The Effects of Inner- and Outer-Layer Turbulence in a Convective Boundary Layer on the Near-Neutral Inertial Sublayer Over an Urban-Like Surface     

Marieta Cristina Castillo  Atsushi Inagaki  Manabu Kanda 《Boundary-Layer Meteorology》2011,140(3):453-469

A large-eddy simulation of the atmospheric boundary layer, large enough to contain both an urban surface layer and a convective mixed layer, was performed to investigate inner-layer and outer-layer scale motions. The objective was to determine the applicability of Monin–Obukhov similarity theory to inner-layer motions, to investigate the influence of outer-layer motions on surface-layer structure, as well as to assess the interaction of the two scales of motion. The urban surface roughness consisted of square-patterned cubic buildings of dimension H (40 m). A spatial filter was used to decompose the two scales in the inertial sublayer. The horizontal square filter of size 10H was effective in separating the inner-layer (surface-layer height ≈ 2 H) and outer-layer scales (boundary-layer height δ ≈ 30H), where the Reynolds stress contribution of the inner layer dominates in the logarithmic layer (depth 2H). Similarity coefficients for velocity fluctuations were successfully determined for inner-layer motions in the surface layer, proving the robustness of Monin–Obukhov similarity for surface-layer turbulence. The inner-layer structures exhibit streaky structures that have similar streamwise length but narrower spanwise width relative to the streamwise velocity fluctuation field, consistent with observations from an outdoor scale model. The outer-layer motions to some extent influence the location of ejections and sweeps through updraft and downdraft motions, respectively, thus, disturbing the homogeneity and similarity of inner-layer motions. Although the horizontal averages of the variances and covariance of motions reveal that the Reynolds stresses are dominated by inner-layer structures, the localized influence of the interaction of outer-layer horizontal and inner-layer vertical motions on the Reynolds stress is not insignificant.  相似文献   

Assessment of phosphogypsum impact on the salt-marshes of the Tinto river (SW Spain): role of natural attenuation processes   总被引：2，自引：0，他引：2  

Pérez-López R  Castillo J  Sarmiento AM  Nieto JM 《Marine pollution bulletin》2011,62(12):2787-2796

About 120 Mton of phosphogypsum from the fertiliser industry were stack-piled on the salt-marshes of the Tinto river (Spain). This paper investigates the capacity of salt-marshes to attenuate contamination due to downward leaching from phosphogypsum. Solids and pore-waters were characterized at different depths of the pile to reach the marsh-ground. In superficial zones, metals were highly mobile, and no reduced sulphur was found. However, pollutant concentration decreased in the pore-water in deeper oxygen-restricted zones. Metal removal occurred by precipitation of newly formed sulphides, being this process main responsible for the contamination attenuation. Pyrite-S was the main sulphide component (up to 2528 mg/kg) and occurred as framboids, leading to high degrees of pyritization (up to 97%). The sulphidization reaction is Fe-limited; however, excess of acid-volatile sulphide over other metals cause precipitation of other sulphides, mainly of Cu and As. This decrease in metal mobility significantly minimises the impact of phosphogypsums on the salt-marshes.  相似文献   

Downscaling projections of climate change in Sao Tome and Principe Islands,Africa     

Sin Chan Chou  Andr&#; de Arruda Lyra  Jorge Lu&#;s Gomes  Daniel Andr&#;s Rodriguez  Minella Alves Martins  Nicole Costa Resende  Priscila da Silva Tavares  Claudine Pereira Dereczynski  Isabel Lopes Pilotto  Alessandro Marques Martins  Lu&#;s Felipe Alves de Carvalho  Jos&#; Luiz Lima Onofre  Idal&#;cio Major  Manuel Penhor  Ad&#;rito Santana 《Climate Dynamics》2020,54(9):4021-4042

Sao Tome and Principe is a small insular African country extremely vulnerable to rising sea levels and impacts such as inundation, shore line change, and salt water intrusion into underground aquifers. Projections of climate change have considered coarse model resolutions. The objective of this work is to dynamically downscale the global model projections to 4-km resolution and to assess the climate change in the Sao Tome and Principe islands. The global climate projections are provided by the Canadian Earth System Model under two Representative Concentration Pathways greenhouse gas scenarios, RCP4.5 and RCP8.5. The downscaling is produced by the Eta regional climate model. The baseline period is taken between 1971 and 2000, and the future climate period is taken between 2041 and 2070. The 2-m temperature simulations show good agreement with station data. The model simulates temperature more accurately than precipitation. The precipitation simulations systematically show underestimation and delay of the rainy and the dry seasons by about 1 month, a feature inherited from the global climate model. In the middle of the 21st century, projections show the strongest warming in the elevated parts of the Sao Tome Island, especially in February under RCP8.5. Warmer nights and warmer days become more frequent in the islands when compared with those in the present. While under RCP4.5, precipitation increases in the islands; under RCP8.5, it decreases everywhere in both islands. Heavy precipitation rates should increase, especially in the south-southwestern parts of the Sao Tome islands. Detailed spatial variability of the temperature and precipitation changes in the islands can only be revealed at very high spatial model resolution. Implications for the potential energy production from two major river basins are assessed in this work.  相似文献   

Does the proton-to-electron mass ratio μ = m p /m e vary in the course of cosmological evolution?     

A. Ivanchik  P. Petitjean  E. Rodriguez  D. Varshalovich 《Astrophysics and Space Science》2003,283(4):583-588

The possible cosmological variation of the proton-to-electron mass ratio μ = m _p /m _e was estimated by measuring the H₂ wavelengths in the high-resolution spectrum of the quasar Q 0347-382. Our analysis yielded an estimate for the possible deviation ofμ value in the past, 10 Gyr ago: for the unweighted valueΔ μ / μ = (3.0±2.4)×10^-5; for the weightedvalueΔ μ / μ = (5.02±1.82)×10^-5.Since the significance of the both results does not exceed3σ, further observations are needed to increase the statistical significance. In any case, this result may be considered as the most stringent estimate on an upper limit of a possible variation of μ (95% C.L.):|Δ μ / μ| < 8× 10^-5 .This value serves as an effective tool for selection of models determining a relation between possible cosmological deviations of the fine-structure constant α and the elementary particle masses (m_p, m_e, etc.). This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Hydrological and erosional response to natural rainfall in a semi‐arid area of south‐east Spain     

M. Martinez‐Mena  V. Castillo  J. Albaladejo 《水文研究》2001,15(4):557-571

A better knowledge of soil erosion by water is essential for planning effective soil and water conservation practices in semi‐arid Mediterranean environments. The special climatic and hydrological characteristics of these areas, however, make accurate soil loss predictions difficult, particularly in the absence of minimal data. Two zero‐order experimental microcatchments (328–759 m²), representative of an extensive semi‐arid watershed with a high potential erosion risk in the south‐east of Spain, were selected and monitored for 3 years (1991–93) in order to provide information on the hydrological and erosional response. A pluviogram and hydrograph recorded data at 1‐min intervals during each storm, after which the soil loss was collected and the particle size of the sediment was analysed. Runoff coefficients of about 9% and soil losses of between 84·83 and 298·9 g m^?2 year^?1 were observed in the area. Rapid response times (geometric mean values lower than 2 h) and low runoff thresholds (mean values between 3·5 to 5·9 mm) were the norm in the experimental areas. A rain intensity of over 15 mm h^?1 was considered as ‘erosive rainfall’ in these areas because of the total soil loss and the transport capacity of the overland flow. Differences in pore‐size distribution explained the different hydrological responses observed between areas. The erosional response was more complex and basically seemed to be determined by soil aggregate stability and topographical properties. A greater proportion of finer particles in the eroded material than in the soil matrix indicated selective erosion and the transport of finer material. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

Cassini/VIMS hyperspectral observations of the HUYGENS landing site on Titan     

S. Rodriguez  S. Le Moulic  C. Sotin  H. Clnet  R.N. Clark  B. Buratti  R.H. Brown  T.B. McCord  P.D. Nicholson  K.H. Baines  the VIMS Science Team 《Planetary and Space Science》2006,54(15):1510-1523

Titan is one of the primary scientific objectives of the NASA–ESA–ASI Cassini–Huygens mission. Scattering by haze particles in Titan's atmosphere and numerous methane absorptions dramatically veil Titan's surface in the visible range, though it can be studied more easily in some narrow infrared windows. The Visual and Infrared Mapping Spectrometer (VIMS) instrument onboard the Cassini spacecraft successfully imaged its surface in the atmospheric windows, taking hyperspectral images in the range 0.4–5.2 μm. On 26 October (TA flyby) and 13 December 2004 (TB flyby), the Cassini–Huygens mission flew over Titan at an altitude lower than 1200 km at closest approach. We report here on the analysis of VIMS images of the Huygens landing site acquired at TA and TB, with a spatial resolution ranging from 16 to14.4 km/pixel. The pure atmospheric backscattering component is corrected by using both an empirical method and a first-order theoretical model. Both approaches provide consistent results. After the removal of scattering, ratio images reveal subtle surface heterogeneities. A particularly contrasted structure appears in ratio images involving the 1.59 and 2.03 μm images north of the Huygens landing site. Although pure water ice cannot be the only component exposed at Titan's surface, this area is consistent with a local enrichment in exposed water ice and seems to be consistent with DISR/Huygens images and spectra interpretations. The images show also a morphological structure that can be interpreted as a 150 km diameter impact crater with a central peak.  相似文献   

PILOT: a balloon-borne experiment to measure the polarized FIR emission of dust grains in the interstellar medium     

J-Ph. Bernard  P. Ade  Y. André  J. Aumont  L. Bautista  N. Bray  P. de Bernardis  O. Boulade  F. Bousquet  M. Bouzit  V. Buttice  A. Caillat  M. Charra  M. Chaigneau  B. Crane  J.-P. Crussaire  F. Douchin  E. Doumayrou  J.-P. Dubois  C. Engel  P. Etcheto  P. Gélot  M. Griffin  G. Foenard  S. Grabarnik  P. Hargrave  A. Hughes  R. Laureijs  Y. Lepennec  B. Leriche  Y. Longval  S. Maestre  B. Maffei  J. Martignac  C. Marty  W. Marty  S. Masi  F. Mirc  R. Misawa  J. Montel  L. Montier  B. Mot  J. Narbonne  J-M. Nicot  F. Pajot  G. Parot  E. Pérot  J. Pimentao  G. Pisano  N. Ponthieu  I. Ristorcelli  L. Rodriguez  G. Roudil  M. Salatino  G. Savini  O. Simonella  M. Saccoccio  P. Tapie  J. Tauber  J.-P. Torre  C. Tucker 《Experimental Astronomy》2016,42(2):199-227

Future cosmology space missions will concentrate on measuring the polarization of the Cosmic Microwave Background, which potentially carries invaluable information about the earliest phases of the evolution of our universe. Such ambitious projects will ultimately be limited by the sensitivity of the instrument and by the accuracy at which polarized foreground emission from our own Galaxy can be subtracted out. We present the PILOT balloon project, which aims at characterizing one of these foreground sources, the polarized continuum emission by dust in the diffuse interstellar medium. The PILOT experiment also constitutes a test-bed for using multiplexed bolometer arrays for polarization measurements. This paper presents the instrument and its expected performances. Performance measured during ground calibrations of the instrument and in flight will be described in a forthcoming paper.  相似文献   

Mantle derived crystal-poor rhyolitic ignimbrites: Eruptive mechanism from geochemical and geochronological data of the Piedra Parada caldera,Southern Argentina     

Eugenio Aragon  Antonio Castro  Juan Diaz-Alvarado  Lucio Pinotti  Fernando D'eramo  Manuel Demartis  Jorge Coniglio  Irene Hernando  Carmen Rodriguez 《地学前缘(英文版)》2018,9(5):1529-1553

Trace elements, isotopic modeling and U-Th-Pb SHRIMP zircon age constraints are used to reconstruct the eruption history and magmatic processes of the Piedra Parada Caldera. In the early Eocene, the crystal-poor Barda Colorada ignimbrite(BCI), having 15% micro-porphyritic crystals with respect to magmatic components, erupted a volume estimated in more than 300 km~3. The Piedra Parada caldera is located in the Patagonian Andes foreland, at the southern end of the calderas field of the Pilcaniyeu Volcanic Belt(PVB). This belt is related to an extensional tectonic setting as a result of the collision of the Farallon-Aluk ridge with South America, which enabled the development of a transform ocean/continental plate margin followed by the detachment of the Aluk plate and the opening of a slab window. The BCI extra-caldera Plateau is a 100 m thick deposit, having a lower unit with high silica(Si O_2 76 wt.%),potassium poor rhyolitic composition(trondhjemitic like magma), and an upper unit with normal to high potassium rhyolitic composition(granitic like magma). A trace elements modeling of the BCI units shows that the BCI lower and upper units did not evolve from fractionation or immiscibility in the shallow magma reservoir. The BCI also have a primitive isotopic signature(initial87 Sr/86 Sr =0.7031-0.7049 and ε_(Nd)= +3.4 to +3.65). Thus, tectonic, compositional and isotopic constraints suggest the fast ascent of high silica magmas to a shallow reservoir, and point to an upper mantle origin for these rhyolitic magmas in a transitional(Orogenic-Anorogenic) tectono-magmatic setting. U-Th-Pb SHRIMP zircon crystallization ages of the Syn-caldera stage BCI units(56 -51.5 Ma) show a protracted life of 5 Ma for this caldera reservoir. The age of 52.9 ± 0.3 Ma is considered the best fit for the possible maximum age for the caldera collapse. The Late-caldera magmatism has trachyandesitic and rhyolitic compositions.The trace element modeling suggests that these rhyolites evolve from the trachyandesites and do not evolve from the BCI residual magma. The trachyandesites have U-Th-Pb SHRIMP zircon crystallization ages of 52 ± 1 Ma, suggesting that the caldera eruption was triggered by the arrival of the trachyandesitic magma.  相似文献   

Geospatial web services pave new ways for server-based on-demand access and processing of Big Earth Data     

Julia Wagemann  Oliver Clements  Ramiro Marco Figuera  Angelo Pio Rossi  Simone Mantovani 《International Journal of Digital Earth》2018,11(1):7-25

ABSTRACT

Big Earth Data has experienced a considerable increase in volume in recent years due to improved sensing technologies and improvement of numerical-weather prediction models. The traditional geospatial data analysis workflow hinders the use of large volumes of geospatial data due to limited disc space and computing capacity. Geospatial web service technologies bring new opportunities to access large volumes of Big Earth Data via the Internet and to process them at server-side. Four practical examples are presented from the marine, climate, planetary and earth observation science communities to show how the standard interface Web Coverage Service and its processing extension can be integrated into the traditional geospatial data workflow. Web service technologies offer a time- and cost-effective way to access multi-dimensional data in a user-tailored format and allow for rapid application development or time-series extraction. Data transport is minimised and enhanced processing capabilities are offered. More research is required to investigate web service implementations in an operational mode and large data centres have to become more progressive towards the adoption of geo-data standard interfaces. At the same time, data users have to become aware of the advantages of web services and be trained how to benefit from them most.  相似文献   

Progress and opportunities for monitoring greenhouse gases fluxes in Mexican ecosystems: the MexFlux network     

R. Vargas  E.A. Yépez  J.L. Andrade  G. Ángeles  T. Arredondo  A.E. Castellanos  J. Delgado-Balbuena  J. Garatuza-Payán  E. González Del Castillo  W. Oechel  J.C. Rodríguez  A. Sánchez-Azofeifa  E. Velasco  E.R. Vivoni  C. Watts 《Atmósfera》2013,26(3):325-336

Understanding ecosystem processes from a functional point of view is essential to study relationships among climate variability, biogeochemical cycles, and surface-atmosphere interactions. Increasingly during the last decades, the eddy covariance (EC) method has been applied in terrestrial, marine and urban ecosystems to quantify fluxes of greenhouse gases (e.g., CO₂, H₂O) and energy (e.g., sensible and latent heat). Networks of EC systems have been established in different regions and have provided scientific information that has been used for designing environmental and adaptation policies. In this context, this article outlines the conceptual and technical framework for the establishment of an EC regional network (i.e., MexFlux) to measure the surface-atmosphere exchange of heat and greenhouse gases in Mexico. The goal of the network is to improve our understanding of how climate variability and environmental change influence the dynamics of Mexican ecosystems. First, we discuss the relevance of CO₂ and water vapor exchange between terrestrial ecosystems and the atmosphere. Second, we briefly describe the EC basis and present examples of measurements in terrestrial and urban ecosystems of Mexico. Finally, we describe the conceptual and operational goals at short-, medium-, and long-term scales for continuity of the MexFlux network.  相似文献