bluuebunny/crossref_metadata_2025 huggingface dataset:
Pacific Plate subduction beneath the central Mariana and Izu‐Bonin fore arcs: New insights from an old margin
Authors: Oakley A. J. , Taylor B. , Moore G. F.
Published: June 2008

Multichannel seismic (MCS) profiles and bathymetric data from the central Mariana and Izu‐Bonin subduction systems image the subducting Pacific Plate from the outer trench slope to beneath serpentinite seamounts on the outer fore arc. Subducting oceanic crust varies along the Mariana margin from 5.3 to 7 km thick and is covered by 0.5–2 km thick sediments and numerous seamounts. Oceanic crustal thickness east of the Izu‐Bonin Trench is ∼6 km. Faulting resulting from flexure of the incoming Pacific Plate begins up to 100 km east of the trench axis, near the 6 km depth contour. The plate is cut by normal faults that reactivate inherited tectonic fabric where that fabric strikes <25° to the trench. Where the strike is >25°, incoming crust breaks along new faults with a trench‐parallel strike. The Mariana Trench axis is commonly a graben that accommodates an abrupt change (within <25 km) of plate dip from <4° (commonly ≤2°) on the incoming plate to >8° beneath the outer fore arc. We infer that the plate fails there rather than simply bends under the applied loads. Along portions of the Mariana margin, subducting seamounts displace the trench axis westward and uplift the toe of the slope. Surprisingly, west of the toe, there is no geophysical evidence of disturbance of the upper plate in response to seamount subduction, nor of significant subduction erosion or sediment underplating. MCS profiles across the base of the Mariana inner trench slope provide evidence for both complete subduction and small‐scale accretion of Pacific Plate sediments; however, we found no evidence for long‐term sediment accretion. The subducting plate dips 9–12° beneath serpentinite seamounts on the Izu‐Bonin and Mariana fore arcs. Along the Mariana margin, the majority of these seamounts are located ∼50–70 km west of the trench where the mantle wedge is 3–7 km thick between 8–10 km thick fore‐arc crust and the top of the subducting plate. The apparent lack of significant deformation of the Mariana fore arc crust by subducting seamounts may be the result of a weak serpentinized mantle wedge and/or progressive fracturing as the subducting plate increases in dip as it passes through the trench graben.
On analyses of satellite ion scale reconnection data
Authors: Mozer F. S. , Cully C. M.
Published: June 2008

Analyses of satellite‐measured fields and flows through reconnecting current sheets have assumed that the relative velocity of the satellite and the current sheet is in the direction of the current sheet normal. During analyses, this relative normal velocity has been removed by translation of the satellite data. The assumption that the relative motion is along the normal may be invalid such that, in the satellite reference frame, the reconnection structure moves in the plane of the current sheet during the crossing. In this case, the fields and flows are not measured in the reconnection rest frame although they must be known in this frame for quantitative analyses of the reconnection data. Consequences of this slippage of the reconnection rest frame in the plane of the current sheet are investigated to show that errors may be large and that rotation (minimum variance, maximum variance, or Faraday Residue) or translation (to the normal incidence frame, the deHoffman‐Teller frame, etc.) can exacerbate them. It is often the case that little can be done to guarantee a meaningful event analysis because of the insufficiency of the data collected in single satellite crossings of a reconnecting current sheet.
A linear analysis of the hybrid Kelvin‐Helmholtz/Rayleigh‐Taylor instability in an electrostatic magnetosphere‐ionosphere coupling system
Authors: Yamamoto T.
Published: June 2008

A linear analysis of the hybrid Kelvin‐Helmholtz/Rayleigh‐Taylor (KH/RT) instability in the magnetosphere‐ionosphere coupling system is presented. In the magnetosphere plasma particles can move by the electric (E × B) drift, magnetic drift (gradient B drift plus curvature drift), and inertia drift. Field‐aligned currents are generated primarily from divergence of the magnetic drift flux. They are closed via Pedersen currents in the ionosphere. As a simple model, there is a surface of discontinuity both in the azimuthal flow and the particle energy density, which extends longitudinally as projected to the ionospheric plane. The gradient of the energy density is directed inward or outward so that the plasma is RT unstable or stable, respectively. The present analysis shows that only a velocity shear cannot drive the system KH unstable when the growth rate, γKH, of the KH instability without Pedersen coupling is less than the inertial relaxation rate, ν, and that the presence of an energy density gradient allows a hybrid wave to grow even when γKH < ν. The wave growth is due to the active charge separation driving originally the RT instability. The picture of auroral deformations now changes drastically. The traditional picture is such that if the Pedersen coupling is properly taken into account, KH waves of long wavelengths (≳100 km at the ionospheric height) are found evanescent in the main body of the auroral oval. A new one is such that wavy structures therein can develop, only in the KH/RT hybrid mode, at the places where the particle energy density has an inward gradient. Similarly, the stability of the inner boundary of the low‐latitude boundary layer is controlled by the RT stability conditions more influentially than the KH conditions.
Efficient approximations of quasi‐linear diffusion coefficients in the radiation belts
Authors: Albert J. M.
Published: June 2008

Combined pitch angle and energy diffusion are key ingredients in current models of radiation belt electron dynamics. Bounce‐averaged quasi‐linear diffusion coefficients can be approximated with a recently developed approach based on the ranges of wave normal angle compatible with cyclotron and Landau resonance within a prescribed wave frequency band, as has been demonstrated for a model of chorus waves. The method casts nested, multiple integrals over wave normal angle as a single weighted average, which is further approximated by evaluation at only a few, carefully chosen points. Here, the method is shown to agree well with results for more recent models of chorus, electromagnetic ion cyclotron waves, and whistler mode hiss. Highly oblique magnetosonic waves are also considered, and a related approach is developed which is shown to give a good approximation for their diffusion rates.
Bulk heat transfer coefficient in the ice–upper ocean system in the ice melt season derived from concentration–temperature relationship
Authors: Nihashi Sohey , Ohshima Kay I.
Published: June 2008

The bulk heat transfer coefficient in the ice–upper ocean system (Kb) in the ice melt season is estimated by a new method at 18 areas that cover much of the Antarctic seasonal ice zone. The method is based on a model in which ice melting is caused only by heat input through open water and is treated in a bulk fashion in the ice–upper ocean system. Kb is estimated by fitting a convergent curve derived from the model to an observed ice concentration–temperature plot (CT‐plot). Estimated Kb is 1.15 ± 0.72 × 10−4 m s−1 on average. If Kb can be expressed by the product of the heat transfer coefficient (ch) and the friction velocity (uτ), ch is 0.0113 ± 0.0055. This value is about two times larger than that estimated at the ice bottom. The relationship between Kb and the geostrophic wind speed (Uw), which is roughly proportional to uτ, shows a significant positive correlation, as expected. Further, Kb seems more likely to be proportional to the square or cube of Uw rather than a linear relationship. Since Kb estimated from our method is associated with ice melting in a bulk fashion in the ice–upper ocean system, this relationship likely indicates both the mixing process of heat in the upper ocean (proportional to uτ3) and the local heat transfer process at the ice–ocean interface (proportional to uτ).
Effect of phytoplankton growth on air bubble residence time in seawater
Authors: Kuhnhenn‐Dauben V. , Purdie D. A. , Knispel U. , Voss H. , Horstmann U.
Published: June 2008

Laboratory experiments were carried out in a seawater mesocosm tank to investigate the influence of marine phytoplankton growth on air bubble residence time (BRT). Air bubbles of 10–1000 μm in diameter were injected by flushing a water jet into the top of the tank and BRT was determined acoustically. The tank was filled with seawater containing a natural phytoplankton population and growth stimulated by irradiating with artificial fluorescent light. A second experiment was conducted using a monoculture of the diatom Cylindrotheca closterium. BRT and several phytoplankton growth‐related parameters (chlorophyll concentration, dissolved inorganic nutrients, dissolved organic carbon (DOC), oxygen saturation and bacteria numbers) as well as the water viscosity were monitored over periods of up to 24 days. BRT showed a statistically significant covariation with oxygen saturation (r = 0.69, α = 0.01 for natural phytoplankton; r = 0.93, α = 0.01 for the Cylindrotheca closterium) and chlorophyll concentration (r = 0.69, α = 0.05 natural phytoplankton; r = 0.76, α = 0.01 Cylindrotheca closterium) during phytoplankton growth periods. Increases in BRT of a factor >2 were found during the chlorophyll maximum, when the water was sufficiently supersaturated with oxygen (∼>110%). No clear relationship was evident between BRT and measurements of DOC or water viscosity. Model experiments with highly oxygen‐supersaturated water and artificial polysaccharide compounds indicated that oxygen supersaturation alone is not the main factor causing increased BRT during phytoplankton growth, but it is most likely a combination of the degree of gas saturation and the composition of the organic exudates derived from the microalgal population.
Decadal increases of anthropogenic CO2 in the subtropical South Atlantic Ocean along 30°S
Authors: Murata Akihiko , Kumamoto Yuichiro , Sasaki Ken'ichi , Watanabe Shuichi , Fukasawa Masao
Published: June 2008

Using high‐quality data for dissolved inorganic carbon and related properties obtained about 10 years apart (1992/1993–2003), we examined decadal increases of anthropogenic CO2 (ΔnCTCAL) along 30°S (WHP A10 section) in the subtropical South Atlantic. Significant ΔnCTCAL was detectable down to an isopycnal surface of σθ = 27.3 (∼1000 m water depth). Averaged ΔnCTCAL in Sub‐Antarctic Mode Water (SAMW; 26.6–27.0 σθ, 350–700 m) was 6.8 ± 1.6 μmol kg−1 and that in Antarctic Intermediate Water (AAIW; 27.1–27.4 σθ, 700–1200 m) was 3.6 ± 1.4 μmol kg−1. In SAMW, ΔnCTCAL was higher by ∼7 μmol kg−1 west of 15°W than east of it, while ΔnCTCAL in AAIW did not show such a distinct east‐west difference. For deep waters, significant ΔnCTCAL was detected in Antarctic Bottom Water at depths greater than 4500 m in the Cape Basin (longitude 2°E–10°E). No significant ΔnCTCAL could be detected for North Atlantic Deep Water (NADW). We attributed ΔnCTCAL being higher west of 15°W in SAMW to differences of water mass distributions and flows. From a water column inventory, we estimated the uptake rate of anthropogenic CO2 over the decade from 1992/1993 to 2003 to be 0.6 ± 0.1 mol m−2 a−1, which is half the rate in the South Pacific (1.0 ± 0.4 mol m−2 a−1).
Description and validation of the OMI very fast delivery products
Authors: Hassinen S. , Tamminen J. , Tanskanen A. , Leppelmeier G. , Mälkki A. , Koskela T. , Karhu J. M. , Lakkala K. , Veefkind P. , Krotkov N. , Aulamo O.
Published: June 2008

The Dutch‐Finnish Ozone Monitoring Instrument (OMI) is on board the NASA's Earth Observing System (EOS) Aura satellite. The Aura satellite has a so‐called direct broadcast (DB) capability to broadcast the measurements to ground stations at the same time as the measurements are being stored in the spacecraft's memory for later transmission to Earth. The Finnish Meteorological Institute's very fast delivery (VFD) processing system utilizes this direct broadcast to produces maps of total ozone and ultraviolet radiation over Europe within 15 min after the satellite overpass Sodankylä ground station in northern Finland. The VFD products include maps of total ozone, ultraviolet index, and ultraviolet daily dose. The aim of this service is to provide up‐to‐date information on the ozone and ultraviolet situation for the general public and snapshots of the current situation for scientists. The accuracy of the VFD products compares well with standard off‐line OMI ozone products as well as ground‐based Brewer measurements. After the VFD update in May 2006, the differences with Brewer measurements are −1.0 ± 7.2 DU for Sodankylä and −0.6 ± 8.0 DU for Jokioinen. Differences to OMDOAO3 and OMTO3 products are 2.1 ± 3.3 DU and 1.6 ± 6.6 DU for Sodankylä and 1.7 ± 2.0 DU and 0.0 ± 6.1 DU for Jokioinen, respectively. Between the VFD and Brewer measured UV daily dose products the relative error is generally less than 30%, which compares well to the global off‐line OMUVB product.
Use of Antarctica for validating reflected solar radiation measured by satellite sensors
Authors: Jaross G. , Warner J.
Published: June 2008

A technique is presented for validating Sun‐normalized radiances measured by polar orbiting sensors over Antarctica in the wavelength range 330–800 nm using model calculations for top of the atmosphere reflectances. An important input to these calculations is a model for the reflective properties of the snow surface, especially its directional nature. Details of this model are presented. Evaluations of the radiance calculations using OMI/Aura, MODIS/Aqua, and MISR/Terra data suggest that the surface representation is the largest source of uncertainty, representing ±1% in radiance at solar zenith angles less than 70°. Radiometric evaluations for limited wavelengths of MODIS, TOMS/Earth Probe, and OMI indicate that the first two are accurate to within the ±2% uncertainties in the technique. The OMI reflectances are lower than predictions by 2.5% to 8%, the smallest difference being near the nadir view and the largest at far off‐nadir view angles. A time series of Antarctic 360 nm radiances measured by OMI from launch until 2007 is consistent with no change in sensor response in excess of 1%.
Initial validation of ozone measurements from the High Resolution Dynamics Limb Sounder
Authors: Nardi Bruno , Gille John C. , Barnett John J. , Randall Cora E. , Harvey V. Lynn , Waterfall Alison , Reburn W. Jolyon , Leblanc Thierry , McGee Tom J. , Twigg Laurence W. , Thompson Anne M. , Godin‐Beekmann Sophie , Bernath Peter F. , Bojkov Bojan R. , Boone Chris D. , Cavanaugh Charles , Coffey Michael T. , Craft James , Craig Cheryl , Dean Vincil , Eden Thomas D. , Francis Gene , Froidevaux Lucien , Halvorson Chris , Hannigan James W. , Hepplewhite Christopher L. , Kinnison Douglas E. , Khosravi Rashid , Krinsky Charlie , Lambert Alyn , Lee Hyunah , Loh Joanne , Massie Steven T. , McDermid I. Stuart , Packman Daniel , Torpy Brendan , Valverde‐Canossa Jessica , Walker Kaley A. , Whiteman David N. , Witte Jacquelyn C. , Young Greg
Published: June 2008

Comparisons of the latest High Resolution Dynamics Limb Sounder (HIRDLS) ozone retrievals (v2.04.09) are made with ozonesondes, ground‐based lidars, airborne lidar measurements made during the Intercontinental Chemical Transport Experiment–B, and satellite observations. A large visual obstruction blocking over 80% of the HIRDLS field of view presents significant challenges to the data analysis methods and implementation, to the extent that the radiative properties of the obstruction must be accurately characterized in order to adequately correct measured radiances. The radiance correction algorithms updated as of August 2007 are used in the HIRDLS v2.04.09 data presented here. Comparisons indicate that HIRDLS ozone is recoverable between 1 and 100 hPa at middle and high latitudes and between 1 and 50 hPa at low latitudes. Accuracy of better than 10% is indicated between 1 and 30 hPa (HIRDLS generally low) by the majority of the comparisons with coincident measurements, and 5% is indicated between 2 and 10 hPa when compared with some lidars. Between 50 and 100 hPa, at middle and high latitudes, accuracy is 10–20%. The ozone precision is estimated to be generally 5–10% between 1 and 50 hPa. Comparisons with ozonesondes and lidars give strong indication that HIRDLS is capable of resolving fine vertical ozone features (1–2 km) in the region between 1 and 50 hPa. Development is continuing on the radiance correction and the cloud detection and filtering algorithms, and it is hoped that it will be possible to achieve a further reduction in the systematic bias and an increase in the measurement range downward to lower heights (at pressures greater than 50–100 hPa).
Implementation of cloud retrievals for TES atmospheric retrievals: 2. Characterization of cloud top pressure and effective optical depth retrievals
Authors: Eldering Annmarie , Kulawik Susan S. , Worden John , Bowman Kevin , Osterman Greg
Published: June 2008

We characterize and validate the cloud products from the Tropospheric Emission Spectrometer (TES) by comparing TES estimates of effective cloud optical depth and cloud top height to those from the Moderate Resolution Imaging Spectroradiometer (on EOS) (MODIS), the Atmospheric Infrared Sounder (AIRS), and to simulated data. TES measures in the infrared spectral region (650–2260 cm−1), where clouds have a ubiquitous impact on measured radiances and therefore on trace gas profile retrievals. The radiance contribution of clouds is parameterized in TES retrievals in terms of a set of frequency‐dependent nonscattering effective optical depths and a cloud height. This unique approach jointly retrieves cloud parameters with surface temperature, emissivity, atmospheric temperature, and trace gases such as ozone from TES spectral radiances. We calculate the relationship between the true optical depth and the TES effective optical depth for a range of single‐scatter albedo and phase functions to show how this varies with cloud type. We estimate the errors on retrieved cloud parameters using a simulated data set covering a wide range of cloud cases. For simulations with no noise on the radiances, cloud height errors are less than 30 hPa, and effective optical depth follows expected behavior for input optical depths of less than 3. When random noise is included on the radiances, and atmospheric variables are included in the retrieval, cloud height errors are approximately 200 hPa, and the estimated effective optical depth has sensitivity between optical depths of 0.3 and 10. The estimated errors from simulation are consistent with differences between TES and cloud top heights and optical depth from MODIS and AIRS.
Impact of perturbations to nitrogen oxide emissions from global aviation
Authors: Köhler Marcus O. , Rädel Gaby , Dessens Olivier , Shine Keith P. , Rogers Helen L. , Wild Oliver , Pyle John A.
Published: June 2008

The atmospheric response to perturbations in NOx emissions from global air traffic is investigated by performing a coherent set of sensitivity experiments. The importance of cruise altitude, size of the emission perturbation and geographical distribution of emissions is systematically analyzed using two global chemistry transport models and an off‐line radiative transfer model. NOx emissions from a contemporary aircraft inventory have been used to assess the impact of global air traffic on ozone and methane. In further experiments the NOx emissions are perturbed, in turn, in 16 cruise altitude bands between 5 and 15 km altitude. In the p‐TOMCAT model we diagnose an annual mean ozone increase of up to 6 ppbv and a decrease in the methane lifetime of 3% due to global air traffic in 2002. Associated radiative forcings of 30 mWm−2 for ozone and −19 mWm−2 for methane are diagnosed; a simple method is used to estimate the forcing due to the methane‐induced ozone change and this yields an additional −11 mWm−2. Results show that up to the tropopause, ozone production efficiency and resulting impacts increase per emitted mass of NOx with the altitude of the perturbation. Between 11 and 15 km we find that the geographical location of the NOx emissions plays a crucial role in the potential O3 impact and lifetime change of CH4. We show that changes in flight routing in this altitude range can have significant consequences for O3 and CH4 concentrations. Overall, we demonstrate a linear relationship in the atmospheric response to small emission changes which can be used to predict the importance of perturbations about the reference aircraft emissions profile, provided the geographical distribution of the emissions is not altered significantly.
Global distribution of solid and aqueous sulfate aerosols: Effect of the hysteresis of particle phase transitions
Authors: Wang Jun , Hoffmann Andrew A. , Park Rokjin J. , Jacob Daniel J. , Martin Scot T.
Published: June 2008

The partitioning between solid and aqueous phases of tropospheric sulfate‐ammonium particles is simulated with a global 3‐D chemical transport model (CTM). The simulation explicitly accounts for the hysteresis of particle phase transitions by transporting aqueous sulfate and three solid sulfate forms (namely, ammonium sulfate, letovicite, and ammonium bisulfate). Composition‐dependent deliquescence relative humidities (DRH) and crystallization relative humidities (CRH) are based on recent laboratory data. We find that the solids mass fraction on a sulfate basis is 0.34, partitioned as 93% ammonium sulfate, 6% letovicite, and 1% ammonium bisulfate. The fraction increases with altitude from 0.10 to 0.30 in the boundary layer to 0.60–0.80 in the upper troposphere. The dominance of solids in the upper troposphere arises in part from high sulfate neutralization, reflecting in our simulation a low retention efficiency of NH3 upon cloud freezing. High sulfate neutralization is consistent with the few available observations in the upper troposphere. High acidity with a dominant aqueous phase, however, can occur following volcanic eruptions. Seasonal variation of the solids mass fraction in both the lower and upper troposphere is modulated by emissions of NH3 from the terrestrial biosphere and biomass burning as well as by emissions of dimethylsulfide from the ocean biosphere. The timescale of phase transitions, as driven by changes in relative humidity, varies from 10 to 50 h in the boundary layer to 150–400 h in the upper troposphere. Omission of the hysteresis effect in the CTM by assuming that particle phase follows the lower side of the hysteresis loop increases the solids mass fraction from 0.34 to 0.56. An upper side assumption decreases the fraction to 0.17. Lower and upper side assumptions better approximate particle phase for high and low altitudes, respectively. Fluctuations in the CRH, which can be induced by other constituents in sulfate particles such as minerals or organic molecules, strongly affect the solids mass fraction in the boundary layer but not at higher altitudes. Further studies are needed to determine the effects of large solids mass fraction on heterogeneous chemistry and cirrus cloud formation.
Sensitivity of sulfate direct climate forcing to the hysteresis of particle phase transitions
Authors: Wang Jun , Jacob Daniel J. , Martin Scot T.
Published: June 2008

The effects of solid‐aqueous phase transitions on sulfate direct climate forcing (SDCF) are investigated by using both a column model and a global chemical transport model. Aqueous particles have a larger mass extinction efficiency but a smaller backscattered fraction than their solid counterparts. The column model shows that the hysteresis of the phase transition can result in an uncertainty in the SDCF of 20%. The global chemical transport model explicitly accounts for the relative humidity processing of particles and the associated hysteresis. The model also treats the extent of sulfate neutralization by ammonia. For the anthropogenic sulfate, the base case simulation finds that solid particles contribute 41% of the global burden, 26% of the clear‐sky optical thickness, 31% of the clear‐sky SDCF, and 37% of the full‐sky SDCF, a trend that reflects the correlation of solid particles with clear skies. A perturbation to the model, omitting hysteresis by assuming that all particles are aqueous, results in an overestimate of the SDCF by +8% compared to the base case. A converse assumption that crystallization occurs at the deliquescence relative humidity underestimates the SDCF by −8%. A case that assumes that aqueous particles occur whenever the ambient relative humidity exceeds the crystallization relative humidity biases the SDCF by +5%. A case that includes hysteresis but omits the difference in the fraction of radiation backscattered to space by aqueous compared to solid particles changes the SDCF by +15%. Seasonal and regional differences can be much larger. We recommend that the ratio of the sulfate aerosol optical thickness calculated with versus without consideration of particle hygroscopicity be reported as a standard output of SDCF models to facilitate meaningful intercomparisons among different models.
Late summer changes in burning conditions in the boreal regions and their implications for NOxand CO emissions from boreal fires
Authors: Lapina K. , Honrath R. E. , Owen R. C. , Val Martín M. , Hyer E. J. , Fialho P.
Published: June 2008

Building emission inventories for the fires in boreal regions remains a challenging task with significant uncertainties in the methods used. In this work, we assess the impact of seasonal trends in fuel consumption and flaming/smoldering ratios on emissions of species dominated by flaming combustion (e.g., NOx) and species dominated by smoldering combustion (e.g., CO). This is accomplished using measurements of CO and NOyat the free tropospheric Pico Mountain observatory in the central North Atlantic during the active boreal fire seasons of 2004 and 2005. ΔNOy/ΔCO enhancement ratios in aged fire plumes had higher values in June‐July (7.3 × 10−3mol mol−1) relative to the values in August‐September (2.8 × 10−3mol mol−1), indicating that NOx/CO emission ratios declined significantly as the fire season progressed. This is consistent with our understanding that an increased amount of fuel is consumed via smoldering combustion during late summer, as deeper burning of the drying organic soil layer occurs. A major growth in fuel consumption per unit area is also expected, due to deeper burning. Emissions of CO and NOxfrom North American boreal fires were estimated using the Boreal Wildland Fire Emissions Model, and their long‐range transport to the sampling site was modeled using FLEXPART. These simulations were generally consistent with the observations, but the modeled seasonal decline in the ΔNOy/ΔCO enhancement ratio was less than observed. Comparisons using alternative fire emission injection height scenarios suggest that plumes with the highest CO levels at the observatory were lofted well above the boundary layer, likely as a result of intense crown fires.
Introduction to special section on Aura Validation
Authors: Schoeberl M. R. , Douglass A. R. , Joiner J.
Published: June 2008

Aura, the last of the large EOS observatories, was launched on 15 July 2004 and has now been operating for several years. Aura is designed to make comprehensive stratospheric, mesospheric, and tropospheric constituent measurements from its four instruments HIRDLS, MLS, OMI, and TES. All of the instruments are performing well and observations of stratospheric and tropospheric trace gases and aerosols are revolutionizing our understanding of stratospheric chemistry and transport processes, ozone depletion, air quality, and the hydrological cycle. In this special section, the instrument teams and collaborators report on the validation of the released Aura data products.
Comparison of stratospheric measurements made by CHAMP radio occultation and Stratéole/Vorcore in situ data
Authors: McDonald A. J. , Hertzog A.
Published: June 2008

This paper compares measurements in the Antarctic stratosphere during austral spring and summer made by the CHAMP radio‐occultation satellite and in situ long‐duration super‐pressure balloon (SPB) observations during the Stratéole/Vorcore campaign. Initial analysis compares near‐simultaneous and co‐located temperature observations made by these instruments and finds excellent agreement between these two very different sets of measurements. The mean bias between the data sets is −0.52 K, CHAMP RO temperature being cooler than the balloon measurements, and the standard deviation of the temperature differences is 1.6 K for the paired observations. This paired data set also allows us to show that an empirical correction used to remove the influence of radiative heating on the balloon sensors does not produce any bias. An initial comparison of the magnitude of gravity wave activity observed by each instrument shows relatively poor agreement. Analysis suggests that this agreement can be improved slightly by accounting for the observational filtering associated with the CHAMP measurements.
THEMIS observations of long‐lived regions of large‐amplitude whistler waves in the inner magnetosphere
Authors: Cully C. M. , Bonnell J. W. , Ergun R. E.
Published: June 2008

Recent reports of large‐amplitude whistler waves (>100 mV/m) in the radiation belts have intensified interest in the role of whistler waves in accelerating radiation belt electrons to MeV energies. Several critical parameters for addressing this issue have not previously been observed, including the occurrence frequency, spatial extent and longevity of regions of large‐amplitude whistlers. The THEMIS mission, with multiple satellites in a near‐equatorial orbit, offers an excellent opportunity to study these waves. We use data from the Electric Field Instrument (EFI) to show that in the dawn‐side radiation belts, especially near L‐shells from 3.5 to 5.5, the probability distribution of wave activity has a significant high‐amplitude tail and is hence not well‐described by long‐term time averages. Regions of enhanced wave activity exhibit four‐second averaged wave power above 1 mV/m and sub‐second bursts up to several hundred mV/m. These regions are spatially localized to at most several hours of local time azimuthally, but can persist in the same location for several days. With large regions of space persistently covered by bursty, large‐amplitude waves, the mechanisms and rates of radiation belt electron acceleration may need to be reconsidered.
Structure of plasmaspheric plumes and their participation in magnetopause reconnection: First results from THEMIS
Authors: McFadden J. P. , Carlson C. W. , Larson D. , Bonnell J. , Mozer F. S. , Angelopoulos V. , Glassmeier K.‐H. , Auster U.
Published: June 2008

New observations by the THEMIS spacecraft have revealed dense (>10 cm−3) plasmaspheric plumes extending to the magnetopause. The large scale radial structure of these plumes is revealed by multi‐spacecraft measurements. Temporal variations in the radial distribution of plume plasma, caused by azimuthal density gradients coupled with azimuthal flow, are also shown to contribute to plume structure. In addition, flux tubes with cold plume plasma are shown to participate in reconnection, with simultaneous observations of cold ions and reconnection flow jets on open flux tubes as revealed by the loss of hot magnetospheric electrons.
Winter‐time dissolved iron and nutrient distributions in the Subantarctic Zone from 40–52S; 155–160E
Authors: Ellwood Michael J. , Boyd Philip W. , Sutton Philip
Published: June 2008

In HNLC oceanic regions, iron (Fe) controls phytoplankton productivity yet large gaps remain in our understanding of iron's biogeochemical cycle. Here we present the first comprehensive winter dataset for dissolved Fe (dFe) and nitrate (NO3) distributions (0–1000 m depth) between 40S–52S, which transects the Subantarctic zone (SAZ), west of New Zealand. Surface concentrations (<0.2 nmol Fe kg−1) were conspicuously low, i.e., probably biologically limiting even at winter‐reserve levels, at frontal zones between 43S (Subtropical Front) and ∼51S (Subantarctic Front). A fivefold range in Fe:NO3 molar ratios was observed along the transect, with Subtropical waters, where blooms occur, having the highest ratios in subsurface waters. The major wintertime supply of dFe in the SAZ is from Ekman advection of waters from the south (but calculated source water dFe is ∼0.2 nmol Fe kg−1), suggesting that mixed‐layer dFe concentration is controlled by how long these southern waters remain at the surface (∼3 years).
Structure and dynamics of the solar wind/ionosphere interface on Mars: MEX‐ASPERA‐3 and MEX‐MARSIS observations
Authors: Dubinin E. , Modolo R. , Fraenz M. , Woch J. , Duru F. , Akalin F. , Gurnett D. , Lundin R. , Barabash S. , Plaut J. J. , Picardi G.
Published: June 2008

The measurements of the local plasma parameters of the ionospheric and solar wind plasmas and the magnetic field strength carried out by the ASPERA‐3 and MARSIS experiments onboard Mars Express (MEX) in the subsolar region of the induced Martian magnetosphere provide us with a first test of the pressure balance across the solar wind/ionosphere interface. The structure of this transition is very dynamic and is controlled by the solar wind. For a broad range of the solar wind dynamic pressures, the magnetic field in the boundary layer raises to the values just sufficient to balance the solar wind pressure. The magnetic field frozen into the electrons is transported across the magnetospheric boundary (MB) where solar wind terminates and the planetary plasma begins to prevail. The dense ionospheric plasma has a sharp outer boundary the position of which is usually a little closer to the planet than the MB. Although the number density reaches on this boundary ∼103 cm−3 the contribution of the ionospheric thermal pressure is rather small and the ionosphere is magnetized. There are also cases when the magnetic field almost does not vary across both boundaries.
Rock type leaves topographic signature in landslide‐dominated mountain ranges
Authors: Korup Oliver
Published: June 2008

The idea that hillslopes in active mountain belts are limited to a threshold inclination by the rate of landsliding has guided landscape evolution models for over a decade. However, widely applied topographic diagnostics of threshold hillslopes remain debated and unverified. This study relates landslide occurrence to hillslope metrics of several active mountain ranges throughout New Zealand, which are formed in uniform greywacke and its schist derivative. All these ranges share a distinctive peak in hillslope inclination despite order‐of‐magnitude variations in rates of rock uplift and precipitation, landslide density, and extent of Quaternary glaciation. Comparison with landslide‐dominated terrain in different lithologies highlights this peak as diagnostic of rock type, reflecting a conspicuous tendency in hillslope evolution to adjust to rock‐mass strength irrespective of the intensity of tectonic and climatic forcing. This finding expands the model perspective that only undisturbed strength‐equilibrium slopes may adjust to their rock‐mass strength.
Translocation of the insulin‐regulated aminopeptidase to the cell surface: detection by radioligand binding
Authors: Demaegdt H , Smitz L , De Backer J‐P , Le M T , Bauwens M , Szemenyei E , Tóth G , Michotte Y , Vanderheyden P , Vauquelin G
Published: June 2008

Background and purpose:

Insulin‐regulated aminopeptidase (IRAP) and the insulin‐dependent glucose transporter GLUT4 colocalize in specific intracellular vesicles (that is, GLUT4 vesicles). These vesicles move slowly to the cell surface, but their translocation is markedly enhanced by insulin, resulting in higher glucose uptake. Previous studies of the insulin‐mediated translocation of IRAP to the cell surface have been hampered by the laborious detection of IRAP at the cell surface. We aimed to develop a more direct and faster method to detect IRAP. To this end, we used model systems with well‐characterized IRAP: CHO‐K1 cells expressing endogenous IRAP and recombinant HEK293 cells expressing human IRAP. A more widespread application of the method was demonstrated by the use of 3T3‐L1 adipocytes.

Experimental approach:

After stimulation of the cells with insulin, internalization of IRAP was inhibited by the addition of phenyl arsine oxide (PAO). Then, cell‐surface IRAP was detected by the high‐affinity binding of radiolabelled angiotensin (Ang) IV (either125I or3H).

Key Results:

We monitored the time‐ and concentration dependence of insulin‐mediated translocation of IRAP in both cell lines and 3T3‐L1 adipocytes. A plateau was reached between 6 and 8 min, and 10−7 Minsulin led to the highest amount of IRAP at the cell surface.

Conclusions and implications:

Based on the capacity of the IRAP apoenzyme to display high affinity for radiolabelled Ang IV and on the ability of PAO to inhibit IRAP internalization, we developed a more direct and faster method to measure insulin‐mediated translocation of IRAP to the cell surface.

British Journal of Pharmacology(2008)154, 872–881; doi:10.1038/bjp.2008.117; published online 21 April 2008
Characterization of (R,S)‐5,7‐di‐tert‐butyl‐3‐hydroxy‐3‐trifluoromethyl‐3H‐benzofuran‐2‐one as a positive allosteric modulator of GABABreceptors
Authors: Malherbe P , Masciadri R , Norcross R D , Knoflach F , Kratzeisen C , Zenner M‐T , Kolb Y , Marcuz A , Huwyler J , Nakagawa T , Porter R H P , Thomas A W , Wettstein J G , Sleight A J , Spooren W , Prinssen E P
Published: June 2008

Background and purpose:

As baclofen is active in patients with anxiety disorders, GABABreceptors have been implicated in the modulation of anxiety. To avoid the side effects of baclofen, allosteric enhancers of GABABreceptors have been studied to provide an alternative therapeutic avenue for modulation of GABABreceptors. The aim of this study was to characterize derivatives of (R,S)‐5,7‐di‐tert‐butyl‐3‐hydroxy‐3‐trifluoromethyl‐3H‐benzofuran‐2‐one (rac‐BHFF) as enhancers of GABABreceptors.

Experimental approach:

Enhancing properties ofrac‐BHFF were assessed in the Chinese hamster ovary (CHO)‐Gα16‐hGABAB(1a,2a)cells by Fluorometric Imaging Plate Reader and GTPγ[35S]‐binding assays, and in rat hippocampal slices by population spike (PS) recordings.In vivoactivities ofrac‐BHFF were assessed using the loss of righting reflex (LRR) and stress‐induced hyperthermia (SIH) models.

Key results:

In GTPγ[35S]‐binding assays, 0.3 μMrac‐BHFF or its pure enantiomer (+)‐BHFF shifted the GABA concentration–response curve to the left, an effect that resulted in a large increase in both GABA potency (by 15.3‐ and 87.3‐fold) and efficacy (149% and 181%), respectively. In hippocampal slices,rac‐BHFF enhanced baclofen‐induced inhibition of PS of CA1 pyramidal cells. In anin vivomechanism‐based model in mice,rac‐BHFF increased dose‐dependently the LRR induced by baclofen with a minimum effective dose of 3 mg kg−1p.o.rac‐BHFF (100 mg kg−1p.o.) tested alone had no effect on LRR nor on spontaneous locomotor activity, but exhibited anxiolytic‐like activity in the SIH model in mice.

Conclusions and implications:

rac‐BHFF derivatives may serve as valuable pharmacological tools to elucidate the pathophysiological roles played by GABABreceptors in the central and peripheral nervous systems.

British Journal of Pharmacology(2008)154, 797–811; doi:10.1038/bjp.2008.135; published online 21 April 2008
Pattern recognition receptors and interleukin‐8 mediate effects of Gram‐positive and Gram‐negative bacteria on lung epithelial cell function
Authors: Sorrentino R , De Souza P M , Sriskandan S , Duffin C , Paul‐Clark M J , Mitchell J A
Published: June 2008

Background and purpose:

Lung epithelial cells express pattern recognition receptors, which react to bacteria. We have evaluated the effect of Gram‐positive and Gram‐negative bacteria on interleukin‐8 (CXCL8) release from epithelial cells and the integrity of the epithelial barrier.

Experimental approach:

Primary cultures of human airway epithelial cells and the epithelial cell line A549 were used, and CXCL8 release was measured after exposure to Gram‐negative or Gram‐positive bacteria. Epithelial barrier function was assessed in monolayer cultures of A549 cells.

Results:

Gram‐positive bacteria Staphylococcus aureus or Streptococcus pneumoniae, induced release of CXCL8 from human airway epithelial cells. These bacteria also disrupted barrier function in A549 cells, an effect mimicked by CXCL8 and blocked by specific binding antibodies to CXCL8. Gram–negative bacteria Escherichia coli or Pseudomonas aeruginosa induced greater release of CXCL8 than Gram‐positive bacteria. However, Gram‐negative bacteria did not affect epithelial barrier function directly, but prevented disruption induced by Gram‐positive bacteria. These effects of Gram‐negative bacteria on barrier function were mimicked by FK565, an agonist of the nucleotide‐binding oligomerization domain 1 (NOD1) receptor, but not by the Toll‐like receptor (TLR) 4 agonist bacterial lipopolysaccharide. Neither the Gram‐negative bacteria nor FK565 blocked CXCL8 release.

Conclusions:

These data show differential functional responses induced by Gram‐negative and Gram‐positive bacteria in human lung epithelial cells. The NOD1 receptors may have a role in preventing disruption of the epithelial barrier in lung, during inflammatory states.

British Journal of Pharmacology (2008) 154, 864–871; doi:10.1038/bjp.2008.139; published online 21 April 2008
Examination of signalling pathways involved in muscarinic responses in bovine ciliary muscle using YM‐254890, an inhibitor of the Gq/11 protein
Authors: Yasui F , Miyazu M , Yoshida A , Naruse K , Takai A
Published: June 2008

Background and purpose:

In the ciliary muscle, the tonic component of the contraction produced by cholinergic agonists is highly dependent on Ca2+ provided by influx through non‐selective cation channels (NSCCs) opened by stimulation of M3 muscarinic receptors. We examined effects of YM‐254890 (YM), a Gq/11‐specific inhibitor, on contraction, NSCC currents and [Ca2+]i elevation induced by carbachol (CCh).

Experimental approach:

Isometric tension was recorded from ciliary muscle bundles excised from bovine eyes. In ciliary myocytes dispersed with collagenase and cultured for 1–5 days, whole‐cell currents were recorded by voltage clamp and the intracellular free Ca2+ concentration [Ca2+]i was monitored using the Fluo‐4 fluorophore. Existence and localization of M3 receptors and the α subunit of Gq/11 (Gαq/11) were examined by immunofluorescence microscopy using AlexaFluor‐conjugated antibodies.

Key results:

Both phasic and tonic components of contractions evoked by 2 μM CCh were inhibited by YM (3–10 μM) in a dose‐dependent manner. In the cultured cells, CCh (0.05–10 μM) evoked an NSCC current as well as an elevation of the [Ca2+]i. Both initial and sustained phases of these CCh‐evoked responses were abolished by YM (3–10 μM). Immunostaining of the cytoplasmic side of the plasma membrane of ciliary myocytes revealed a dense distribution of M3 receptors and Gαq/11.

Conclusions and implications:

The tonic as well as phasic component of the ciliary muscle contraction appears to be under control of signals conveyed by a Gq/11‐coupled pathway. YM is a useful tool to assess whether Gq/11 is involved in a signal transduction system.

British Journal of Pharmacology (2008) 154, 890–900; doi:10.1038/bjp.2008.140; published online 21 April 2008
Vardenafil, but not sildenafil or tadalafil, has calcium‐channel blocking activity in rabbit isolated pulmonary artery and human washed platelets
Authors: Toque H A , Teixeira C E , Priviero F B M , Morganti R P , Antunes E , De Nucci G
Published: June 2008

Background and purpose:

Phosphodiesterase type‐5 (PDE5) inhibitors constitute a novel and important therapeutic option for the treatment of pulmonary hypertension. The effects of the PDE5 inhibitors sildenafil, tadalafil and vardenafil on rabbit isolated pulmonary artery ring preparations and on intracellular Ca2+ concentration of thrombin‐stimulated human platelets were investigated.

Experimental approach:

Rabbit pulmonary artery rings were mounted in 10 mL organ bath containing Krebs solution. Tissues were connected to force‐displacement transducers, and changes in isometric force were recorded. Ca2+ flux in human washed platelets was measured.

Key results:

Sildenafil, tadalafil and vardenafil (0.0001–10 μM) concentration‐dependently relaxed endothelium‐intact and endothelium‐denuded pulmonary artery rings. Endothelium denudation caused rightward shifts in the concentration–response curves to sildenafil, tadalafil and vardenafil (9‐, 12‐ and 123‐fold, respectively). Incubation with Nω‐nitro‐L‐arginine methyl ester (100 μM) or ODQ (1H‐[1,2,4] oxadiazolo [4,3,‐a]quinoxalin‐1‐one) (10 μM) caused similar reductions of PDE5‐induced vasorelaxations in intact rings. Sildenafil and tadalafil did not affect the phenylephrine‐induced contractions, whereas vardenafil reduced the maximal responses, and shifted the phenylephrine‐induced contraction curves to the right in endothelium‐denuded rings (5‐ and 19‐fold for 1 and 10 μM, respectively). Vardenafil (but neither sildenafil nor tadalafil) caused a marked rightward shift and a decrease of maximal contractile response to CaCl2. Vardenafil, but neither sildenafil nor tadalafil, significantly reduced the Ca2+ mobilization and Ca2+ influx in thrombin‐stimulated washed platelets.

Conclusions and implications:

Our results indicate that vardenafil, in contrast to sildenafil or tadalafil, also blocked Ca2+ fluxes, thus enhancing its vasorelaxation of the pulmonary artery.

British Journal of Pharmacology (2008) 154, 787–796; doi:10.1038/bjp.2008.141; published online 21 April 2008
Pathology‐specific effects of the IKur/Ito/IK,ACh blocker AVE0118 on ion channels in human chronic atrial fibrillation
Authors: Christ T , Wettwer E , Voigt N , Hála O , Radicke S , Matschke K , Várro A , Dobrev D , Ravens U
Published: June 2008

Background and purpose

This study was designed to establish the pathology‐specific inhibitory effects of the IKur/Ito/IK,ACh blocker AVE0118 on atrium‐selective channels and its corresponding effects on action potential shape and effective refractory period in patients with chronic AF (cAF).

Experimental approach

Outward K+‐currents of right atrial myocytes and action potentials of atrial trabeculae were measured with whole‐cell voltage clamp and microelectrode techniques, respectively. Outward currents were dissected by curve fitting.

Key results

Four components of outward K+‐currents and AF‐specific alterations in their properties were identified. Ito was smaller in cAF than in SR, and AVE0118 (10 μM) apparently accelerated its inactivation in both groups without reducing its amplitude. Amplitudes of rapidly and slowly inactivating components of IKur were lower in cAF than in SR. The former was abolished by AVE0118 in both groups, the latter was partially blocked in SR, but not in cAF, even though its inactivation was apparently accelerated in cAF. The large non‐inactivating current component was similar in magnitude in both groups, but decreased by AVE0118 only in SR. AVE0118 strongly suppressed AF‐related constitutively active IK,ACh and prolonged atrial action potential and effective refractory period exclusively in cAF.

Conclusions and implications

In atrial myocytes of cAF patients, we detected reduced function of distinct IKur components that possessed decreased component‐specific sensitivity to AVE0118 most likely as a consequence of AF‐induced electrical remodelling. Inhibition of profibrillatory constitutively active IK,ACh may lead to pathology‐specific efficacy of AVE0118 that is likely to contribute to its ability to convert AF into SR.

British Journal of Pharmacology (2008) 154, 1619–1630; doi: 10.1038/bjp.2008.209; published online 9 June 2008