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Li Z.-L.,CAS Beijing Institute of Geographic Sciences and Nature Resources Research | Li Z.-L.,French National Center for Scientific Research | Tang B.-H.,CAS Beijing Institute of Geographic Sciences and Nature Resources Research | Wu H.,CAS Beijing Institute of Geographic Sciences and Nature Resources Research | And 6 more authors.
Remote Sensing of Environment | Year: 2013

Land surface temperature (LST) is one of the key parameters in the physics of land surface processes from local through global scales. The importance of LST is being increasingly recognized and there is a strong interest in developing methodologies to measure LST from space. However, retrieving LST is still a challenging task since the LST retrieval problem is ill-posed. This paper reviews the current status of selected remote sensing algorithms for estimating LST from thermal infrared (TIR) data. A brief theoretical background of the subject is presented along with a survey of the algorithms employed for obtaining LST from space-based TIR measurements. The discussion focuses on TIR data acquired from polar-orbiting satellites because of their widespread use, global applicability and higher spatial resolution compared to geostationary satellites. The theoretical framework and methodologies used to derive the LST from the data are reviewed followed by the methodologies for validating satellite-derived LST. Directions for future research to improve the accuracy of satellite-derived LST are then suggested. © 2012 Elsevier Inc.

Russo A.,University of Lisbon | Trigo R.M.,University of Lisbon | Martins H.,University of Aveiro | Mendes M.T.,Instituto Portugues do Mar e da Atmosfera
Atmospheric Environment | Year: 2014

High levels of atmospheric pollutants are frequently measured in Portugal, a country which has been affected by several pollution episodes, exceeding PM10, O3 and NO2 legal limits repeatedly during the last decade. The occurrence of these episodes is often related to either local-scale conditions or regional-scale transport. In order to better understand the atmospheric factors responsible for poor air quality, the relationships between air pollution and meteorological variables or atmospheric synoptic patterns represent an important research area. Here an objective classification scheme of the atmospheric circulation affecting Portugal, between 2002 and 2010, is presented, where daily circulation is characterized through the use of a set of indices associated with the direction and vorticity of the geostrophic flow in the lower atmosphere. The synoptic characteristics and the frequency of ten basic circulation weather types (CWTs) are discussed and a framework that permits the identification of the main characteristics associated to the occurrence of pollution episodes is mapped based on the identified patterns. The relationship between CWTs and poor air quality allowed distinguishing between which types are most frequently associated to pollution episodes. It is shown that the anticyclonic and north types, although being the most frequent classes during the majority of the year, do not prevail during pollution episodes that are dominated by easterly types. In general, higher concentration of all three pollutants and the two extreme events analysed occur associated predominantly with synoptic circulation characterized by an eastern component and advection of dry air masses. Moreover, results on the link between CWTs and air quality for Lisbon and Porto urban areas suggest that air quality regimes are generally similar for the northern and southern regions considered with the exception of spring and autumn PM10. Results obtained highlight the existence of strong links between the interannual variability of daily air quality and interannual variability of CWTs. © 2014 Elsevier Ltd.

Soares P.M.M.,University of Lisbon | Cardoso R.M.,University of Lisbon | Ferreira J.J.,Instituto Portugues do Mar e da Atmosfera | Miranda P.M.A.,University of Lisbon
Climate Dynamics | Year: 2015

In Portugal, the precipitation regimes present one of the highest volumes of extreme precipitation occurrence in Europe, and one of the largest mean precipitation spatial gradient (annual observed values above 2,500 mm in the NW and under 400 mm in the SE). Moreover, southern Europe is one of the most vulnerable regions in the world to climate change. In the ENSEMBLES framework many climate change assessment studies were performed, but none focused on Portuguese precipitation. An extensive evaluation and ranking of the RCMs results addressing the representation of mean precipitation and frequency distributions was performed through the computation of statistical errors and frequency distribution scores. With these results, an ensemble was constructed; giving the same weight to mean precipitation and distribution model skills. This ensemble reveals a good ability to describe the precipitation regime in Portugal, and enables the evaluation of the eventual impact of climate change on Portuguese precipitation according to the A1B scenario. The mean seasonal precipitation is expected to decrease substantially in all seasons, excluding winter. This reduction is statistically significant; it spans from less than 20 % in the north to 40 % in the south in the intermediate seasons, and is above 50 % in the largest portion of mainland in summer. At a basin level the precipitation diminishes in all months for all the basins with exception of December. Total precipitation PDFs reveal an important decrease of the contribution from low to moderate/high precipitation bins, and a striking rise for days with extreme rainfall, up to 30 %. © 2014, Springer-Verlag Berlin Heidelberg.

Wendling C.C.,Alfred Wegener Institute for Polar and Marine Research | Wendling C.C.,Leibniz Institute of Marine Science | Batista F.M.,Instituto Portugues Do Mar e da Atmosfera | Wegner K.M.,Alfred Wegener Institute for Polar and Marine Research
PLoS ONE | Year: 2014

Bacteria of the genus Vibrio occur at a continuum from free-living to symbiotic life forms, including opportunists and pathogens, that can contribute to severe diseases, for instance summer mortality events of Pacific oysters Crassostrea gigas. While most studies focused on Vibrio isolated from moribund oysters during mortality outbreaks, investigations of the Vibrio community in healthy oysters are rare. Therefore, we characterized the persistence, diversity, seasonal dynamics, and pathogenicity of the Vibrio community isolated from healthy Pacific oysters. In a reciprocal transplant experiment we repeatedly sampled hemolymph from adult Pacific oysters to differentiate population from site-specific effects during six months of in situ incubation in the field. We characterized virulence phenotypes and genomic diversity based on multilocus sequence typing in a total of 70 Vibrio strains. Based on controlled infection experiments we could show that strains with the ability to colonize healthy adult oysters can also have the potential to induce high mortality rates on larvae. Diversity and abundance of Vibrio varied significantly over time with highest values during and after spawning season. Vibrio communities from transplanted and stationary oysters converged over time, indicating that communities were not population specific, but rather assemble from the surrounding environment forming communities, some of which can persist over longer periods. © 2014 Wendling et al.

Miranda J.M.,Instituto Portugues do Mar e da Atmosfera | Luis J.F.,University of Algarve | Lourenco N.,Instituto Portugues do Mar e da Atmosfera | Goslin J.,University of Western Brittany
Marine Geology | Year: 2014

Terceira Rift and the northern and southern branches of the Mid-Atlantic Ridge (MAR) form a triple junction close to 39°N known as the Azores Triple Junction. New swath bathymetric data are used to investigate the surface expression of faulting close to the triple junction, by the systematic mapping of MAR-generated abyssal hills. It is shown that close to the geometrical intersection between the three spreading axes there exists no single transform fault connecting Terceira Rift to the MAR but a distributed tectonic deformation area characterized by mesoscale brittle deformation close to the surface, covering approximately 90. km by 100. km, and almost no volcanism, which links Terceira Rift to the MAR, accommodating the relative displacement of the three plates close to the geometrically triple point. Magnetic chrons are used to compute the spatial variation of spreading velocity at the Mid-Atlantic Ridge and confirm the above interpretation: they show a progressive increase of spreading velocity along a single MAR segment, between pure "Nubian" at 38°30'N and pure "Eurasian" at 39°25'N, without the development of a transform fault that would integrate the Eurasia-Nubia plate boundary. The comparison of similar triple junctions where a slower axis joins two faster ridges, shows that the slower arm does not reach the "triple point" and that there is always a finite triple junction area, highly tectonized, in which size is dependent on the angle between the two faster arms and, consequently, on the relative spreading velocity of the slower arm. © 2014 Elsevier B.V.

Neves M.C.,University of Algarve | Miranda J.M.,Instituto Portugues do Mar e da Atmosfera | Luis J.F.,University of Algarve
Tectonophysics | Year: 2013

Linear volcanic ridges (LVRs) are widespread along the Azores plateau and are often used as a tectonic marker of the surface stress field. Nevertheless, the mechanisms that drive the emplacement and development of these structures are not well established and they have been attributed to the plateau diffuse deformation, off-rift extension or the result of the interaction between a hotspot and the brittle lithosphere. This study hypothesizes that linear volcanic ridges are the result of magma emplacement into pre-existing damaged lithosphere, using a 3D finite-element representation of the brittle lithosphere and underlying ductile mantle, and assuming that the deformation is driven by plate boundary forces applied at the edges, as describe by global plate kinematic models. The brittle layer is described by an elastoplastic rheology with progressive damage, where fractures are assumed to be analogous to localized shear bands. The ductile mantle underneath is modeled as a viscoelastic layer that exerts a shear drag at the base of the brittle layer. The modeling shows that lithospheric processes alone can justify the spatial distribution of linear volcanic ridges, and even the development of the Faial Ridge. The factors controlling the fracturing pattern are the plate geometry and velocity boundary conditions, the shearing introduced at the East Azores Fracture Zone/Gloria fault limit and the interaction between the viscous mantle and the spatially varying brittle plate thickness. Along the Terceira Rift the predicted fractures match the orientation of the LVRs in the second (~N135°-N140°) and third (N150° to N-S) sectors and provide an explanation for the arcuate shape of the rift itself. The brittle plate thickness variations are crucial for the development of the more recent LVRs, which are predicted to occur along the Faial Ridge. In the best fit model the top mantle viscosity is 1×1022Pas at 5-15km depth, and the present-day fracture network takes ~3Ma to develop. © 2013 Elsevier B.V.

Vale P.,Instituto Portugues Do Mar e da Atmosfera
Photochemistry and Photobiology | Year: 2015

Mycosporine-like amino acids (MAAs) were analyzed in a Portuguese Gymnodinium catenatum strain when transferred to high salinity and high light conditions. Total MAA concentrations increased progressively between 30 and 36 psu, attaining at 36 psu 2.9-fold the 30 psu treatment. When abruptly transferred to solar light in an outdoor shadowed location, MAA concentration increased steadily along the day for most compounds. After 8 h, mycosporine-glycine, palythene and M-319 attained or surpassed 25-fold their initial concentration, while M-370 only attained 4-fold concentration. When transferred from halogen to fluorescent light, polar MAAs such as shinorine and porphyra-334, increased until day two and then declined, while M-370 increase slowly, becoming the dominant compound from the profile after 1 week. These experiments put into evidence the relation of palythene with M-319, which was further identified as its acid degradation product, palythine. Acid degradation of M-370 originated M-324, while M-311 seems to be the precursor of M-370. Under high salinity and high light conditions chain formation was altered toward shorter chains or solitary cells. This alteration can represent a morphological stress sign, which in the natural environment could affect average population speed during daily vertical migrations. Mycosporine-like amino acids concentration increased with salinity, in particular high polar MAAs. Abrupt changes in light intensity increased rapidly the low polar palythene. In both cases, mycosporine-glycine was one of the MAAs with the greatest increase, while biosynthesis of M370, a major MAA in G. catenatum, progressed slowly. Experiments put into evidence the biosynthetic relations between MAAs and its degradation pathways. MAAs might play a multifunctional role to cope with salinity (shinorine, porphyra-334) and photooxidative (mycosporine-glycine, palythene, M-370) stresses. High salinity and high light conditions also altered chain formation toward shorter chains or solitary cells. © 2015 The American Society of Photobiology.

Martins J.H.,University of Porto | Camanho A.S.,University of Porto | Gaspar M.B.,Instituto Portugues do Mar e da Atmosfera
Ocean and Coastal Management | Year: 2012

This paper provides a review of the literature on applications of the Driving forces, Pressure, State, Impact, Response (DPSIR) framework to fisheries. The interpretation given to each DPSIR category differs in existing studies, and as a result the indicators used to support fisheries management also vary considerably. This impairs comparisons concerning the state of different fishery systems, and does not provide a common base of knowledge concerning potential management measures that can be adopted in a given context. This paper clarifies the interpretation of each DPSIR category and proposes a set of indicators that can be applied in fishery contexts. The set of indicators proposed is also classified according to sustainability dimensions. It is argued that organising the indicators according to the DPSIR framework and sustainability dimensions (ecologic, economic, social and governance) is a positive contribution to serve as a guideline for future applications to adopt standardized indicators and improve fisheries management. © 2012 Elsevier Ltd.

Vale P.,Instituto Portugues do Mar e da Atmosfera
Biophysics (Russian Federation) | Year: 2014

Accumulation of paralytic shellfish poisoning toxins (PSTs) in bivalves attributed to Gymnodinium catenatum blooms at the NW Portuguese coast was previously associated with periods of low solar activity (measured by the radio flux R), or low geomagnetic Aa index. It was also observed that reduction of R preceded the occurrence of toxin accumulation, while the Aa index increase could be related to its absence during periods of low activity. For modeling toxin accumulation, the monthly decrease in R was studied along the decade 2003-2012. A match that helped explaining the highly toxic years of 2007 and 2008 was obtained by plotting the formula: ΔR = (Rn - 1 - Rn)/(Rn - 65)2, where 65 represented the lowest radio activity known to date. The complex denominator was required to take into account the sunspot cycle. A 1-2-month lag was observed between maximal relative decline and maximal PST accumulation. PSTs in bivalves from the Portuguese south coast were related with natural electromagnetic cycles for the first time, and were not statistically associated with low R. A statistically significant association with low Aa index also was not achieved, due to the low number of occurrences, although the 25-75 percentile was restricted to low Aa indexes in a similar way to that found for the NW coast. PST accumulation outside solar minima could be triggered by a steep decline in the Aa index (ΔA), but no lag was observed in this case. While the ΔR amplitude helped explaining the highly toxic years of 2007 and 2008 at the NW coast, the amplitude of ΔA was not related to the severity of the accumulation. Another kind of local electromagnetic signaling was investigated resorting to the occurrence of seismologic phenomena, because these events can trigger electric activities. No statistical association was found between seism number or magnitude and PSTs at the south coast, located near the boundary between the African and Eurasian plates, and marked by moderate seismicity. © 2014 Pleiades Publishing, Inc.

Vale P.,Instituto Portugues Do Mar e da Atmosfera
Journal of Photochemistry and Photobiology B: Biology | Year: 2015

A Portuguese Gymnodinium catenatum Graham strain was studied for its ultraviolet (UV) photoprotective pigments. This strain presented high absorption in the UVA region, in particular in the near UVA region around 370 nm, followed by the far-UVA region around 340 nm. Absorption in the near-UVA increased when grown under fluorescent when compared to halogen light. This was even more relevant when grown under nutrient-limiting conditions, which even surpassed absorption in the blue region, closely resembling absorption in natural plankton assemblages reported in the literature. HPLC analysis for mycosporine-like amino acids (MAAs), revealed several UV photoprotective pigments common in other marine microalgae from the northwest Atlantic. Amongst the compounds absorbing in the far-UVA region, three were identified by spectra and retention time characteristics: shinorine, porphyra-334, and mycosporine-glycine. In the near-UVA region, the unknown M-370 was usually the most abundant, followed by palythene. The proportional and absolute cellular concentrations of MAAs absorbing in the near-UVA region increased with fluorescent light when compared to halogen light. Additional experiments with light filtration suggest the set of MAAs absorbing in the near-UVA region seem to be regulated separately from the other set of MAAs absorbing in the far-UVA region, and those from the near-UVA region might be stimulated not only by UV but by blue light also. Nutrient availability affected profile: a shift towards MAAs with low nitrogen:carbon ratio (e.g.: mycosporine-glycine) was observed. As G. catenatum requires extensive UV-photoprotection over the entire UVA range, nitrogen availability might strongly restrict blooming, as MAAs are nitrogen-based. This UV sensitivity might help explaining its pronounced autumnal seasonality, tied to a reduced solar exposure. © 2014 Elsevier B.V. All rights reserved.

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