Enhanced data and methods for improving open and free global population grids: putting ‘leaving no one behind’ into practice     

Sergio Freire  Marcello Schiavina  Aneta J. Florczyk  Kytt MacManus  Martino Pesaresi  Christina Corbane 《International Journal of Digital Earth》2020,13(1):61-77

ABSTRACT

Data on global population distribution are a strategic resource currently in high demand in an age of new Development Agendas that call for universal inclusiveness of people. However, quality, detail, and age of census data varies significantly by country and suffers from shortcomings that propagate to derived population grids and their applications. In this work, the improved capabilities of recent remote sensing-derived global settlement data to detect and mitigate major discrepancies with census data is explored. Open layers mapping built-up presence were used to revise census units deemed as ‘unpopulated’ and to harmonize population distribution along coastlines. Automated procedures to detect and mitigate these anomalies, while minimizing changes to census geometry, preserving the regional distribution of population, and the overall counts were developed, tested, and applied. The two procedures employed for the detection of deficiencies in global census data obtained high rates of true positives, after verification and validation. Results also show that the targeted anomalies were significantly mitigated and are encouraging for further uses of free and open geospatial data derived from remote sensing in complementing and improving conventional sources of fundamental population statistics.  相似文献   

The effect of chlorite interlayering on <Superscript>40</Superscript>Ar–<Superscript>39</Superscript>Ar biotite dating: an <Superscript>40</Superscript>Ar–<Superscript>39</Superscript>Ar laser-probe and TEM investigations of variably chloritised biotites     

Gianfranco?Di VincenzoEmail author  Cecilia?Viti  Sergio?Rocchi 《Contributions to Mineralogy and Petrology》2003,145(6):643-658

Biotite is one of the most common minerals dated by the ⁴⁰Ar–³⁹Ar method. It frequently shows K contents below the expected stoichiometric value, suggesting the presence of low-K impurities. The most common low-K alteration product of biotite is chlorite. Therefore, it is important to understand the effects of chlorite interlayering on ⁴⁰Ar–³⁹Ar ages in order to correctly interpret ⁴⁰Ar–³⁹Ar data. This study examines the outcome of ⁴⁰Ar–³⁹Ar dating analyses on variably chloritised biotites from Ordovician intrusive rocks. The infrared (IR) laser-probe technique and different gas extraction methods were adopted. Incremental laser-heating data on bulk samples yielded hump-shaped age profiles with meaningless young and old age steps. Both the extent of anomalous old age steps and the degree of discordance of the age spectra were much more pronounced in the more chloritised biotite samples. In contrast, in situ data on rock chips and total-fusion ages on single biotite flakes yielded ages concordant with, or younger than, the inferred emplacement ages. Transmission electron microscopy (TEM) was used to texturally characterise biotite samples at the nanometre scale. It was also used to document the complex decomposition-transformation process affecting interlayered biotite–chlorite during in-vacuo IR-laser heating to temperatures ranging from ~600 to >1,000 °C. TEM results suggest that hump-shaped age profiles result from an interplay between ³⁹Ar_K redistribution by recoil during sample irradiation and differential release of argon isotopes hosted in three main reservoirs. These reservoirs are (from least to most retentive): extended defects, chlorite and biotite. The final descending age segment is attributed to the progressive release of argon with increasing temperature from large biotite domains for which ³⁹Ar_K recoil loss was less important. ⁴⁰Ar–³⁹Ar data support previous findings, which suggest that ⁴⁰Ar–³⁹Ar ages when recoil effects are minimised, provide minimum estimates that approach the true biotite age, when the pristine domains are analysed. The most effective approach for obtaining meaningful ⁴⁰Ar–³⁹Ar ages was using individual total-fusion analyses on carefully selected, single flakes previously split along the basal cleavage by wet-grinding and corresponding to a sample mass of a few micrograms.Editorial responsibility: I Parsons  相似文献   

Radio Emission from Three-dimensional Relativistic Hydrodynamic Jets: Observational Evidence of Jet Stratification     

Aloy MA  Gómez JL  Ibáñez JM  Martí JM  Müller E 《The Astrophysical journal》2000,536(2):L85-L88

High-resolution, high signal-to-noise ratio, blue-violet spectra of three red giant branch tip stars in M15 have been obtained with the Keck I High-Resolution Echelle Spectrograph. These spectra have been analyzed to determine the abundances of several neutron-capture elements, including the radioactive chronometer element thorium. There are two principal results of this study. First, the abundances of the heavier (Z>/=56) elements for each of the three stars is well matched by a scaled solar system r-process abundance distribution. Second, a weighted mean-observed Th/Eu ratio for the stars implies an age for the neutron-capture material in M15 stars of 14+/-3 Gyr, in reasonable agreement with other recent age estimates for Galactic globular clusters.  相似文献   

A Lost Realm in the Internal Domains of the Betic-Rif Orogen (Spain and Morocco): Evidence from Conglomerates and Consequences for Alpine Geodynamic Evolution     

Martín-Algarra A  Messina A  Perrone V  Russo S  Maate A  Martín-Martín M 《The Journal of geology》2000,108(4):447-467

The Malaguide-Ghomaride Complex is capped by Upper Oligocene-Aquitanian clastic deposits postdating early Alpine orogenesis but predating the main tectonic-metamorphic evolution, end of nappe emplacement, unroofing, and exhumation of the metamorphic units of the Betic-Rif Orogen. Two conglomerate intervals within these deposits are characterized by clasts of sedimentary, epimetamorphic, and mafic volcanic rocks derived from Malaguide-Ghomaride units and by clasts of acidic magmatic and orthogneissic rocks of unknown provenance, here studied. Magmatic rocks originated from late-Variscan two-mica cordierite-bearing granitoids and, subordinately, from aplitic dikes. Orthogneisses derive from similar plutonic rocks but are affected by an Alpine metamorphic overprint evolving from greenschist (T=510&j0;-530 degrees C and P=5-6 kbar) to low-temperature amphibolite facies (T>550&j0;C and P<3 kbar). Such a plutonic rock suite is unknown in any Betic-Rif unit or in the basement of the Alboran Sea, and the metamorphic evolution in the orthogneisses is different from (and older than) that of Alpujarride-Sebtide rocks to which they were formerly ascribed. Magmatic and metamorphic rocks very similar to those studied characterize the basements of some Kabylia and Calabria-Peloritani units. Therefore, the source area is a currently lost continental-crust realm of Calabria-Peloritani-Kabylia type, located to the ESE of the Malaguide-Ghomaride Domain and affected by a pre-latest Oligocene Alpine metamorphism. Increasingly active tectonics transformed this realm into rising areas from which erosion fed small subsiding synorogenic basins formed on the Malaguide-Ghomaride Complex. This provenance analysis demonstrates that all these domains constituted a single continental-crust block until Aquitanian-Burdigalian times, before its dispersal around nascent western Mediterranean basins.  相似文献   

Validation of a homogeneous 41-year (1961–2001) winter precipitation hindcasted dataset over the Iberian Peninsula: assessment of the regional improvement of global reanalysis     

M. G. Sotillo  M. L. Martín  F. Valero  M. Y. Luna 《Climate Dynamics》2006,27(6):627-645

A 44-year (1958–2001) homogeneous, Mediterranean, high-resolution atmospheric database was generated through dynamical downscaling within the HIPOCAS (Hindcast of Dynamic Processes of the Ocean and Coastal Areas of Europe) Project framework. This work attempts to provide a validation of the monthly winter HIPOCAS precipitation over the Iberian Peninsula and the Balearic Islands and to evaluate the potential improvement of these new hindcasted data versus global reanalysis datasets. The validation was performed through the comparative analysis with a precipitation database derived from 4,617 in situ stations located over Iberia and the Balearics. The statistical comparative analysis between the observed and the HIPOCAS fields highlights their very good agreement not only in terms of spatial and time distribution, but also in terms of total amount of precipitation. A principal component analysis is carried out, showing that the patterns derived from the HIPOCAS data largely capture the main characteristics of the observed field. Moreover, it is worth to note that the HIPOCAS patterns reproduce accurately the observed regional characteristics linked to the main orographic features of the study domain. The existence of high correlations between the hindcasted and observed principal component time series gives a measure of the model performance ability. An additional comparative study of the HIPOCAS winter precipitation with global reanalysis data (NCEP and ERA) is performed. This study reveals the important regional improvement in the characterization of the observed precipitation introduced by the HIPOCAS hindcast relative to the above global reanalyses. Such improvement is effective not only in terms of total amount values, but also in the spatial distribution, the observed field being much more realistically reproduced by HIPOCAS than by the global reanalysis data.  相似文献   

Groundwater resource degradation in coastal plains: The example of the Cecina area (Tuscany – Central Italy)     

Sergio Grassi  Gianni CortecciPaolo Squarci 《Applied Geochemistry》2007

The paper describes the degradation of the groundwater resources in the Cecina area, where seawater intrusion, B contamination and NO₃ pollution are all affecting the heavily exploited Pleistocene aquifer. Over-pumping has brought water levels to about 0 m.a.s.l. as far as about 7 km from the shore line, thereby promoting the seawater intrusion. The intrusion, which is characterized by cation exchange phenomena and Ca–Cl type waters, enters the plain mostly through the shallower horizons. The saline front, which advanced from 0.5 to 1 km in 4 a, has by now reached the foot of the hills to the east of the town, where it is also affecting wells of the local aqueduct. Boron contamination, linked to past discharge of industrial waste transported downstream by the river, reached concentrations as high as 3.5 mg/L in the mid-1980s. Although a decreasing trend is now under way, B content is still close to 1 mg/L. The presence of high NO₃, which, together with the seawater intrusion, represents a major issue for groundwater management in the area, is linked to the widespread utilization of fertilizers. Nitrate concentration, which reaches a maximum of about 300 mg/L in the shallow aquifer horizons and then decreases rather regularly with depth, is strongly influenced by precipitation. However, irrigation also contributes significantly to transporting the NO₃ contamination to depth, as clearly shown by δ¹⁸O data. The severe decline in the quality of the groundwater resource in the Cecina area is further compounded by an overall decrease in water availability in the region of Tuscany, as evidenced by long-term monitoring of precipitation and fluvial discharge.  相似文献   

Importance of geochemical transformations in determining submarine groundwater discharge-derived trace metal and nutrient fluxes     

Aaron J. Beck  Yoko Tsukamoto  Antonio Tovar-Sanchez  Miguel Huerta-Diaz  Henry J. Bokuniewicz  Sergio A. Sañudo-Wilhelmy 《Applied Geochemistry》2007

Seasonal (Spring and Summer 2002) concentrations of dissolved (<0.22 μm) trace metals (Ag, Al, Co, Cu, Mn, Ni, Pb), inorganic nutrients (NO₃, PO₄, Si), and DOC were determined in groundwater samples from 5 wells aligned along a 30 m shore-normal transect in West Neck Bay, Long Island, NY. Results show that significant, systematic changes in groundwater trace metal and nutrient composition occur along the flowpath from land to sea. While conservative mixing between West Neck Bay water and the groundwaters explains the behavior of Si and DOC, non-conservative inputs for Co and Ni were observed (concentration increases of 10- and 2-fold, respectively) and removal of PO₄ and NO₃ (decreases to about half) along the transport pathway. Groundwater-associated chemical fluxes from the aquifer to the embayment calculated for constituents not exhibiting conservative behavior can vary by orders of magnitude depending on sampling location and season (e.g. Co, 3.4 × 10²– 8.2 × 10³ μmol d⁻¹). Using measured values from different wells as being representative of the true groundwater endmember chemical composition also results in calculation of very different fluxes (e.g., Cu, 6.3 × 10³ μmol d⁻¹ (inland, freshwater well) vs. 2.1 × 10⁵ μmol d⁻¹(seaward well, S = 17 ppt)). This study suggests that seasonal variability and chemical changes occurring within the subterranean estuary must be taken into account when determining the groundwater flux of dissolved trace metals and nutrients to the coastal ocean.  相似文献   

Velocity Oscillations in Active Sunspot Groups     

Balthasar  H.  MartÍnez Pillet  V.  Schleicher  H.  Wöhl  H. 《Solar physics》1998,182(1):65-72

Time series of two-dimensional spectra were taken with the Göttingen 2D spectrometer at the VTT on Tenerife in 1996. They were investigated for Doppler velocities and velocity oscillations in small spots and pores of rapidly evolving sunspot groups. For the present measurements the magnetically insensitive lines Fe i 557.6 nm and Fe i 709.0 nm were selected. Spots with penumbrae exhibit the Evershed effect. Some pores seem to be connected with downflows, but the centres of the downflows are somewhat displaced from their associated pores. The surroundings of the pores show red shifts relative to the whole field of view. The power in the 5-min range is reduced inside the spots and pores as well as in their immediate vicinity. This reduction inside the spots is in agreement with former results. Outside the area of the spot group the 5-min power has a patchy structure with a typical size of 5 arc sec. For periods below 3.3 min, the behaviour of individual spots and pores is different. Some spots show clearly enhanced power for these periods, and it remains high down to the Nyquist period at 1.5 min. The small pores do not show enhanced three-minute oscillations compared with their vicinity. Inside one spot we find a ring of enhanced power in the period range between 8 and 20 min corresponding to the time scales of granular variations. This result could be an indication of a relation between spots and convection, but magneto-accoustic waves are also possible. The same ring exhibits also enhanced power for short periods.  相似文献   

Globalization: a geographical discourse     

Sergio Conti  Paolo Giaccaria 《GeoJournal》1998,45(1-2):17-25

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Relationship between waterfowl and the seagrassRuppia maritima in a Southwestern Atlantic coastal lagoon     

Alejandro Bortolus  Oscar O. Iribarne  Mariano M. Martínez 《Estuaries and Coasts》1998,21(4):710-717

We evaluated the distribution of waterfowl in relation to a seagrass (Ruppia maritima) patch, to infauna, and on its relationship with substrate characteristics. An experiment performed in the Mar Chiquita coastal lagoon (37°46′S, 57°27′W; Argentina) was used to evaluate the effect of herbivory on widgeon grass,R. maritima. Control plots of equal size, located between bird exclosures, were exposed to herbivory. The experiment ran for 31 d, starting on December 1, 1994. Censuses showed that black-necked swan ( $\bar x = 50$ birds ha^?1, SD = 37, n = 10) and coots ( $\bar x = 42$ birds ha^?1, SD = 28, n = 10) were the most important (always present) of the waterfowl seen feeding onR. maritima. The results of the experiment showed greater leaf lengths, lower belowground (rhizomes and roots) biomass, greater aboveground (leaves and shoots) biomass, and greater abundance of the polychaeteHeteromastus similis in exclosure plots. There were no exclosure effects on total biomass (belowground plus aboveground), reproductive parts (fruits and pre- and postpollination flowers), or abundance of most benthic infauna. Topographic surveys showed that sediment surface was higher within theR. maritima patches, but there were no significant differences in granulometric composition. Surveys also showed that bird distribution was strongly associated with the presence ofR. maritima.  相似文献