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Journal articleMatteini L, Alexandrova O, Chen CHK, et al., 2017,
Electric and magnetic spectra from MHD to electron scales in the magnetosheath
, Monthly Notices of the Royal Astronomical Society, Vol: 466, Pages: 945-951, ISSN: 0035-8711We investigate the transition of the turbulence from large to kinetic scales using Cluster observations. Simultaneous spectra of magnetic and electric fields in the Earth's magnetosheath from magnetohydrodynamic (MHD) to electron scales are presented for the first time. While the two spectra have approximatively similar behaviour in the fluid-MHD regime, they show different trends in the kinetic range. As the magnetic field spectrum steepens at ion scales, the electric field spectrum is characterized by a shallower power law continuing down to electron scales. Such an evolution is consistent with theoretical expectations, assuming that the turbulence is dominated by highly oblique k-vectors and that between ion and electron scales the electric field is governed by the non-ideal terms in the generalized Ohm's law. This leads to an expected linear increase of the electric-to-magnetic ratio of fluctuations, consistent with observations presented here. The influence of local whistler wave activity on electron-scale spectra is also discussed.
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Journal articleLiu F, Fiencke C, Guo J, et al., 2017,
Bioscrubber treatment of exhaust air from intensive pig production: Case study in northern Germany at mild climate condition
, Engineering in Life Sciences, Vol: 17, Pages: 458-466, ISSN: 1618-0240<jats:p>Treatment by field‐scale bioscrubber of exhaust air, including ammonia (NH<jats:sub>3</jats:sub>) and the greenhouse gases methane (CH<jats:sub>4</jats:sub>), nitrous oxide (N<jats:sub>2</jats:sub>O), and carbon dioxide (CO<jats:sub>2</jats:sub>), from 13 intensive pig production houses located in northern Germany were investigated in 2013 and 2015. NH<jats:sub>3</jats:sub> removal efficiencies varied between 35 and 100% with an overall average value of 79% under the NH<jats:sub>3</jats:sub> inlet fluctuations from 34 to 755 g d<jats:sup>−1</jats:sup> m<jats:sup>−3</jats:sup> in both 2013 and 2015. Results of the electron microscopic analyses demonstrated that the bacteria <jats:italic>Nitrosomonas</jats:italic> sp. and methanotrophs <jats:italic>type I</jats:italic> were the dominant NH<jats:sub>3</jats:sub> and CH<jats:sub>4</jats:sub> oxidizers, respectively. However, overall average removal efficiencies of CH<jats:sub>4</jats:sub> was approximately zero, which means CH<jats:sub>4</jats:sub> is hard to remove in bioscrubbers under normal operation. The pH of recirculation water in the bioscrubber varied from 6.1 to 8.1, and the bioscrubbers with low pH values (<7.0) had high NH<jats:sub>3</jats:sub> removal efficiencies (>79%). Electrical conductivity was commonly used to diagnose the bioscrubbers’ performance; in the present study, electrical conductivity presented a significant linear relationship with dissolved inorganic nitrogen, which indicates the performance stability of the 13 selected bioscrubbers.</jats:p>
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Conference paperBelmonte MT, Pickering JC, Clear C, et al., 2017,
Accurate atomic data for Galactic Surveys
, 330th Symposium of the International-Astronomical-Union (IAU), Publisher: CAMBRIDGE UNIV PRESS, Pages: 203-205, ISSN: 1743-9213 -
Journal articleCerri SS, Franci L, Califano F, et al., 2017,
Plasma turbulence at ion scales: a comparison between particle in cell and Eulerian hybrid-kinetic approaches
, JOURNAL OF PLASMA PHYSICS, Vol: 83, ISSN: 0022-3778 -
Journal articleGershman DJ, F-Vinas A, Dorelli JC, et al., 2017,
Wave-particle energy exchange directly observed in a kinetic Alfven-branch wave
, NATURE COMMUNICATIONS, Vol: 8, ISSN: 2041-1723Alfvén waves are fundamental plasma wave modes that permeate the universe. At small kinetic scales, they provide a critical mechanism for the transfer of energy between electromagnetic fields and charged particles. These waves are important not only in planetary magnetospheres, heliospheres and astrophysical systems but also in laboratory plasma experiments and fusion reactors. Through measurement of charged particles and electromagnetic fields with NASA’s Magnetospheric Multiscale (MMS) mission, we utilize Earth’s magnetosphere as a plasma physics laboratory. Here we confirm the conservative energy exchange between the electromagnetic field fluctuations and the charged particles that comprise an undamped kinetic Alfvén wave. Electrons confined between adjacent wave peaks may have contributed to saturation of damping effects via nonlinear particle trapping. The investigation of these detailed wave dynamics has been unexplored territory in experimental plasma physics and is only recently enabled by high-resolution MMS observations.
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Journal articleFischer ML, Parazoo N, Brophy K, et al., 2017,
Simulating estimation of California fossil fuel and biosphere carbon dioxide exchanges combining in situ tower and satellite column observations
, Journal of Geophysical Research: Atmospheres, Vol: 122, Pages: 3653-3671, ISSN: 2169-897XWe report simulation experiments estimating the uncertainties in California regional fossil fuel and biosphere CO2 exchanges that might be obtained by using an atmospheric inverse modeling system driven by the combination of ground‐based observations of radiocarbon and total CO2, together with column‐mean CO2 observations from NASA's Orbiting Carbon Observatory (OCO‐2). The work includes an initial examination of statistical uncertainties in prior models for CO2 exchange, in radiocarbon‐based fossil fuel CO2 measurements, in OCO‐2 measurements, and in a regional atmospheric transport modeling system. Using these nominal assumptions for measurement and model uncertainties, we find that flask measurements of radiocarbon and total CO2 at 10 towers can be used to distinguish between different fossil fuel emission data products for major urban regions of California. We then show that the combination of flask and OCO‐2 observations yields posterior uncertainties in monthly‐mean fossil fuel emissions of ~5–10%, levels likely useful for policy relevant evaluation of bottom‐up fossil fuel emission estimates. Similarly, we find that inversions yield uncertainties in monthly biosphere CO2 exchange of ~6%–12%, depending on season, providing useful information on net carbon uptake in California's forests and agricultural lands. Finally, initial sensitivity analysis suggests that obtaining the above results requires control of systematic biases below approximately 0.5 ppm, placing requirements on accuracy of the atmospheric measurements, background subtraction, and atmospheric transport modeling.
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Journal articleBanks J, Brindley HE, Stenchikov G, et al., 2017,
Satellite retrievals of dust aerosol over the Red Sea and the Persian Gulf (2005–2015)
, Atmospheric Chemistry and Physics, Vol: 17, Pages: 3987-4003, ISSN: 1680-7316The inter-annual variability of the dust aerosol presence over the Red Sea and the Persian Gulf is analysed over the period 2005–2015. Particular attention is paid to the variation in loading across the Red Sea, which has previously been shown to have a strong, seasonally dependent latitudinal gradient. Over the 11 years considered, the July mean 630 nm aerosol optical depth (AOD) derived from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) varies between 0.48 and 1.45 in the southern half of the Red Sea. In the north, the equivalent variation is between 0.22 and 0.66. The temporal and spatial pattern of variability captured by SEVIRI is also seen in AOD retrievals from the MODerate Imaging Spectroradiometer (MODIS), but there is a systematic offset between the two records. Comparisons of both sets of retrievals with ship- and land-based AERONET measurements show a high degree of correlation with biases of < 0.08. However, these comparisons typically only sample relatively low aerosol loadings. When both records are stratified by AOD retrievals from the Multi-angle Imaging SpectroRadiometer (MISR), opposing behaviour is revealed at high MISR AODs ( > 1), with offsets of +0.19 for MODIS and −0.06 for SEVIRI. Similar behaviour is also seen over the Persian Gulf. Analysis of the scattering angles at which retrievals from the SEVIRI and MODIS measurements are typically performed in these regions suggests that assumptions concerning particle sphericity may be responsible for the differences seen.
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Journal articleSheldon L, Czaja A, Vanniere B, et al., 2017,
A warm path for Gulf Stream - troposphere interactions
, Tellus Series A-Dynamic Meteorology and Oceanography, Vol: 69, ISSN: 1600-0870Warm advection by the Gulf Stream creates a characteristic ‘tongue’ of warm water leaving a strong imprint on the sea surface temperature (SST) distribution in the western North Atlantic. This study aims at quantifying the climatological impact of this feature on cyclones travelling across this region in winter using a combination of reanalysis data and numerical experiments. It is suggested that the Gulf Stream ‘warm tongue’ is conducive to enhanced upward motion in cyclones because (i) it helps maintain a high equivalent potential temperature of air parcels at low levels which favors deep ascent in the warm conveyor belt of cyclones and (ii) because the large SST gradients to the north of the warm tongue drive a thermally direct circulation reinforcing and, possibly, destabilizing, the transverse circulation embedded in cyclones. This hypothesis is confirmed by comparing simulations at 12 km resolution from the Met Office Unified Model forced with realistic SST distribution to simulations with an SST distribution from which the Gulf Stream warm tongue was artificially removed or made colder by. It is also supported by a dynamical diagnostic applied to the ERA interim data-set over the wintertime period (1979–2012). The mechanism of oceanic forcing highlighted in this study is associated with near thermal equilibration of low level air masses with SST in the warm sector of cyclones passing over the Gulf Stream warm tongue, which is in sharp contrast to what occurs in their cold sector. It is suggested that this ‘warm path’ for the climatic impact of the Gulf Stream on the North Atlantic storm-track is not currently represented in climate models because of their coarse horizontal resolution.
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Journal articleRabin SS, Melton JR, Lasslop G, et al., 2017,
The Fire Modeling Intercomparison Project (FireMIP), phase 1: experimental and analytical protocols with detailed model descriptions
, GEOSCIENTIFIC MODEL DEVELOPMENT, Vol: 10, Pages: 1175-1197, ISSN: 1991-959XThe important role of fire in regulating vegetation community composition and contributions to emissions of greenhouse gases and aerosols make it a critical component of dynamic global vegetation models and Earth system models. Over 2 decades of development, a wide variety of model structures and mechanisms have been designed and incorporated into global fire models, which have been linked to different vegetation models. However, there has not yet been a systematic examination of how these different strategies contribute to model performance. Here we describe the structure of the first phase of the Fire Model Intercomparison Project (FireMIP), which for the first time seeks to systematically compare a number of models. By combining a standardized set of input data and model experiments with a rigorous comparison of model outputs to each other and to observations, we will improve the understanding of what drives vegetation fire, how it can best be simulated, and what new or improved observational data could allow better constraints on model behavior. In this paper, we introduce the fire models used in the first phase of FireMIP, the simulation protocols applied, and the benchmarking system used to evaluate the models. We have also created supplementary tables that describe, in thorough mathematical detail, the structure of each model.
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Journal articleDorfman S, Hietala H, Astfalk P, et al., 2017,
Growth rate measurement of ULF waves in the ion foreshock
, GEOPHYSICAL RESEARCH LETTERS, Vol: 44, Pages: 2120-2128, ISSN: 0094-8276 -
Journal articleVolwerk M, Jones GH, Broiles T, et al., 2017,
Current sheets in comet 67P/Churyumov-Gerasimenko's coma
, Journal of Geophysical Research: Space Physics, Vol: 122, Pages: 3308-3321, ISSN: 2169-9402The Rosetta Plasma Consortium (RPC) data are used to investigate the presence of current sheets in the coma of comet 67P/Churyumov-Gerasimenko. The interaction of the interplanetary magnetic field (IMF) transported by the solar wind toward the outgassing comet consists amongst others of mass loading and field line draping near the nucleus. The draped field lines lead to so-called nested draping because of the constantly changing direction of the IMF. It is shown that the draping pattern is strongly variable over the period of one month. Nested draping results in neighbouring regions with oppositely directed magnetic fields, which are separated by current sheets. Selected events on 5 and 6 June 2015 are studied, which show that there are strong rotations of the magnetic field with associated current sheets that have strengths from several tens up to hundreds of nA/m2. Not all discussed current sheets show the characteristic peak in plasma density at the centre of the sheet, which might be related to the presence of a guide field. There is no evidence for different kinds of plasmas on either side of a current sheet, and no strongly accelerated ions have been observed which could have been an indication of magnetic reconnection in the current sheets.
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Journal articleRiley P, Ben-Nun M, Linker JA, et al., 2017,
Forecasting the properties of the solar wind using simple pattern recognition
, SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS, Vol: 15, Pages: 526-540, ISSN: 1542-7390 -
Journal articleHoilijoki S, Ganse U, Pfau-Kempf Y, et al., 2017,
Reconnection rates and X line motion at the magnetopause: Global 2D-3V hybrid-Vlasov simulation results
, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 122, Pages: 2877-2888, ISSN: 2169-9380 -
Journal articlePulupa M, Bale SD, Bonnell JW, et al., 2017,
The solar probe plus radio frequency spectrometer: Measurement requirements, analog design, and digital signal processing
, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 122, Pages: 2836-2854, ISSN: 2169-9380- Author Web Link
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- Citations: 58
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Journal articleHietala H, Artemyev AV, Angelopoulos V, 2017,
Ion dynamics in magnetotail reconnection in the presence of density asymmetry
, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 122, Pages: 2010-2023, ISSN: 2169-9380 -
Journal articleCahill B, Toumi R, Stenchikov G, et al., 2017,
Evaluation of thermal and dynamic impacts of summer dust aerosols on the Red Sea
, Journal of Geophysical Research: Oceans, Vol: 122, Pages: 1325-1346, ISSN: 2169-9275The seasonal response of upper ocean processes in the Red Sea to summer-time dust aerosol perturbations is investigated using an uncoupled regional ocean model. We find that the upper limit response is highly sensitive to dust-induced reductions in radiative fluxes. Sea surface cooling of −1°C and −2°C is predicted in the northern and southern regions, respectively. This cooling is associated with a net radiation reduction of −40 W m−2 and −90 W m−2 over the northern and southern regions, respectively. Larger cooling occurs below the mixed layer at 75 m in autumn, −1.2°C (north) and −1.9°C (south). SSTs adjust more rapidly (ca. 30 days) than the subsurface temperatures (seasonal time scales), due to stronger stratification and increased mixed layer stability inhibiting the extent of vertical mixing. The basin average annual heat flux reverses sign and becomes positive, +4.2 W m−2 (as compared to observed estimates −17.3 W m−2) indicating a small gain of heat from the atmosphere. When we consider missing feedbacks from atmospheric processes in our uncoupled experiment, we postulate that the magnitude of cooling and the time scales for adjustment will be much less, and that the annual heat flux will not reverse sign but nevertheless be reduced as a result of dust perturbations. While our study highlights the importance of considering coupled ocean-atmosphere processes on the net surface energy flux in dust perturbation studies, the results of our uncoupled dust experiment still provide an upper limit estimate of the response of the upper ocean to dust-induced radiative forcing perturbations.
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Journal articleWu Y, Han Y, Voulgarakis A, et al., 2017,
An agricultural biomass burning episode in eastern China: transport, optical properties, and impacts on regional air quality
, Journal of Geophysical Research: Atmospheres, Vol: 122, Pages: 2304-2324, ISSN: 2169-897XAgricultural biomass burning (ABB) has been of particular concern due to its influence on air quality and atmospheric radiation, as it produces large amounts of gaseous and aerosol emissions. This paper presents an integrated observation of a significant ABB episode in Nanjing, China, during early June 2011, using combined ground-based and satellite sensors (Moderate Resolution Imaging Spectroradiometer, Atmospheric Infrared Sounder, Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO), and Ozone Monitoring Instrument products). The time-height distribution, optical properties, sources and transport of smoke, and its impacts on air quality are investigated. Lidar profiles indicate that the smoke aerosols are confined to the planetary boundary layer (PBL) and have a depolarization ratio of less than 0.08. The aerosol optical depths increase from 0.5 to 3.0 at 500 nm, while the extinction-related Angstrom exponent increases from 1.1 to 1.6 at the wavelength pair of 440–870 nm. The single-scattering albedo becomes lower at 670–1020 nm following the ABB intrusion and particularly shows a decreasing tendency between wavelengths of 440 to 1020 nm. The absorption Angstrom exponent (0.7) is smaller than 1.0, which may indicate the aged smoke particles mixed or coated with the urban aerosols. Surface particular matter PM10 and PM2.5 show a dramatic increase, reaching hourly mean of 800 µg/m3 and 485 µg/m3, respectively, which results in a heavy air pollution event. The stagnant and high-moisture weather provides favorable conditions for the aerosols to accumulate near the surface. Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) also illustrate that the large-scale aerosols are primarily present in the PBL and transported to the ocean, but some dense smoke plumes are misclassified as cloud or polluted dust. By comparing with the observations, we found that the
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Journal articleKhurana KK, Fatemi S, Lindkvist J, et al., 2017,
The role of plasma slowdown in the generation of Rhea's Alfven wings
, Journal of Geophysical Research: Space Physics, Vol: 122, Pages: 1778-1788, ISSN: 2169-9380Alfvén wings are known to form when a conducting or mass-loading object slows down a flowing plasma in its vicinity. Alfvén wings are not expected to be generated when an inert moon such as Rhea interacts with Saturn's magnetosphere, where the plasma impacting the moon is absorbed and the magnetic flux passes unimpeded through the moon. However, in two close polar passes of Rhea, Cassini clearly observed magnetic field signatures consistent with Alfvén wings. In addition, observations from a high-inclination flyby (Distance > 100 RRh) of Rhea on 3 June 2010 showed that the Alfvén wings continue to propagate away from Rhea even at this large distance. We have performed three-dimensional hybrid simulations of Rhea's interaction with Saturn's magnetosphere which show that the wake refilling process generates a plasma density gradient directed in the direction of corotating plasma. The resulting plasma pressure gradient exerts a force directed toward Rhea and slows down the plasma streaming into the wake along field lines. As on the same field lines, outside of the wake, the plasma continues to move close to its full speed, this differential motion of plasma bends the magnetic flux tubes, generating Alfvén wings in the wake. The current system excited by the Alfvén wings transfers momentum to the wake plasma extracting it from plasma outside the wake. Our work demonstrates that Alfvén wings can be excited even when a moon does not possess a conducting exosphere.
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Journal articleSergis N, Jackman CM, Thomsen MF, et al., 2017,
Radial and local time structure of the Saturnian ring current, revealed by Cassini
, Journal of Geophysical Research: Space Physics, Vol: 122, Pages: 1803-1815, ISSN: 2169-9380We analyze particle and magnetic field data obtained between July 2004 and December 2013 in the equatorial magnetosphere of Saturn, by the Cassini spacecraft. The radial and local time distribution of the total (thermal and suprathermal) particle pressure and total plasma beta (ratio of particle to magnetic pressure) over radial distances from 5 to 16 Saturn radii (RS = 60,258 km) is presented. The average azimuthal current density Jϕ and its separate components (inertial, pressure gradient, and anisotropy) are computed as a function of radial distance and local time and presented as equatorial maps. We explore the relative contribution of different physical mechanisms that drive the ring current at Saturn. Results show that (a) the particle pressure is controlled by thermal plasma inside of ~8 RS and by the hot ions beyond ~12 RS, exhibiting strong local time asymmetry with higher pressures measured at the dusk and night sectors; (b) the plasma beta increases with radial distance and remains >1 beyond 8–10 RS for all local times; (c) the ring current is asymmetric in local time and forms a maximum region between ~7 and ~13 RS, with values up to 100–115 pA/m2; and (d) the ring current is inertial everywhere inside of 7 RS, exhibits a mixed nature between 7 and 11 RS and is pressure gradient driven beyond 11 RS, with the exception of the noon sector where the mixed nature persists. In the dawn sector, it appears strongly pressure gradient driven for a wider range of radial distance, consistent with fast return flow of hot, tenuous magnetospheric plasma following tail reconnection.
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Journal articleBadia A, Jorba O, Voulgarakis A, et al., 2017,
Description and evaluation of the Multiscale Online Nonhydrostatic AtmospheRe CHemistry model (NMMB-MONARCH) version 1.0: gas-phase chemistry at global scale
, Geoscientific Model Development, Vol: 10, Pages: 609-638, ISSN: 1991-959XThis paper presents a comprehensive description and benchmark evaluation of the tropospheric gas-phase chemistry component of the Multiscale Online Nonhydrostatic AtmospheRe CHemistry model (NMMB-MONARCH), formerly known as NMMB/BSC-CTM, that can be run on both regional and global domains. Here, we provide an extensive evaluation of a global annual cycle simulation using a variety of background surface stations (EMEP, WDCGG and CASTNET), ozonesondes (WOUDC, CMD and SHADOZ), aircraft data (MOZAIC and several campaigns), and satellite observations (SCIAMACHY and MOPITT). We also include an extensive discussion of our results in comparison to other state-of-the-art models. We note that in this study, we omitted aerosol processes and some natural emissions (lightning and volcano emissions).The model shows a realistic oxidative capacity across the globe. The seasonal cycle for CO is fairly well represented at different locations (correlations around 0.3–0.7 in surface concentrations), although concentrations are underestimated in spring and winter in the Northern Hemisphere, and are overestimated throughout the year at 800 and 500 hPa in the Southern Hemisphere.Nitrogen species are well represented in almost all locations, particularly NO2 in Europe (root mean square error – RMSE – below 5 ppb). The modeled vertical distributions of NOx and HNO3 are in excellent agreement with the observed values and the spatial and seasonal trends of tropospheric NO2 columns correspond well to observations from SCIAMACHY, capturing the highly polluted areas and the biomass burning cycle throughout the year. Over Asia, the model underestimates NOx from March to August, probably due to an underestimation of NOx emissions in the region. Overall, the comparison of the modeled CO and NO2 with MOPITT and SCIAMACHY observations emphasizes the need for more accurate emission rates from anthropogenic and biomass burning sources (i.e., specification of temporal variability).The
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Journal articleSundberg T, Burgess D, Scholer M, et al., 2017,
The dynamics of very high Alfvén Mach number shocks in space plasmas
, Astrophysical Journal Letters, Vol: 836, ISSN: 2041-8213Astrophysical shocks, such as planetary bow shocks or supernova remnant shocks, are often in the high or very-high Mach number regime, and the structure of such shocks is crucial for understanding particle acceleration and plasma heating, as well inherently interesting. Recent magnetic field observations at Saturn's bow shock, for Alfvén Mach numbers greater than about 25, have provided evidence for periodic non-stationarity, although the details of the ion- and electron-scale processes remain unclear due to limited plasma data. High-resolution, multi-spacecraft data are available for the terrestrial bow shock, but here the very high Mach number regime is only attained on extremely rare occasions. Here we present magnetic field and particle data from three such quasi-perpendicular shock crossings observed by the four-spacecraft Cluster mission. Although both ion reflection and the shock profile are modulated at the upstream ion gyroperiod timescale, the dominant wave growth in the foot takes place at sub-proton length scales and is consistent with being driven by the ion Weibel instability. The observed large-scale behavior depends strongly on cross-scale coupling between ion and electron processes, with ion reflection never fully suppressed, and this suggests a model of the shock dynamics that is in conflict with previous models of non-stationarity. Thus, the observations offer insight into the conditions prevalent in many inaccessible astrophysical environments, and provide important constraints for acceleration processes at such shocks.
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Journal articleCzaja A, Vanniere B, Dacre H, 2017,
A "cold path" for Gulf Stream - troposphere connection
, Journal of Climate, Vol: 30, Pages: 1363-1379, ISSN: 1520-0442The mechanism by which the Gulf Stream sea surface temperature (SST)front anchors a band of precipitation on its warm edge is still a matter of debateand little is known about how synoptic activity contributes to the meanstate. In the present study, the influence of the SST front on precipitationis investigated during the course of a single extratropical cyclone using a regionalconfiguration of the Met Office Unified Model. The comparison of acontrol run with a simulation in which SST gradients were smoothed broughtthe following conclusions: a band of precipitation is reproduced for a singleextratropical cyclone and the response to the SST gradient is dominated bya change of convective precipitation in the cold sector of the storm. Severalclimatological features described by previous studies, such as surface windconvergence on the warm edge or a meridional circulation cell across the SSTfront, are also reproduced at synoptic time scales in the cold sector. Based onthese results, a simple boundary layer model is proposed to explain the convectiveand dynamical response to the SST gradient in the cold sector. In thismodel, cold and dry air parcels acquire more buoyancy over a sharp SST gradientand become more convectively unstable. The convection sets a pressureanomaly over the entire depth of the boundary layer which drives wind convergence.This case study offers a new pathway by which the SST gradientcan anchor a climatological band of precipitation.
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Journal articleEastwood J, Biffis E, Hapgood MA, et al., 2017,
The economic impact of space weather: where do we stand?
, Risk Analysis, Vol: 37, Pages: 206-218, ISSN: 0272-4332Space weather describes the way in which the Sun, and conditions in space more generally, impact human activity and technology both in space and on the ground. It is now well understood that space weather represents a significant threat to infrastructure resilience, and is a source of risk that is wide‐ranging in its impact and the pathways by which this impact may occur. Although space weather is growing rapidly as a field, work rigorously assessing the overall economic cost of space weather appears to be in its infancy. Here, we provide an initial literature review to gather and assess the quality of any published assessments of space weather impacts and socioeconomic studies. Generally speaking, there is a good volume of scientific peer‐reviewed literature detailing the likelihood and statistics of different types of space weather phenomena. These phenomena all typically exhibit “power‐law” behavior in their severity. The literature on documented impacts is not as extensive, with many case studies, but few statistical studies. The literature on the economic impacts of space weather is rather sparse and not as well developed when compared to the other sections, most probably due to the somewhat limited data that are available from end‐users. The major risk is attached to power distribution systems and there is disagreement as to the severity of the technological footprint. This strongly controls the economic impact. Consequently, urgent work is required to better quantify the risk of future space weather events.
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Journal articleChen P, Wang T, Lu X, et al., 2017,
Source apportionment of size-fractionated particles during the 2013 Asian Youth Games and the 2014 Youth Olympic Games in Nanjing, China
, SCIENCE OF THE TOTAL ENVIRONMENT, Vol: 579, Pages: 860-870, ISSN: 0048-9697- Author Web Link
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- Citations: 22
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Journal articleGingell IL, Sorriso-Valvo L, Burgess D, et al., 2017,
Three dimensional simulations of sheared current sheets: transition to turbulence?
, Journal of Plasma Physics, Vol: 83, ISSN: 1469-7807Systems of multiple current sheets arise in various situations in natural plasmas, such asat the heliospheric current sheet in the solar wind and in the outer heliosphere in theheliosheath. Previous three-dimensional simulations have shown that such systems candevelop turbulent-like fluctuations resulting from forward and inverse cascade in wavevector space. We present a study of the transition to turbulenceof such multiple currentsheet systems, including the effects of adding a magnetic guide field and velocity shearsacross the current sheets. Three-dimensional hybrid simulationsare performed of systemswith eight narrow current sheets in a triply-periodic geometry. We carry out a numberof different analyses of the evolution of the fluctuations as the initially highly orderedstate relaxes to one which resembles turbulence. Despite the evidence of forward andinverse cascade in the fluctuation power spectra, we find that none of the simulated caseshave evidence of intermittency after the initial period of fast reconnection associatedwith the ion tearing instability at the current sheets. Cancellation analysis confirms thatthe simulations have not evolved to a state which can be identified as fully developedturbulence. The addition of velocity shears across the current sheets slows the evolutionin the properties of the fluctuations, but by the end of the simulation they are broadlysimilar. However, if the simulation is constrained to be two-dimensional, differences arefound, indicating that fully three-dimensional simulations are important when studyingthe evolution of an ordered equilibrium towards a turbulent-like state.
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Journal articleLiu F, Fiencke C, Guo J, et al., 2017,
Performance evaluation and optimization of field-scale bioscrubbers for intensive pig house exhaust air treatment in northern Germany
, Science of The Total Environment, Vol: 579, Pages: 694-701, ISSN: 0048-9697 -
Journal articleHan D-S, Hietala H, Chen X-C, et al., 2017,
Observational properties of dayside throat aurora and implications on the possible generation mechanisms
, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 122, Pages: 1853-1870, ISSN: 2169-9380 -
Journal articleArtemyev AV, Angelopoulos V, Hietala H, et al., 2017,
Ion density and temperature profiles along (X-GSM) and across (Z(GSM)) the magnetotail as observed by THEMIS, Geotail, and ARTEMIS
, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 122, Pages: 1590-1599, ISSN: 2169-9380 -
Journal articleHeyn I, Block K, Mülmenstädt J, et al., 2017,
Assessment of simulated aerosol effective radiative forcings in the terrestrial spectrum
, Geophysical Research Letters, Vol: 44, Pages: 1001-1007, ISSN: 1944-8007In its fifth assessment report (AR5), the Intergovernmental Panel on Climate Change provides a best estimate of the effective radiative forcing (ERF) due to anthropogenic aerosol at −0.9 W m−2. This value is considerably weaker than the estimate of −1.2 W m−2 in AR4. A part of the difference can be explained by an offset of +0.2 W m−2 which AR5 added to all published estimates that only considered the solar spectrum, in order to account for adjustments in the terrestrial spectrum. We find that, in the CMIP5 multimodel median, the ERF in the terrestrial spectrum is small, unless microphysical effects on ice- and mixed-phase clouds are parameterized. In the latter case it is large but accompanied by a very strong ERF in the solar spectrum. The total adjustments can be separated into microphysical adjustments (aerosol “effects”) and thermodynamic adjustments. Using a kernel technique, we quantify the latter and find that the rapid thermodynamic adjustments of water vapor and temperature profiles are small. Observation-based constraints on these model results are urgently needed.
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Journal articleSorba AM, Achilleos NA, Guio P, et al., 2017,
Modeling the compressibility of Saturn's magnetosphere in response to internal and external influences
, Journal of Geophysical Research: Space Physics, Vol: 122, Pages: 1572-1589, ISSN: 2169-9402The location of a planetary magnetopause is principally determined by the balance between solar wind dynamic pressure DP and magnetic and plasma pressures inside the magnetopause boundary. Previous empirical studies assumed that Saturn's magnetopause standoff distance varies as math formula and measured a constant compressibility parameter α corresponding to behavior intermediate between a vacuum dipole appropriate for Earth (α≈6) and a more easily compressible case appropriate for Jupiter (α≈4). In this study we employ a 2-D force balance model of Saturn's magnetosphere to investigate magnetospheric compressibility in response to changes in DP and global hot plasma content. For hot plasma levels compatible with Saturn observations, we model the magnetosphere at a range of standoff distances and estimate the corresponding DP values by assuming pressure balance across the magnetopause boundary. We find that for “average” hot plasma levels, our estimates of α are not constant with DP but vary from ∼4.8 for high DP conditions, when the magnetosphere is compressed (≤25 RS), to ∼3.5 for low DP conditions. This corresponds to the magnetosphere becoming more easily compressible as it expands. We find that the global hot plasma content influences magnetospheric compressibility even at fixed DP, with α estimates ranging from ∼5.4 to ∼3.3 across the range of our parameterized hot plasma content. We suggest that this behavior is predominantly driven by reconfiguration of the magnetospheric magnetic field into a more disk-like structure under such conditions. In a broader context, the compressibility of the magnetopause reveals information about global stress balance in the magnetosphere.
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