bluuebunny/crossref_metadata_2025 huggingface dataset:
Goddard Earth Observing System chemistry‐climate model simulations of stratospheric ozone‐temperature coupling between 1950 and 2005
Authors: Pawson Steven , Stolarski Richard S. , Douglass Anne R. , Newman Paul A. , Nielsen J. Eric , Frith Stacey M. , Gupta Mohan L.
Published: June 2008

Links between the stratospheric thermal structure and the ozone distribution are explored in the Goddard Earth Observing System chemistry‐climate model (CCM). Ozone and temperature fields are validated using estimates based on observations. An experimental strategy is used to explore sensitivities of temperature and ozone using the CCM alongside the underlying general circulation model (GCM) with ozone specified from either observations or from a chemistry‐transport model (CTM), which uses the same chemical modules as the CCM. In the CTM, upper stratospheric ozone is biased low compared to observations; GCM experiments reveal that using CTM ozone reduces a warm temperature bias near the stratopause in the GCM, and this improvement is also seen in the CCM. Near 5 hPa, the global‐mean ozone profile is biased low in the CTM but is close to observations in the CCM, which suggests that the temperature feedbacks are important in simulating the ozone distribution in the middle stratosphere. In the low stratosphere there is a high bias in simulated ozone, which forces a warm bias in the CCM. The high ozone also leads to an overestimate in total column ozone of several tens of Dobson units in the polar regions. In the late part of the twentieth century the seasonal activation of chlorine, especially over Antarctica, destroys ozone as expected, so that chlorine‐induced ozone decreases are overestimated in the CCM compared to the real atmosphere. Ozone‐change experiments reveal that the thermal structures of the GCM and CCM respond in a similar manner to ozone differences between 1980 and 2000, with a peak ozone‐induced temperature change of about 1.5 K (over 20 years) near the stratopause, which is at the low end of the range computed by other models. Greenhouse‐gas‐induced cooling increases with altitude and, near the stratopause, contributes an additional 1.3 K to the cooling near 1 hPa between 1980 and 2000. In the Antarctic, the ozone hole is simulated with some success by the CCM. As with many other models, the polar vortex is too persistent in late winter, but counteracting this, the CCM undergoes too much midwinter variability, meaning the ozone hole is more variable than it is in the real atmosphere. Temperature decreases associated with the ozone hole in the CCM are similar to those computed with other models.
MGS‐TES thermal inertia study of the Arsia Mons Caldera
Authors: Cushing Glen E. , Titus Timothy N.
Published: June 2008

Temperatures of the Arsia Mons caldera floor and two nearby control areas were obtained by the Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES). These observations revealed that the Arsia Mons caldera floor exhibits thermal behavior different from the surrounding Tharsis region when compared with thermal models. Our technique compares modeled and observed data to determine best fit values of thermal inertia, layer depth, and albedo. Best fit modeled values are accurate in the two control regions, but those in the Arsia Mons' caldera are consistently either up to 15 K warmer than afternoon observations, or have albedo values that are more than two standard deviations higher than the observed mean. Models of both homogeneous and layered (such as dust over bedrock) cases were compared, with layered‐cases indicating a surface layer at least thick enough to insulate itself from diurnal effects of an underlying substrate material. Because best fit models of the caldera floor poorly match observations, it is likely that the caldera floor experiences some physical process not incorporated into our thermal model. Even on Mars, Arsia Mons is an extreme environment where CO2 condenses upon the caldera floor every night, diurnal temperatures range each day by a factor of nearly 2, and annual average atmospheric pressure is only around one millibar. Here, we explore several possibilities that may explain the poor modeled fits to caldera floor and conclude that temperature dependent thermal conductivity may cause thermal inertia to vary diurnally, and this effect may be exaggerated by presence of water‐ice clouds, which occur frequently above Arsia Mons.
Martian dunite NWA 2737: Integrated spectroscopic analyses of brown olivine
Authors: Pieters Carle M. , Klima Rachel L. , Hiroi Takahiro , Dyar M. Darby , Lane Melissa D. , Treiman Allan H. , Noble Sarah K. , Sunshine Jessica M. , Bishop Janice L.
Published: June 2008

A second Martian meteorite has been identified that is composed primarily of heavily shocked dunite, Northwest Africa (NWA) 2737. This meteorite has several similarities to the Chassigny dunite cumulate, but the olivine is more Mg rich and, most notably, is very dark and visually brown. Carefully coordinated analyses of NWA 2737 whole‐rock and olivine separates were undertaken using visible and near‐infrared reflectance, midinfrared emission and reflectance, and Mössbauer spectroscopic studies of the same samples along with detailed petrography, chemistry, scanning electron microscopy, and transmission electron microscopy analyses. Midinfrared spectra of this sample indicate that the olivine is fully crystalline and that its molecular structure remains intact. The unusual color and spectral properties that extend from the visible through the near‐infrared part of the spectrum are shown to be due to nanophase metallic iron particles dispersed throughout the olivine during a major shock event on Mars. Although a minor amount of Fe3+ is present, it cannot account for the well‐documented unusual optical properties of Martian meteorite NWA 2737. Perhaps unique to the Martian environment, this “brown” olivine exhibits spectral properties that can potentially be used to remotely explore the pressure‐temperature history of surface geology as well as assess surface composition.
North and south subice gas flow and venting of the seasonal caps of Mars: A major geomorphological agent
Authors: Piqueux Sylvain , Christensen Philip R.
Published: June 2008

Dark polygons associated with fans and spots appear during the spring on the southern seasonal cap. The basal sublimation of the translucent cap and the venting of the CO2 gas are responsible for their formation, as previously proposed for the spots and fans. Dark polygons appear when dark material emerges from elongated vents, whereas spots and fans form from point sources. A class of erosive features (etched polygons) is associated with depressions a few meters to tens of meters in diameters connected to a network of radiating troughs (“spiders”). Spiders are shaped by the scouring action of the confined gas converging toward point sources, whereas the etched polygons result from the forced migration of the CO2 gas over longer distances. The minimum age of the spiders is 104 years. They result from one of the most efficient erosive processes on Mars, displacing 2 orders of magnitude more dust per year than a typical dust storm or than all the dust devils during the same time period. In the north, parts of the seasonal cap are translucent between Ls = 355° and Ls = 60° and are associated with spots, fans, dark polygons, and possibly spiders, suggesting that the basal sublimation and venting of the cap triggers a subice gas and dust flow that is modifying the morphology of the surface layer. However, perennial features are extremely uncommon on the north regolith, indicating that the conditions for their formation or conservation are not met. The reduced basal energy budget of the north cap compared to the south and the shorter seasonal life time of the north translucent ice may explain the relative scarcity of features in the north. The polar layered deposits contain the stratigraphic record of climatic changes and catastrophic events. Both polar deposits may have been locally disrupted by the seasonal subice gas flow and the stratigraphic record may have been partially lost.
Arctic patterned‐ground ecosystems: A synthesis of field studies and models along a North American Arctic Transect
Authors: Walker D. A. , Epstein H. E. , Romanovsky V. E. , Ping C. L. , Michaelson G. J. , Daanen R. P. , Shur Y. , Peterson R. A. , Krantz W. B. , Raynolds M. K. , Gould W. A. , Gonzalez G. , Nicolsky D. J. , Vonlanthen C. M. , Kade A. N. , Kuss P. , Kelley A. M. , Munger C. A. , Tarnocai C. T. , Matveyeva N. V. , Daniëls F. J. A.
Published: June 2008

Arctic landscapes have visually striking patterns of small polygons, circles, and hummocks. The linkages between the geophysical and biological components of these systems and their responses to climate changes are not well understood. The “Biocomplexity of Patterned Ground Ecosystems” project examined patterned‐ground features (PGFs) in all five Arctic bioclimate subzones along an 1800‐km trans‐Arctic temperature gradient in northern Alaska and northwestern Canada. This paper provides an overview of the transect to illustrate the trends in climate, PGFs, vegetation, n‐factors, soils, active‐layer depth, and frost heave along the climate gradient. We emphasize the thermal effects of the vegetation and snow on the heat and water fluxes within patterned‐ground systems. Four new modeling approaches build on the theme that vegetation controls microscale soil temperature differences between the centers and margins of the PGFs, and these in turn drive the movement of water, affect the formation of aggradation ice, promote differential soil heave, and regulate a host of system properties that affect the ability of plants to colonize the centers of these features. We conclude with an examination of the possible effects of a climate warming on patterned‐ground ecosystems.
Diurnal, seasonal, and interannual variation in carbon dioxide and energy exchange in shrub savanna in Burkina Faso (West Africa)
Authors: Brümmer Christian , Falk Ulrike , Papen Hans , Szarzynski Jörg , Wassmann Reiner , Brüggemann Nicolas
Published: June 2008

Savannas cover large areas of the Earth's surface and play an important role in global carbon cycling. West Africa is dominated by a variety of savanna ecosystems; however, they have been poorly studied up to now. In the present study, energy and carbon dioxide exchange was measured over a 2‐year period using the eddy covariance technique at a southern Sudanian savanna site in Burkina Faso that was not subject to human disturbances except for annual burning. Turbulent energy exchange was dominated by sensible heat flux in the dry season (November–May) and by latent heat flux in the wet season (June–September), with peak values higher than 300 W m−2 and lower than 100 W m−2 for the dominating and the minor component, respectively. The ecosystem was a marginal CO2 source in the dry season, whereas significant CO2 uptake was found in the rainy season. CO2 fluxes showed a clear diurnal pattern, with mean release rates of 0.2 mg CO2 m−2 s−1 during nighttime and mean maximum uptake rates of 1.0 mg CO2 m−2 s−1 in July and August around midday. Diurnal courses of CO2 flux were in phase with photosynthetically active radiation (PAR). Highest CO2 uptake rates of more than 0.8 mg CO2 m−2 s−1 occurred at PAR levels in excess of 1000 μmol m−2 s−1. Total net ecosystem CO2 uptake was 179 ± 98 g C m−2 in the first year and 429 ± 100 g C m−2 in the second year of investigation, including an estimate of annual fire C loss of 149 g C m−2. The remarkable difference in net CO2 uptake between the two years could be explained by higher rainfall in 2006, revealing the sensitivity of the ecosystem to water availability and rainfall distribution that could lead to a significant change in C sequestration patterns under a changing climate.
Opal (Zn/Si) ratios as a nearshore geochemical proxy in coastal Antarctica
Authors: Hendry Katharine R. , Rickaby Rosalind E. M.
Published: June 2008

During the last 50 years, the Antarctic Peninsula has experienced rapid warming with associated retreat of 87% of marine and tidewater glacier fronts. Accelerated glacial retreat and iceberg calving may have a significant impact on the freshwater and nutrient supply to the phytoplankton communities of the highly productive coastal regions. However, commonly used biogenic carbonate proxies for nutrient and salinity conditions are not preserved in sediments from coastal Antarctica. Here we describe a method for the measurement of zinc to silicon ratios in diatom opal, (Zn/Si)opal, which is a potential archive in Antarctic marine sediments. A core top calibration from the West Antarctic Peninsula shows (Zn/Si)opal is a proxy for mixed layer salinity. We present down‐core (Zn/Si)opal paleosalinity records from two rapidly accumulating sites taken from nearshore environments off the West Antarctic Peninsula which show an increase in meltwater input in recent decades. Our records show that the recent melting in this region is unprecedented for over 120 years.
Continuous time random walk analysis of solute transport in fractured porous media
Authors: Cortis Andrea , Birkholzer Jens
Published: June 2008

The objective of this work is to discuss solute transport phenomena in fractured porous media, where the macroscopic transport of contaminants in the highly permeable inter‐connected fractures can be strongly affected by solute exchange with the porous rock matrix. We are interested in a wide range of rock types, with matrix hydraulic conductivities varying from almost impermeable (e.g., granites) to somewhat permeable (e.g., porous sandstones). In the first case, molecular diffusion is the only transport process causing the transfer of contaminants between the fractures and the matrix blocks. In the second case, additional solute transfer occurs as a result of a combination of advective and dispersive transport mechanisms, with considerable impact on the macroscopic transport behavior. We start our study by conducting numerical tracer experiments employing a discrete (microscopic) representation of fractures and matrix. Using the discrete simulations as a surrogate for the “correct” transport behavior, we then evaluate the accuracy of macroscopic (continuum) approaches in comparison with the discrete results. However, instead of using dual‐continuum models, which are quite often used to account for this type of heterogeneity, we develop a macroscopic model based on the Continuous Time Random Walk (CTRW) framework, which characterizes the interaction between the fractured and porous rock domains by using a probability distribution function of residence times. A parametric study of how CTRW parameters evolve is presented, describing transport as a function of the hydraulic conductivity ratio between fractured and porous domains.
Three‐dimensional structure of oceanic core complexes: Effects on gravity signature and ridge flank morphology, Mid‐Atlantic Ridge, 30°N
Authors: Blackman Donna K. , Karner Garry D. , Searle Roger C.
Published: June 2008

Our gravity modeling of oceanic core complexes formed at the Mid‐Atlantic Ridge near 30°N suggests that their shallow, domal “cores” could be dominated by mafic intrusive rocks, consistent with recent drilling results at Atlantis Massif. The three‐dimensional gravity analysis incorporates additional underway geophysics data in a new compilation and uses a higher‐resolution bathymetry model to remove the gravity contribution of seafloor topography. The additional detail is required in order to confidently relate few‐kilometer‐scale gravity anomalies to specific morphologic/tectonic blocks. Different models of subseafloor core complex structure and density are tested to determine which minimizes the local gravity anomaly. A 3‐D core with density 2900 kg/m3, as measured in the gabbroic section drilled at the central dome, and juxtaposed 3‐D hanging wall of fractured basalt, density ∼2600 kg/m3, satisfactorily explains most of the Bouguer gravity anomaly at Atlantis Massif. The capping detachment fault terminates or plunges northward beneath the seafloor at the northern limit of the central dome. The southwest shoulder of the massif has lower density, consistent with an upper crustal section ∼1 km thick, whereas the summit and southeastern shoulder have overall density similar to the central dome. The older core complexes distributed along Atlantis fracture zone are similar in size, depth, and distance of their summit from the transform fault. However, weathering/alteration probably has reduced their density somewhat compared to Atlantis Massif. Bathymetric embayments occur adjacent to the fracture zone in several places on the ridge flanks and are consistently associated with core complexes.
Temperature and pressure dependence of the rain‐snow phase transition over land and ocean
Authors: Dai Aiguo
Published: June 2008

The phase of precipitation is important for weather forecasts, land hydrology and remote sensing. To quantify the temperature and pressure dependence of snow frequency (F, in %) when precipitation occurs, we have analyzed 3‐hourly weather reports of surface air temperature (Ts, °C) and pressure (Ps), and snow and rain occurrences from over 15,000 land stations and available ship observations from 1977–2007. It is found that the phase transition occurs over a fairly wide range of temperature from about −2°C to +4°C over (low‐elevation) land and −3°C to +6°C over ocean. The F‐Ts relationship can be represented by a hyperbolic tangent: F(Ts) = a [tanh (b (Ts – c)) – d], with the slope parameter b close to 0.7 over land and 0.4 over ocean. The pressure‐dependence is only secondary and reflected in the parameters. Results show that snow occurs often (F > 50%) for Ts ≤ 1.2°C over land and Ts ≤ 1.9°C over ocean, and are non‐negligible (F > 5%) for Ts ≤ 3.8°C over land and Ts ≤ 5.5°C over ocean. This “warm bias” results from the falling of snowflakes into warmer surface layers, which is especially true over ocean. The warm bias is higher when air pressure is below ∼750 hPa because snow falls faster in thin air.
Coupled interactions of the monsoons
Authors: Misra Vasubandhu
Published: June 2008

A case is made to show that all continental summer monsoon regions of the globe are manifestations of strong, coupled ocean‐land‐atmosphere interactions. It is shown from observations that the auto‐decorrelation time of the daily rainfall in the summer monsoon regions is usually in excess of 3 days. This characteristic feature of the monsoon rainfall is well simulated in a global coupled ocean‐land‐atmosphere model. The atmospheric general circulation model component integrations of the same coupled model forced with observed SST show a distinctly shorter auto‐decorrelation time of the daily monsoon precipitation. An obvious conclusion is that air‐sea coupling is essential for this feature of the monsoon rainfall to be simulated. But through additional diagnostic calculations it is also shown that the robust land‐atmosphere interactions over these regions also contribute to the lengthening of the auto‐decorrelation time of the daily continental summer monsoon rainfall.
Land use impact on the Uruguay River discharge
Authors: Saurral Ramiro I. , Barros Vicente R. , Lettenmaier Dennis P.
Published: June 2008

The Uruguay River basin experienced extensive land use change during the second half of the twentieth century as a result of expansion of agricultural area, while streamflow and precipitation increased during the same period. This study assesses the impact of land use change between 1960 and 2000 on streamflow using a hydrology model that explicitly accounts for the role of land cover. Although the model suggests that land use change could have large effects on streamflow, changes in mean streamflow are attributable to climatic variations and not to land cover change. On the other hand, a faster runoff response to precipitation was observed toward the end of the period, which does appear to be attributable to land cover change. Overall, however, the positive trend observed in the Uruguay River streamflow during the second half of the past century should be attributed to increased precipitation, rather than land cover change.
Model performance, model robustness, and model fitness scores: A new method for identifying good land‐surface models
Authors: Gulden Lindsey E. , Rosero Enrique , Yang Zong‐Liang , Wagener Thorsten , Niu Guo‐Yue
Published: June 2008

We introduce three metrics for rigorous evaluation of land‐surface models (LSMs). This framework explicitly acknowledges perennial sources of uncertainty in LSM output. The model performance score (ζ) quantifies the likelihood that a representative model ensemble will bracket most observations and be highly skilled with low spread. The robustness score (ρ) quantifies the sensitivity of performance to parameter and/or data error. The fitness score (ϕ) combines performance and robustness, ranking models' suitability for broad application. We demonstrate the use of the metrics by comparing three versions of the Noah LSM. Using time‐varying ζ for hypothesis testing and model development, we show that representing short‐term phenological change improves Noah's simulation of surface energy partitioning and subsurface water dynamics at a semi‐humid site. The least complex version of Noah is most fit for broad application. The framework and metrics presented here can significantly improve the confidence that can be placed in LSM predictions.
Total gaseous mercury concentrations at the Cape Point GAW station and their seasonality
Authors: Slemr F. , Brunke E.‐G. , Labuschagne C. , Ebinghaus R.
Published: June 2008

Total gaseous mercury (TGM) has been measured at the WMO Global Atmosphere Watch (GAW) station at Cape Point, South Africa, since September 1995, representing the only long term TGM measurement in the Southern Hemisphere (SH) so far. Annual medians suggest a small but significant decrease of TGM concentrations from 1.29 ng m−3 in 1996 to 1.19 ng m−3 in 2004. Background TGM concentrations at Cape Point varied seasonally, with a summer maximum and a winter minimum. Comparison with the seasonal variation of CO concentrations in both hemispheres calls into question the influence of mercury sink by the Hg0 + OH reaction. If confirmed at other sites in the SH, the observed TGM seasonal variation may pose an important constraint on the global models of atmospheric mercury.
Temporal and spectral variations of the photoelectron flux and solar irradiance during an X class solar flare
Authors: Peterson W. K. , Chamberlin P. C. , Woods T. N. , Richards P. G.
Published: June 2008

Photoelectrons are the main energy source of airglow used to diagnose the state of the ionosphere‐thermosphere system. Because of measurement uncertainties and substantial gaps in the historical record, parameterized models of the EUV irradiance and photoelectron flux are generally used to estimate airglow intensities. This paper compares observed and modeled photoelectron spectra from an X3 class flare that occurred on July 15, 2002. The photoelectron data were obtained from the FAST satellite. Model photoelectron spectra were obtained from the Field Line Inter‐hemispheric Plasma (FLIP) model using 10 s cadence solar spectra at 1 nm resolution from the Flare Irradiance Spectral Model (FISM). The observed and modeled spectra agree well temporally and spectrally within the uncertainties of the models and data. Systematic differences found between observed and modeled photoelectron spectra suggest that the solar irradiance from FISM could be improved at wavelengths shortward of 17 nm.
Imaging meddy finestructure using multichannel seismic reflection data
Authors: Biescas B. , Sallarès V. , Pelegrí J. L. , Machín F. , Carbonell R. , Buffett G. , Dañobeitia J. J. , Calahorrano A.
Published: June 2008

This work illustrates the great potential of multichannel seismic reflection data to extract information from the finestructure of meddies with exceptional lateral resolution (10–15 m). We present seismic images of three meddies acquired in the Gulf of Cadiz (SW Iberian Peninsula), which consist of concentric reflectors forming oval shapes that sharply contrast with the background oceanic structure. The seismic images reveal the presence of different regions within the meddies that are consistent with those observed in historical temperature (T) and salinity (S) data. The core region, characterized by smooth T and S variations, is weakly reflective. The double‐diffusive upper and lower boundaries and the lateral‐interleaving outer edges, characterized by stronger T and S contrasts, display strong reflectivity bands. These new observations clearly show differences between layers developed at the upper and lower boundaries that can contribute to the knowledge of mixing processes and layering formation in oceans.
Resonant scattering of plasma sheet electrons by whistler‐mode chorus: Contribution to diffuse auroral precipitation
Authors: Ni Binbin , Thorne Richard M. , Shprits Yuri Y. , Bortnik Jacob
Published: June 2008

A quantitative analysis is presented of the resonant scattering of plasma sheet electrons (∼100 eV–20 keV) at L = 6 due to resonant interactions with whistler‐mode chorus. Using wave parameters modeled from observations under geomagnetically disturbed conditions, it is demonstrated that the rate of pitch angle scattering can exceed the level of strong diffusion over a broad energy range (200 eV–10 keV) containing the bulk of the injected plasma sheet population. Scattering by chorus appears to be more effective than previous analyses of resonant interaction with electrostatic electron cyclotron waves. Chorus scattering is therefore a major contributor to the origin of the diffuse aurora and should also control the MLT distribution of injected plasma sheet electrons. The rates of scattering are sensitive to the distributions of wave power with respect to wave normal direction and wave frequency spectrum. Upper‐band chorus (ω/Ωe > 0.5) is the dominant scattering process for electrons below ≈5 keV while lower‐band chorus (0.1 ≤ ω/Ωe ≤ 0.5) is more effective at higher energies especially near the loss cone.
A coastal ocean extreme bloom incubator
Authors: Ryan John P. , Gower James F. R. , King Stephanie A. , Bissett W. Paul , Fischer Andrew M. , Kudela Raphael M. , Kolber Zbigniew , Mazzillo Fernanda , Rienecker Erich V. , Chavez Francisco P.
Published: June 2008

Novel remote sensing methods and in situ observations reveal that intense dinoflagellate blooms occur frequently in Monterey Bay, California. Blooms can contain surface chlorophyll concentrations exceeding 500 μg l−1 and occupy ∼5 to 80 km2. They occur primarily during August through November and can persist for > 1 month. Maximum bloom frequency and mean intensity are in a shallow (< 25 m depth) area of the northeastern bay, in coincidence with the warmest surface water, low wind stress, and retentive circulation. These conditions favor dinoflagellates, which can vertically migrate to acquire nutrients in the thermocline and aggregate as "red tide" near the surface. Bloom incubation areas, also indicated in other coastal upwelling systems, may disproportionately influence regional bloom ecology.
Future southern African summer rainfall variability related to a southwest Indian Ocean dipole in HadCM3
Authors: Kay Gillian , Washington Richard
Published: June 2008

Southern Africa is subject to strong interannual summer rainfall extremes associated with modes of climate variability. Interaction between these modes and the climate change signal make improving understanding of their future operation and links with southern African rainfall a priority. This paper examines future southern African summer rainfall variability related to a meridional dipole mode of southwest Indian Ocean SST variability (the SWIOD) in coupled climate model HadCM3. The SWIOD is central to southern African rainfall in a 1000‐year control simulation, and remains so during the twenty‐first century under two different CO2 forcing scenarios: SRES A2 and B1. Future rainfall variability connected with this mode is found to be sensitive to the emissions pathway, particularly in the second half of the century. Flooding episodes with anomalies near 4 mm day−1 in already wet regions and which are unprecedented in a 1000 year control run are simulated under A2 SRES forcing.
Secular temperature changes in Hawai‘i
Authors: Giambelluca Thomas W. , Diaz Henry F. , Luke Mark S. A.
Published: June 2008

While the upward trend in global mean temperature has been intensively studied, some regional temperature trends are less well known. We document secular temperature changes in the Hawaiian Islands for the past ∼85 years based on an index of 21 stations. Results show a relatively rapid rise in surface temperature in the last ∼30 years, with stronger warming at the higher elevations. The bulk of the increase in mean temperature is related to a much larger increase in minimum temperatures compared to the maximum—a net warming about 3 times as large—resulting in a reduction of the diurnal range. For much of the period of record analyzed here, surface temperature in Hawai‘i has varied coherently with changes in the Pacific Decadal Oscillation (PDO). However, in recent decades, the secular warming has begun to predominate, such that despite the recent cooling associated with the PDO, surface temperatures in Hawai‘i have remained elevated. The greater warming trend at the higher elevations may have significant ecological impacts.
Separation of Cowling channel and local closure currents in the vicinity of a substorm breakup spiral
Authors: Amm O. , Fujii R.
Published: June 2008

The substorm breakup spiral demarcates the westernmost terminator of the substorm current wedge. A long‐standing debate has been devoted to the question of to what extent the strong upward field‐aligned currents (FAC) in that spiral are either closed by downward FAC through Pedersen currents flowing radially to the center of the spiral (“local closure”) or by currents that flow westward though a Cowling channel which extends in the region eastward of the spiral (“Cowling closure”). In particular, studies using ground‐based and space‐based instrumentation came to systematically different results. In order to address this question, we reanalyze a pseudobreakup spiral event on 3 February 1999, ∼2204 UT, that has been observed with the MIRACLE network of ground‐based instruments in Fennoscandia and for which spatial results of electric fields, conductances, and currents have been calculated by Amm et al. (2001). We apply a new technique that allows, under certain geometrical assumptions, the current systems to separate in the vicinity of the breakup spiral into their local closure and Cowling closure parts. The result shows that for the event analyzed, ∼68% of the upward FAC in the spiral is closed via the local closure current system and the remaining ∼32% via the Cowling closure current system. Therefore, the local closure mechanism is the dominating provider of the upward FAC in the breakup spiral overall. However, a localized area at the western flank of the spiral, where conductance gradients are largest, exists in which the Cowling closure dominates and feeds more than 80% of the upward FAC in that area. Further studies are required in order to examine the generality of the results obtained for our specific event.
Thermospheric density oscillations due to periodic solar wind high‐speed streams
Authors: Thayer Jeffrey P. , Lei Jiuhou , Forbes Jeffrey M. , Sutton Eric K. , Nerem R. Steven
Published: June 2008

We report on periodic oscillations in thermosphere density, measured by the accelerometer on the CHAMP satellite during 2006, and relate these periodicities to oscillations observed in solar wind speed and Kp index. Common periodic oscillations at 4–5, 6–7, and 9–11 day periods are observed in the neutral density at 400 km in the 2006 data set, with the 7 day period being the predominant oscillation. Spectral analysis reveals that similar periodicities are present in both the solar wind and the planetary magnetic index Kp but not in the EUV solar flux proxy F10.7. We suggest that the periodic oscillations observed in thermosphere density are a direct response to recurrent geomagnetic activity and associated high‐speed streams in the solar wind. The lack of response in F10.7 at the 7 day period enables storm effects on the thermosphere density to be isolated from solar flux effects. The Kp index for these events correspond to moderate levels of geomagnetic activity, and the resultant perturbations in thermosphere density are ±20–30% of background levels. Although these levels of perturbation are small compared to major magnetic storms, their much higher occurrence frequency and characteristic long recovery time may lead to a cumulative effect on the state of the thermosphere and ionosphere.
Moving towards better predictors of drug‐induced torsades de pointes
Authors: Bass A S , Darpo B , Valentin J‐P , Sager P , Thomas K
Published: June 2008

Drug‐induced torsades de pointes (TdP) remains a significant public health concern that has challenged scientists who have the responsibility of advancing new medicines through development to the patient, while assuring public safety. As a result, from the point of discovering a new molecule to the time of its registration, significant efforts are made to recognize potential liabilities, including the potential for TdP. With this background, the ILSI (HESI) Proarrhythmia Models Project Committee recognized that there was little practical understanding of the relationship between drug effects on cardiac ventricular repolarization and the rare clinical event of TdP. A workshop was therefore convened at which four topics were considered including: Molecular and Cellular Biology Underlying TdP, Dynamics of Periodicity, Models of TdP Proarrhythmia and Key Considerations for Demonstrating Utility of Pre‐Clinical Models. The series of publications in this special edition has established the background, areas of debate and those that deserve scientific pursuit. This is intented to encourage the research community to contribute to these important areas of investigation in advancing the science and our understanding of drug‐induced proarrhythmia.

British Journal of Pharmacology (2008) 154, 1550–1553; doi:fn1; published online 23 June 2008
High‐affinity blockade of voltage‐operated skeletal muscle and neuronal sodium channels by halogenated propofol analogues
Authors: Haeseler G , Karst M , Foadi N , Gudehus S , Roeder A , Hecker H , Dengler R , Leuwer M
Published: June 2008

Background and purpose:

Voltage‐operated sodium channels constitute major target sites for local anaesthetic‐like action. The clinical use of local anaesthetics is still limited by severe side effects, in particular, arrhythmias and convulsions. These side effects render the search for new local anaesthetics a matter of high interest.

Experimental approach:

We have investigated the effects of three halogenated structural analogues of propofol on voltage‐operated human skeletal muscle sodium channels (NaV1.4) and the effect of one compound (4‐chloropropofol) on neuronal sodium channels (NaV1.2) heterologously expressed in human embryonic kidney cell line 293.

Key results:

4‐Iodo‐, 4‐bromo‐ and 4‐chloropropofol reversibly suppressed depolarization‐induced whole‐cell sodium inward currents with high potency. The IC50for block of resting channels at −150 mV was 2.3, 3.9 and 11.3 μMin NaV1.4, respectively, and 29.2 μMfor 4‐chloropropofol in NaV1.2. Membrane depolarization inducing inactivation strongly increased the blocking potency of all compounds. Estimated affinities for the fast‐inactivated channel state were 81 nM, 312 nMand 227 nMfor 4‐iodopropofol, 4‐bromopropofol and 4‐chloropropofol in NaV1.4, and 450 nMfor 4‐chloropropofol in NaV1.2. Recovery from fast inactivation was prolonged in the presence of drug leading to an accumulation of block during repetitive stimulation at high frequencies (100 Hz).

Conclusions and implications:

Halogenated propofol analogues constitute a novel class of sodium channel‐blocking drugs possessing almost 100‐fold higher potency compared with the local anaesthetic and anti‐arrhythmic drug lidocaine. Preferential drug binding to inactivated channel states suggests that halogenated propofol analogues might be especially effective in suppressing ectopic discharges in a variety of pathological conditions.

British Journal of Pharmacology(2008)155, 265–275; doi:10.1038/bjp.2008.255; published online 23 June 2008
Hypertension and the absence of EDHF‐mediated responses favour endothelium‐dependent contractions in renal arteries of the rat
Authors: Michel F S , Man G S , Man R Y K , Vanhoutte P M
Published: June 2008

Background and purpose:

Experiments were designed to determine the modulation by nitric oxide (NO) and endothelium‐dependent hyperpolarizations (EDHF‐mediated responses) of endothelium‐dependent contractions in renal arteries of normotensive and hypertensive rats.

Experimental approach:

Rings, with or without endothelium, of renal arteries of 8‐month‐old Wistar Kyoto rats (WKY) and spontaneously hypertensive rats (SHR) were suspended in myographs for isometric force recording.

Key results:

ACh evoked relaxations in preparations contracted with phenylephrine. L‐NAME (inhibitor of NOS) attenuated (WKY) or abolished (SHR) these relaxations. TRAM‐34 plus UCL 1684 (inhibitors of EDHF‐mediated responses) did not decrease the relaxation, except in rings of WKY when L‐NAME was also present. High concentrations of ACh caused a secondary increase in tension, augmented in rings of WKY by L‐NAME or TRAM‐34 plus UCL 1684. The increase in tension was prevented by indomethacin. Under baseline tension, ACh induced endothelium‐dependent contractions, prevented by indomethacin (COX inhibitor) or terutroban (TP receptor antagonist). The calculated endothelium‐dependent contractions were larger in rings of SHR compared with those of WKY. In preparations of SHR, the contractions were augmented by L‐NAME in the presence of SC19220 (EP‐1 receptor antagonist). In arteries of WKY, the endothelium‐dependent contractions were augmented by TRAM‐34 plus UCL 1684. The responses were reduced by SC19220.

Conclusions and implications:

In the renal artery of the rat, EDCF‐mediated contractions are augmented by hypertension. The endothelium‐dependent contractions are facilitated by NOS inhibition (in the presence of an EP‐1 receptor antagonist) and by the withdrawal of EDHF‐mediated responses.

British Journal of Pharmacology (2008) 155, 217–226; doi:10.1038/bjp.2008.256; published online 23 June 2008
PEGylated cholecystokinin is more potent in inducing anorexia than conditioned taste aversion in rats
Authors: Verbaeys I , León‐Tamariz F , Pottel H , Decuypere E , Swennen Q , Cokelaere M
Published: June 2008

Background and purpose:

The physiological involvement of endogenous cholecystokinin (CCK) in the termination of feeding has been challenged by evidence of aversive effects of exogenous CCK8. We previously prolonged the anorectic effect of CCK by conjugation to polyethylene glycol (PEGylation) to produce PEG‐CCK9. In this study, we investigated the ability of different doses of PEG‐CCK9 to induce conditioned taste aversion (CTA) and satiety and identified the receptors involved in CTA induction.

Experimental approach:

Induction of CTA, measured by the saccharin preference ratio determined in a two‐bottle CTA procedure, and of satiety in adult male Wistar rats after intraperitoneal (i.p.) injection of different doses of PEG‐CCK9 (1, 2, 4, 8, 16 or 32 μg kg−1) was compared. Devazepide (100 μg kg−1) and 2‐NAP (3 mg kg−1), two selective CCK1‐receptor antagonists, were co‐administered i.p. with PEG‐CCK9 (8 μg kg−1) and the CTA effects monitored.

Key results:

PEG‐CCK9 dose‐dependently induced CTA, with a minimal effective dose of 8 μg kg−1, whereas the minimal effective dose to induce satiety was 1 μg kg−1. The CTA effects of PEG‐CCK9 were completely abolished by i.p. administration of devazepide prior to PEG‐CCK9 treatment and only partially abolished by administration of 2‐NAP.

Conclusions and implications:

Although PEG‐CCK9‐induced satiety and PEG‐CCK9‐induced CTA both increased with dose, the conjugate was more potent in inducing satiety, suggesting that the anorexia could not be completely attributed to the aversiveness of the drug. As observed with induction of satiety, PEG‐CCK9‐induced CTA was mediated by CCK1‐receptors.

British Journal of Pharmacology (2008) 155, 417–423; doi:10.1038/bjp.2008.257; published online 23 June 2008
Effects of pregabalin on visceral pain responses and colonic compliance in rats
Authors: Ravnefjord A , Brusberg M , Larsson H , Lindström E , Martínez V
Published: June 2008

Background and purpose:

Pregabalin, which binds to the α2‐δ subunit of voltage‐gated calcium channels, increased the threshold for pain during colorectal distension (CRD) in irritable bowel syndrome (IBS) patients. We tested the effects of oral pregabalin on the visceral pain‐related viscerosomatic and autonomic cardiovascular responses to CRD and colonic compliance in rats.

Experimental approach:

The activity of the abdominal musculature (viscerosomatic response), monitored by electromyography and intracolonic manometry, and changes in blood pressure and heart rate, monitored by telemetry, were assessed simultaneously in conscious rats during CRD.

Key results:

Pregabalin (10–200 μmol kg−1, p.o.) inhibited dose dependently the viscerosomatic response to phasic, noxious CRD (12 distensions at 80 mm Hg). At 200 μmol kg−1, pregabalin also reduced the increase in blood pressure and heart rate associated with noxious CRD. Moreover, pregabalin (200 μmol kg−1, p.o.) reduced the visceromotor response to ascending phasic CRD (10–80 mm Hg) and significantly increased the threshold pressure for response. During phasic CRD (2–20 mm Hg), pregabalin (200 μmol kg−1, p.o.) increased intracolonic volume, resulting in a shift to the left of the pressure–volume relationship curve, indicative of an increase of compliance.

Conclusions and implications:

Pregabalin reduced the viscerosomatic and autonomic responses associated with CRD‐induced visceral pain and increased colonic compliance in rats. These observations confirm the analgesic activity of pregabalin on visceral pain and support the translational value of the CRD model to humans. Ligands for the α2‐δ subunit might represent interesting compounds for the treatment of visceral pain disorders, such as IBS.

British Journal of Pharmacology (2008) 155, 407–416; doi:10.1038/bjp.2008.259; published online 23 June 2008
Antitumour activity of ANG1005, a conjugate between paclitaxel and the new brain delivery vector Angiopep‐2
Authors: Régina A , Demeule M , Ché C , Lavallée I , Poirier J , Gabathuler R , Béliveau R , Castaigne J‐P
Published: June 2008

Background and purpose:

Paclitaxel is highly efficacious in the treatment of breast, head and neck, non‐small cell lung cancers and ovarian carcinoma. For malignant gliomas, paclitaxel is prevented from reaching its target by the presence of the efflux pump P‐glycoprotein (P‐gp) at the blood–brain barrier. We investigated the utilization of a new drug delivery system to increase brain delivery of paclitaxel.

Experimental approach:

Paclitaxel molecules were conjugated to a brain peptide vector, Angiopep‐2, to provide a paclitaxel–Angiopep‐2 conjugate named ANG1005. We determined the brain uptake capacity, intracellular effects and antitumour properties of ANG1005 in vitro against human tumour cell lines and in vivo in human xenografts. We then determined ANG1005 activity on brain tumours with intracerebral human tumour models in nude mice.

Key results:

We show by in situ brain perfusion that ANG1005 enters the brain to a greater extent than paclitaxel and bypasses the P‐gp. ANG1005 has an antineoplastic potency similar to that of paclitaxel against human cancer cell lines. We also demonstrate that ANG1005 caused a more potent inhibition of human tumour xenografts than paclitaxel. Finally, ANG1005 administration led to a significant increase in the survival of mice with intracerebral implantation of U87 MG glioblastoma cells or NCI‐H460 lung carcinoma cells.

Conclusions and implications:

These results demonstrate the antitumour potential of a new drug, ANG1005, and establish that conjugation of anticancer agents with the Angiopep‐2 peptide vector could increase their efficacy in the treatment of brain cancer.

British Journal of Pharmacology (2008) 155, 185–197; doi:fn1; published online 23 June 2008
The 5‐HT2antagonist ketanserin is an open channel blocker of human cardiacether‐à‐go‐go‐related gene (hERG) potassium channels
Authors: Tang Q , Li Z‐Q , Li W , Guo J , Sun H‐Y , Zhang X‐H , Lau C‐P , Tse H‐F , Zhang S , Li G‐R
Published: June 2008

Background and purpose:

Ketanserin, a selective 5‐HT receptor antagonist, prolongs the QT interval of ECG in patients. The purpose of the present study was to determine whether ketanserin would block human cardiacether‐à‐go‐go‐related gene (hERG) potassium channels.

Experimental approach:

Whole‐cell patch voltage‐clamp technique was used to record membrane currents in HEK 293 cells expressing wild type or mutant hERG channel genes.

Key results:

Ketanserin blocked hERG current (IhERG) in a concentration‐dependent manner (IC50=0.11 μM). The drug showed an open channel blocking property, the block increasing significantly at depolarizing voltages between +10 to +60 mV. Voltage‐dependence for inactivation of hERG channels was negatively shifted by 0.3 μMketanserin. A 2.8 fold attenuation of inhibition by elevation of external K+concentration (from 5.0 to 20 mM) was observed, whereas the inactivation‐deficient mutants S620T and S631A had the IC50s of 0.84±0.2 and 1.7±0.4 μM(7.6 and 15.4 fold attenuation of block). In addition, the hERG mutants in pore helix and S6 also significantly reduced the channel block (2–59 fold) by ketanserin.

Conclusions and implications:

These results suggest that ketanserin binds to and blocks the open hERG channels in the pore helix and the S6 domain; channel inactivation is also involved in the blockade of hERG channels. Blockade of hERG channels most likely contributes to the prolongation of QT intervals in ECG observed clinically at therapeutic concentrations of ketanserin.

British Journal of Pharmacology(2008)155, 365–373; doi:10.1038/bjp.2008.261; published online 23 June 2008
The enigma of nitroglycerin bioactivation and nitrate tolerance: news, views and troubles
Authors: Mayer B , Beretta M
Published: June 2008

Nitroglycerin (glyceryl trinitrate; GTN) is the most prominent representative of the organic nitrates or nitrovasodilators, a class of compounds that have been used clinically since the late nineteenth century for the treatment of coronary artery disease (angina pectoris), congestive heart failure and myocardial infarction. Medline lists more than 15 000 publications on GTN and other organic nitrates, but the mode of action of these drugs is still largely a mystery. In the first part of this article, we give an overview on the molecular mechanisms of GTN biotransformation resulting in vascular cyclic GMP accumulation and vasodilation with focus on the role of mitochondrial aldehyde dehydrogenase (ALDH2) and the link between the ALDH2 reaction and activation of vascular soluble guanylate cyclase (sGC). In particular, we address the identity of the bioactive species that activates sGC and the potential involvement of nitrite as an intermediate, describe our recent findings suggesting that ALDH2 catalyses direct 3‐electron reduction of GTN to NO and discuss possible reaction mechanisms. In the second part, we discuss contingent processes leading to markedly reduced sensitivity of blood vessels to GTN, referred to as vascular nitrate tolerance. Again, we focus on ALDH2 and describe the current controversy on the role of ALDH2 inactivation in tolerance development. Finally, we emphasize some of the most intriguing, in our opinion, unresolved puzzles of GTN pharmacology that urgently need to be addressed in future studies.

British Journal of Pharmacology(2008)155, 170–184; doi:10.1038/bjp.2008.263; published online 23 June 2008