bluuebunny/crossref_metadata_2025 huggingface dataset:
Die Erfassung der allgemeinen und gesundheitsbezogenen Lebensqualität bei Patienten mit peripherer arterieller Verschlusskrankheit – eine Übersicht
Authors: Knipfer  , Reeps  , Dolezal  , Zimmermann  , Pelisek  , Behrens  , Eckstein
Published: May 2008

Die Abbildung und Verbesserung der Versorgungsqualität bei zunehmenden chronischen Erkrankungen einer alternden Gesellschaft bedarf der Auseinandersetzung mit dem mehrdimensionalen Konstrukt «Lebensqualität». Gesundheitsbezogene Lebensqualität gilt inzwischen als ein Outcome-Kriterium in der Medizin. Da keine allgemeingültige Definition von Lebensqualität besteht, werden Komponenten des Befindens und Verhaltens in Fragebögen erfasst. Dieser subjektiv wahrgenommene Gesundheitszustand umfasst körperliche Beschwerden, die psychische Verfassung, die Funktionstüchtigkeit im Alltagsleben und die Ausgestaltung der zwischenmenschlichen Interaktionen. Diese Grunddimensionen finden sich in verschiedener Ausprägung in den Lebensqualitätsinstrumenten wieder. Die Erfassung der subjektiven Lebensqualität spiegelt eine zunehmende Anerkennung der Sichtweise des Patienten wider. Eine Auswahl der gängigen generischen Instrumente wie SF-36, FLZM, MLDL, EQ-5D, WHOQOL-100, NHP, SIP und Instrumente zur krankheitsspezifischen Lebensqualitätsmessung bei peripherer AVK wie PAVK-86, CLAU-S, VASCUQOL, SIPIC und WIQ werden vorgestellt. Der SF-36 stellt momentan den am besten etablierten krankheitsübergreifenden Fragebogen dar. Der FLZM berücksichtigt die Wichtigkeit der einzelnen LQ-Bereiche für den Patienten und verfügt so über die Möglichkeit die Wichtigkeit und die tatsächliche Lebenszufriedenheit miteinander zu korrelieren. Um die Effektivität medizinischer Maßnahmen zu prüfen und den Erfolg therapeutischer Verfahren bei gefäßerkrankten Patienten zu vergleichen, wird für den VASCUQOL gegenwärtig der beste Nutzen beschrieben. Ein paralleler Einsatz von krankheitsübergreifenden und krankheitsspezifischen Fragebögen bildet sowohl das subjektive Allgemeinbefinden, als auch die subjektive Beeinträchtigung durch die spezifische Erkrankung des Patienten ab und ist dem alleinigen Einsatz eines krankheitsübergreifenden Instrumentes überlegen.
Gender Differences in Psychophysiological Responses to Disgust
Authors: Rohrmann Sonja , Hopp Henrik , Quirin Markus
Published: May 2008

Several studies have revealed that women report stronger feelings of disgust than men ( Gross & Levenson, 1995 ; Schienle, Schäfer, Stark, Walter, & Vaitl, 2005 ). However, the extent to which this gender difference also influences physiological disgust responses remains an open question. In Experiment 1, 54 female and 41 male participants were exposed to slides of different disgust-content. In Experiment 2, 47 women and 53 men watched two film clips showing hygiene-related or food-related disgust stimuli, respectively. Differences between males and females in reported and physiological disgust responses (heart rate, electrodermal activity, salivary cortisol, secretory immunoglobulin A) were tested by analysis of variance. Replicating previous studies, women reported stronger feelings of disgust than men across all disgust inductions. Additionally, in Study 1, women showed a higher increase in skin conductance level than men. In conclusion, gender moderates subjective responses to disgust, whereas physiological disgust responses are only marginally moderated by gender. Gender stereotypes as an explanation for the results are discussed.
Evaluation of Serum Ghrelin and Leptin Levels in Suicide Attempters
Authors: Kurt Erhan , Güler Özkan , Ozbulut Omer , Altınbaş Kürşat , Işingör Melek , Serteser Mustafa , Gecici Omer
Published: May 2008

Previous studies have reported a relationship between cholesterol and leptin levels, and suicide attempts, impulsivity, and aggressive behaviors. An orexigenic hormone seems to be strongly associated with lipid metabolism and leptin levels. Therefore, we aimed to compare serum cholesterol, leptin, and ghrelin levels in 36 patients with suicide attempts and 25 healthy controls. Patients with suicide attempts had decreased leptin levels and significantly higher ghrelin levels compared to healthy controls. While the serum ghrelin level did not show any correlation with the demographic and clinical factors, leptin showed a correlation with body mass index (BMI), and cholesterol levels were correlated with the age, BMI, and number of suicide attempts in the suicidal group. The results suggest that suicide attempts seem to be related with higher serum ghrelin values, decreased leptin, and cholesterol levels.
Uncoupling of acetate degradation from methane formation in Alaskan wetlands: Connections to vegetation distribution
Authors: Hines Mark E. , Duddleston Khrystyne N. , Rooney‐Varga Juliette N. , Fields Dana , Chanton Jeffrey P.
Published: May 2008

Laboratory incubations, gas and solute analyses, and stable isotope methods were used to investigate the pathway of methanogenesis in 25 wetland peats of varying vegetation composition along a latitudinal gradient in Alaska. Sites were divided into gross vegetation classes indicative of tropic status: mostly Sphagnum (class 1); Sphagnum plus vascular plants (i.e., Carex) (class 2); mostly vascular plants, but still containing Sphagnum (class 3), and; sites dominated by vascular plants with no visible Sphagnum species (class 4). The magnitude of CO2, acetate and CH4 as end products of anaerobic metabolism varied greatly, but ratios of end product formation indicative of differences in the pathway of C flow and methanogenesis corresponded with vegetation classes, especially at the extremes, e.g., acetate‐C accounted for 67% of total C production in Sphagnum‐rich sites (class 1) decreasing to 13% in sites devoid of sphagna (class 4). Conversely, CH4 comprised only 0.4% of products in class 1 sites, but increased to 14% in class 4. Total respiration rates (sum of all three products) varied by only a factor of ∼2 among vegetation classes (200–440 nmol ml−1 day−1), but rates differed greatly if acetate formation was not included suggesting that belowground C cycling can be much more rapid than previously thought. Apparent fractionation factors (α = δ13CDIC + 1000/δ13CCH4 + 1000) that estimate methanogenic pathway, i.e., the relative contribution of CO2 reduction or acetate as precursors of methane, varied from ∼1.030 to ∼1.080 and agreed with incubation end product ratios, underscoring the importance of the presence or absence of vascular plants and Sphagnum mosses in affecting the pathway of anaerobic C flow. We contend that methanogenesis in general, including CO2 reduction, is impeded in northern wetlands compared to the production of other C compounds and that its importance decreases with oligotrophy. The connection with vegetation suggests that climate change scenarios leading to increases in vascular plant cover in northern wetlands may shift methanogenic pathways toward increased acetotrophy and increased methane formation, which is a positive feedback on warming.
Geometric, kinematic, and erosional history of the central Andean Plateau, Bolivia (15–17°S)
Authors: McQuarrie Nadine , Barnes Jason B. , Ehlers Todd A.
Published: May 2008

Latitudinal changes in topography, climate, and thrust belt geometry in the central Andes have led to conflicting hypotheses that climate or tectonics exert a first‐order control on orogen evolution. The relative roles of climate and tectonics in the evolution of the Andean orogen are difficult to quantify because of a lack of detailed observations for both the long‐term deformation and erosion history of the Andean fold‐thrust belt. We contribute to the resolution of this problem by presenting a sequentially restored, balanced cross section based on new mapping across the northern Bolivia portion of the thrust belt (15–17°S). The timing and magnitude of exhumation across the cross section are determined by synthesizing 10 new and ∼70 previously published mineral cooling ages. Once balanced and restored, the section was sequentially forward modeled using stratigraphic and cooling age constraints. Results indicate the Eastern Cordillera (EC) records the highest magnitudes of shortening (123 km or 55%). The Interandean zone (IA) has shortened 48 km or 30%. In both the EC and IA individual thrust sheets are tightly folded and have minor offsets of 1–5 km. The Subandes (SA) has multiple levels of detachments allowing for thrust sheets with relatively large offsets (6–17 km). Total shortening in the SA is 66 km or 40%. Total magnitude of shortening for the entire fold‐thrust belt in this region is 276 km (40%). New apatite and zircon fission track cooling ages in conjunction with published ages indicate two phases of rapid exhumation; an earlier phase from ∼40 to 25 Ma in the EC and one prior to ∼25 Ma in the IA, followed by distributed exhumation of the entire fold‐thrust belt from ∼15–0 Ma. Combined exhumation estimates from the balanced cross section and thermochronology suggest ∼9–11 km of exhumation in the EC, ∼5–9 km in the IA, and ∼3–4 km in the SA. Long‐term shortening rates are 7 mm/a for the EC and IA and 4–8 mm/a for the SA. The SA shortening rates are based on a ∼15–0 Ma or 8–0 Ma deformation window. By linking cooling ages to location and magnitude of shortening, we suggest an ∼10–17 Ma pause or a dramatic deceleration in the rate of deformation and propagation of the fold‐thrust belt between 25 and ∼15 or 8 Ma.
Spatial and temporal variability in sedimentation rates associated with cutoff channel infill deposits: Ain River, France
Authors: Piégay H. , Hupp C. R. , Citterio A. , Dufour S. , Moulin B. , Walling D. E.
Published: May 2008

Floodplain development is associated with lateral accretion along stable channel geometry. Along shifting rivers, the floodplain sedimentation is more complex because of changes in channel position but also cutoff channel presence, which exhibit specific overflow patterns. In this contribution, the spatial and temporal variability of sedimentation rates in cutoff channel infill deposits is related to channel changes of a shifting gravel bed river (Ain River, France). The sedimentation rates estimated from dendrogeomorphic analysis are compared between and within 14 cutoff channel infills. Detailed analyses along a single channel infill are performed to assess changes in the sedimentation rates through time by analyzing activity profiles of the fallout radionuclides 137Cs and unsupported 210Pb. Sedimentation rates are also compared within the channel infills with rates in other plots located in the adjacent floodplain. Sedimentation rates range between 0.65 and 2.4 cm a−1 over a period of 10 to 40 years. The data provide additional information on the role of distance from the bank, overbank flow frequency, and channel geometry in controlling the sedimentation rate. Channel infills, lower than adjacent floodplains, exhibit higher sedimentation rates and convey overbank sediment farther away within the floodplain. Additionally, channel degradation, aggradation, and bank erosion, which reduce or increase the distance between the main channel and the cutoff channel aquatic zone, affect local overbank flow magnitude and frequency and therefore sedimentation rates, thereby creating a complex mosaic of sedimentation zones within the floodplain and along the cutoff channel infills. Last, the dendrogeomorphic and 137Cs approaches are cross validated for estimating the sedimentation rate within a channel infill.
Pan‐Arctic patterns in black carbon sources and fluvial discharges deduced from radiocarbon and PAH source apportionment markers in estuarine surface sediments
Authors: Elmquist Marie , Semiletov Igor , Guo Laodong , Gustafsson Örjan
Published: May 2008

A pan‐arctic geospatial picture of black carbon (BC) characteristics was obtained from the seven largest arctic rivers by combining with molecular combustion markers (polycyclic aromatic hydrocarbons) and radiocarbon (14C) analysis. The results suggested that the contribution from modern biomass burning to BC ranged from low in the Yukon (8%) and Lena (5%) Rivers to high in the Yenisey River (88%). The Mackenzie River contributed almost half of the total arctic fluvial BC export of 202 kton a−1 (kton = 109 g), with the five Russian‐Arctic rivers contributing 10–36 kton a−1 each. The 14C‐based source estimate of fluvially exported BC to the Arctic Ocean, weighted by the riverine BC fluxes, amount to about 20% from vegetation/biofuel burning and 80% from 14C‐extinct sources such as fossil fuel combustion and relict BC in uplifted source rocks. Combining these pan‐arctic data with available estimates of BC export from other rivers gave a revised estimate of global riverine BC export flux of 26 × 103 kton a−1. This is twice higher than a single previous estimate and confirms that river export of BC is a more important pathway of BC to the oceans than direct atmospheric deposition.
Ocean temperature forcing by aerosols across the Atlantic tropical cyclone development region
Authors: Evan Amato T. , Heidinger Andrew K. , Bennartz Ralf , Bennington Val , Mahowald Natalie M. , Corrada‐Bravo Hector , Velden Christopher S. , Myhre Gunnar , Kossin James P.
Published: May 2008

Recent work has shown a statistical climatological link between African dust outbreaks and North Atlantic tropical cyclone frequency and intensity. However, a definite causal link between year‐to‐year changes in African dust and Atlantic tropical cyclones has yet to be proven. Here we show that variability in Atlantic dust cover is linked to changes in tropical cyclone activity through the aerosols' surface radiative forcing, which has a net cooling effect on tropical Atlantic Ocean temperatures. In this manuscript we describe a new methodology for incorporating more than 25 years of satellite observations of aerosols into a simple model that estimates the aerosol direct effect and its impact on tropical eastern Atlantic Ocean temperatures. The output from our model suggests that African dust outbreaks play a nonnegligible role in the evolution of eastern Atlantic Ocean temperatures. Using the strong relationship between temperatures in the so‐called main development region and the seasonal power dissipation index (PDI), we estimate that about one third of the increase in PDI over the last 25 years can be attributed to decreases in dust loadings over the same period. Our results imply that efforts aimed at attributing causality to past variability of, or at predicting future changes in, North Atlantic tropical cyclone activity must consider the important radiative influence of African dust.
Characteristics of middle‐ to low‐latitude Pi2 excited by bursty bulk flows
Authors: Cao Jinbin , Duan Juntao , Du Aiming , Ma Yuduan , Liu Zhenxin , Zhou G. C. , Yang Dongmei , Zhang Tielong , Li Xinlin , Vellante Massimo , Reme Henri , Dandouras Iannis , Lucek E. , Carr C. M. , Zong Qiugang , Li Qi
Published: May 2008

This paper, by using the data of Cluster, TC‐1, GOES, and eight ground stations on 22 October 2004, studied the characteristics of low‐latitude Pi2s generated by an earthward bursty bulk flow (BBF) in the near‐Earth tail plasma sheet. The BBF excited simultaneously two distinct classes of Pi2s: one is long‐period Pi2 (90–130 s) and the other is short‐period Pi2 (∼50 s). The long‐period Pi2 is transient response type Pi2 associated with field‐aligned current produced by the braking of BBFs. The spectrum analysis show that the amplitude spectrum peak of long‐period Pi2 increases with increasing latitude, indicating that the source is at higher latitudes. The time delay for the propagation of Alfven waves from Cluster to the Earth is very close to the time difference between the onset time of the BBFs at Cluster and the starting time of the long‐period Pi2 on the ground. The short‐period Pi2 is a global cavity mode since the Pi2s in H components at eight stations have almost the same starting time, same oscillation period, and same waveform, which are all typical characteristics of cavity mode. The amplitude spectrum peak of short‐period Pi2 at NCK (N42.7) is larger than those at higher‐station UPS (N56.5) and lower‐station CST (N40.8). The polarization analysis at three lower‐latitude stations shows that the polarization underwent two reversals. The major axis of the polarization ellipse points to approximately the north, indicating that the short‐period Pi2s are not excited by nightside current system. TC‐1 observed transverse mode Pi2s. Its period is almost identical with the periods of Pi2 on the ground, indicating they belong to the same wave.
Field line resonant frequencies and ionospheric conductance: Results from a 2‐D MHD model
Authors: Waters C. L. , Sciffer M. D.
Published: May 2008

The magnetised plasma of the near‐Earth space environment supports ultra‐low frequency (ULF; 1–100 mHz), magnetohydrodynamic (MHD) oscillations. For sufficiently large ionospheric conductances, field line resonances (FLRs) form between the northern and southern ionospheres. These conditions are usually met for daytime ionosphere conductance values. The FLRs are normal modes of the system and may be used to remote sense plasma mass densities in the magnetosphere. The oscillations lose energy in the ionosphere whose properties determine the boundary conditions, particularly resonance damping effects. Using a two dimensional (2D) MHD model of the magnetosphere and realistic ionosphere boundary conditions, the variation in resonant frequency with ionosphere conductivity is reported. For typical mid to low latitude summer and winter ionosphere parameters, the FLRs change by less than 5%. This translates to an uncertainty of 7% in plasma mass density.
Solar wind driving of magnetospheric ULF waves: Pulsations driven by velocity shear at the magnetopause
Authors: Claudepierre S. G. , Elkington S. R. , Wiltberger M.
Published: May 2008

We present results from global, three‐dimensional magnetohydrodynamic (MHD) simulations of the solar wind/magnetosphere interaction. These MHD simulations are used to study ultra low frequency (ULF) pulsations in the Earth's magnetosphere driven by shear instabilities at the flanks of the magnetopause. We drive the simulations with idealized, constant solar wind input parameters, ensuring that any discrete ULF pulsations generated in the simulation magnetosphere are not due to fluctuations in the solar wind. The simulations presented in this study are driven by purely southward interplanetary magnetic field (IMF) conditions, changing only the solar wind driving velocity while holding all of the other solar wind input parameters constant. We find surface waves near the dawn and dusk flank magnetopause and show that these waves are generated by the Kelvin‐Helmholtz (KH) instability. We also find that two KH modes are generated near the magnetopause boundary. One mode, the magnetopause KH mode, propagates tailward along the magnetopause boundary. The other mode, the inner KH mode, propagates tailward along the inner edge of the boundary layer (IEBL). We find large vortical structures associated with the inner KH mode that are centered on the IEBL. The phase velocities, wavelengths, and frequencies of the two KH modes are computed. The KH waves are found to be fairly monochromatic with well‐defined wavelengths. In addition, the inner and magnetopause KH modes are coupled and lead to a coupled oscillation of the low‐latitude boundary layer. The boundary layer thickness, d, is computed and we find maximum wave growth for kd = 0.5–1.0, where k is the wave number, consistent with the linear theory of the KH instability. We comment briefly on the effectiveness of these KH waves in the energization and transport of radiation belt electrons.
Evaluating the effects of historical land cover change on summertime weather and climate in New Jersey: Land cover and surface energy budget changes
Authors: Wichansky Paul S. , Steyaert Louis T. , Walko Robert L. , Weaver Christopher P.
Published: May 2008

The 19th‐century agrarian landscape of New Jersey (NJ) and the surrounding region has been extensively transformed to the present‐day land cover by urbanization, reforestation, and localized areas of deforestation. This study used a mesoscale atmospheric numerical model to investigate the sensitivity of the warm season climate of NJ to these land cover changes. Reconstructed 1880s‐era and present‐day land cover data sets were used as surface boundary conditions for a set of simulations performed with the Regional Atmospheric Modeling System (RAMS). Three‐member ensembles with historical and present‐day land cover were compared to examine the sensitivity of surface air and dew point temperatures, rainfall, and the individual components of the surface energy budget to these land cover changes. Mean temperatures for the present‐day landscape were 0.3–0.6°C warmer than for the historical landscape over a considerable portion of NJ and the surrounding region, with daily maximum temperatures at least 1.0°C warmer over some of the highly urbanized locations. Reforested regions, however, were slightly cooler. Dew point temperatures decreased by 0.3–0.6°C, suggesting drier, less humid near‐surface air for the present‐day landscape. Surface warming was generally associated with repartitioning of net radiation from latent to sensible heat flux, and conversely for cooling. While urbanization was accompanied by strong surface albedo decreases and increases in net shortwave radiation, reforestation and potential changes in forest composition have generally increased albedos and also enhanced landscape heterogeneity. The increased deciduousness of forests may have further reduced net downward longwave radiation.
Verification of the T213 global spectral model of China National Meteorology Center over the East‐Asia area
Authors: Wang Yuan , Qian Hao , Song Jin‐Jie , Jiao Mei‐Yan
Published: May 2008

From September 2002, the global spectral model T213L31 has been put into operational use at the National Meteorology Center of China. To acquire a comprehensive assessment of T213's performance, four verifications have been implemented, (1) temporal analysis of its forecast accuracy series; (2) spatial analysis and lag correlation analysis of the forecast accuracy; (3) precipitation verification and (4) comparison between the models of T213, T106 (prior version of T213) and ECMWF. The verification illustrates that, after adopting a finer grid and improving many physical schemes, T213 has largely enhanced its forecast accuracy over its prior version. However, its forecast is still poorer than the ECMWF model, and T213 needs to especially improve its 3∼5 days' forecast performance. The precipitation verification indicates that T213's forecast for light rain is up‐to‐standard (0.561 for 24 h forecast), but the forecast accuracy for the larger precipitation drops rapidly. The time series verification shows that the T213's daily forecast exhibits a seasonal trend: the forecast for summer is worse than other seasons and the forecast accuracy decreases to the minimum at July, which suggests the possible impact of the moisture forecast error on the decreases of weather forecast accuracy. This impact is confirmed by the spatial analysis and lag correlation analysis, which show that the specific humidity's forecast has a lagged influence on the accuracies of both the temperature forecast and the geo‐potential height forecast, and therefore indicates that the further improvement on specific humidity forecasting and the related moisture parameterization schemes are the crucial points in the future development of the T213 model.
Systematic lidar observations of Saharan dust over Europe in the frame of EARLINET (2000–2002)
Authors: Papayannis A. , Amiridis V. , Mona L. , Tsaknakis G. , Balis D. , Bösenberg J. , Chaikovski A. , De Tomasi F. , Grigorov I. , Mattis I. , Mitev V. , Müller D. , Nickovic S. , Pérez C. , Pietruczuk A. , Pisani G. , Ravetta F. , Rizi V. , Sicard M. , Trickl T. , Wiegner M. , Gerding M. , Mamouri R. E. , D'Amico G. , Pappalardo G.
Published: May 2008

More than 130 observation days of the horizontal and vertical extent of Saharan dust intrusions over Europe during the period May 2000 to December 2002 were studied by means of a coordinated lidar network in the frame of the European Aerosol Research Lidar Network (EARLINET). The number of dust events was greatest in late spring, summer, and early autumn periods, mainly in southern (S) and southeastern (SE) Europe. Multiple aerosol dust layers of variable thickness (300–7500 m) were observed. The center of mass of these layers was located in altitudes between 850 and 8000 m. However, the mean thickness of the dust layer typically stayed around 1500–3400 m and the corresponding mean center of mass ranged from 2500 to 6000 m. In exceptional cases, dust aerosols reached northwestern (NW), northern (N), or northeastern (NE) Europe, penetrating the geographical area located between 4°W–28°E (longitude) and 38°N–58°N (latitude). Mean aerosol optical depths (AOD), extinction‐to‐backscatter ratios (lidar ratios, LR), and linear depolarization ratios of desert aerosols ranged from 0.1 to 0.25 at the wavelength of 355 or 351 nm, 30 to 80 sr at 355 or 351 nm, and 10 to 25% at 532 nm, respectively, within the lofted dust plumes. In these plumes typical Saharan dust backscatter coefficients ranged from 0.5 to 2 Mm−1sr−1. Southern European stations presented higher variability of the LR values and the backscatter‐related Ångström exponent values (BRAE) (LR: 20–100 sr; BRAE: −0.5 to 3) than northern ones (LR: 30–80 sr; BRAE: −0.5 to 1).
Source spectra information derived from U.S. high‐resolution radiosonde data
Authors: Gong Jie , Geller Marvin A. , Wang Ling
Published: May 2008

A ray‐tracing model is used to study the climatology of the source properties for gravity waves in the lower stratosphere using 8 years of U.S. high‐resolution radiosonde data. If the simulated total energy density and zonal momentum flux correlate well with those two parameters derived from the observations simultaneously, we claim a “best fit” is found. Eighty‐five stations with sufficient completeness and quality are analyzed, and we are able to obtain “best fit” source spectra for 61 of them. Two conditions are found to be necessary to achieve a “best fit.” First, the kinetic energy density and the zonal momentum flux derived from observations need to be highly correlated. Second, the source altitude needs to be located right below the lower stratosphere since the observed gravity waves represent the average climatology of the cumulative effect on a monthly average basis of the various time‐varying physical sources together with their propagation from different altitudes. All the sources we found are anisotropic, with most of momentum flux directed upstream of the dominant wind direction. This might be caused by wave propagation effects or the nature of the sources themselves. The latitudinal variation of the horizontal wavelength of the source spectra corresponds well with that derived independently from the observations, but other variable parameters do not show obvious latitudinal dependence. A source spectrum type representing convection works well for lower latitudes, while another more general source works better for middle to high latitudes. The central U.S. and the North American monsoon region are two regions where it is difficult to obtain “best fit” source spectra. We suspect that the reason for this is that during the summer, mesoscale convective systems are dominant sources for inertia‐gravity waves, which may not be well represented by our chosen spectral source functions.
Ensemble calibration and sensitivity study of a surface CO2 flux scheme using an optimization algorithm
Authors: Xue Lulin , Pan Zaitao
Published: May 2008

Carbon exchange between the atmosphere and terrestrial ecosystem is a key component affecting climate changes. Because the in situ measurements are not dense enough to resolve CO2 exchange spatial variation on various scales, the variation has been mainly simulated by numerical ecosystem models. These models contain large uncertainties in estimating CO2 exchange owing to incorporating a number of empirical parameters on different scales. This study applied a global optimization algorithm and ensemble approach to a surface CO2 flux scheme to (1) identify sensitive photosynthetic and respirational parameters, and (2) optimize the sensitive parameters in the modeling sense and improve the model skills. The photosynthetic and respirational parameters of corn (C4 species) and soybean (C3 species) in NCAR land surface model (LSM) are calibrated against observations from AmeriFlux site at Bondville, IL during 1999 and 2000 growing seasons. Results showed that the most sensitive parameters are maximum carboxylation rate at 25°C and its temperature sensitivity parameter (Vcmax25 and avc), quantum efficiency at 25°C (Qe25), temperature sensitivity parameter for maintenance respiration (arm), and temperature sensitivity parameter for microbial respiration (amr). After adopting calibrated parameter values, simulated seasonal averaged CO2 fluxes were improved for both the C4 and the C3 crops (relative bias reduced from 0.09 to −0.02 for the C4 case and from 0.28 to −0.01 for the C3 case). An updated scheme incorporating new parameters and a revised flux‐integration treatment is also proposed.
Vertical distribution of mercury, CO, ozone, and aerosol scattering coefficient in the Pacific Northwest during the spring 2006 INTEX‐B campaign
Authors: Swartzendruber P. C. , Chand D. , Jaffe D. A. , Smith J. , Reidmiller D. , Gratz L. , Keeler J. , Strode S. , Jaeglé L. , Talbot R.
Published: May 2008

In the spring of 2006, we measured the vertical distribution of gaseous elemental mercury (GEM), CO, ozone, and aerosol scattering coefficient in the Pacific Northwest concurrent with NASA's INTEX‐B campaign. Seven profiles from the surface to 6 km were conducted from 12 April to 8 May along with one flight in the Seattle‐Tacoma boundary layer. Ozone had a bimodal distribution with the lower mode occurring primarily in the mixed layer and the higher mode occurring in the free troposphere. In the free troposphere, the mixing ratios (1 − σ) of GEM, CO, ozone, and aerosol scattering coefficient were 1.52 (0.165) ng/m3, 142 (14.9) ppbv, 78 (7.7) ppbv, and 3.0 (1.8) Mm−1, respectively. GEM and CO were correlated in the high ozone mode (r2 = 0.30) but were uncorrelated in the lower mode (r2 = 0.05). Three flights observed enhancements of GEM and CO with good correlations and with regression slopes (0.0067 (±0.0027) ng/m3/ppbv by ordinary least squares regression and 0.0097 (±0.0018) ng/m3/ppbv by reduced major axis regression) slightly higher than previous observations of enhancements due to Asian industrial long‐range transport (LRT). The influence of Asian LRT is supported by back trajectories and a global chemical transport model. In the Seattle‐Tacoma boundary layer flight, CO was uncorrelated with GEM, which reflects relatively weaker local GEM sources. On three flights, pockets of air were observed with strong inverse GEM‐ozone and ozone‐CO correlations (in contrast to all data), which is evidence of upper tropospheric/lower stratospheric (UTLS) influence. An extrapolation of the GEM‐CO and GEM‐ozone slopes suggests the UTLS can be depleted of GEM.
Using observations of deep convective systems to constrain atmospheric column absorption of solar radiation in the optically thick limit
Authors: Dong Xiquan , Wielicki Bruce A. , Xi Baike , Hu Yongxiang , Mace Gerald G. , Benson Sally , Rose Fred , Kato Seiji , Charlock Thomas , Minnis Patrick
Published: May 2008

Atmospheric column absorption of solar radiation (Acol) is a fundamental part of the Earth's energy cycle but is an extremely difficult quantity to measure directly. To investigate Acol, we have collocated satellite‐surface observations for the optically thick Deep Convective Systems (DCS) at the Department of Energy Atmosphere Radiation Measurement (ARM) Tropical Western Pacific (TWP) and Southern Great Plains (SGP) sites during the period of March 2000–December 2004. The surface data were averaged over a 2‐h interval centered at the time of the satellite overpass, and the satellite data were averaged within a 1° × 1° area centered on the ARM sites. In the DCS, cloud particle size is important for top‐of‐atmosphere (TOA) albedo and Acol although the surface absorption is independent of cloud particle size. In this study, we find that the Acol in the tropics is ∼0.011 more than that in the middle latitudes. This difference, however, disappears, i.e., the Acol values at both regions converge to the same value (∼0.27 of the total incoming solar radiation) in the optically thick limit (τ > 80). Comparing the observations with the NASA Langley modified Fu_Liou 2‐stream radiative transfer model for optically thick cases, the difference between observed and model‐calculated surface absorption, on average, is less than 0.01, but the model‐calculated TOA albedo and Acol differ by 0.01 to 0.04, depending primarily on the cloud particle size observation used. The model versus observation discrepancies found are smaller than many previous studies and are just within the estimated error bounds. We did not find evidence for a large cloud absorption anomaly for the optically thick limit of extensive ice cloud layers. A more modest cloud absorption difference of 0.01 to 0.04 cannot yet be ruled out. The remaining uncertainty could be reduced with additional cases, and by reducing the current uncertainty in cloud particle size.
Mineralogy of volcanic rocks in Gusev Crater, Mars: Reconciling Mössbauer, Alpha Particle X‐Ray Spectrometer, and Miniature Thermal Emission Spectrometer spectra
Authors: McSween H. Y. , Ruff S. W. , Morris R. V. , Gellert R. , Klingelhöfer G. , Christensen P. R. , McCoy T. J. , Ghosh A. , Moersch J. M. , Cohen B. A. , Rogers A. D. , Schröder C. , Squyres S. W. , Crisp J. , Yen A.
Published: May 2008

Complete sets of mineral abundances for relatively unaltered volcanic or volcaniclastic rocks in Gusev Crater have been determined by modeling Mössbauer subspectral areas as mineral weight percentages, and combining those percentages with the proportions of iron‐free minerals not detected by Mössbauer (normative plagioclase, apatite, and chromite, as calculated from Alpha Particle X‐Ray Spectrometer (APXS) chemical analyses). Comparisons of synthetic thermal emission spectra calculated for these mineral modes with measured Miniature Thermal Emission Spectrometer (Mini‐TES) spectra for the same rock classes show either good agreements or discrepancies that we attribute to sodic plagioclase compositions or unmodeled sulfate, glass, or pigeonite. The normative compositions of olivine, pyroxene, and feldspar calculated from APXS data are consistent with spectroscopic constraints on mineral compositions. Systematic variations between olivine abundances in APXS norms (which sample tens of micrometers depth) and olivine proportions measured by Mössbauer (which sample hundreds of micrometers depth) support the hypothesis that dissolution of olivine by acidic fluids has occurred on weathered rock surfaces.
Hemispheric difference in the momentum transport by waves encircling the summer polar region of Mars observed by MGS TES
Authors: Fukuhara Tetsuya , Imamura Takeshi
Published: May 2008

Hemispheric difference in the momentum transport by atmospheric waves in the Martian summer polar region was investigated by using the atmospheric temperature profiles taken by MGS TES. In the southern polar region, isolated zonal wave number‐1 temperature disturbances were prominent and upward EP (Eliassen‐Palm) fluxes were found indicating the existence of planetary waves, while they were obscure in the northern polar region. This north‐south difference is attributed to the difference in CO2 polar cap retreat: the asymmetric retreat of the southern polar cap which remains throughout the summer creates near‐surface temperature anomalies with the zonal wave number of unity and resultant planetary waves, while the nearly symmetric retreat of the northern polar cap do not create such disturbances. The momentum transport in the southern polar region will drive a localized meridional circulation with ascent at 70°S–80°S and descent over the pole. This meridional circulation would increase the atmospheric temperature by ∼10 K near the pole and transport dust that is lifted up by local dust storms.
Nonlinear responses to nitrogen and strong interactions with nitrogen and phosphorus additions drastically alter the structure and function of a high arctic ecosystem
Authors: Arens Seth J. T. , Sullivan Patrick F. , Welker Jeffrey M.
Published: May 2008

Significant changes in ecosystem CO2 exchange and vegetation characteristics were observed following multiple additions of nitrogen (N) and factorial additions of N and phosphorus (P) to prostrate dwarf‐shrub, herb tundra in Northwest Greenland. Ecosystem CO2 exchange and vegetation cover and composition were very sensitive to low rates of N inputs (0.5 g m−2 y−1), indicating that even low rates of atmospheric N deposition may alter high arctic ecosystem structure and function. Increasing N addition from 1 to 5 g N m−2 y−1 did not alter CO2 exchange or vegetation characteristics, suggesting the ecosystem had become N saturated. Factorial additions of both N and P released the ecosystem from N saturation and dramatically increased gross ecosystem photosynthesis (+500%) and ecosystem respiration (+250%), such that the ecosystem switched from a small source of CO2 to a small sink for CO2 at midday during the 2005 growing season. Changes in the component fluxes of CO2 exchange were largely explained by a doubling of the normalized difference vegetation index, a 100% increase in vascular plant cover and dramatic increases in the abundance of several previously rare grass species. Our results clearly demonstrate that high arctic prostrate dwarf‐shrub, herb tundra is highly sensitive to low levels of N addition and that future increases in N deposition or N mineralization will likely lead to change in carbon cycling and vegetation characteristics, but the magnitude of the response will be constrained by P availability.
Modeling biogeophysical interactions in nonsorted circles in the Low Arctic
Authors: Nicolsky D. J. , Romanovsky V. E. , Tipenko G. S. , Walker D. A.
Published: May 2008

We investigate biogeophysical processes that cause differential frost heave in nonsorted circles north of the Alaska's Brooks Range. The main objective is the development of a numerical thermo‐mechanical model of a nonsorted circle. The presented model includes mass, momentum and energy conservation laws for water, ice and soil. We applied this model to simulate differential frost heave at the Franklin Bluffs site and obtained a good quantitative agreement with measured dynamics of soil temperature, water content, and frost heave. For other locations such as at the Sagwon Hills and Howe Island sites we obtained qualitative agreement with frost‐heave measurements. Sensitivity analysis shows that the most active development of differential frost heave occurs for nonsorted circles within waterlogged areas, as observed in field measurements. For well drained sites, model results and field observations show that the differential frost heave is much smaller in magnitude comparing to that of the water‐logged sites. Sensitivity of the model to alternation of the vegetation cover shows that a strong heterogeneity in the vegetation cover promotes active development of the differential frost heave. For nonsorted circles with vegetation on top of the circle, the computed differential heave is less pronounced. The radius of the nonsorted circle influences the magnitude of the frost heave. The computed maximum frost heave in the center of the circle corresponds to 1–1.5 meter diameter nonsorted circles. For nonsorted circles with larger diameters, computed frost heave in the center of a circle is smaller compared to the heave at the circle circumference.
Impact of geo‐engineering on the ion composition of the stratosphere
Authors: Beig Gufran
Published: May 2008

A remedy called “geo‐engineering solution” has been recently proposed by some scientists to handle the global warming problem through injection of sulfates high aloft into the stratosphere. However, this idea may have some other side impacts. We have investigated the perturbation caused by geo‐engineering solution on the stratospheric charged species using a coupled neutral‐ion photochemical model. Model calculations indicate additional production of sulfuric acid immediately after the injection which further leads to increased abundance of heavy negative ion family by several orders of magnitude over the ambient. After 2 months, most of the H2SO4 vapor condensed to H2SO4 aerosols and the density of charged aerosol increases several folds and the effect spread further in the tropics. The perturbation in ionic species spread globally after about 1 year but became weaker in magnitude. The ion perturbation has implications on the electrical properties of the atmospheric medium.
Evaluation of AMSR‐E soil moisture product based on ground measurements over temperate and semi‐arid regions
Authors: Gruhier C. , de Rosnay P. , Kerr Y. , Mougin E. , Ceschia E. , Calvet J.‐C. , Richaume P.
Published: May 2008

Soil moisture (SM) products provided by remote sensing approaches at continental scale are of great importance for land surface modeling and numerical weather prediction. Before using remotely sensed SM products it is crucial to validate them. This paper presents an evaluation of AMSR‐E (Advanced Microwave Scanning Radiometer ‐ Earth Observing System) SM products over two sites. They are located in the south‐west of France and in the Sahelian part of Mali in West Africa, in the framework of the SMOSREX (Surface Monitoring Of Soil Reservoir Experiment) and AMMA (African Monsoon Multidisciplinary Analysis) projects respectively. The most representative station of the four stations of each site is used for the comparison of AMSR‐E derived and in‐situ SM measurements in absolute and normalized values. Results suggest that, although AMSR‐E SM product is not able to capture absolute SM values, it provides reliable information on surface SM temporal variability, at seasonal and rainy event scale. It is shown, however, that the use of radiometric products, such as polarization ratio, provides better agreement with ground stations than the derived SM products.
Rock falls in high‐alpine rock walls quantified by terrestrial lidar measurements: A case study in the Mont Blanc area
Authors: Rabatel Antoine , Deline Philip , Jaillet Stéphane , Ravanel Ludovic
Published: May 2008

The global warming observed in recent decades and its future increase may affect permafrost distribution on high‐mountain faces with consequences for their stability. In this paper, we show that rock falls from high‐alpine rock walls can be computed with a decimetre‐resolution using lidar measurements. A laser scanner was used to create point clouds and triangulated irregular network models on the east face of the Tour Ronde at 3792 m asl (Mont Blanc massif). Comparison of the models realised from measurements of July 2005 and July 2006 enabled quantification of rock falls with reduced uncertainty. The volume of rock fall reached a total of 536 m3 in the scanned area, which matches an erosion rate of 8.4 mm yr−1. This rate slightly higher to the ones reported in former studies enable to assume that this rock fall may be the consequence of the permafrost degradation in this rock face.
Effect of obliteration on crater‐count chronologies for Martian surfaces
Authors: Smith Matthew R. , Gillespie Alan R. , Montgomery David R.
Published: May 2008

The density of impact craters calibrated against lunar data is currently the only quantitative measure of surface age for terrestrial planetary surfaces. Unlike the Moon, however, Mars has been weathered and eroded, obliterating some small (<10 km diameter) craters, a phenomenon addressed in the Mariner/Viking days of Mars exploration but commonly overlooked in recent studies. We present a quantitative model that extends this earlier work to assess the effect of erosion and infilling on surface ages inferred from crater‐frequency distributions. Our work affirms that small‐crater size distributions can be interpreted quantitatively in terms of effects of erosion and crater infilling at rates comparable to those reported for Mars. A reanalysis of prior studies indicates that low to moderate long‐term rates of erosion and crater infilling can mask an ancient age and result in small‐crater populations similar to those offered as evidence for young and geologically significant surface activity.
A summer phytoplankton bloom triggered by high wind events in the Labrador Sea, July 2006
Authors: Wu Yongsheng , Platt Trevor , Tang Charles C.L. , Sathyendranath Shubha , Devred Emmanuel , Gu Shue
Published: May 2008

The mechanisms of nutrient resupply for an episodic phytoplankton bloom observed in the central Labrador Sea in July 2006 were investigated. Two physical processes, mixed‐layer deepening and Ekman pumping, are proposed to account for the implied nutrient replenishment. The nutrient flux and chlorophyll concentration before and during the bloom were estimated from a simple coupled nitrate‐phytoplankton model. The model results show that the enrichment of nutrients in the euphotic layer and the subsequent bloom were related to two wind events (storms) in the period July 7–10. As the mixed layer deepened, nutrient from below the nitricline were entrained into the euphotic zone. The Ekman pumping, which was most intense at the storm centre, enhanced the transport of the nutrients by raising the nitricline. However, Ekman pumping alone was not able to transport sufficient nitrate to the euphotic layer to support the observed phytoplankton bloom.
How Rossby wave breaking over the Pacific forces the North Atlantic Oscillation
Authors: Strong Courtenay , Magnusdottir Gudrun
Published: May 2008

Anticyclonic Rossby wave breaking (RWB) over a well‐defined, limited‐area region of the east Pacific leads to the positive polarity of the North Atlantic Oscillation (NAO) by locally piling up wave activity where it may be advected downstream, resulting in increased wave activity flux and anticyclonic RWB over the subtropical Atlantic. A composite time series shows that Pacific RWB occurs several days prior to the Atlantic RWB and the peak of the NAO index. Following Pacific RWB, a channel of increased pseudomomentum flux extends from the Pacific wave breaking region, northeastward toward midlatitudes of eastern North America where pseudomomentum density accumulates for several days prior to moving eastward and leading to anticyclonic RWB over the Atlantic.
No evidence of unusually large postseismic deformation in Andaman region immediately after 2004 Sumatra‐Andaman earthquake
Authors: Gahalaut V. K. , Catherine J. K. , Jade Sridevi , Gireesh R. , Gupta D. C. , Narsaiah M. , Ambikapathy A. , Bansal A. , Chadha R. K.
Published: May 2008

Static offsets due to the 26 December 2004 Sumatra‐Andaman earthquake have been reported from the campaign mode GPS measurements in the Andaman‐Nicobar region. However, these measurements contain contributions from postseismic deformation that must have occurred in the 16–25 days period between the earthquake and the measurements. We analyse these and tide gauge measurements of coseismic deformation, a longer time series of postseismic deformation from GPS measurements at Port Blair in the South Andaman and aftershocks, to suggest that postseismic displacement not larger than 7 cm occurred in the 16–25 days following the earthquake in the South Andaman and probably elsewhere in the Andaman Nicobar region. Earlier, this contribution was estimated to be as large as 1 m in the Andaman region, which implied that the magnitude of the earthquake based on these campaign mode measurements should be decreased. We suggest an Mw for this earthquake as 9.23.