Fresh Ammonia Ice Clouds in Jupiter: I. Spectroscopic Identification, Spatial Distribution, and Dynamical Implications

We report the first spectroscopic detection of discrete ammonia ice clouds in the atmosphere of Jupiter, as discovered utilizing the Galileo Near-Infrared Mapping Spectrometer (NIMS). Spectrally identifiable ammonia clouds (SIACs) cover less than 1% of the globe, as measured in complete global imagery obtained in September 1996 during Galileo's second orbit. More than half of the most spectrally prominent SIACs reside within a small latitudinal band, extending from 2° to 7° N latitude, just south of the 5-μm hot spots. The most prominent of these are spatially correlated with nearby 5-μm-bright hot spots lying 1.5°-3.0° of latitude to the north: they reside over a small range of relative longitudes on the eastward side of hot spots, about 37% of the longitudinal distance to the next hot spot to the east. This strong correlation between the positions of hot spots and the most prominent equatorial SIACs suggests that they are linked by a common planetary wave. Good agreement is demonstrated between regions of condensation predicted by the Rossby wave model of A. J. Friedson and G. S. Orton (1999, Bull. Am. Astron. Assoc31, 1155-1156) and the observed longitudinal positions of fresh ammonia clouds relative to 5-μm hot spots. Consistency is also demonstrated between (1) the lifetime of particles as determined by the wave phase speed and cloud width and (2) the sedimentation time for 10-μm radius particles consistent with previously reported ammonia particle size by T. Y. Brooke et al. (1998, Icarus136, 1-13). A young age (<two days) for most SIAC cloud particles is indicated. To the south, the most prominent SIACs are located to the northwest of the Great Red Spot, in a region where a westward flow of jovian air, diverted approximately 10° of latitude northward by the Great Red Spot, encounters a large eastward flow. SIACs have been observed repeatedly by NIMS at this location during Galileo's first four years in Jupiter orbit. It is speculated that due to the three-dimensional interactions of these flows, relatively large amounts of ammonia gas are steadily transported from the sub-cloud troposphere (below the ∼600-mbar level) to the high troposphere, nearly continuously forming fresh ammonia ice clouds to the northwest of the Great Red Spot.     

MINQUE for block diagonal bordered systems such as those encountered in VLBI data analysis

A sparse matrix method is developed for computing variance factors for block-diagonal, bordered systems of equations using MINQUE (Minimum Norm Quadratic Unbiased Estimation). This method greatly reduces the computational effort required to apply MINQUE, thus making it practical to compute variance factors for some very large systems of equations. The computer implementation of the method is described and applied to the computation of variance factors for a combination of 1609 VLBI (Very Long Baseline Interferometry) observing sessions. The purpose of this test was to compute a variance factor for each of the data sets and, perhaps, to obtain more realistic variance estimates to replace those in common use for the analysis of VLBI data. It was found that the method is satisfactory for use with such large problems, and the test served to verify that the variances in current use in VLBI data adjustments are adequate. Received: 26 November 1996 / Accepted: 12 December 1997     

Updating the Phase 1 habitat map of Wales, UK, using satellite sensor data

The Phase 1 Survey is the most comprehensive and widely used national level map of semi-natural habitats in Wales. However, the survey was based largely on field survey and was conducted over several decades, before being completed in 1997. Given that resources for a repeat survey were limited, this study has used an object-orientated rule-based classification implemented within eCognition of multi-temporal satellite sensor data acquired between 2003 and 2006 to map semi-natural habitats and agricultural land across Wales, thereby allowing a progressive update of the Phase 1 Survey. The classification of objects to Phase 1 habitat classes was undertaken in two steps; firstly the landscape of Wales was divided into objects using orthorectified SPOT-5 High Resolution Geometric (HRG) reflectance data (10 m spatial resolution) and Land Parcel Information System (LPIS) boundaries. A rule-base was then developed to progressively discriminate and map the distribution of 105 sub-habitats across Wales based on time-series of SPOT HRG, Terra-1 Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Indian Remote Sensing Satellite (IRS) LISS-3 data, derived datasets (e.g., vegetation indices, fractional images) and ancillary information (e.g., topography). The rules coupled knowledge of ecology and the information content of these remote sensing data using a combination of thresholds, Boolean operations and fuzzy membership functions. A second rule-base was then developed to translate the more detailed sub-habitat classification to Phase 1 habitat classes. Indicative accuracies of the revised Phase 1 mapping, based on comparisons with the later Phase 2 survey (for selected habitats), were >80% overall and typically between 70% and 90% for many classes. Through this exercise, Wales has become the first country in Europe to produce a national map of habitats (as opposed to land cover) through object-orientated classification of satellite sensor data. Furthermore, the approach can be adapted to allow continual monitoring of the extent and condition of habitats and agricultural land.     

VISTA Variables in the Via Lactea (VVV): The public ESO near-IR variability survey of the Milky Way

We describe the public ESO near-IR variability survey (VVV) scanning the Milky Way bulge and an adjacent section of the mid-plane where star formation activity is high. The survey will take 1929 h of observations with the 4-m VISTA telescope during 5 years (2010–2014), covering ～10⁹ point sources across an area of 520 deg², including 33 known globular clusters and ～350 open clusters. The final product will be a deep near-IR atlas in five passbands (0.9–2.5 μm) and a catalogue of more than 10⁶ variable point sources. Unlike single-epoch surveys that, in most cases, only produce 2-D maps, the VVV variable star survey will enable the construction of a 3-D map of the surveyed region using well-understood distance indicators such as RR Lyrae stars, and Cepheids. It will yield important information on the ages of the populations. The observations will be combined with data from MACHO, OGLE, EROS, VST, Spitzer, HST, Chandra, INTEGRAL, WISE, Fermi LAT, XMM-Newton, GAIA and ALMA for a complete understanding of the variable sources in the inner Milky Way. This public survey will provide data available to the whole community and therefore will enable further studies of the history of the Milky Way, its globular cluster evolution, and the population census of the Galactic Bulge and center, as well as the investigations of the star forming regions in the disk. The combined variable star catalogues will have important implications for theoretical investigations of pulsation properties of stars.     

Phytoplankton, nutrients and hydrography in the frontal zone between the Southwest Indian Subtropical gyre and the Southern Ocean

A survey was made of the Southwest Indian Ocean frontal region between 30 and 50°E containing the Agulhas Return, Subtropical and Subantarctic Fronts. From CTD, SeaSoar and extracted samples the distribution of nitrate, silicate and chlorophyll a is shown to be strongly linked to the front and water mass structure, varying zonally and meridionally. Surface chlorophyll a concentrations were low to the north and south leaving a band of elevated chlorophyll between the Subtropical and Subantarctic Fronts. The low concentration of chlorophyll a to the north, in Subtropical Water, was clearly due to nitrate limitation. Between the Subtropical and Subantarctic Fronts, where the chlorophyll a concentrations were highest, the surface layer showed silicate depletion limiting diatom growth. South of the Subantarctic Front there were deep extending, low concentrations of chlorophyll a, but despite plentiful supplies of macro-nutrients and a well-stratified surface layer, high concentrations of chlorophyll a were absent. Changes from west to east were associated with the meandering of the Southern Ocean Fronts, especially the Subtropical Front, and their strength and proximity to each other. Concentrations of chlorophyll a peaked where the Agulhas Return, Subtropical and Subantarctic Fronts were in close proximity. Combined frontal structures appear to have particularly pronounced vertical stability and are associated with enhanced upwelling of nutrients and leakage of nutrients across the front. Light levels are high within the shallow stable layer. Such conditions are clearly favourable for biological growth and support the development of larger-celled phytoplankton communities.     

Observations of resuspended diatoms in the turbid tidal edge

Observations of resuspended diatoms in the shallow waters (<60 cm) of the turbid tidal edge are described for single sites on two tidal flats–the Molenplaat in the Westerschelde estuary, and the Hond in the Ems-Dollard estuary, The Netherlands. High concentrations of chlorophyll-a (chl-a) were observed in the trailing edge of the ebbing tide in water depths of <20 cm, after which concentrations decreased markedly. Peak mean values were 19 μg chl-a l⁻¹ in 10 cm of water at the Molenplaat, and 45 μg chl-a l⁻¹ in 5 cm of water at the Hond. Similar trends were observed on the flooding tide, although peak values were far less pronounced (6 and 30 μg chl-a l⁻¹ respectively). Microscopic examination of the diatom community within the turbid tidal edge at the Molenplaat revealed that peaks in biomass were caused by suspended benthic diatoms, as well as the large centric diatom Coscinodiscus sp., particularly on the ebb tide. Planktonic diatoms other than Coscinodiscus sp. were more randomly distributed and did not appear to follow any particular trend. It would seem that as the tide recedes, resuspended benthic diatoms and large Coscinodiscus sp. cells become concentrated in the shallow water. However, the virtual absence of Coscinodiscus sp. from the leading edge of the flooding tide suggests that most of the resuspended cells do not settle to the seabed, but are washed away into the channels. The small peak of benthic diatoms at the leading edge of the flood tide is most likely resuspended locally from the sediment, along with large numbers of diatom frustules.     

Longitudinal strength of a high-speed ferry

The longitudinal strength of the high-speed ferry was investigated by subjecting the ship's hull girder to long-term loads obtained from a frequency-domain panel code. Prior to the statistical analysis, linearly computed transfer functions were corrected for nonlinear effects, yielding two sets of transfer functions valid for different wave amplitudes. One set corresponded to the hogging condition; the other set, to the sagging condition. Two regular equivalent design waves were specified that resulted in loads representing the most severe global design load conditions. The still-water loading condition, yielding a still-water vertical bending moment in hogging, was superimposed on the wave-induced loads to obtain the total (design) loads in hogging. For the sagging condition only, additional impact-related loads were superimposed to obtain the total (design) loads in sagging. A finite element model of the ship's structure was subjected to pressure distributions according to the two regular design waves. For comparison with classification society rule values, a simple beam theory strength analysis of the ship's midship section was performed first, and then another finite element analysis was carried out, whereby the imposed loads were tuned to the rule values of vertical bending moments. Rule-based magnitudes of nominal maximum longitudinal stress deviated significantly (25–39%) from comparable stresses obtained by the panel code based finite element analysis. However, stresses obtained from the rule-based finite element analysis agreed more favorably, especially in hogging. In the uppermost deck, for example, the panel code based compressive stress was only 9% larger than the comparable stress from the rule-based finite element analysis.     

Composition and heterogeneity of the microbial community in a coastal microbial mat as revealed by the analysis of pigments and phospholipid-derived fatty acids

The beaches of the North Sea barrier island Schiermonnikoog (The Netherlands) are covered by microbial mats. Five types of microbial mats were distinguished based on a variety of characteristics, located along a transect perpendicular to the coast. Biomass abundance and composition of the microbial community were analyzed in these mats using pigments and phospholipid-derived fatty acids (PLFA) as biomarkers. Biomass per gram sediment increased more than six-fold from the mats at the low water mark to mats found at the edge of the dunes. Microscopic analysis revealed that the increase in biomass was accompanied by a change in species composition. Pigment- and PLFA composition reflected the changes in species composition. The PLFA data could be used to estimate the relative group abundance using the matrix factorization program CHEMTAX., whereas the pigment data were found not to be suitable for this purpose.     

Seismic characterization of switching platform geometries and dominant carbonate producers (Miocene,Las Negras,Spain)

The primary goals of seismic interpretation and quantification are to understand and define reservoir architecture and the distribution of petrophysical properties. Since seismic interpretation is associated with major uncertainties, outcrop analogues are used to support and improve the resulting conceptual models. In this study, the Miocene carbonates of Cerro de la Molata (Las Negras, south‐east Spain) have been selected as an outcrop analogue. The heterogeneous carbonate rocks of the Cerro de la Molata Platform were formed by a variety of carbonate‐producing factories, resulting in various platform morphologies and a wide range of physical properties. Based on textural (thin sections) and petrophysical (porosity, density, carbonate content and acoustic properties) analyses of the sediments, eleven individual facies types were determined. The data were used to produce synthetic seismic profiles of the outcrop. The profiles demonstrate that the spatial distribution of the facies and the linked petrophysical properties are of key importance in the appearance of the synthetic seismic sections. They reveal that carbonate factory and facies‐specific reflection patterns are determined by porosity contrasts, diagenetic modifications and the input of non‐carbonate sediment. The reflectors of the seismograms created with high‐frequency wavelets are coherent with the spatial distribution of the predefined facies within the depositional sequences. The synthetic seismograms resulting from convolution with lower frequency wavelets do not show these details – the major reflectors coincide with: (i) the boundary between the volcanic basement and the overlying carbonates; (ii) the platform geometries related to changes in carbonate factories, thus sequence boundaries; and (iii) diagenetic zones. Changes in seismic response related to diagenesis, switching carbonate producers and linked platform geometries are important findings that need to be considered when interpreting seismic data sets.