Showing papers by "Universities Space Research Association published in 2012"

Xenon-133 and caesium-137 releases into the atmosphere from the Fukushima Dai-ichi nuclear power plant: determination of the source term, atmospheric dispersion, and deposition

Abstract: . On 11 March 2011, an earthquake occurred about 130 km off the Pacific coast of Japan's main island Honshu, followed by a large tsunami. The resulting loss of electric power at the Fukushima Dai-ichi nuclear power plant developed into a disaster causing massive release of radioactivity into the atmosphere. In this study, we determine the emissions into the atmosphere of two isotopes, the noble gas xenon-133 (133Xe) and the aerosol-bound caesium-137 (137Cs), which have very different release characteristics as well as behavior in the atmosphere. To determine radionuclide emissions as a function of height and time until 20 April, we made a first guess of release rates based on fuel inventories and documented accident events at the site. This first guess was subsequently improved by inverse modeling, which combined it with the results of an atmospheric transport model, FLEXPART, and measurement data from several dozen stations in Japan, North America and other regions. We used both atmospheric activity concentration measurements as well as, for 137Cs, measurements of bulk deposition. Regarding 133Xe, we find a total release of 15.3 (uncertainty range 12.2–18.3) EBq, which is more than twice as high as the total release from Chernobyl and likely the largest radioactive noble gas release in history. The entire noble gas inventory of reactor units 1–3 was set free into the atmosphere between 11 and 15 March 2011. In fact, our release estimate is higher than the entire estimated 133Xe inventory of the Fukushima Dai-ichi nuclear power plant, which we explain with the decay of iodine-133 (half-life of 20.8 h) into 133Xe. There is strong evidence that the 133Xe release started before the first active venting was made, possibly indicating structural damage to reactor components and/or leaks due to overpressure which would have allowed early release of noble gases. For 137Cs, the inversion results give a total emission of 36.6 (20.1–53.1) PBq, or about 43% of the estimated Chernobyl emission. Our results indicate that 137Cs emissions peaked on 14–15 March but were generally high from 12 until 19 March, when they suddenly dropped by orders of magnitude at the time when spraying of water on the spent-fuel pool of unit 4 started. This indicates that emissions may not have originated only from the damaged reactor cores, but also from the spent-fuel pool of unit 4. This would also confirm that the spraying was an effective countermeasure. We explore the main dispersion and deposition patterns of the radioactive cloud, both regionally for Japan as well as for the entire Northern Hemisphere. While at first sight it seemed fortunate that westerly winds prevailed most of the time during the accident, a different picture emerges from our detailed analysis. Exactly during and following the period of the strongest 137Cs emissions on 14 and 15 March as well as after another period with strong emissions on 19 March, the radioactive plume was advected over Eastern Honshu Island, where precipitation deposited a large fraction of 137Cs on land surfaces. Radioactive clouds reached North America on 15 March and Europe on 22 March. By middle of April, 133Xe was fairly uniformly distributed in the middle latitudes of the entire Northern Hemisphere and was for the first time also measured in the Southern Hemisphere (Darwin station, Australia). In general, simulated and observed concentrations of 133Xe and 137Cs both at Japanese as well as at remote sites were in good quantitative agreement. Altogether, we estimate that 6.4 PBq of 137Cs, or 18% of the total fallout until 20 April, were deposited over Japanese land areas, while most of the rest fell over the North Pacific Ocean. Only 0.7 PBq, or 1.9% of the total fallout were deposited on land areas other than Japan.

Xenon-133 and caesium-137 releases into the atmosphere from the Fukushima Dai-ichi nuclear power plant: determination of the source term, atmospheric dispersion, and deposition

Abstract: . On 11 March 2011, an earthquake occurred about 130 km off the Pacific coast of Japan's main island Honshu, followed by a large tsunami. The resulting loss of electric power at the Fukushima Dai-ichi nuclear power plant developed into a disaster causing massive release of radioactivity into the atmosphere. In this study, we determine the emissions into the atmosphere of two isotopes, the noble gas xenon-133 (133Xe) and the aerosol-bound caesium-137 (137Cs), which have very different release characteristics as well as behavior in the atmosphere. To determine radionuclide emissions as a function of height and time until 20 April, we made a first guess of release rates based on fuel inventories and documented accident events at the site. This first guess was subsequently improved by inverse modeling, which combined it with the results of an atmospheric transport model, FLEXPART, and measurement data from several dozen stations in Japan, North America and other regions. We used both atmospheric activity concentration measurements as well as, for 137Cs, measurements of bulk deposition. Regarding 133Xe, we find a total release of 15.3 (uncertainty range 12.2–18.3) EBq, which is more than twice as high as the total release from Chernobyl and likely the largest radioactive noble gas release in history. The entire noble gas inventory of reactor units 1–3 was set free into the atmosphere between 11 and 15 March 2011. In fact, our release estimate is higher than the entire estimated 133Xe inventory of the Fukushima Dai-ichi nuclear power plant, which we explain with the decay of iodine-133 (half-life of 20.8 h) into 133Xe. There is strong evidence that the 133Xe release started before the first active venting was made, possibly indicating structural damage to reactor components and/or leaks due to overpressure which would have allowed early release of noble gases. For 137Cs, the inversion results give a total emission of 36.6 (20.1–53.1) PBq, or about 43% of the estimated Chernobyl emission. Our results indicate that 137Cs emissions peaked on 14–15 March but were generally high from 12 until 19 March, when they suddenly dropped by orders of magnitude at the time when spraying of water on the spent-fuel pool of unit 4 started. This indicates that emissions may not have originated only from the damaged reactor cores, but also from the spent-fuel pool of unit 4. This would also confirm that the spraying was an effective countermeasure. We explore the main dispersion and deposition patterns of the radioactive cloud, both regionally for Japan as well as for the entire Northern Hemisphere. While at first sight it seemed fortunate that westerly winds prevailed most of the time during the accident, a different picture emerges from our detailed analysis. Exactly during and following the period of the strongest 137Cs emissions on 14 and 15 March as well as after another period with strong emissions on 19 March, the radioactive plume was advected over Eastern Honshu Island, where precipitation deposited a large fraction of 137Cs on land surfaces. Radioactive clouds reached North America on 15 March and Europe on 22 March. By middle of April, 133Xe was fairly uniformly distributed in the middle latitudes of the entire Northern Hemisphere and was for the first time also measured in the Southern Hemisphere (Darwin station, Australia). In general, simulated and observed concentrations of 133Xe and 137Cs both at Japanese as well as at remote sites were in good quantitative agreement. Altogether, we estimate that 6.4 PBq of 137Cs, or 18% of the total fallout until 20 April, were deposited over Japanese land areas, while most of the rest fell over the North Pacific Ocean. Only 0.7 PBq, or 1.9% of the total fallout were deposited on land areas other than Japan.

The Spitzer Space Telescope Survey of the Orion A and B Molecular Clouds. I. A Census of Dusty Young Stellar Objects and a Study of Their Mid-infrared Variability

Abstract: We present a survey of the Orion A and B molecular clouds undertaken with the IRAC and MIPS instruments on board Spitzer. In total, five distinct fields were mapped, covering 9 deg^2 in five mid-IR bands spanning 3-24 μm. The survey includes the Orion Nebula Cluster, the Lynds 1641, 1630, and 1622 dark clouds, and the NGC 2023, 2024, 2068, and 2071 nebulae. These data are merged with the Two Micron All Sky Survey point source catalog to generate a catalog of eight-band photometry. We identify 3479 dusty young stellar objects (YSOs) in the Orion molecular clouds by searching for point sources with mid-IR colors indicative of reprocessed light from dusty disks or infalling envelopes. The YSOs are subsequently classified on the basis of their mid-IR colors and their spatial distributions are presented. We classify 2991 of the YSOs as pre-main-sequence stars with disks and 488 as likely protostars. Most of the sources were observed with IRAC in two to three epochs over six months; we search for variability between the epochs by looking for correlated variability in the 3.6 and 4.5 μm bands. We find that 50% of the dusty YSOs show variability. The variations are typically small (~0.2 mag) with the protostars showing a higher incidence of variability and larger variations. The observed correlations between the 3.6, 4.5, 5.8, and 8 μm variability suggests that we are observing variations in the heating of the inner disk due to changes in the accretion luminosity or rotating accretion hot spots.

Swift j2058.4+0516: discovery of a possible second relativistic tidal disruption flare?

Abstract: We report the discovery by the Swift hard X-ray monitor of the transient source Swift J2058.4+0516 (Sw J2058+05). Our multi-wavelength follow-up campaign uncovered a long-lived (duration ≳ months), luminous X-ray (L_(X, iso) ≈ 3 × 10^(47) erg s^(–1)) and radio (νL_(ν, iso) ≈ 10^(42) erg s^(–1)) counterpart. The associated optical emission, however, from which we measure a redshift of 1.1853, is relatively faint, and this is not due to a large amount of dust extinction in the host galaxy. Based on numerous similarities with the recently discovered GRB 110328A/Swift J164449.3+573451 (Sw J1644+57), we suggest that Sw J2058+05 may be the second member of a new class of relativistic outbursts resulting from the tidal disruption of a star by a supermassive black hole. If so, the relative rarity of these sources (compared with the expected rate of tidal disruptions) implies that either these outflows are extremely narrowly collimated (θ < 1°) or only a small fraction of tidal disruptions generate relativistic ejecta. Analogous to the case of long-duration gamma-ray bursts and core-collapse supernovae, we speculate that rapid spin of the black hole may be a necessary condition to generate the relativistic component. Alternatively, if powered by gas accretion (i.e., an active galactic nucleus (AGN)), Sw J2058+05 would seem to represent a new mode of variability in these sources, as the observed properties appear largely inconsistent with known classes of AGNs capable of generating relativistic jets (blazars, narrow-line Seyfert 1 galaxies).

Global and regional trends of aerosol optical depth over land and ocean using SeaWiFS measurements from 1997 to 2010

Abstract: . Both sensor calibration and satellite retrieval algorithm play an important role in the ability to determine accurately long-term trends from satellite data. Owing to the unprecedented accuracy and long-term stability of its radiometric calibration, SeaWiFS measurements exhibit minimal uncertainty with respect to sensor calibration. In this study, we take advantage of this well-calibrated set of measurements by applying a newly-developed aerosol optical depth (AOD) retrieval algorithm over land and ocean to investigate the distribution of AOD, and to identify emerging patterns and trends in global and regional aerosol loading during its 13-yr mission. Our correlation analysis between climatic indices (such as ENSO) and AOD suggests strong relationships for Saharan dust export as well as biomass-burning activity in the tropics, associated with large-scale feedbacks. The results also indicate that the averaged AOD trend over global ocean is weakly positive from 1998 to 2010 and comparable to that observed by MODIS but opposite in sign to that observed by AVHRR during overlapping years. On regional scales, distinct tendencies are found for different regions associated with natural and anthropogenic aerosol emission and transport. For example, large upward trends are found over the Arabian Peninsula that indicate a strengthening of the seasonal cycle of dust emission and transport processes over the whole region as well as over downwind oceanic regions. In contrast, a negative-neutral tendency is observed over the desert/arid Saharan region as well as in the associated dust outflow over the north Atlantic. Additionally, we found decreasing trends over the eastern US and Europe, and increasing trends over countries such as China and India that are experiencing rapid economic development. In general, these results are consistent with those derived from ground-based AERONET measurements.

An analysis of AERONET aerosol absorption properties and classifications representative of aerosol source regions

Abstract: Partitioning of mineral dust, pollution, smoke, and mixtures using remote sensing techniques can help improve accuracy of satellite retrievals and assessments of the aerosol radiative impact on climate. Spectral aerosol optical depth (tau) and single scattering albedo (omega (sub 0) ) from Aerosol Robotic Network (AERONET) measurements are used to form absorption [i.e., omega (sub 0) and absorption Angstrom exponent (alpha(sub abs))] and size [i.e., extinction Angstrom exponent (alpha(sub ext)) and fine mode fraction of tau] relationships to infer dominant aerosol types. Using the long-term AERONET data set (1999-2010), 19 sites are grouped by aerosol type based on known source regions to: (1) determine the average omega (sub 0) and alpha(sub abs) at each site (expanding upon previous work); (2) perform a sensitivity study on alpha(sub abs) by varying the spectral omega (sub 0); and (3) test the ability of each absorption and size relationship to distinguish aerosol types. The spectral omega (sub 0) averages indicate slightly more aerosol absorption (i.e., a 0.0 < delta omega (sub 0) <= 0.02 decrease) than in previous work and optical mixtures of pollution and smoke with dust show stronger absorption than dust alone. Frequency distributions of alpha(sub abs) show significant overlap among aerosol type categories and at least 10% of the alpha(sub abs) retrievals in each category are below 1.0. Perturbing the spectral omega (sub 0) by +/- 0.03 induces significant alpha(sub abs) changes from the unperturbed value by at least approx. +/- 0.6 for Dust, approx. +/-0.2 for Mixed, and approx. +/-0.1 for Urban/Industrial and Biomass Burning. The omega (sub 0)440nm and alpha(sub ext) 440-870nm relationship shows the best separation among aerosol type clusters, providing a simple technique for determining aerosol type from surface- and future space-based instrumentation.

Early science with sofia, the stratospheric observatory for infrared astronomy

Abstract: The Stratospheric Observatory For Infrared Astronomy (SOFIA) is an airborne observatory consisting of a specially modified Boeing 747SP with a 2.7 m telescope, flying at altitudes as high as 13.7 km (45,000 ft). Designed to observe at wavelengths from 0.3 μm to 1.6 mm, SOFIA operates above 99.8% of the water vapor that obscures much of the infrared and submillimeter. SOFIA has seven science instruments under development, including an occultation photometer, near-, mid-, and far-infrared cameras, infrared spectrometers, and heterodyne receivers. SOFIA, a joint project between NASA and the German Aerospace Center Deutsches Zentrum fur Luft und-Raumfahrt, began initial science flights in 2010 December, and has conducted 30 science flights in the subsequent year. During this early science period three instruments have flown: the mid-infrared camera FORCAST, the heterodyne spectrometer GREAT, and the occultation photometer HIPO. This Letter provides an overview of the observatory and its early performance.

The Neutron star Interior Composition ExploreR (NICER): an Explorer mission of opportunity for soft x-ray timing spectroscopy

Abstract: The Neutron star Interior Composition ExploreR (NICER) is a proposed NASA Explorer Mission of Opportunity dedicated to the study of the extraordinary gravitational, electromagnetic, and nuclear-physics environments embodied by neutron stars. NICER will explore the exotic states of matter within neutron stars, where density and pressure are higher than in atomic nuclei, confronting theory with unique observational constraints. NICER will enable rotation-resolved spectroscopy of the thermal and non-thermal emissions of neutron stars in the soft (0.2–12 keV) X-ray band with unprecedented sensitivity, probing interior structure, the origins of dynamic phenomena, and the mechanisms that underlie the most powerful cosmic particle accelerators known. NICER will achieve these goals by deploying, following launch in December 2016, an X-ray timing and spectroscopy instrument as an attached payload aboard the International Space Station (ISS). A robust design compatible with the ISS visibility, vibration, and contamination environments allows NICER to exploit established infrastructure with low risk. Grazing-incidence optics coupled with silicon drift detectors, actively pointed for a full hemisphere of sky coverage, will provide photon-counting spectroscopy and timing registered to GPS time and position, with high throughput and relatively low background. In addition to advancing a vital multi-wavelength approach to neutron star studies through coordination with radio and γ-ray observations, NICER will provide a rapid-response capability for targeting of transients, continuity in X-ray timing astrophysics investigations post-RXTE through a proposed Guest Observer program, and new discovery space in soft X-ray timing science.

The GOES-R Geostationary Lightning Mapper (GLM)

Abstract: The Geostationary Operational Environmental Satellite R-series (GOES-R) is the next block of four satellites to follow the existing GOES constellation currently operating over the Western Hemisphere. Advanced spacecraft and instrument technology will support expanded detection of environmental phenomena, resulting in more timely and accurate forecasts and warnings. Advancements over current GOES capabilities include a new capability for total lightning detection (cloud and cloud-to-ground flashes) from the Geostationary Lightning Mapper (GLM), and improved cloud and moisture imagery with the 16-channel Advanced Baseline Imager (ABI). The GLM will map total lightning activity continuously day and night with near-uniform storm-scale spatial resolution of 8 km with a product refresh rate of less than 20 s over the Americas and adjacent oceanic regions in the western hemisphere. This will aid in forecasting severe storms and tornado activity, and convective weather impacts on aviation safety and efficiency. In parallel with the instrument development, an Algorithm Working Group (AWG) Lightning Detection Science and Applications Team developed the Level 2 (stroke and flash) algorithms from the Level 1 lightning event (pixel level) data. Proxy data sets used to develop the GLM operational algorithms as well as cal/val performance monitoring tools were derived from the NASA Lightning Imaging Sensor (LIS) and Optical Transient Detector (OTD) instruments in low Earth orbit, and from ground-based lightning networks and intensive prelaunch field campaigns. The GLM will produce the same or similar lightning flash attributes provided by the LIS and OTD, and thus extend their combined climatology over the western hemisphere into the coming decades. Science and application development along with preoperational product demonstrations and evaluations at NWS forecast offices and NOAA testbeds will prepare the forecasters to use GLM as soon as possible after the planned launch and checkout of GOES-R in late 2015. New applications will use GLM alone, in combination with the ABI, or integrated (fused) with other available tools (weather radar and ground strike networks, nowcasting systems, mesoscale analysis, and numerical weather prediction models) in the hands of the forecaster responsible for issuing more timely and accurate forecasts and warnings.

Benefits for bone from resistance exercise and nutrition in long-duration spaceflight: Evidence from biochemistry and densitometry

Abstract: Exercise has shown little success in mitigating bone loss from long-duration spaceflight. The first crews of the International Space Station (ISS) used the “interim resistive exercise device” (iRED), which allowed loads of up to 297 lbf (or 1337 N) but provided little protection of bone or no greater protection than aerobic exercise. In 2008, the Advanced Resistive Exercise Device (ARED), which allowed absolute loads of up to 600 lbf (1675 N), was launched to the ISS. We report dietary intake, bone densitometry, and biochemical markers in 13 crewmembers on ISS missions from 2006 to 2009. Of these 13, 8 had access to the iRED and 5 had access to the ARED. In both groups, bone-specific alkaline phosphatase tended to increase during flight toward the end of the mission (p = 0.06) and increased 30 days after landing (p < 0.001). Most markers of bone resorption were also increased in both groups during flight and 30 days after landing (p < 0.05). Bone densitometry revealed significant interactions (time and exercise device) for pelvis bone mineral density (BMD) and bone mineral content (p < 0.01), hip femoral neck BMD (p < 0.05), trochanter BMD (p < 0.05), and total hip BMD (p < 0.05). These variables were unchanged from preflight only for ARED crewmembers, who also returned from flight with higher percent lean mass and lower percent fat mass. Body mass was unchanged after flight in both groups. All crewmembers had nominal vitamin D status (75 ± 17 nmol/L) before and during flight. These data document that resistance exercise, coupled with adequate energy intake (shown by maintenance of body mass determined by dual-energy X-ray absorptiometry [DXA]) and vitamin D, can maintain bone in most regions during 4- to 6-month missions in microgravity. This is the first evidence that improving nutrition and resistance exercise during spaceflight can attenuate the expected BMD deficits previously observed after prolonged missions. © 2012 American Society for Bone and Mineral Research.

Grb110721a: an extreme peak energy and signatures of the photosphere

Abstract: GRB110721A was observed by the Fermi Gamma-ray Space Telescope using its two instruments, the Large Area Telescope (LAT) and the Gamma-ray Burst Monitor (GBM). The burst consisted of one major emission episode which lasted for approximately 24.5 s (in the GBM) and had a peak flux of (5.7 +/- 0.2) 10(exp -5) erg s(exp -1) cm(exp -2). The time-resolved emission spectrum is best modeled with a combination of a Band function and a blackbody spectrum. The peak energy of the Band component was initially 15 +/- 2 MeV, which is the highest value ever detected in a GRB. This measurement was made possible by combining GBM/BGO data with LAT Low Energy events to achieve continuous 10-100 MeV coverage. The peak energy later decreased as a power law in time with an index of -1.89 +/- 0.10. The temperature of the blackbody component also decreased, starting from approximately 80 keV, and the decay showed a significant break after approximately 2s. The spectrum provides strong constraints on the standard synchrotron model, indicating that alternative mechanisms may give rise to the emission at these energies.

The Fermi GBM Gamma-Ray Burst Spectral Catalog: The First Two Years

Abstract: We present systematic spectral analyses of gamma-ray bursts (GRBs) detected by the Fermi Gamma-Ray Burst Monitor (GBM) during its first two years of operation. This catalog contains two types of spectra extracted from 487 GRBs, and by fitting four different spectral models, this results in a compendium of over 3800 spectra. The models were selected based on their empirical importance to the spectral shape of many GRBs, and the analysis performed was devised to be as thorough and objective as possible. We describe in detail our procedure and criteria for the analyses, and present the bulk results in the form of parameter distributions. This catalog should be considered an official product from the Fermi GBM Science Team, and the data files containing the complete results are available from the High-Energy Astrophysics Science Archive Research Center.

Assimilation of passive and active microwave soil moisture retrievals

Abstract: Root-zone soil moisture is an important control over the partition of land surface energy and moisture, and the assimilation of remotely sensed near-surface soil moisture has been shown to improve model profile soil moisture [1]. To date, efforts to assimilate remotely sensed near-surface soil moisture at large scales have focused on soil moisture derived from the passive microwave Advanced Microwave Scanning Radiometer (AMSR-E) and the active Advanced Scatterometer (ASCAT; together with its predecessor on the European Remote Sensing satellites (ERS. The assimilation of passive and active microwave soil moisture observations has not yet been directly compared, and so this study compares the impact of assimilating ASCAT and AMSR-E soil moisture data, both separately and together. Since the soil moisture retrieval skill from active and passive microwave data is thought to differ according to surface characteristics [2], the impact of each assimilation on the model soil moisture skill is assessed according to land cover type, by comparison to in situ soil moisture observations.

Anthropogenic, biomass burning, and volcanic emissions of black carbon, organic carbon, and SO 2 from 1980 to 2010 for hindcast model experiments

Abstract: . Two historical emission inventories of black carbon (BC), primary organic carbon (OC), and SO2 emissions from land-based anthropogenic sources, ocean-going vessels, air traffic, biomass burning, and volcanoes are presented and discussed for the period 1980–2010. These gridded inventories are provided to the internationally coordinated AeroCom Phase II multi-model hindcast experiments. The horizontal resolution is 0.5°×0.5° and 1.0°×1.0°, while the temporal resolution varies from daily for volcanoes to monthly for biomass burning and aircraft emissions, and annual averages for land-based and ship emissions. One inventory is based on inter-annually varying activity rates of land-based anthropogenic emissions and shows strong variability within a decade, while the other one is derived from interpolation between decadal endpoints and thus exhibits linear trends within a decade. Both datasets capture the major trends of decreasing anthropogenic emissions over the USA and Western Europe since 1980, a sharp decrease around 1990 over Eastern Europe and the former USSR, and a steep increase after 2000 over East and South Asia. The inventory differences for the combined anthropogenic and biomass burning emissions in the year 2005 are 34% for BC, 46% for OC, and 13% for SO2. They vary strongly depending on species, year and region, from about 10% to 40% in most cases, but in some cases the inventories differ by 100% or more. Differences in emissions from wild-land fires are caused only by different choices of the emission factors for years after 1996 which vary by a factor of about 1 to 2 for OC depending on region, and by a combination of emission factors and the amount of dry mass burned for years up to 1996. Volcanic SO2 emissions, which are only provided in one inventory, include emissions from explosive, effusive, and quiescent degassing events for 1167 volcanoes.

Aerosols from Overseas Rival Domestic Emissions over North America

Abstract: Many types of aerosols have lifetimes long enough for their transcontinental transport, making them potentially important contributors to air quality and climate change in remote locations. We estimate that the mass of aerosols arriving at North American shores from overseas is comparable with the total mass of particulates emitted domestically. Curbing domestic emissions of particulates and precursor gases, therefore, is not sufficient to mitigate aerosol impacts in North America. The imported contribution is dominated by dust leaving Asia, not by combustion-generated particles. Thus, even a reduction of industrial emissions of the emerging economies of Asia could be overwhelmed by an increase of dust emissions due to changes in meteorological conditions and potential desertification.

A cool dust factory in the crab nebula: a herschel * study of the filaments

Abstract: Whether supernovae are major sources of dust in galaxies is a long-standing debate. We present infrared and submillimeter photometry and spectroscopy from the Herschel Space Observatory of the Crab Nebula between 51 and 670 μm as part of the Mass Loss from Evolved StarS program. We compare the emission detected with Herschel with multiwavelength data including millimeter, radio, mid-infrared, and archive optical images. We carefully remove the synchrotron component using the Herschel and Planck fluxes measured in the same epoch. The contribution from line emission is removed using Herschel spectroscopy combined with Infrared Space Observatory archive data. Several forbidden lines of carbon, oxygen, and nitrogen are detected where multiple velocity components are resolved, deduced to be from the nitrogen-depleted, carbon-rich ejecta. No spectral lines are detected in the SPIRE wavebands; in the PACS bands, the line contribution is 5% and 10% at 70 and 100 μm and negligible at 160 μm. After subtracting the synchrotron and line emission, the remaining far-infrared continuum can be fit with two dust components. Assuming standard interstellar silicates, the mass of the cooler component is 0.24+0.32 – 0.08 M ☉ for T = 28.1+5.5 – 3.2 K. Amorphous carbon grains require 0.11 ± 0.01 M ☉ of dust with T = 33.8+2.3 – 1.8 K. A single temperature modified blackbody with 0.14 M ☉ and 0.08 M ☉ for silicate and carbon dust, respectively, provides an adequate fit to the far-infrared region of the spectral energy distribution but is a poor fit at 24-500 μm. The Crab Nebula has condensed most of the relevant refractory elements into dust, suggesting the formation of dust in core-collapse supernova ejecta is efficient.

Tropospheric bromine chemistry: implications for present and pre-industrial ozone and mercury

Abstract: We present a new model for the global tro- pospheric chemistry of inorganic bromine (Bry) coupled to oxidant-aerosol chemistry in the GEOS-Chem chemical transport model (CTM). Sources of tropospheric Bry include debromination of sea-salt aerosol, photolysis and oxidation of short-lived bromocarbons, and transport from the strato- sphere. Comparison to a GOME-2 satellite climatology of tropospheric BrO columns shows that the model can repro- duce the observed increase of BrO with latitude, the northern mid-latitudes maximum in winter, and the Arctic maximum in spring. This successful simulation is contingent on the HOBr + HBr reaction taking place in aqueous aerosols and ice clouds. Bromine chemistry in the model decreases tro- pospheric ozone mixing ratios by < 1-8 nmol mol 1 (6.5 % globally), with the largest effects in the northern extratropics in spring. The global mean tropospheric OH concentration decreases by 4 %. Inclusion of bromine chemistry improves the ability of global models (GEOS-Chem and p-TOMCAT) to simulate observed 19th-century ozone and its seasonality. Bromine effects on tropospheric ozone are comparable in the present-day and pre-industrial atmospheres so that estimates of anthropogenic radiative forcing are minimally affected. Br atom concentrations are 40 % higher in the pre-industrial at- mosphere due to lower ozone, which would decrease by a factor of 2 the atmospheric lifetime of elemental mercury against oxidation by Br. This suggests that historical anthro- pogenic mercury emissions may have mostly deposited to northern mid-latitudes, enriching the corresponding surface reservoirs. The persistent rise in background surface ozone at northern mid-latitudes during the past decades could pos- sibly contribute to the observations of elevated mercury in subsurface waters of the North Atlantic.

How well do current climate models simulate two types of El Nino

Abstract: In this study, we evaluate the fidelity of current climate models in simulating the two types of El Nino events using the pre-industrial output in CMIP3 archives. It is shown that a few climate models simulate the two types of El Nino events to some extent, while most of the models have serious systematic problems in simulating distinctive patterns of sea-surface temperature (SST) and precipitation anomaly associated with the two types of El Nino; that is, they tend to simulate a single type of El Nino. It is shown that the ability of climate models in simulating the two types of El Nino is related to the sensitivity of the atmospheric responses to the SST anomaly patterns. Models whose convective location is shifted to the east (west) as the SST anomaly center moves to the east (west) tends to simulate the two types of El Nino events successfully. On the other hand, models whose location of convective anomaly is confined over the western or central Pacific tends to simulate only the single type of El Nino event. It is also shown that the confinement of the convective anomaly over the western or central Pacific is closely linked to the dry bias and the associated cold bias over the eastern Pacific. That is, because positive El Nino SST anomalies over the eastern Pacific cannot increase local convection effectively when the total SSTs are still too cold due to a cold bias. This implies that the realistic simulation of climatology, especially over the equatorial eastern Pacific, is essential to the successful simulation of the two types of El Nino.

Application of the CALIOP layer product to evaluate the vertical distribution of aerosols estimated by global models: AeroCom phase I results

Abstract: The CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) layer product is used for a multimodel evaluation of the vertical distribution of aerosols. Annual and seasonal aerosol extinction profiles are analyzed over 13 sub-continental regions representative of industrial, dust, and biomass burning pollution, from CALIOP 2007-2009 observations and from AeroCom (Aerosol Comparisons between Observations and Models) 2000 simulations. An extinction mean height diagnostic (Z-alpha) is defined to quantitatively assess the models' performance. It is calculated over the 0-6 km and 0-10 km altitude ranges by weighting the altitude of each 100 m altitude layer by its aerosol extinction coefficient. The mean extinction profiles derived from CALIOP layer products provide consistent regional and seasonal specificities and a low inter-annual variability. While the outputs from most models are significantly correlated with the observed Z-alpha climatologies, some do better than others, and 2 of the 12 models perform particularly well in all seasons. Over industrial and maritime regions, most models show higher Z-alpha than observed by CALIOP, whereas over the African and Chinese dust source regions, Z-alpha is underestimated during Northern Hemisphere Spring and Summer. The positive model bias in Z-alpha is mainly due to an overestimate of the extinction above 6 km. Potential CALIOP and model limitations, and methodological factors that might contribute to the differences are discussed.

Toward a Global Climatology of Severe Hailstorms as Estimated by Satellite Passive Microwave Imagers

Abstract: An 8-yr climatology of storms producing large hail is estimated from satellite measurements using Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E). This allows a unique, consistent comparison between regions that cannot be consistently compared using ground-based records because of varying data collection standards. Severe hailstorms are indicated most often in a broad region of northern Argentina and southern Paraguay and a smaller region in Bangladesh and eastern India. Numerous hailstorms are also estimated in the central and southeastern United States, northern Pakistan and northwestern India, central and western Africa, and southeastern Africa (and adjacent waters). Fewer hailstorms are estimated for other regions over land and scattered across subtropical oceans. Very few are estimated in the deep tropics other than in Africa. Most continental regions show seasonality with hailstorms peaking in late spring or summer. The South Asian monsoon alters the hailstorm clim...

Gamma-Ray Burst Afterglow Broadband Fitting Based Directly on Hydrodynamics Simulations

Abstract: We present a powerful new tool for fitting broadband gamma-ray burst afterglow data, which can be used to determine the burst explosion parameters and the synchrotron radiation parameters. By making use of scale invariance between relativistic jets of different energies and different circumburst medium densities, and by capturing the output of high-resolution two-dimensional relativistic hydrodynamical (RHD) jet simulations in a concise summary, the jet dynamics are generated quickly. Our method calculates the full light curves and spectra using linear radiative transfer sufficiently fast to allow for a direct iterative fit of RHD simulations to the data. The fit properly accounts for jet features that so far have not been successfully modeled analytically, such as jet decollimation, inhomogeneity along the shock front, and the transitory phase between the early-time relativistic and late-time non-relativistic outflow. As a first application of the model we simultaneously fit the radio, X-ray, and optical data of GRB 990510. We find not only noticeable differences between our findings for the explosion and radiation parameters and those of earlier authors, but also an improved model fit when we include the observer angle in the data fit. The fit method will be made freely available on request and online at http://cosmo.nyu.edu/afterglowlibrary. In addition to data fitting, the software tools can also be used to quickly generate a light curve or spectrum for arbitrary observer position, jet, and radiation parameters.

The fermi gbm gamma-ray burst catalog: the first two years

Abstract: The Fermi Gamma-ray Burst Monitor (GBM) is designed to enhance the scientific return from Fermi in studying gamma-ray bursts (GRBs). In its first two years of operation GBM triggered on 491 GRBs. We summarize the criteria used for triggering and quantify the general characteristics of the triggered GRBs, including their locations, durations, peak flux, and fluence. This catalog is an official product of the Fermi GBM science team, and the data files containing the complete results are available from the High-Energy Astrophysics Science Archive Research Center.

Growth in NO x emissions from power plants in China: bottom-up estimates and satellite observations

Abstract: . Using OMI (Ozone Monitoring Instrument) tropospheric NO2 columns and a nested-grid 3-D global chemical transport model (GEOS-Chem), we investigated the growth in NOx emissions from coal-fired power plants and their contributions to the growth in NO2 columns in 2005–2007 in China. We first developed a unit-based power plant NOx emission inventory for 2005–2007 to support this investigation. The total capacities of coal-fired power generation have increased by 48.8% in 2005–2007, with 92.2% of the total capacity additions coming from generator units with size ≥300 MW. The annual NOx emissions from coal-fired power plants were estimated to be 8.11 Tg NO2 for 2005 and 9.58 Tg NO2 for 2007, respectively. The modeled summer average tropospheric NO2 columns were highly correlated (R2 = 0.79–0.82) with OMI measurements over grids dominated by power plant emissions, with only 7–14% low bias, lending support to the high accuracy of the unit-based power plant NOx emission inventory. The ratios of OMI-derived annual and summer average tropospheric NO2 columns between 2007 and 2005 indicated that most of the grids with significant NO2 increases were related to power plant construction activities. OMI had the capability to trace the changes of NOx emissions from individual large power plants in cases where there is less interference from other NOx sources. Scenario runs from GEOS-Chem model suggested that the new power plants contributed 18.5% and 10% to the annual average NO2 columns in 2007 in Inner Mongolia and North China, respectively. The massive new power plant NOx emissions significantly changed the local NO2 profiles, especially in less polluted areas. A sensitivity study found that changes of NO2 shape factors due to including new power plant emissions increased the summer average OMI tropospheric NO2 columns by 3.8–17.2% for six selected locations, indicating that the updated emission information could help to improve the satellite retrievals.

Early Age at Time of Primary Epstein–Barr Virus Infection Results in Poorly Controlled Viral Infection in Infants From Western Kenya: Clues to the Etiology of Endemic Burkitt Lymphoma

Abstract: Background. Infection with Epstein–Barr virus (EBV) early in life and repeated malaria exposure have been proposed as risk factors for endemic Burkitt lymphoma (eBL). Methods. Infants were enrolled from 2 rural sites in Kenya: the Kisumu District, where malaria transmission is holoendemic and risk for eBL is high, and the Nandi District, where malaria transmission is limited and the risk for eBL is low. Blood samples were taken from infants through 2 years of age to measure EBV viral load, EBV antibodies, and malaria parasitemia. Results. We observed a significantly younger age at time of primary EBV infection in children from Kisumu compared with children from Nandi (mean age, 7.28 months [60.33 SEM] in Kisumu vs 8.39 months [60.26 SEM] in Nandi), with 35.3% of children in Kisumu infected before 6 months of age. To analyze how different predictors affected EBV viral load over time, we performed multilevel mixed modeling. This modeling revealed that residence in Kisumu and younger age at first EBV infection were significant predictors for having a higher EBV viral load throughout the period of observation. Conclusions. Children from a region at high risk for eBL were infected very early in life with EBV, resulting in higher viral loads throughout infancy.

Variability and trends of aerosol properties over Kanpur, northern India using AERONET data (2001–10)

Abstract: Natural and anthropogenic aerosols over northern India play an important role in influencing the regional radiation budget, causing climate implications to the overall hydrological cycle of South Asia. In the context of regional climate change and air quality, we discuss aerosol loading variability and trends at Kanpur AERONET station located in the central part of the Indo-Gangetic plains (IGP), during the last decade (2001‐10). Ground-based radiometric measurements show an overall increase in column-integrated aerosol optical depth (AOD) on a yearly basis. This upward trend is mainly due to a sustained increase in the seasonal/monthly averaged AOD during the winter (Dec‐Feb) and post-monsoon (Oct‐Nov) seasons (dominated by anthropogenic emissions). In contrast, a neutral to weak declining trend is observed during late pre-monsoon (Mar‐May) and monsoon (Jun‐Sep) months, mainly influenced by inter-annual variations of dust outbreaks. A general decrease in coarse-mode aerosols associated with variable dust activity is observed, whereas the statistically significant increasing post-monsoon/winter AOD is reflected in a shift of the columnar size distribution towards relatively larger particles in the accumulation mode. Overall, the present study provides an insight into the pronounced seasonal behavior in aerosol loading trends and, in general, is in agreement with that associating the findings with those recently reported by satellite observations (MODIS and MISR) over northern India. Our results further suggest that anthropogenic emissions (due mainly to fossil-fuel and biomass combustion) over the IGP have continued to increase in the last decade.

First Science Observations with SOFIA/FORCAST: The FORCAST Mid-infrared Camera

Abstract: The Stratospheric Observatory For Infrared Astronomy (SOFIA) completed its first light flight in May of 2010 using the facility mid-infrared instrument FORCAST. Since then, FORCAST has successfully completed 13 science flights on SOFIA. In this Letter, we describe the design, operation, and performance of FORCAST as it relates to the initial three Short Science flights. FORCAST was able to achieve near-diffraction-limited images for λ > 30 μm allowing unique science results from the start with SOFIA. We also describe ongoing and future modifications that will improve overall capabilities and performance of FORCAST.

PANCHROMATIC OBSERVATIONS OF SN 2011dh POINT TO A COMPACT PROGENITOR STAR

Abstract: We report the discovery and detailed monitoring of X-ray emission associated with the Type IIb SN2011dh using data from the Swift and Chandra satellites, placing it among the best studied X-ray supernovae to date. We further present millimeter and radio data obtained with the SMA, CARMA, and EVLA during the first three weeks after explosion. Combining these observations with early optical photometry, we show that the panchromatic dataset is well-described by non-thermal synchrotron emission (radio/mm) with inverse Compton scattering (X-ray) of a thermal population of optical photons. We derive the properties of the shockwave and the circumstellar environment and find a time-averaged shock velocity of v approximately equals 0.1c and a progenitor mass loss rate of M-dot approximately equals 6 X 10 (exp 5) Solar M/ yr (wind velocity, v(sub w) = 1000 km/s). We show that these properties are consistent with the sub-class of Type IIb supernovae characterized by compact progenitors (Type cIIb) and dissimilar from those with extended progenitors (Type eIIb). Furthermore, we consider the early optical emission in the context of a cooling envelope model to estimate a progenitor radius of R(sub star) approximately equals 10(exp 11) cm, in line with the expectations for a Type cIIb supernova. Together, these diagnostics suggest that the putative yellow supergiant progenitor star identified in archival HST observations is instead a binary companion or unrelated to the supernova. Finally, we searched for the high energy shock breakout pulse using X-ray and gamma-ray observations obtained during the purported explosion date range. Based on the compact radius of the progenitor, we estimate that the shock breakout pulse was detectable with current instruments but likely missed due to their limited temporal/ spatial coverage. Future all-sky missions will regularly detect shock breakout emission from compact SN progenitors enabling prompt follow-up observations of the shockwave with the EVLA and ALMA.

A Cool Dust Factory in the Crab Nebula: A Herschel Study of the Filaments

Abstract: Whether supernovae are major sources of dust in galaxies is a long-standing debate. We present infrared and submillimeter photometry and spectroscopy from the Herschel Space Observatory of the Crab Nebula between 51 and 670 micron as part of the Mass Loss from Evolved StarS program. We compare the emission detected with Herschel with multiwavelength data including millimeter, radio, mid-infrared and archive optical images. We carefully remove the synchrotron component using the Herschel and Planck fluxes measured in the same epoch. The contribution from line emission is removed using Herschel spectroscopy combined with Infrared Space Observatory archive data. Several forbidden lines of carbon, oxygen and nitrogen are detected where multiple velocity components are resolved, deduced to be from the nitrogen-depleted, carbon-rich ejecta. No spectral lines are detected in the SPIRE wavebands; in the PACS bands, the line contribution is 5% and 10% at 70 and 100 micron and negligible at 160 micron. After subtracting the synchrotron and line emission, the remaining far-infrared continuum can be fit with two dust components. Assuming standard interstellar silicates, the mass of the cooler component is 0.24(+0.32)(-0.08) Msolar for T = 28.1(+5.5)(-3.2)K. Amorphous carbon grains require 0.11 +/- 0.01 Msolar of dust with T = 33.8(+2.3)(-1.8) K. A single temperature modified-blackbody with 0.14Msolar and 0.08Msolar for silicate and carbon dust respectively, provides an adequate fit to the far- infrared region of the spectral energy distribution but is a poor fit at 24-500 micron. The Crab Nebula has condensed most of the relevant refractory elements into dust, suggesting the formation of dust in core-collapse supernova ejecta is efficient.