bluuebunny/crossref_metadata_2025_split huggingface dataset:
Trends and Variability of Surface Solar Radiation in Europe Based On Surface‐ and Satellite‐Based Data Records
Authors: Pfeifroth Uwe , Sanchez‐Lorenzo Arturo , Manara Veronica , Trentmann Jörg , Hollmann Rainer 
Published: January 2018

AbstractThe incoming solar radiation is the essential climate variable that determines the Earth's energy cycle and climate. As long‐term high‐quality surface measurements of solar radiation are rare, satellite data are used to derive more information on its spatial pattern and its temporal variability. Recently, the EUMETSAT Satellite Application on Climate Monitoring (CM SAF) has published two satellite‐based climate data records: Surface Solar Radiation Data Set‐Heliosat, Edition 2 (SARAH‐2), and Clouds and Radiation Data Set based on AVHRR (advanced very high resolution radiometer) Satellite Measurements, Edition 2 (CLARA‐A2). Both data records provide estimates of surface solar radiation. In this study, these new climate data records are compared to surface measurements in Europe during the period 1983–2015. SARAH‐2 and CLARA‐A2 show a high accuracy compared to ground‐based observations (mean absolute deviations of 6.9 and 7.3 W/m2, respectively) highlighting a good agreement considering the temporal behavior and the spatial distribution. The results show an overall brightening period since the 1980s onward (comprised between 1.9 and 2.4 W/m2/decade), with substantial decadal and spatial variability. The strongest brightening is found in eastern Europe in spring. An exception is found for northern and southern Europe, where the trends shown by the station data are not completely reproduced by satellite data, especially in summer in southern Europe. We conclude that the major part of the observed trends in surface solar radiation in Europe is caused by changes in clouds and that remaining differences between the satellite‐ and the station‐based data might be connected to changes in the direct aerosol effect and in snow cover.
The Identification of Hail Storms in the Early Stage Using Time Series Analysis
Authors: Wang Ping , Shi Jinyu , Hou Jinyi , Hu Yan 
Published: January 2018

AbstractThis study investigates the characteristics of hail storms and cumulonimbus storms in China from 2005 to 2016. Ten features are proposed to identify storm cells that can produce hail, especially in the early stage of hail formation. These features describe hail storms based on three factors: the height and thickness of the cell core, the radar echo intensity, and the overhang structure and the horizontal reflectivity gradient. The 10 features are transformed into two‐dimensional comprehensive features by principal component analysis (PCA). The two comprehensive features are named the volume measurement comprehensive feature (VMCF) and the height‐gradient comprehensive feature (HGCF). Through an analysis of 49 hail cases and 35 heavy rainfall cases with S‐band radar data, the time series exhibit a distinct increase in VMCF or HGCF values in the early stage of a hail storm. However, the VMCF and HGCF values of heavy rainfall events remain relatively stable throughout the storm life cycle. An experiment involving real‐storm events, including 31 hail cases and 33 heavy rainfall cases, indicated that the probability of detection of hail storms was 93.33% and the false alarm ratio was 15.66%. In the cases that could be successfully identified as hail storms, 80.00% were detected within 18 min of reaching a hail storm reflectivity of 40 dBZ.
Generalized Dynamic Equations Related to Condensation and Freezing Processes
Authors: Wang Xingrong , Huang Yong 
Published: January 2018

AbstractThe generalized thermodynamic equation related to condensation and freezing processes was derived by introducing the condensation and freezing probability function into the dynamic framework based on the statistical thermodynamic fluctuation theory. As a result, the physical mechanism of some weather phenomena covered by using δ(0,1) can in turn be studied and uncovered. From the generalized dynamic equations, the tendency equation of the generalized potential vorticity (GPV) is derived. From the discussion of tendency equation of GPV, in some very thin transitional areas, GPV is found nonconserved because of the introduction of the condensation and freezing probability function, even in frictionless and moist adiabatic air motion.
On the Ability of Space‐Based Passive and Active Remote Sensing Observations of CO2 to Detect Flux Perturbations to the Carbon Cycle
Authors: Crowell Sean M. R. , Randolph Kawa S. , Browell Edward V. , Hammerling Dorit M. , Moore Berrien , Schaefer Kevin , Doney Scott C. 
Published: January 2018

AbstractSpace‐borne observations of CO2 are vital to gaining understanding of the carbon cycle in regions of the world that are difficult to measure directly, such as the tropical terrestrial biosphere, the high northern and southern latitudes, and in developing nations such as China. Measurements from passive instruments such as GOSAT and OCO‐2, however, are constrained by solar zenith angle limitations as well as sensitivity to the presence of clouds and aerosols. Active measurements such as those in development for the Active Sensing of CO2 Emissions over Nights, Days and Seasons (ASCENDS) mission show strong potential for making measurements in the high‐latitude winter and in cloudy regions. In this work we examine the enhanced flux constraint provided by the improved coverage from an active measurement such as ASCENDS. The simulation studies presented here show that with sufficient precision, ASCENDS will detect permafrost thaw and fossil fuel emissions shifts at annual and seasonal time scales, even in the presence of transport errors, representativeness errors, and biogenic flux errors. While OCO‐2 can detect some of these perturbations at the annual scale, the seasonal sampling provided by ASCENDS provides the stronger constraint.
Parameterization of In‐Cloud Aerosol Scavenging Due To Atmospheric Ionization: 2. Effects of Varying Particle Density
Authors: Zhang Liang , Tinsley Brian A. 
Published: January 2018

AbstractSimulations and parameterization of collision rate coefficients for aerosol particles with 3 μm radius droplets have been extended to a range of particle densities up to 2,000 kg m−3 for midtropospheric (~5 km) conditions (540 hPa, −17°C). The increasing weight has no effect on collisions for particle radii less than 0.2 μm, but for greater radii the weight effect becomes significant and usually decreases the collision rate coefficient. When increasing size and density of particles make the fall speed of the particle relative to undisturbed air approach to that of the droplet, the effect of the particle falling away in the stagnation region ahead of the droplet becomes important, and the probability of frontside collisions can decrease to zero. Collisions on the rear side of the droplet can be enhanced as particle weight increases, and for this the weight effect tends to increase the rate coefficients. For charges on the droplet and for large particles with density ρ < 1,000 kg m−3 the predominant effect increases in rate coefficient due to the short‐range attractive image electric force. With density ρ above about 1,000 kg m−3, the stagnation region prevents particles moving close to the droplet and reduces the effect of these short‐range forces. Together with previous work, it is now possible to obtain collision rate coefficients for realistic combinations of droplet charge, particle charge, droplet radius, particle radius, particle density, and relative humidity in clouds. The parameterization allows rapid access to these values for use in cloud models.
Interannual and Diurnal Variability in Water Ice Clouds Observed from MSL Over Two Martian Years
Authors: Kloos J. L. , Moores J. E. , Whiteway J. A. , Aggarwal M. 
Published: January 2018

AbstractWe update the results of cloud imaging sequences from the Mars Science Laboratory (MSL) rover Curiosity to complete two Mars years of observations (LS=160° of Mars year (MY) 31 to LS=160° of MY 33). Relatively good seasonal coverage is achieved within the study period, with just over 500 observations obtained, averaging one observation every 2–3 sols. Cloud opacity measurements are made using differential photometry and a simplified radiative transfer method. These opacity measurements are used to assess the interannual variability of the aphelion cloud belt (ACB) for MY 32 and 33. Upon accounting for a statistical bias in the data set, the variation is found to be <30% within uncertainty. Diurnal variation of the ACB is also able to be examined in MY 33 owing to an increased number of early morning observations in this year. Although a gap in data around local noon prevents a complete assessment, we find that cloud opacity is moderately increased in the morning hours (07:00–09:00) compared to the late afternoon (15:00–17:00).
Venus Upper Clouds and the UV Absorber From MESSENGER/MASCS Observations
Authors: Pérez‐Hoyos S. , Sánchez‐Lavega A. , García‐Muñoz A. , Irwin P. G. J. , Peralta J. , Holsclaw G. , McClintock W. M. , Sanz‐Requena J. F. 
Published: January 2018

AbstractOne of the most intriguing, long‐standing questions regarding Venus's atmosphere is the origin and distribution of the unknown UV absorber, responsible for the absorption band detected at the near‐UV and blue range of Venus's spectrum. In this work, we use data collected by Mercury Atmospheric and Surface Composition Spectrometer (MASCS) spectrograph on board the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission during its second Venus flyby in June 2007 to address this issue. Spectra range from 0.3 μm to 1.5 μm including some gaseous H2O and CO2 bands, as well as part of the SO2 absorption band and the core of the UV absorption. We used the NEMESIS radiative transfer code and retrieval suite to investigate the vertical distribution of particles in the equatorial atmosphere and to retrieve the imaginary refractive indices of the UV absorber, assumed to be well mixed with Venus's small mode 1 particles. The results show a homogeneous equatorial atmosphere, with cloud tops (height for unity optical depth) at 75 ± 2 km above surface. The UV absorption is found to be centered at 0.34 ± 0.03 μm with a full width at half maximum of 0.14 ± 0.01 μm. Our values are compared with previous candidates for the UV aerosol absorber, among which disulfur oxide (S2O) and dioxide disulfur (S2O2) provide the best agreement with our results.
Three‐Dimensional Structures of Thermal Tides Simulated by a Venus GCM
Authors: Takagi Masahiro , Sugimoto Norihiko , Ando Hiroki , Matsuda Yoshihisa 
Published: January 2018

AbstractThermal tides in the Venus atmosphere are investigated by using a GCM named as AFES‐Venus. The three‐dimensional structures of wind and temperature associated with the thermal tides obtained in our model are fully examined and compared with observations. The result shows that the wind and temperature distributions of the thermal tides depend complexly on latitude and altitude in the cloud layer, mainly because they consist of vertically propagating and trapped modes with zonal wave numbers of 1–4, each of which predominates in different latitudes and altitudes under the influence of mid‐ and high‐latitude jets. A strong circulation between the subsolar and antisolar (SS‐AS) points, which is equivalent to a diurnal component of the thermal tides, is superposed on the superrotation. The vertical velocity of SS‐AS circulation is about 10 times larger than that of the zonal‐mean meridional circulation (ZMMC) in 60–70 km altitudes. It is suggested that the SS‐AS circulation could contribute to the material transport, and its upward motion might be related to the UV dark region observed in the subsolar and early afternoon regions in low latitudes. The terdiurnal and quaterdiurnal tides, which may be excited by the nonlinear interactions among the diurnal and semidiurnal tides in middle and high latitudes, are detected in the solar‐fixed Y‐shape structure formed in the vertical wind field in the upper cloud layer. The ZMMC is weak and has a complex structure in the cloud layer; the Hadley circulation is confined to latitudes equatorward of 30°, and the Ferrel‐like one appears in middle and high latitudes.
Linking the Modern Distribution of Biogenic Proxies in High Arctic Greenland Shelf Sediments to Sea Ice, Primary Production, and Arctic‐Atlantic Inflow
Authors: Limoges Audrey , Ribeiro Sofia , Weckström Kaarina , Heikkilä Maija , Zamelczyk Katarzyna , Andersen Thorbjørn J. , Tallberg Petra , Massé Guillaume , Rysgaard Søren , Nørgaard‐Pedersen Niels , Seidenkrantz Marit‐Solveig 
Published: January 2018

AbstractThe eastern north coast of Greenland is considered to be highly sensitive to the ongoing Arctic warming, but there is a general lack of data on modern conditions and in particular on the modern distribution of climate and environmental proxies to provide a baseline and context for studies on past variability. Here we present a detailed investigation of 11 biogenic proxies preserved in surface sediments from the remote High Arctic Wandel Sea shelf, the entrance to the Independence, Hagen, and Danmark fjords. The composition of organic matter (organic carbon, C:N ratios, δ13C, δ15N, biogenic silica, and IP25) and microfossil assemblages revealed an overall low primary production dominated by benthic diatoms, especially at the shallow sites. While the benthic and planktic foraminiferal assemblages underline the intrusion of chilled Atlantic waters into the deeper parts of the study area, the distribution of organic‐walled dinoflagellate cysts is controlled by the local bathymetry and sea ice conditions. The distribution of the dinoflagellate cyst Polarella glacialis matches that of seasonal sea ice and the specific biomarker IP25, highlighting the potential of this species for paleo sea ice studies. The information inferred from our multiproxy study has important implications for the interpretation of the biogenic‐proxy signal preserved in sediments from circum‐Arctic fjords and shelf regions and can serve as a baseline for future studies. This is the first study of its kind in this area.
Watershed‐Scale Drivers of Air‐Water CO2 Exchanges in Two Lagoonal North Carolina (USA) Estuaries
Authors: Van Dam Bryce R. , Crosswell Joseph R. , Anderson Iris C. , Paerl Hans W. 
Published: January 2018

AbstractRiverine loading of nutrients and organic matter act in concert to modulate CO2 fluxes in estuaries, yet quantitative relationships between these factors remain poorly defined. This study explored watershed‐scale mechanisms responsible for the relatively low CO2 fluxes observed in two microtidal, lagoonal estuaries. Air‐water CO2 fluxes were quantified with 74 high‐resolution spatial surveys in the neighboring New River Estuary (NewRE) and Neuse River Estuary (NeuseRE), North Carolina, which experience a common climatology but differ in marine versus riverine influence. Annually, both estuaries were relatively small sources of CO2 to the atmosphere, 12.5 and 16.3 mmol C m−2 d−1 in the NeuseRE and NewRE, respectively. Large‐scale pCO2 variations were driven by changes in freshwater age, which modulates nutrient and organic carbon supply and phytoplankton flushing. Greatest pCO2 undersaturation was observed at intermediate freshwater ages, between 2 and 3 weeks. Biological controls on CO2 fluxes were obscured by variable inputs of river‐borne CO2, which drove CO2 degassing in the river‐dominated NeuseRE. Internally produced CO2 exceeded river‐borne CO2 in the marine‐dominated NewRE, suggesting that net ecosystem heterotrophy, rather than riverine inputs, drove CO2 fluxes in this system. Variations in riverine alkalinity and inorganic carbon loading caused zones of minimum buffering capacity to occur at different locations in each estuary, enhancing the sensitivity of estuarine inorganic C chemistry to acidification. Although annual CO2 fluxes were similar between systems, watershed‐specific hydrologic factors led to disparate controls on internal carbonate chemistry, which can influence ecosystem biogeochemical cycling, trophic state, and response to future perturbations.
Adjoint‐Based Climate Model Tuning: Application to the Planet Simulator
Authors: Lyu Guokun , Köhl Armin , Matei Ion , Stammer Detlef 
Published: January 2018

AbstractThe adjoint method is used to calibrate the medium complexity climate model “Planet Simulator” through parameter estimation. Identical twin experiments demonstrate that this method can retrieve default values of the control parameters when using a long assimilation window of the order of 2 months. Chaos synchronization through nudging, required to overcome limits in the temporal assimilation window in the adjoint method, is employed successfully to reach this assimilation window length. When assimilating ERA‐Interim reanalysis data, the observations of air temperature and the radiative fluxes are the most important data for adjusting the control parameters. The global mean net longwave fluxes at the surface and at the top of the atmosphere are significantly improved by tuning two model parameters controlling the absorption of clouds and water vapor. The global mean net shortwave radiation at the surface is improved by optimizing three model parameters controlling cloud optical properties. The optimized parameters improve the free model (without nudging terms) simulation in a way similar to that in the assimilation experiments. Results suggest a promising way for tuning uncertain parameters in nonlinear coupled climate models.
Zircon U‐Pb Dating of a Lower Crustal Shear Zone: A Case Study From the Northern Sector of the Ivrea‐Verbano Zone (Val Cannobina, Italy)
Authors: Langone A. , Zanetti A. , Daczko N. R. , Piazolo S. , Tiepolo M. , Mazzucchelli M. 
Published: January 2018

AbstractA geochronological study was performed on zircon grains from a middle‐lower crustal shear zone exposed in the northern sector of the Ivrea‐Verbano Zone (Southern Alps, Italy) for the first time. The shear zone developed at the boundary between mafic rocks of the External Gabbro unit and ultramafic rocks of the Amphibole Peridotite unit. It is ~10–20 m wide, can be followed along a NE strike for several kilometers, and consists of an anastomosing network of mylonites and ultramylonites. Zircon grains were studied in thin sections and as separates from three representative outcrops along the shear zone. Zircon grains are more abundant in the shear zone compared to wall rocks and are generally equant, rounded to subrounded with dimensions up to 500 μm. U‐Pb data are mainly discordant, and the apparent 206Pb/238U dates show a large variation from Permian to Jurassic. Isotopic data, combined with microstructural, morphological, and internal features of zircon, reveal an inherited age component and suggest partial zircon recrystallization under high‐temperature conditions during Late Triassic to Early Jurassic. High‐temperature deformation in the shear zone, at lower crustal levels, was coeval with amphibolite to greenschist facies mylonitic deformation at upper crustal levels and is inferred to be related to Mesozoic rifting processes at the Adriatic margin.
Concentration‐Discharge Responses to Storm Events in Coastal California Watersheds
Authors: Aguilera Rosana , Melack John M. 
Published: January 2018

AbstractStorm events in montane catchments are the main cause of mobilization of solutes and particulates into and within stream channels in coastal California. Nonlinear behavior of nutrients and suspended sediments during storms is evident in the hysteresis that arises in concentration‐discharge (C‐Q) relationships. We examined patterns in the C‐Q hysteresis of nutrients (
,
, DON, and
) and total suspended solids (TSS) during storms across 10 sites and water years 2002–2015 by quantifying the slope of the C‐Q relationship and the rotational pattern of the hysteresis loop. We observed several hysteresis types in the ∼400 storms included in our study. Concentrations of constituents associated with sediment transport (
and TSS) peaked during high flows. Conversely, nitrogen species had hysteretic responses such as dilution with clockwise rotation in urban sites and enrichment with anticlockwise rotation in undeveloped sites. The wide range of C‐Q responses that occurred among sites and seasons reflected the variable hydrological and biogeochemical characteristics of catchments and storms. Responses for nitrate in nested catchments differed in slope and rotation of C‐Q hysteresis. Upland undeveloped and lowland urban sites had anticlockwise rotation at the onset of the rainy season following a dry year, which implied a delay in the transport of this solute to the streams. Slopes by the middle of the rainy season showed that the urban site switched from dilution to enrichment, and then again to dilution with clockwise rotation at the end of the season, which implied high initial concentrations and proximal sources.
Nanostructured Lipid‐Based Films for Substrate‐Mediated Applications in Biotechnology
Authors: Kang Minjee , Tuteja Mohit , Centrone Andrea , Topgaard Daniel , Leal Cecilia 
Published: January 2018

AbstractAmphiphilic in nature, lipids spontaneously self‐assemble into a range of nanostructures in the presence of water. Among lipid self‐assembled structures, liposomes and supported lipid bilayers have long held scientific interest for their main applications in drug delivery and plasma membrane models, respectively. In contrast, lipid‐based multilayered membranes on solid supports only recently begin drawing scientists' attention. Current studies show that the stacking of multiple bilayers on a solid support yields cooperative structural and dynamic behavior that enables new functionalities. Lipid films provide compartmentalization, templating, and enhanced release of molecules of interest. Importantly, supported lipid phases exhibit long‐range periodic nanoscale order and orientation that is tunable in response to a changing environment. Herein, the current understanding of lipid‐based film research is summarized focusing on how unique structural characteristics enable the emergence of new applications including label‐free biosensors, macroscale drug delivery, and substrate‐mediated gene delivery. The authors' recent contributions focusing on the structural characterization of lipid‐based films using small‐angle X‐ray scattering and atomic force microscopy are highlighted. In addition, new photothermally induced resonance and solid‐state nuclear magnetic resonance data are described, providing insights into drug partition in lipid‐based films as well as structure and dynamics at the molecular scale.