Optimal Routefinding Across Landscapes Featuring High‐cost Linear Obstacles

Existing GIS‐based least‐cost routefinding approaches can in some cases be confounded by linear features in the landscape whose crossing costs are high relative to other traversing costs found throughout the landscape. Unfortunately, such high‐cost linear features are not uncommon; they frequently occur in the form of hydrologic features whose crossing costs are high relative to costs of traversing the surrounding dry land. This study (1) enumerates the situations where existing approaches can fail, (2) proposes a simple method for overcoming the limitations of the existing approaches, and (3) conducts an experiment to assess the impact of the weaknesses of existing approaches and the magnitude of the differences between the results produced by existing and revised approaches. Our results show that in mountainous terrain, linear hydrologic features with high crossing costs can have a profound impact on least‐cost routes, and the choice of solution method has equally profound impacts on the optimal route produced by the analysis.     

Integrated satellite observations of the 2001 eruption of Mt. Cleveland, Alaska

Satellite data were the primary source of information for the eruption of Mt. Cleveland, Alaska on 19 February, and 11 and 19 March 2001. Multiple data sets were used pre-, syn- and post-eruption to mitigate the hazard and determine an eruption chronology. The 19 February eruption was the largest of the three, resulting in a volcanic cloud that formed an arc over 1000 km long, moved to the NE across Alaska and was tracked using satellite data over more than a 50-h period. The volcanic cloud was “concurrently” detected on the GOES, AVHRR and MODIS data at various times and their respective signals compared. All three sensors detected a cloud that had a very similar shape and position but there were differences in their areal extent and internal structural detail. GOES data showed the largest volcanic cloud in terms of area, probably due to its oblique geometry. MODIS bands 31 and 32, which are comparable to GOES and AVHRR thermal infrared wavelengths, were the least effective single channels at detecting the volcanic cloud of those investigated (MODIS bands 28, 29, 31 and 32). MODIS bands 28 and 29 detected the largest volcanic clouds that could easily be distinguished from weather clouds. Of the split-window data, MODIS bands 29 minus band 32 detected the largest cloud, but the band 31 minus band 32 data showed the volcanic cloud with the most internal structural detail. The Puff tracking model accurately tracked the movement, and predicted the extent and shape of this complex cloud even into areas beyond satellite detection. Numerous thermal anomalies were also observed during the eruption on the twice-daily AVHRR data and the high spatial-resolution Landsat data. The high-resolution Radarsat data showed that the AVHRR thermal anomalies were due to lava and debris flow features and a newly formed fan along the west coast of the island. Field observations and images from a hand-held Forward Looking Infrared Radiometer (FLIR) showed that the flow features were ′a′a lava, debris flows and a warm debris fan along the west coast. Real-time satellite data were the primary tool used to monitor the eruption, track changes and to mitigate hazards. High-resolution data, even though coverage is infrequent, were critical in helping to identify volcanic processes and to compile an eruption chronology.     

Mantle lithosphere,asthenosphere and transition zone beneath Eastern Anatolia

Journal of Seismology - By using P and S wave receiver functions and P and S wave travel time residuals, we have found velocity models for 16 seismograph stations in Eastern Anatolia. Our study is...     

Landward limit of wind setup on beaches

Open coast storm surge water levels consist of a wind shear forcing component generally referred to as wind setup; a wave setup component caused by wind-induced waves transferring momentum to the water column; an atmospheric pressure head component due to the atmospheric pressure deficit over the spatial extent of the storm system; a Coriolis-forced component due to effects of the rotation of the earth acting on the wind-driven alongshore current at the coast; and, if astronomical tides are present, an astronomical tide component. Astronomical tide is considered to be predictable and, therefore, not a meteorological driven component of storm surge although there may be interaction between the tide and meteorological driven water levels. Typically the most important component of storm surge on the US East Coast and Gulf of Mexico shorelines is the wind setup component. The importance of inland flooding due to the wind setup component of storm surge is considered herein with special reference to the effect of subaerial slope on inland flooding where three different linear slopes are considered and storm surge is calculated for the region above still water level, using an analytic solution. The present study findings show that the inland storm surge from the wind setup component can be of considerable importance and lead to significantly higher storm surges than found for storm surge at the still water level intersection of the beach/land. It is shown that mild slopes can lead to very high water levels at the land–water interface (i.e. above the still water level intersection of the beach).     

Flow Adjustments Across Sea-Surface Temperature Changes

The adjustment of airflow across sea-surface temperature changes is examinedusing aircraft eddy-correlation data. Major features of the observed flow adjustmentare not included in the theory of internal boundary layers. However, the data samplesize and coverage are not sufficient to accurately quantify the additional influences.With flow from warm water over cooler water, substantial turbulence intermittentlydevelops above the newly formed surface inversion layer. The corresponding,spatially-averaged, downward momentum flux is stronger than that close to the surface.With stably stratified flow over modest increases of sea-surface temperature, areduction of stratification can trigger episodic shear generation of turbulence. Inthese cases, the primary role of increasing surface temperature in the downwinddirection is to induce shear generation of turbulence. With larger increases ofsurface temperature, upward heat flux generates turbulence, warms the air and generates a significant horizontal gradient of hydrostatic pressure. This contributionto the pressure field appears to strongly modify the flow. Major inadequacies inexisting data and future needs are noted.     

The INTEGRAL complete sample of type 1 AGN

In this paper we discuss the broad-band X-ray characteristics of a complete sample of 36 type 1 active galactic nuclei (AGN), detected by INTEGRAL in the 20–40 keV band above the 5.5σ level. We present, for all the objects in the sample, the broad-band (1–110 keV) spectral analysis obtained by using INTEGRAL / Swift /Burst Alert Telescope observations together with XMM–Newton , Chandra , ASCA and Swift /X-Ray Telescope data. We also present the general average properties of the sample, i.e. the distribution of photon indices, high-energy cut-offs, reflection fractions and absorption properties, together with an in-depth analysis of their parameter space. We find that the average Seyfert 1 power law has an index of 1.7 with a dispersion of 0.2. The mean cut-off energy is at around 100 keV, with most objects displaying E _c in the range 50–150 keV; the average amount of Compton reflection is 1.5 with a typical dispersion of 0.7. We do not find any convincing correlation between the various parameters, an indication that our analysis is not strongly dependent by the interplay between them. Finally, we investigate how the results presented in this work fit into current frameworks for AGN spectral modelling and cosmic diffuse X-ray background synthesis models.     

High-resolution computed microtomography for the characterization of a diffusion tensor imaging phantom

This paper addresses the issue of the quantitative characterization of the structure of the calibration model (phantom) for b-matrix spatial distribution diffusion tensor imaging (BSD-DTI) scanners. The aim of this study was to verify manufacturing assumptions of the structure of materials, since phantoms are used for BSD-DTI calibration directly after manufacturing. Visualization of the phantoms’ structure was achieved through optical microscopy and high-resolution computed microtomography (µCT). Using µCT images, a numerical model of the materials structure was developed for further quantitative analysis. 3D image characterization was performed to determine crucial structural parameters of the phantom: porosity, uniformity and distribution of equivalent diameter of capillary bundles. Additionally calculations of hypothetical flow streamlines were also performed based on the numerical model that was developed. The results obtained in this study can be used in the calibration of DTI-BST measurements. However, it was found that the structure of the phantom exhibits flaws and discrepancies from the assumed geometry which might affect BSD-DTI calibration.     

An Early Prediction of the Amplitude of Solar Cycle 25

A “Solar Dynamo” (SODA) Index prediction of the amplitude of Solar Cycle 25 is described. The SODA Index combines values of the solar polar magnetic field and the solar spectral irradiance at 10.7 cm to create a precursor of future solar activity. The result is an envelope of solar activity that minimizes the 11-year period of the sunspot cycle. We show that the variation in time of the SODA Index is similar to several wavelet transforms of the solar spectral irradiance at 10.7 cm. Polar field predictions for Solar Cycles 21?–?24 are used to show the success of the polar field precursor in previous sunspot cycles. Using the present value of the SODA index, we estimate that the next cycle’s smoothed peak activity will be about \(140 \pm30\) solar flux units for the 10.7 cm radio flux and a Version 2 sunspot number of \(135 \pm25\). This suggests that Solar Cycle 25 will be comparable to Solar Cycle 24. The estimated peak is expected to occur near \(2025.2 \pm1.5\) year. Because the current approach uses data prior to solar minimum, these estimates may improve as the upcoming solar minimum draws closer.