problems of provision and appropriation. Cooperation in the provision can be affected by the rival nature of the appropriation and the asymmetries in the access. We report two field experiments conducted in Colombia and Kenya. The Irrigation Game was used to explore the provision and appropriation decisions under asymmetric or sequential appropriation, complemented with a Voluntary Contribution Mechanism experiment which looks at provision decisions under symmetric appropriation. The overall results were consistent with the patterns of previous studies: the zero contribution hypotheses is rejected whereas the most effective institution to increase cooperation was face-to-face communication, and above external regulations, although we find that communication works much more effectively in Colombia. We also find that the asymmetric appropriation did reduce cooperation, though the magnitude of the social loss and the effectiveness of alternative institutional options varied across sites.Collective Action, Watersheds, Field Experiments, Colombia, Kenya, Community/Rural/Urban Development, Environmental Economics and Policy, Institutional and Behavioral Economics, Q0, Q2, C9, H3, H4,

TRADABILITY AND MARKET EQUILIBRIUM FOR U.S.-MEXICO FRESH TOMATOES

Tomato trade between the U.S. and Mexico has grown significantly during the past decade. This increased trade, together with major structural changes in US produce marketing channels, has increased the complexity of conducting analysis of market integration and equilibrium. This study implements an Extended Parity Bounds Model (EPBM), following the work of Barrett and Li, to examine fresh tomato trade relationships between major shipping points and terminal markets for Mexican imported and Florida and California tomatoes. Findings suggest that, although markets seem relatively integrated and efficient, there exist some potential for claims of inefficient or overly competitive behavior. As is expected, the more complex the marketing channels between producer and wholesaler (distance or international boundaries), the more likely that markets operate suboptimally.International Relations/Trade,

New Measurements of Venus Winds with Ground-Based Doppler Velocimetry at CFHT

operations with observations from the ground using various techniques and spectral domains (Lellouch and Witasse, 2008). We present an analysis of Venus Doppler winds at cloud tops based on observations made at the Canada France Hawaii 3.6-m telescope (CFHT) with the ESPaDOnS visible spectrograph. These observations consisted of high-resolution spectra of Fraunhofer lines in the visible range (0.37-1.05 μm) to measure the winds at cloud tops using the Doppler shift of solar radiation scattered by cloud top particles in the observer's direction (Widemann et al., 2007, 2008). The observations were made during 19-20 February 2011 and were coordinated with Visual Monitoring Camera (VMC) observations by Venus Express. The complete optical spectrum was collected over 40 spectral orders at each point with 2-5 seconds exposures, at a resolution of about 80000. The observations included various points of the dayside hemisphere at a phase angle of 67°, between +10° and -60° latitude, in steps of 10° , and from +70° to -12° longitude relative to sub-Earth meridian in steps of 12°. The Doppler shift measured in scattered solar light on Venus dayside results from two instantaneous motions: (1) a motion between the Sun and Venus upper cloud particles; (2) a motion between the observer and Venus clouds. The measured Doppler shift, which results from these two terms combined, varies with the planetocentric longitude and latitude and is minimum at meridian ΦN = ΦSun - ΦEarth where the two components subtract to each other for a pure zonal regime. Due to the need for maintaining a stable velocity reference during the course of acquisition using high resolution spectroscopy, we measure relative Doppler shifts to ΦN. The main purpose of our work is to provide variable wind measurements with respect to the background atmosphere, complementary to simultaneous measurements made with the VMC camera onboard the Venus Express. We will present first results from this work, comparing with previous results by the CFHT/ESPaDOnS and VLT-UVES spectrographs (Machado et al., 2012), with Galileo fly-by measurements and with VEx nominal mission observations (Peralta et al., 2007, Luz et al., 2011). Acknowledgements: The authors acknowledge support from FCT through projects PTDC/CTE-AST/110702/2009 and PEst-OE/FIS/UI2751/2011. PM and TW also acknowledge support from the Observatoire de Paris. Lellouch, E., and Witasse, O., A coordinated campaign of Venus ground-based observations and Venus Express measurements, Planetary and Space Science 56 (2008) 1317-1319. Luz, D., et al., Venus's polar vortex reveals precessing circulation, Science 332 (2011) 577-580. Machado, P., Luz, D. Widemann, T., Lellouch, E., Witasse, O, Characterizing the atmospheric dynamics of Venus from ground-based Doppler velocimetry, Icarus, submitted. Peralta J., R. Hueso, A. Sánchez-Lavega, A reanalysis of Venus winds at two cloud levels from Galileo SSI images, Icarus 190 (2007) 469-477. Widemann, T., Lellouch, E., Donati, J.-F., 2008, Venus Doppler winds at Cloud Tops Observed with ESPaDOnS at CFHT, Planetary and Space Science, 56, 1320-1334