Vertical structure of Jupiter’s Oval BA before and after it reddened: What changed?

To constrain the properties of Oval BA before and after it reddened, we use Hubble methane band images from 1994 to 2009 to find that the distribution of upper tropospheric haze atop the oval and its progenitors remained unchanged, with reflectivity variations of less than 10% over this time span. We quantify measurement uncertainties and short-term fluctuations in velocity fields extracted from Cassini and Hubble data, and show that there were no significant changes in the horizontal velocity field of Oval BA in 2000, 2006, and 2009. Based on models of the oval’s dynamics, the static stability of the oval’s surroundings was also unchanged.The vertical extent of the oval did not change, based on the unchanged haze reflectivity and unchanged stratification. Published vortex models require Brunt-Väisälä frequencies of about 0.08 s⁻¹ at the base of the vortex, and we combine this value with a review of prior constraints on the vertically variable static stability in Jupiter’s troposphere to show that the vortex must extend down to the condensation level of water in supersolar abundance.The only observable change was an increase in short-wavelength optical absorption that appeared not at the core of the oval, but in a red annulus. The secondary circulation in the vortex keeps this red annulus warmer than the vortex core. Although the underlying cause of the color change cannot be proven, we explore the idea that the new chromophores in the red annulus may be related to a global or hemispheric temperature change.     

Comparison of dew point temperature estimation methods in Southwestern Georgia

Recent upward trends in acres irrigated have been linked to increasing near-surface moisture. Unfortunately, stations with dew point data for monitoring near-surface moisture are sparse. Thus, models that estimate dew points from more readily observed data sources are useful. Daily average dew temperatures were estimated and evaluated at 14 stations in Southwest Georgia using linear regression models and artificial neural networks (ANN). Estimation methods were drawn from simple and readily available meteorological observations, therefore only temperature and precipitation were considered as input variables. In total, three linear regression models and 27 ANN were analyzed. The two methods were evaluated using root mean square error (RMSE), mean absolute error (MAE), and other model evaluation techniques to assess the skill of the estimation methods. Both methods produced adequate estimates of daily averaged dew point temperatures, with the ANN displaying the best overall skill. The optimal performance of both models was during the warm season. Both methods had higher error associated with colder dew points, potentially due to the lack of observed values at those ranges. On average, the ANN reduced RMSE by 6.86% and MAE by 8.30% when compared to the best performing linear regression model.     

Estimating tsunami potential of earthquakes in the Sumatra–Andaman region based on broadband seismograms in India

In this paper, we report that the ratio of broadband energy (0.01?C2?Hz) to high-frequency energy (0.3?C2?Hz), E _r, estimated from regional seismograms of India, might be a useful parameter in estimating tsunami potential of earthquakes in the Sumatra?CAndaman region. E _r is expected to be sensitive to the depth as well as to the source characteristics of an earthquake. Since a shallow and slow earthquake has a greater tsunamigenic potential, E _r may be a useful diagnostic parameter. We base our analysis on broadband seismograms of the great earthquakes of Sumatra?CAndaman (2004, M _w?~?9.2) and Nias (2005, M _w 8.6), 41 of their aftershocks, and the earthquakes of north Sumatra (2010, M _w 7.8) and Nicobar (2010, M _w 7.4) recorded at VISK, a station located on the east coast of India. In the analysis, we also included the two recent, great strike-slip earthquakes of north Sumatra (2012, M _w 8.6, 8.2) recorded at VISK and three south Sumatra earthquakes (2007, M _w 8.5; 2007, M _w 7.9; 2010, M _w 7.8) recorded at PALK, a station in Sri Lanka. We find that E _r is a function of depth; shallower earthquakes have higher E _r values than the deeper ones. Thus, E _r may be indicative of tsunamigenic potential of an earthquake. As M _w and E _r increase so does the tsunami potential. In addition to the parameter E _r, the radiated seismic energy, E _s, may be estimated from the regional seismograms in India using empirical Green??s function technique. The technique yields reliable E _s for the great Sumatra and Nias earthquakes. E _r and E _s computed from VISK data, along with M _w and focal mechanism, may be useful in estimating tsunami potential along the east coast of India from earthquakes in the Sumatra?CAndaman region in less than ~20?min.     

Simulating Australian Urban Climate in a Mesoscale Atmospheric Numerical Model

We develop an urban canopy scheme coupled to a mesoscale atmospheric numerical model and evaluate the simulated climate of an Australian city. The urban canopy scheme is based on the Town Energy Budget approach, but is modified to efficiently represent the predominately suburban component of Australian cities in regional climate simulations. Energy conservation is improved by adding a simple model of air-conditioning to prevent the urban parametrization acting as an energy sink during the Australian summer. In-canyon vegetation for suburban areas is represented by a big-leaf model, but with a largely reduced set of prognostic variables compared to previous approaches. Although we have used a recirculation/venting based parametrization of in-canyon turbulent heat fluxes that employs two canyon wall energy budgets, we avoid using a fixed canyon orientation by averaging the canyon fluxes after integrating over 180° of possible canyon orientations. The urban canopy scheme is evaluated by simulating the climate for Melbourne, Australia after coupling it to The Air Pollution Model. The combined system was found to predict a realistic climatology of air temperatures and winds when compared with observations from Environmental Protection Authority monitoring stations. The model also produced a plausible partitioning of the urban energy budget when compared to urban flux-tower studies. Overall, the urban canyon parametrization appears to have reasonable potential for studying present and predicting changes in future Australian urban climates in regional climate simulations.     

Statistical Assessment of Unidirectional Propagation of a Leachate Contamination Plume

The leachate produced by the Municipal Solid Waste Landfill of São Pedro da Aldeia (State of Rio de Janeiro, Brazil) flows almost entirely in one direction guided by a natural ditch in the bottom of a gentle valley. This landfill has been in operation with no concern to environmental protection, such as containment systems or leachate drainage and treatment. This inadequate operation causes severe damage to flora, wildlife and local farmers, due to continuous propagation of contaminants in the groundwater. Field and laboratory measurements of ionic concentrations of several contaminants found in the groundwater adjacent the landfill are presented and interpreted in this paper. Several farms are located adjacent to the landfill, comprising about 1,000 inhabitants that use the ground water for personal use and land farming activities. The main purpose of this paper is to assess the environmental hazard to the surrounding properties as the landfill is still in operation. This is accomplished by estimating the maximum distance travelled by the leachate plume based on the statistical interpretation of the measured ionic concentration of several contaminants found commonly in landfills. The main recommendation coming from the statistical assessment is that safe groundwater consumption should be limited to a minimum distance of 400 m from the contamination source, provided that the quality of ground water is continuously monitored while the MSW landfill is still in operation.     

Early Ipswichian (last interglacial) sea level rise in the channel region: Stone Point Site of Special Scientific Interest,Hampshire, England

Constraining the speed of sea level rise at the start of an interglacial is important to understanding the size of the ‘window of opportunity’ available for hominin migration. This is particularly important during the last interglacial when there is no evidence for significant hominin occupation anywhere in Britain. There are very few finer grained fossiliferous sequences in the Channel region that can be used to constrain sea level rise and they are preserved only to the north of the Channel, in England. Of these, the sequence at Stone Point SSSI is by far the most complete. Data from this sequence has been previously reported, and discussed at a Quaternary Research Association Field Meeting, where a number of further questions were raised that necessitated further data generation. In this paper, we report new data from this sequence – thin section analysis, isotopic determinations on ostracod shells, new Optical Stimulated Luminescence ages and Amino Acid Recem analyses. These show early sea level rise in this sequence, starting during the pre-temperate vegetation zone IpI, but no early warming. The implications of this almost certainly last interglacial sequence for the human colonisation of Britain and our understanding of the stratigraphic relationship of interglacial estuarine deposits with their related fluvial terrace sequences is explored.     

High resolution,basin extent observations and implications for understanding river form and process

Fifty years of fluvial studies have posited a variety of conceptual frameworks for characterizing river forms and processes throughout entire basins, including hydraulic geometry, the river continuum concept, self‐organized criticality, and sediment links. This article uses basin‐extent, high resolution observations of fluvial forms in the Nueces River basin, Texas, and Yellowstone National Park to evaluate the ability of these frameworks to characterize system behavior across a multitude of scales. The Nueces data were collected with remote sensing methods and the Yellowstone data were collected through extensive field surveys. The data resolution, spatial extent, and quality of these data sets allow direct comparison between the two areas. The ‘hyperscale’ comparison supports using of each these frameworks at specific scales, but also indicates an irreducible amount of variation in both datasets across many different scales that is not captured by the conceptual frameworks. Moreover, the scales and locations where one framework, such as hydraulic geometry, works well are often not the same scales and locations where another framework, such as the river continuum concept, works well. Because the conceptual frameworks appear to operate at scales and locations distinct from one another, the measurement approaches necessary to observe them must also be at different scales and locations. For example, ‘seeing’ self‐organized criticality in a river system is difficult without an extensive survey through space, whereas the recognition of sediment links requires quite intense sampling in specific river regions. We suggest that these separations between measurement scales represent an incommensurability issue in river studies, making it very difficult to both communicate among and test between two or more competing theories. Making simultaneous hyperscale observations of the river is one approach to minimizing the theory‐ladeness of observation, as deviations from different predictions can be plotted at every scale. Copyright © 2010 John Wiley & Sons, Ltd.     

Remote sensing of rivers: the emergence of a subdiscipline in the river sciences

This article reports on the special issue of Earth Surface Processes and Landforms dedicated to remote sensing of rivers. This emerging subdiscipline of river science has grown at a rapid rate in recent years because of: (a) the growing desire and need for data to document and explore the full range of spatial and temporal variations in river systems; (b) evolving technologies that enable lower cost data acquisition, processing and analysis at reach to catchment to continental scales; and (c) the increasing engagement of river scientists with GIScience. The convergence of these factors and the ever growing number of practitioners speaks to the need for more communication among researchers, a major reason for creating this special issue. The 12 articles in the volume cover a broad spectrum of applications that use a variety of platforms and sensors, ranging from photogrammetric mapping of riffle‐pool morphology beneath forest canopy using a camera mounted on a hand held pole to satellite‐based synthetic radar mapping of subcontinental scale hydrology of large rivers. In this overview each of the 12 articles is briefly summarized. Based on these works and other research, it is concluded that the time for more widespread application of river remote sensing techniques is now. To promote more widespread use of remote sensing techniques for river science and management, the following are advocated: (a) developing stand alone or plug‐in software products that enable non‐expert users to implement these new methods, (b) incorporating remote sensing of rivers training into classes, workshops, and on‐line tutorials; and (c) promoting more intentional and formal collaboration among members of the river remote sensing community. Copyright © 2010 John Wiley & Sons, Ltd.     

Numerical issues in computing inundation areas over natural terrains using Savage-Hutter theory

When characterizing geologic natural hazards, specifically granular flows including pyroclastic flows, debris avalanches and debris flows, perhaps the most important factor to consider is the area of inundation. One of the key parameters demarcating the leading edge of inundation is the run-out distance. To define the run-out distance, it is necessary to know when the flow stops. Numerical experiments are presented for determining a stopping criterion and exploring the suitability of the Savage-Hutter theory for computing inundation areas of granular flows. The stopping criterion is a function of dimensionless average velocity, pile aspect ratio and internal and bed friction angle and can be implemented on either a global (entire flow) or local (small areas of the flow) level. Slumping piles on a horizontal surface, and geophysical flows over complex topography were simulated. Mountainous areas, such as Colima volcano, Mexico; Casita, Nicaragua; Little Tahoma Peak, USA, and the San Bernardino Mountains, USA, were used as test regions. These areas have combinations of steep, open slopes and sinuous channels. Because of differences in topography and physical scaling, slumping piles in the laboratory and geophysical flows in natural terrain must be scaled differently to determine a reasonable dimensionless relationship for the stopping criterion.