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Satellite
Kinds of Satellite Terms modified by Satellite Selected AbstractsAn assessment of the differences between three satellite snow cover mapping techniques,HYDROLOGICAL PROCESSES, Issue 18 2002David Bitner Abstract The National Operational Hydrologic Remote Sensing Center (NOHRSC) of the National Oceanic and Atmospheric Administration's (NOAA's) National Weather Service (NWS) provides daily satellite-derived snow cover maps to support the NWS Hydrologic Services Program covering the coterminous USA and Alaska. This study compared the NOHRSC snow cover maps with new automated snow cover maps produced by the National Environmental Satellite, Data, and Information Service (NESDIS) and the snow cover maps created from the Moderate Resolution Imaging Spectroradiometer (MODIS) imagery. The purpose of this paper is to demonstrate and account for the differences that occur between the three different snow cover mapping techniques. Because each of these snow cover products uses data from different sensors at different resolutions, the data were degraded to the coarsest relevant resolution. In both comparisons, forest canopy density was examined as a possible explanatory factor to account for those differences. NOHRSC snow cover maps were compared with NESDIS snow cover maps for 32 different dates from November 2000 to February 2001. NOHRSC snow cover maps were also compared with MODIS snow cover maps in the Pacific Northwest and the Great Plains for 18 days and 21 days, respectively, between March and June 2001. In the first comparison, where the NOHRSC product (,1 km) was degraded to match the resolution of the NESDIS data (,5 km), the two products showed an average agreement of 96%. Forest canopy density data provided only weak explanation for the differences between the NOHRSC and the NESDIS snow cover maps. In the second comparison, where the MODIS product (,500 m) was degraded to match the resolution of the NOHRSC product for two sample areas, the agreement was 94% in the study area in the Pacific Northwest, and 95% in the study area in the Great Plains. Published in 2002 by John Wiley & Sons, Ltd. [source] Comparison of different earth radiation budget experiment data sets over tropical oceansINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 3 2002Chang-Hoi Ho Abstract We compare radiation budgets derived from different Earth Radiation Budget Experiment (ERBE) archives over the tropical oceans (30S and 30N) from 1985 to 1989. Two ERBE data sets are used. One is taken from the Earth Radiation Budget Satellite (ERBS), and the other from the combined ERBS, National Oceanic and Atmospheric Administration (NOAA) 9, and NOAA 10 satellites. The domain-mean all-sky outgoing longwave radiation (OLR) derived from the combined data set shows a notable change in early 1987 when NOAA 10 replaced NOAA 9. This change is also found in longwave (LW) cloud radiative forcing (CRF), all-sky shortwave (SW) radiation, and SWCRF. The ERBS, however, does not show such changes. We also examine the sensitivity of cloud,radiation interaction to the sea surface temperature (SST) of the tropical oceans. In general, each component of radiative feedbacks derived from the two ERBE data have the same sign, although they show a certain degree of discrepancy in the magnitude. The discrepancy is more notable for averaged quantities over the entire tropical oceans, particularly over the subtropics where convective activities are relatively weak. The combined data show a larger sensitivity of LWCRF and SWCRF to SST than those of the ERBS, consistent with the above results. The response of clouds to an increase in SST has a net cooling effect when using the combined data but has a net heating effect when using the ERBS data (,0.80 W m,2 K,1 versus 0.48 W m,2 K,1). Most of the discrepancies of the net CRF between the two ERBE data sets can be accounted for by the difference in the sensitivity of all-sky OLR (4.52 W m,2 K,1 versus 1.73 W m,2 K,1). Copyright © 2002 Royal Meteorological Society. [source] Performance evaluation of TCP-based applications over DVB-RCS DAMA schemesINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 3 2009M. Luglio Abstract Transmission Control Protocol (TCP) performance over Digital Video Broadcasting,Return Channel via Satellite (DVB-RCS) standard is greatly affected by the total delay, which is mainly due to two components, propagation delay and access delay. Both are significant because they are dependent on the long propagation path of the satellite link. The former is intrinsic and due to radio wave propagation over the satellite channel for both TCP packets and acknowledgements. It is regulated by the control loop that governs TCP. The latter is due to the control loop that governs the demand assignment multiple access (DAMA) signalling exchange between satellite terminals and the network control center, necessary to manage return link resources. DAMA is adopted in DVB-RCS standard to achieve flexible and efficient use of the shared resources. Therefore, performance of TCP over DVB-RCS may degrade due to the exploitation of two nested control loops also depending on both the selected DAMA algorithm and the traffic profile. This paper analyses the impact of basic DAMA implementation on TCP-based applications over a DVB-RCS link for a large set of study cases. To provide a detailed overview of TCP performance in DVB-RCS environment, the analysis includes both theoretical approach and simulation campaign. Copyright © 2009 John Wiley & Sons, Ltd. [source] Robust frame synchronization for the DVB-S2 system with large frequency offsets,INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 1 2009Pansoo Kim Abstract This paper tackles the problem of frame synchronization design for the Digital Video Broadcasting standard via Satellite (DVB-S2) system. In particular, the design of a novel frame detection scheme exhibiting robustness against large frequency errors is proposed. Post-detection integration (PDI) is exploited to provide coarse frame alignment with limited complexity with respect to classical approximate maximum likelihood (ML) solutions. The novel scheme, denoted as differential generalized post-detection integration, derives from a pragmatic adaptation of the well-known generalized PDI scheme (IEEE Trans. Commun. 2007; 55(11):2159,2171), which eliminates its inherent source of weakness in the presence of large frequency offsets, i.e. its non-differential component given by non-coherent PDI. The proposed approach manages to reduce the remarkable performance gap with respect to approximate ML techniques available in the literature (IEEE Trans. Commun. 2002; 50(7):1062,1065), providing the designer with an interesting performance/complexity trade-off. Performance is numerically evaluated in terms of receiver operating characteristics and mean acquisition time (MAT), handling the acquisition procedure according to a single-dwell approach. Both threshold crossing and MAX criterion are contrasted to identify the best design solution. Copyright © 2008 John Wiley & Sons, Ltd. [source] GSE: A flexible, yet efficient, encapsulation for IP over DVB-S2 continuous generic streamsINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 3 2008Juan Cantillo Abstract The second-generation specification for Digital Video Broadcast over Satellite, DVB-S2, defines an improved and adaptive physical layer. A new framing structure at the link layer, known as the generic stream (GS), is introduced offering an alternative to the well-known MPEG transport stream (TS). This paper presents the requirements for and the design of an encapsulation protocol to transport IPv4 and IPv6 datagrams and other network protocol packets directly over DVB-S2 using this GS profile. The resulting generic stream encapsulation (GSE) is a novel method that provides flexible encapsulation with support for fragmentation. A flexible extension header format allows GSE to carry additional header information, suitable for enhanced features, such as link layer encryption and IP header compression. The paper assesses GSE performance by simulation using realistic traffic profiles and attenuation fading. This demonstrates considerable improvement in efficiency compared with the MPE/MPEG-2 TS, especially when used with adaptive coding and modulation (ACM). Although designed for DVB-S2 systems, the new encapsulation is suitable for other second-generation physical layer standards. Copyright © 2008 John Wiley & Sons, Ltd. [source] IPv6 networks over DVB-RCS satellite systemsINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 1 2008Ricardo Castellot Lou Abstract Satellite plays an important role in global information infrastructure (GII) and next generation networks (NGNs). Similarly, satellite communication systems have great advantages to support IPv6 (Internet Protocol version 6) networks as a technology that allows universal access to broadband e-services (audio, video, VPN, etc.). In the context of DVB-S2 (digital video broadcast-satellite) and DVB-RCS (digital video broadcast-return channel via satellite) standards, this paper presents the current SatSix project (satellite-based communications systems within IPv6 networks) within the European 6th Framework Programme, which is implementing innovative concepts and effective solutions (in relation with the economical cost) for broadband satellite systems and services using the technology presented above. This project is promoting the introduction of the IPv6 protocol into satellite-based communication systems. Moreover, through SatSix, the industry is addressing the next generation Internet, IPv6. It also enhances its competitive position in satellite broadband multimedia systems by exploiting the common components defined by the European DVB-S2 and DVB-RCS satellite broadband standards. Copyright © 2007 John Wiley & Sons, Ltd. [source] Satellite rural communications: telephony and narrowband networksINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 5 2005Roberto Conte Abstract Rural communications are important for large and developing countries, and telecommunications systems have been implemented depending upon the available technology at the time. Rural users do not generate the same amount of revenue as urban users do, thus lowering incentives for rural telecommunications investment with service to those regions delayed as long as possible. Voice and data communications are essential to the economic development of a region, and it has been shown that traffic increases rapidly as soon as the service is available. Satellite-based digital networks provide efficient long-distance service to rural communities at lower cost than similar land-based wired networks with acceptable quality. Small earth stations along with Wireless Local Loops can provide both local and long-distance service efficiently and at low cost, offering digital multimedia services on a global scale. This paper focuses on the description of different narrowband technologies used to service rural communities, namely basic telephone and low-bit-rate data (<64 kbps) applications through the use of satellite and terrestrial wireless systems. A basic network economic planning description is presented, and important parameters such as satellite network size, topology and multiple access are identified in order to improve the process of effective and cost-efficient rural communications network design. Copyright © 2005 John Wiley & Sons, Ltd. [source] Simplifying Detection of Cognitive Impairment: Comparison of the Mini-Cog and Mini-Mental State Examination in a Multiethnic SampleJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 5 2005Soo Borson MD Objectives: To compare detection of cognitive impairment using the Mini-Cog and Mini-Mental State Examination (MMSE) and to identify sociodemographic variables that influence detection in an ethnoculturally diverse sample. Design: Cross-sectional. Setting: A registry of the University of Washington Alzheimer's Disease Research Center Satellite. Participants: A heterogeneous community sample (n=371) of predominantly ethnic minority elderly assessed using a standardized research protocol, 231 of whom met criteria for dementia or mild cognitive impairment (MCI). Measurements: Demographic data, a standardized research protocol for cognitive assessment and dementia diagnosis, MMSE, and Mini-Cog. Results: Both screens effectively detected cognitive impairment, the Mini-Cog slightly better than the MMSE (P<.01). Overall accuracy of classification was 83% for the Mini-Cog and 81% for the MMSE. The Mini-Cog was superior in recognizing patients with Alzheimer-type dementias (P=.05). Low education negatively affected detection using the MMSE (P<.001), whereas education did not affect the Mini-Cog, and low literacy minimally affected it. Conclusion: The Mini-Cog detects clinically significant cognitive impairment as well as or better than the MMSE in multiethnic elderly individuals, is easier to administer to non-English speakers, and is less biased by low education and literacy. [source] Evaluation of the reduction of imidazophenazine dye derivatives under fast-atom-bombardment mass-spectrometric conditions,JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 1 2006Marina V. Kosevich Abstract Satellite [M + 2]+, and [M + 3]+ peaks accompanying the common peak of the protonated molecule [M + H]+ that are known to indicate the occurrence of a reduction process were observed in the fast atom bombardment (FAB) mass spectra of imidazophenazine dye derivatives in glycerol matrix. The distribution of the abundances in the [M + nH]+ peak group varied noticeably for different derivatives. This indicated different levels of the reduction depending on the different structure variations of the studied molecules. In the search for correlations between the mass spectral pattern and the structural features of the dyes, ab initio HF/6-31++G** quantum chemical calculations were performed. They revealed that the abundances of the [M + 2]+, and [M + 3]+ ions show growth proportional to the decrease of the energy of the lowest unoccupied molecular orbital, i.e. proportional to the increase of the electron affinity of the dye molecule. A method for rapid screening of reductive properties of sets of dye derivatives on the basis of the FAB mass spectral data is discussed. Copyright © 2005 John Wiley & Sons, Ltd. [source] Beyond the Courtroom Workgroup: Caseworkers as the New Satellite of Social ControlLAW & POLICY, Issue 4 2009URSULA CASTELLANO Many jurisdictions nationwide are faced with overcrowded jails, backlogged court dockets, and high rates of recidivism for mostly nonviolent offenders. To address these complex problems, law enforcement officials have institutionalized alternatives to incarceration programs, including work furloughs, electronic monitoring, and treatment courts. These recent trends in legal reform are designed to reduce and prevent criminal behavior by helping to reintegrate defendants back into their local communities. One aspect that has been largely unaddressed in prior research is that jail-alternative programs are primarily staffed by caseworkers with outside nonprofit agencies. This important group of nonlegal actors plays a pivotal role in crafting decisions to divert low-level offenders from the criminal justice system; few studies, however, explore the organizational contexts surrounding caseworkers' everyday decision-making practices. In response, I draw upon ethnographic data to analyze the ways that pretrial release caseworkers in a California county evaluate defendants' entitlement to release on their own recognizance. The results of this study suggest that caseworkers exercise discretion beyond the traditional power structure of the courtroom workgroup. I conclude that caseworkers emerge as the new satellite of social control in contemporary courts. [source] The PSCz dipole revisitedMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2006Spyros Basilakos ABSTRACT We re-examine the gravitational acceleration (dipole) induced on the Local Group of galaxies by the Infrared Astronomical Satellite (IRAS) galaxy distribution of the Point Source Catalog redshift (PSCz) survey. We treat the cirrus-affected low galactic latitudes by utilizing a spherical harmonic expansion of the galaxy surface density field up to the octapole order. We find strong indications for significant contributions to the Local Group motion from depths up to ,185 h,1 Mpc and a possible contribution even from ,210 h,1 Mpc, in agreement with the recent analysis of Kocevski & Ebeling of a whole-sky X-ray cluster survey. What changes with respect to the previous PSCz dipole analyses is: (i) the large-scale dipole contributions and (ii) an increase of the overall dipole amplitude due to the important contribution of the local volume (, 4 h,1 Mpc), which we now take into account. This results in a lower value of the , (,,0.6m/b) parameter, which we find to be ,IRAS, 0.49 in real space. Therefore, for the concordance cosmological model (,m= 1 ,,,= 0.3), the IRAS galaxies bias factor is bIRAS, 1, which means that IRAS galaxies are good tracers of the underlying matter distribution. [source] The potential of long-wavelength satellite-borne radar to support implementation of the Ramsar Wetlands ConventionAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 3 2007Ake Rosenqvist Abstract 1.This paper provides an introduction to Synthetic Aperture Radar (SAR) remote sensing and, in particular, the significance of long-wavelength (L-band) SAR for wetland applications relevant to the Ramsar Wetlands Convention. 2.The Convention has long been a supporter of effective wetland inventory being used to support management initiatives and the wise use of all wetlands. 3.Three major application areas have been identified where SAR data may constitute an important additional information source for wetland inventory and management. These comprise mapping of below-canopy inundation, monitoring of environmental disturbances and wetland inventories based on SAR mosaics. These areas have all previously been supported in general terms by formal resolutions on wetland inventory and assessment through the Convention with recognition that further technique development was required. 4.The potential to make further use of remote sensing is increased through wider use of the special features of SAR in situations where other data are less suitable. 5.The Japanese Advanced Land Observing Satellite (ALOS) provides an opportunity to support the Convention and its goal of wise use of all wetlands. Copyright © 2007 John Wiley & Sons, Ltd. [source] The potential of L-band SAR for quantifying mangrove characteristics and change: case studies from the tropicsAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 3 2007Richard M. Lucas Abstract 1.The Japan Aerospace Exploration Agency's (JAXA) Advanced Land Observing Satellite (ALOS) L-band Phased Array Synthetic Aperture Radar (PALSAR), launched successfully in January 2006, will provide new data sets for coastal ecosystems mapping and change monitoring at local to global scales. 2.To evaluate L-band capability for mangrove applications, data acquired by the NASA airborne SAR (AIRSAR) and Japanese Earth Resources Satellite (JERS-1 SAR) over sites in Australia, French Guiana and Malaysia were used to demonstrate benefits for mapping extent and zones, retrieving biomass and structural attributes (e.g. height), and detecting change. 3.The research indicates that mapping is most effective where mangroves border non-forested areas and where differences in structure, as a function of species, growth stage and biomass distributions, occur between zones. 4.Using L-band SAR, biomass can be retrieved up to ,100,140 Mg ha,1, although retrieval is complicated by a noticeable decrease in L-band backscattering coefficient within higher (,>200 Mg ha,1) biomass stands, particularly those with extensive prop root systems. 5.Change detection through multi-temporal comparison of data proved useful for mapping deforestation/regeneration and mangrove dynamics associated with changing patterns of sedimentation. 6.The research highlights the likely benefits and limitations of using ALOS PALSAR data and supports JAXA's Kyoto & Carbon (K&C) Initiative in promoting the use of these data for regional mangrove assessment. Copyright © 2007 John Wiley & Sons, Ltd. [source] Occupancy frequency distributions: patterns, artefacts and mechanismsBIOLOGICAL REVIEWS, Issue 3 2002MELODIE A. McGEOCH ABSTRACT Numerous hypotheses have been proposed to explain the shape of occupancy frequency distributions (distributions of the numbers of species occupying different numbers of areas). Artefactual effects include sampling characteristics, whereas biological mechanisms include organismal, niche-based and metapopulation models. To date, there has been little testing of these models. In addition, although empirically derived occupancy distributions encompass an array of taxa and spatial scales, comparisons between them are often not possible because of differences in sampling protocol and method of construction. In this paper, the effects of sampling protocol (grain, sample number, extent, sampling coverage and intensity) on the shape of occupancy distributions are examined, and approaches for minimising artefactual effects recommended. Evidence for proposed biological determinants of the shape of occupancy distributions is then examined. Good support exists for some mechanisms (habitat and environmental heterogeneity), little for others (dispersal ability), while some hypotheses remain untested (landscape productivity, position in geographic range, range size frequency distributions), or are unlikely to be useful explanations for the shape of occupancy distributions (species specificity and adaptation to habitat, extinction,colonization dynamics). The presence of a core (class containing species with the highest occupancy) mode in occupancy distributions is most likely to be associated with larger sample units, and small homogenous sampling areas positioned well within and towards the range centers of a sufficient proportion of the species in the assemblage. Satellite (class with species with the lowest occupancy) modes are associated with sampling large, heterogeneous areas that incorporate a large proportion of the assemblage range. However, satellite modes commonly also occur in the presence of a core mode, and rare species effects are likely to contribute to the presence of a satellite mode at most sampling scales. In most proposed hypotheses, spatial scale is an important determinant of the shape of the observed occupancy distribution. Because the attributes of the mechanisms associated with these hypotheses change with spatial scale, their predictions for the shape of occupancy distributions also change. To understand occupancy distributions and the mechanisms underlying them, a synthesis of pattern documentation and model testing across scales is thus needed. The development of null models, comparisons of occupancy distributions across spatial scales and taxa, documentation of the movement of individual species between occupancy classes with changes in spatial scale, as well as further testing of biological mechanisms are all necessary for an improved understanding of the distribution of species and assemblages within their geographic ranges. [source] Detection and Analysis of Strong Oscillating Electric Fields in a Picosecond Laser Plasma with the Help of Plasma Satellites of X-ray Spectral LinesCONTRIBUTIONS TO PLASMA PHYSICS, Issue 3-4 2005V. S. Belyaev Abstract X-ray lines of ions in a solid target interacting with picosecond laser pulses of the intensity ,3 × 1017 W/cm2 were studied on the "Neodim" laser facility. We observed X-ray Ly, emission spectra of hydrogen-like fluorine ions. Satellite lines were also recorded, evidencing the presence of intense plasma oscillations with an amplitude of the electric field larger than 108 V/cm and a frequency of about 1015 s,1. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Development and Simulation of an Embedded Hydrogen Peroxide Catalyst Chamber in Low-Temperature Co-Fired CeramicsINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 5 2007Donald Plumlee Satellites in the range of 10,50 kg require small propulsion devices to perform station-keeping tasks in orbit. Low-temperature co-fired ceramic structures provide a unique platform to produce a reliable, low-cost micropropulsion system. The design uses microchannels embedded in the ceramic substrate to create a nozzle and embedded catalyst chamber. A hydrogen peroxide monopropellant is injected into a silver-coated catalyst chamber structure. The monopropellant decomposes into hot gas, which is expelled through the nozzle producing thrust. A thermal energy balance and a kinetic model is presented along with performance testing. [source] Reliable multicast via satellite: a comparison survey and taxonomyINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 1 2001Martin W. Koyabe Abstract IP multicasting is an important service, which will be provided by the next generation Internet. A range of applications has emerged which take the advantage of multicast delivery. However, several factors currently hinder large-scale deployment of terrestrial multicast services. It is particularly difficult to support delivery to large groups of users. Satellites offer a natural way to extend the multicast service to reach this large number of users. They may offer high capacity (especially when using next generation satellite systems) and also eliminate the need for a large number of intermediate routing hops. There are important differences in the way multicast applications operate over satellite. This paper therefore reviews the key design paradigm and offers a critical comparison between different reliable multicast protocol techniques based on a taxonomy. The suitability of a set of the most common reliable multicast protocols is assessed within a satellite environment and conclusions are presented. Copyright © 2001 John Wiley & Sons, Ltd. [source] Satellites to the 7th International Congress of NeuroendocrinologyJOURNAL OF NEUROENDOCRINOLOGY, Issue 5 2010Article first published online: 19 APR 2010 No abstract is available for this article. [source] Conclusion to the Featured Series on Satellites and Transboundary Water: Emerging Ideas,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 4 2010Faisal Hossain Hossain, Faisal, 2010. Conclusion to the Featured Series on Satellites and Transboundary Water: Emerging Ideas. Journal of the American Water Resources Association (JAWRA) 46(4): 663-664. DOI: 10.1111/j.1752-1688.2010.00449.x [source] Satellite Precipitation Measurements for Water Resource Monitoring,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 3 2009Chris Kidd Abstract:, Satellites offer an unrivaled vantage point to observe and measure Earth system processes and parameters. Observations of meteorological phenomena permit a more holistic view of the weather and climate that is not possible through conventional surface observations. Precipitation (rain and snow) in particular, benefit from such observations since precipitation is spatially and temporally highly variable: conventional gauge and radar measurements tend to be land-based with variable coverage. This paper provides an overview of the satellite systems that provide the observations, the techniques used to derive precipitation from the observations, and examples of the precipitation products available for users to access. [source] A Declaration of IndependenceECONOMIC AFFAIRS, Issue 4 2000David Graham Television was a true mass medium, its ,classic' output located within the concerns and lives of ordinary people. Television was also the amphitheatre of the nation, in which great events were played out. As a result of its massive power, regulation was imposed on it. By the 1970s, the unitary power of national channels was beginning to break down, first with the arrival of the VCR, then with satellite and cable. Along with this, came a growing separation of the broadcasting from the creative or programme making function driven by ,independent' producers. This divergence is now being hastened by the end of ,spectrum scarcity'. Creative companies and teams will strive to control their work and share in the rewards of their success in a way that will create a very different kind of entertainment industry in the 21st Century. [source] Can late summer Landsat data be used for locating Asian migratory locust, Locusta migratoria migratoria, oviposition sites in the Amudarya River delta, Uzbekistan?ENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2008Ramesh Sivanpillai Abstract Existing survey methods for assessing the Asian migratory locust, Locusta migratoria migratoria L. (Orthoptera: Acrididae), infestation risk in the Amudarya River delta, Uzbekistan, are largely constrained by economic resources and site accessibility. The surveys are restricted to a few easily accessible areas, which leads to a misinterpretation of the threat of locust infestation. This often results in indiscriminate blanket treatments of vast areas of wetlands with broad-spectrum insecticides, which may adversely impact non-target fauna and flora. In order to minimize the bias during surveys, one approach would be to allocate the sampling locations based on the distribution of the primary food and shelter plant of the locusts, the common reed, Phragmites australis (Cav.) Trin. ex Steud (Poaceae). In this study, we evaluated the utility of satellite-based remotely sensed data (Landsat TM) acquired in August 2006 to characterize reed distribution in the delta and identify potential locust oviposition sites. The overall accuracy of the Landsat data to map land cover classes in the delta was 84%. The Landsat TM data identified 90% of the reeds, but it was less useful in identifying areas where other vegetations (shrubs and grasses) were mixed with reeds. During the following summer field survey in June 2007, we identified 37 sites that were infested with early-instar locusts. The low migration capacity of young nymphs in dense reed vegetation allowed us to presume that these sites were used for oviposition in the previous summer. Twenty-eight (74%) of these 37 sites had reeds in the previous year. Results from these studies demonstrate that reed distribution maps derived from satellite data could be used for targeting locust egg-pod survey locations, in order to minimize sampling bias while predicting locust infestation risks for the following season. [source] Global statistical analysis of MISR aerosol data: a massive data product from NASA's Terra satelliteENVIRONMETRICS, Issue 7 2007Tao Shi Abstract In climate models, aerosol forcing is the major source of uncertainty in climate forcing, over the industrial period. To reduce this uncertainty, instruments on satellites have been put in place to collect global data. However, missing and noisy observations impose considerable difficulties for scientists researching the global distribution of aerosols, aerosol transportation, and comparisons between satellite observations and global-climate-model outputs. In this paper, we fit a Spatial Mixed Effects (SME) statistical model to predict the missing values, denoise the observed values, and quantify the spatial-prediction uncertainties. The computations associated with the SME model are linear scalable to the number of data points, which makes it feasible to process massive global satellite data. We apply the methodology, which is called Fixed Rank Kriging (FRK), to the level-3 Aerosol Optical Depth (AOD) dataset collected by NASA's Multi-angle Imaging SpectroRadiometer (MISR) instrument flying on the Terra satellite. Overall, our results were superior to those from non-statistical methods and, importantly, FRK has an uncertainty measure associated with it that can be used for comparisons over different regions or at different time points. Copyright © 2007 John Wiley & Sons, Ltd. [source] Severe Deep Moist Convective Storms: Forecasting and MitigationGEOGRAPHY COMPASS (ELECTRONIC), Issue 1 2008David L. Arnold Small-scale (2,20 km) circulations, termed ,severe deep moist convective storms', account for a disproportionate share of the world's insured weather-related losses. Spatial frequency maximums of severe convective events occur in South Africa, India, Mexico, the Caucasus, and Great Plains/Prairies region of North America, where the maximum tornado frequency occurs east of the Rocky Mountains. Interest in forecasting severe deep moist convective systems, especially those that produce tornadoes, dates to 1884 when tornado alerts were first provided in the central United States. Modern thunderstorm and tornado forecasting relies on technology and theory, but in the post-World War II era interest in forecasting has also been driven by public pressure. The forecasting process begins with a diagnostic analysis, in which the forecaster considers the potential of the atmospheric environment to produce severe convective storms (which requires knowledge of the evolving kinematic and thermodynamic fields, and the character of the land surface over which the storms will pass), and the likely character of the storms that may develop. Improvements in forecasting will likely depend on technological advancements, such as the development of phased-array radar systems and finer resolution numerical weather prediction models. Once initiated, the evolution of deep convective storms is monitored by satellite and radar. Mitigation of the hazards posed by severe deep moist convective storms is a three-step process, involving preparedness, response, and recovery. Preparedness implies that risks have been identified and organizations and individuals are familiar with a response plan. Response necessitates that potential events are identified before they occur and the developing threat is communicated to the public. Recovery is a function of the awareness of local, regional, and even national governments to the character and magnitude of potential events in specific locations, and whether or not long-term operational plans are in place at the time of disasters. [source] The birth of sedimentology: Henry Clifton Sorby and Johannes WaltherGEOLOGY TODAY, Issue 6 2009Hakuyu Okada Sedimentology is the study of naturally occurring particulate matter with special emphasis on understanding the factors controlling the creation, distribution and accumulation of that matter. Consequently, sedimentology can, and does, embrace geomorphology and climatology, transport mechanisms, depositional environments and lithifaction processes. Its significance lies in the ability of practitioners of the subject,sedimentologists,to determine each and all of the foregoing through the study of samples of sediments and sedimentary rocks. It is, therefore, a basic discipline for the study of past and present environments on Earth, its satellite and its planetary neighbours. The long-standing contributions of two of the nineteenth century founders of the subject, Henry Clifton Sorby (1826,1908) and Johannes Walther (1860,1937), are discussed here. [source] Models of Earth's main magnetic field incorporating flux and radial vorticity constraintsGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2007A. Jackson SUMMARY We describe a new technique for implementing the constraints on magnetic fields arising from two hypotheses about the fluid core of the Earth, namely the frozen-flux hypothesis and the hypothesis that the core is in magnetostrophic force balance with negligible leakage of current into the mantle. These hypotheses lead to time-independence of the integrated flux through certain ,null-flux patches' on the core surface, and to time-independence of their radial vorticity. Although the frozen-flux hypothesis has received attention before, constraining the radial vorticity has not previously been attempted. We describe a parametrization and an algorithm for preserving topology of radial magnetic fields at the core surface while allowing morphological changes. The parametrization is a spherical triangle tesselation of the core surface. Topology with respect to a reference model (based on data from the Oersted satellite) is preserved as models at different epochs are perturbed to optimize the fit to the data; the topology preservation is achieved by the imposition of inequality constraints on the model, and the optimization at each iteration is cast as a bounded value least-squares problem. For epochs 2000, 1980, 1945, 1915 and 1882 we are able to produce models of the core field which are consistent with flux and radial vorticity conservation, thus providing no observational evidence for the failure of the underlying assumptions. These models are a step towards the production of models which are optimal for the retrieval of frozen-flux velocity fields at the core surface. [source] The SGR 1806-20 magnetar signature on the Earth's magnetic fieldGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2006M. Mandea SUMMARY SGRs denote ,soft ,-ray repeaters', a small class of slowly spinning neutron stars with strong magnetic fields. On 2004 December 27, a giant flare was detected from magnetar SGR 1806-20. The initial spike was followed by a hard-X-ray tail persisting for 380 s with a modulation period of 7.56 s. This event has received considerable attention, particularly in the astrophysics area. Its relevance to the geophysics community lies in the importance of investigating the effects of such an event on the near-Earth electromagnetic environment. However, the signature of a magnetar flare on the geomagnetic field has not previously been investigated. Here, by applying wavelet analysis to the high-resolution magnetic data provided by the CHAMP satellite, a modulated signal with a period of 7.5 s over the duration of the giant flare appears in the observed data. Moreover, this event was detected by the energetic ion counters onboard the DEMETER satellite. [source] Sea-surface observations of the magnetic signals of ocean swellsGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2004F. E. M. Lilley SUMMARY Ocean swells have a magnetic signal, caused by the motional induction of sea water moving in the steady main magnetic field of Earth. To check the character of such signals at the sea surface, a magnetometer has been set free from a ship to float unrestricted on the surface of the ocean for periods of several days. The path of the floating magnetometer was tracked by satellite; this procedure enabled also the eventual recovery of the magnetometer by the ship. Superimposed upon a background of slow change of magnetic field, as the magnetometer drifted across different patterns of crustal magnetization, are high-frequency signals generated by the strong ocean swell present at the time. These wave-generated signals are typically up to 5 nT trough-to-peak, consistent with theory for their generation by ocean swells several metres trough-to-peak in height. The power spectra of the magnetic signals show a consistent peak at period 13 s, appropriate for the known characteristics of ocean swell in the area. The power spectra then exhibit a strong (,7 power) fall-off as period decreases below 13 s. This strong fall-off is consistent with oceanographic observations of the spectra of surface swell, combined with motional induction theory. [source] A comprehensive model of the quiet-time, near-Earth magnetic field: phase 3GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2002Terence J. Sabaka Summary The near-Earth magnetic field is caused by sources in the Earth's core, ionosphere, magnetosphere, lithosphere and from coupling currents between the ionosphere and the magnetosphere, and between hemispheres. Traditionally, the main field (low degree internal field) and magnetospheric field have been modelled simultaneously, with fields from other sources being modelled separately. Such a scheme, however, can introduce spurious features, especially when the spatial and temporal scales of the fields overlap. A new model, designated CM3 (Comprehensive Model: phase 3), is the third in a series of efforts to coestimate fields from all of these sources. This model has been derived from quiet-time Magsat and POGO satellite and observatory hourly means measurements for the period 1960,1985. It represents a significant advance in the treatment of the aforementioned field sources over previous attempts, and includes an accounting for main field influences on the magnetosphere, main field and solar activity influences on the ionosphere, seasonal influences on the coupling currents, a priori characterization of the influence of the ionosphere and the magnetosphere on Earth-induced fields, and an explicit parametrization and estimation of the lithospheric field. The result is a model that describes well the 591 432 data with 16 594 parameters, implying a data-to-parameter ratio of 36, which is larger than several popular field models. [source] Correlation between sea surface topography and bathymetry in shallow shelf waters in the Western MediterraneanGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2002G. Rodríguez Velasco Summary In this paper, gravimetric and altimetric data are used to assess an estimation of the sea surface topography in the Western Mediterranean Sea. This is a complex area from different points of view, due to the presence of several islands, coastal lines, shallow waters and a peculiar hydrologic equilibrium due to its proximity to the Atlantic water exchange area. First, a gravimetric geoid was computed using the least-squares collocation (LSC) procedure with the classical remove-restore technique. We also present a local mean sea surface generated from repeat ERS-1 altimeter data fitted to TOPEX. We chose this satellite because it offers a better spatial resolution than the TOPEX data. The time span used in the computations is one year. This is a useful interval for averaging out the regular seasonal variations, which are very large in this area. We present the comparisons between the gravimetric geoidal heights and the adjusted sea surface. This is a way to obtain a rough estimation of the sea surface topography (SST) since we also include the errors in the two surfaces and other oceanic signals. The differences obtained are physically reasonable with a mean of 17 cm and standard deviation (s.d.) of 39 cm. A significant similarity is observed between the features reproduced by these differences and the bathymetry in the area, suggesting some sort of correlation between both magnitudes for the studied region. If we accept such correlation, the SST may be described as a function of depth. This procedure lets us filter out the short wavelength part of the geoid from the first SST estimation. [source] | |||||||||||||||||||||||||||||||