• Other research productsclose
• 2012-2021close
• Fundação para a Ciência e a Tecnologia, I.P. close
• EU close
• DE close
• GR close
• SDSN - Greece close

In this study, Algal Pigment Index 2 (API2) is investigated in Sagres, an area located in the Atlantic off the southwestern Iberian Peninsula. Standard results provided by the MEdium Resolution Image Spectrometer (MERIS) ocean colour sensor were compared with alternative data products, determined through a regional inversion scheme, using both MERIS and in situ remote sensing reflectances (Rrs) as input data. The reference quantity for performance assessment is in situ total chlorophyll a (TChl a) concentration estimated through a phytoplankton absorption coefficient (i.e. equivalent to API2). Additional comparison of data products has also been addressed for TChl a concentration determined by high-performance liquid chromatography. The MERIS matchup analysis revealed a systematic underestimation of TChl a, which was confirmed with an independent comparison of product map analysis. The study demonstrates the importance of regional algorithms for the study area that could complement upcoming standard results of the current Sentinel-3/OLCI space mission.

A procedure is presented that allows identifying large burned scars and the monitoring of vegetation recovery in the years following major fire episodes. The procedure relies on 10-day fields of Maximum Value Composites of Normalized Difference Vegetation Index (MVC-NDVI), with a 1 km×1 km spatial resolution obtained from the VEGETATION instrument. The identification of fire scars during the extremely severe 2003 fire season is performed based on cluster analysis of NDVI anomalies that persist during the vegetative cycle of the year following the fire event. Two regions containing very large burned scars were selected, located in Central and Southwestern Portugal, respectively, and time series of MVC-NDVI analysed before the fire events took place and throughout the post-fire period. It is shown that post-fire vegetation dynamics in the two selected regions may be characterised based on maps of recovery rates as estimated by fitting a monoparametric model of vegetation recovery to MVC-NDVI data over each burned scar. Results indicated that the recovery process in the region located in Central Portugal is mostly related to fire damage rather than to vegetation density before 2003, whereas the latter seems to have a more prominent role than vegetation conditions after the fire episode, e.g. in the case of the region in Southwestern Portugal. These differences are consistent with the respective predominant types of vegetation. The burned area located in Central Portugal is dominated by Pinus Pinaster whose natural regeneration crucially depends on the destruction of seeds present on the soil surface during the fire, whereas the burned scar in Southwestern Portugal was populated by Eucalyptus that may quickly re-sprout from buds after fire. Besides its simplicity, the monoparametric model of vegetation recovery has the advantage of being easily adapted to other low-resolution satellite data, as well as to other types of vegetation indices.

The article discusses a new model of participatory governance in Lisbon by providing theoretical reflection and empirical knowledge fromthe action of two urban agencies: the “Centre of Urban Information of Lisbon” (CIUL) and the “Municipal Offices in Support of Neighbourhoods in Need of Priority Intervention” (Gabips). While the CIUL has provided civil society with information about and space for debate on urban policies, the Gabips have supported urban regeneration in priority areas with the participation of local agents. The CIUL and the Gabips are framed within the political agenda of the Municipality of Lisbon to foster a new relationship between the local government and civil society, which has resulted in new channels and opportunities for citizen participation. Both agencies, however, also point to different stances on citizen participation that are worth analysing. While the CIUL can be understood in light of the literature on the constitution and global spreading of the Urban Centers, the Gabips represent genuine evidence of locally based participatory governance. Insights from the text allow for reflection on the design of a new model of participatory governancebased on the creation of political and administrative conditions to allow the CIUL and the Gabips to connect and maximise their functions. Key-words: Urban Center; participatory governance; CIUL; Gabip; Lisbon

The first record of Antipathella subpinnata ( Ellis and Solander, 1786) for the Azores archipelago is presented based on bottom longline by-catch analysis and ROV seafloor surveys, extending the species western-most boundary of distribution in the NE Atlantic. The species was determined using classic taxonomy and molecular analysis targeting nuclear DNA. Although maximum spine height on Azorean colonies branchlets is slightly smaller than that reported from Mediterranean colonies (0.12 vs 0.16 mm), the analysis of partial 18S rDNA, complete ITS1, 5.8S, ITS2 and partial 28S rDNA suggests that the Azorean and Mediterranean specimens belong to the same species. Video surveys of an A. subpinnata garden detected near Pico Island are used to provide the first in situ description of the species habitat in the region and the first detailed description of a black coral garden in the NE Atlantic. With A. subpinnata being the only coral found between 150 and 196 m depths, this is the deepest black coral garden recorded in the NE Atlantic and the first one to be monospecific. The species exhibited a maximum density of 2.64 colonies/m**2 and occurred across a surface area estimated at 67,333 m**2, yielding a local population estimate of 50,500 colonies.

Global land ecosystems are particularly important in the regulation of the atmospheric carbon dioxide (CO2) balance, removing every year about one quarter of anthropogenic CO2 emissions. Although the oceans constitute a CO2 sink of approximately the same magnitude, most of the inter-annual variability observed in atmospheric CO2 growth rates is due to variability in the land-sink. While the patterns governing variability of vegetation CO2 exchange at the sub-seasonal to seasonal time scales are relatively well understood, large uncertainties remain about the dynamics and drivers of CO2 uptake by ecosystems at continental to global scale, and on time-scales from annual to decadal. This is partly due to the complexity of the interactions between the different processes that regulate CO2 exchange ar the ecosystem level and their physical drivers, as well as to the presence of natural variability in the climate system. In this context, understanding the link between the main modes of coupled atmospheric-ocean circulation and CO2 uptake by ecosystems, as well as the way ecosystems respond to extreme events, is particularly relevant. This Thesis analyses in detail the influence of the El-Niño/Southern Oscillation on the global land-sink and explores the relationship between the European sink and the main large-scale atmospheric circulation patterns in the North-Atlantic sector, in particular the North-Atlantic Oscillation and the East-Atlantic pattern. Furthermore, this work performs a comparative study of the two most outstanding extreme events affecting Europe in the past century - the 2003 heatwave over western Europe, and the 2010 event over western Russia. The results highlight the potential of analyzing ecological variability in the framework of climate variability patterns, which may help to better interpret past and present trends in the land-sink and pave the way to better constrain future projections in Earth-System models. Tese de doutoramento, Ciências Geofísicas e da Geoinformação (Deteção Remota), Universidade de Lisboa, Faculdade de Ciências, 2015 Fundação para a Ciência e a Tecnologia (FCT), PTDC/AAGGLO/4155/2012

The present work aims to study the combined effect of drought and large wildfires in the Iberian Peninsula relying on remotely sensed data of vegetation dynamics and leaf moisture content, in particular monthly NDVI, NDWI and NDDI time series from 1999–2009, derived from VEGETATION dataset. The impact of the exceptional 2004/2005 drought on vegetation was assessed for vegetation recovering from the extraordinary fire season of 2003 and on the conditions that contributed to the onsetting of the fire season of 2005. Drought severity was estimated by the cumulative negative effect on photosynthetic activity (NDVI) and vegetation dryness (NDDI), with about 2/3 of Iberian Peninsula presenting vegetative stress and low water availability conditions, in spring and early summer of 2005. Furthermore, NDDI has shown to be very useful to assess drought, since it combines information on vegetation and water conditions. Moreover, we show that besides looking at the inter-annual variability of NDVI and NDDI, it is useful to evaluate intra-annual changes (δNDVI and δNDDI), as indicators of change in vegetation greenness, allowing a detailed picture of the ability of the different land-cover types to resist to short-term dry conditions. In order to assess drought impact on post-fire regeneration, recovery times were evaluated by a mono-parametric model based on NDVI data and values corresponding to drought months were set to no value. Drought has shown to delay recovery times for several months in all the selected scars from 2003. The analysis of vegetation dynamics and fire selectivity in 2005 suggests that fires tended to occur in pixels presenting lower vegetative and water stress conditions during spring and early summer months. Additionally, pre-fire vegetation dynamics, in particular vegetation density and water availability during spring and early summer, has shown to influence significantly the levels of fire damage. These results stress the role of fuel availability in fire occurrence and impact on the Iberian Peninsula.

This work aims at characterising the seamount physiography and biology in the OSPAR Convention limits (north-east Atlantic Ocean) and Mediterranean Sea. We first inferred potential abundance, location and morphological characteristics of seamounts, and secondly, summarized the existing biological, geological and oceanographic in situ research, identifying examples of well-studied seamounts. Our study showed that the seamount population in the OSPAR area (north-east Atlantic) and in the Mediterranean Sea is large with around 557 and 101 seamount-like features, respectively. Similarly, seamounts occupy large areas of about 616 000 km2 in the OSPAR region and of about 89 500 km2 in the Mediterranean Sea. The presence of seamounts in the north-east Atlantic has been known since the late 19th century, but overall knowledge regarding seamount ecology and geology is still relatively poor. Only 37 seamounts in the OSPAR area (3.5% of all seamounts in the region), 22 in the Mediterranean Sea (9.2% of all seamounts in the region) and 25 in the north-east Atlantic south of the OSPAR area have in situ information. Seamounts mapped in both areas are in general very heterogeneous, showing diverse geophysical characteristics. These differences will likely affect the biological diversity and production of resident and associated organisms.

Apesar de não existir uma definição unanimemente aceite para o conceito de bloqueio atmosférico, este pode ser descrito como uma supressão do fluxo zonal devido à presença de um sistema de alta pressão. Esta circulação anticiclónica, normalmente localizada nas latitudes onde se observa a corrente de jato polar, apresenta uma dimensão espacial de larga-escala, é geralmente quase-estacionária, e tem um tempo de vida útil entre vários dias a várias semanas. Os sectores orientais dos oceanos Atlântico e Pacífico são geralmente as regiões de ocorrência preferencial de bloqueios no Hemisfério Norte. A ocorrência de bloqueios atmosféricos está diretamente associada a condições prolongadas de tempo seco e estável nas regiões diretamente localizadas sob o sistema de altas pressões. O seu posicionamento geralmente origina uma divisão em dois ramos da corrente de jato. Esta perturbação do habitual padrão zonal resulta em alterações significativas das condições meteorológicas a outras latitudes (tanto meridional como setentrional) distintas da zona diretamente afetada pela posição central do bloqueio. Torna-se necessária assim uma compreensão mais detalhada da climatologia associada aos bloqueios atmosféricos centrados no setor Euro-Atlântico, com especial ênfase aos impactos específicos associados às diferentes localizações que os seus centros de ação possam ter. Apesar de serem um fenómeno que ocorre à escala sinóptica, os bloqueios podem implicar impactos climáticos muito distintos à escala regional, ou mesmo local. Desta forma, um dos principais objetivos desta tese centra-se na elaboração de uma climatologia completa da sua ocorrência, e na respetiva caracterização dos impactos climáticos regionais resultantes da ocorrência de bloqueios em diferentes sectores longitudinais: Atlântico (ATL; 30W-0W), Europeu (EUR; 0E-30E) e Russo (RUS; 30E-60E). Tendo-se verificado na literatura uma certa confusão entre bloqueio de alta latitude e outros sistemas comuns de alta pressão que afetam a Europa, nomeadamente as cristas sub-tropicais, foi considerado prioritário obter um novo catálogo de cristas de alta pressão para o setor Euro-Atlântico. Desta forma, um segundo objetivo central da tese foi o do desenvolvimento de um novo algoritmo automático de deteção de cristas sub-tropicais, que permita assim realizar uma clara distinção fenomenológica e dos impactos destes dois padrões atmosféricos (bloqueios versus cristas). Assim, a compreensão das condições sinópticas e dos mecanismos físicos envolvidos em cada um destes padrões é também tema central desta tese. No caso da precipitação, esta análise de mecanismos incluiu o papel da atividade ciclónica (storm-tracks e cut-off lows), do transporte de humidade e da instabilidade atmosférica em larga escala. Para avaliar os impactos na temperatura analisou-se a contribuição da advecção horizontal, da subsidência e das alterações nos vários balanços radiativos. A desagregação bloqueios-cristas permite distinguir fenomenologias por vezes confundidas na literatura, nomeadamente aquando da análise de episódios de calor extremo no sul da Europa. Verifica-se dos resultados obtidos que, devido a uma clara distinção no posicionamento latitudinal dos centros de ação entre bloqueios e cristas, as respostas na temperatura associadas a cada padrão são também bem distintas, sendo estas diferenças particularmente notáveis no inverno. De uma forma geral, nesta estação, os bloqueios (essencialmente os centrados nos sectores ATL e EUR) resultam em valores das temperaturas do ar bastante abaixo da média, provocadas pela advecção de ar frio de latitudes mais elevadas ao longo do flanco este dos anticiclones. Em oposição, as cristas originam anomalias positivas na temperatura na maior parte do continente europeu, essencialmente como resultado do transporte de massas de ar de origem Atlântica, e de uma redução do arrefecimento radiativo, associado ao aumento da nebulosidade. Durante o verão, ambos os padrões atmosféricos estão associados a temperaturas acima da média em vastas áreas da Europa central e do norte. Em contrapartida, nas regiões mais a sul, e em particular na área da bacia do Mediterrâneo, as cristas controlam a ocorrência de dias extremamente quentes (usualmente identificados como ondas de calor). No verão é também de salientar o papel dominante do aquecimento radiativo solar (sob condições de céu limpo) como principal impulsionador destas anomalias positivas de temperatura em dias de ocorrência de bloqueio/crista, particularmente para os sistemas localizados sobre áreas continentais. Relativamente aos impactos nos regimes de precipitação, existe um claro dipolo norte-sul ao analisar as anomalias associadas a dias de bloqueio/crista. A ocorrência de bloqueios leva a uma redução da precipitação na metade norte do continente Europeu (em algumas áreas superior a 50%) devido ao bloqueio dos sistemas depressionários de médias-latitudes (e do correspondente transporte de humidade) provenientes do Atlântico. No entanto, esta configuração sinóptica leva a um aumento da precipitação (relativamente à média) nas zonas mais a sul, fundamentalmente relacionado com o desvio do storm-track nesta direção, e a um consequente aumento da instabilidade atmosférica e da convecção. Este padrão resulta numa clara mudança nas distribuições de regimes de precipitação nos países do sul da Europa, e demonstra também a ligação entre bloqueios atmosféricos e os regimes de precipitação torrencial na área do Mediterrâneo. Em padrões de fluxo zonal intenso as anomalias da precipitação são no geral opostas às encontradas durante bloqueios, originando um deficit de precipitação no sul da Europa. No contexto dos vários regimes possíveis de fluxo zonal forte, as cristas sub-tropicais estão associadas a condições particularmente secas nos países do sul da Europa. Isto naturalmente também se aplica à Península Ibérica, onde os totais anuais de precipitação dependem largamente da atividade frontal de origem Atlântica (em particular nos meses de inverno), sendo esta afastada da região durante a ocorrência de cristas nos sectores ATL e EUR. Neste contexto, mostra-se crucial o recurso a bases de dados de alta-resolução com uma densidade de estações muito mais elevada, permitindo uma análise regional mais detalhada para o domínio da Península Ibérica. Os bloqueios centrados em latitudes elevadas, em particular os que ocorrem no sector ATL, são responsáveis por invernos com maior cobertura de neve no continente Europeu (até cerca de 50% mais dias com a superfície coberta de neve na Europa central), devido a uma maior frequência de dias frios sob os fluxos de norte associados à circulação anticiclónica. Por outro lado, a ocorrência de cristas nos sectores ATL e EUR (que estão associadas a dias de inverno bastante amenos) impõe uma frequência muito mais baixa de dias com neve no solo. Foi também concluído que os padrões de bloqueio/crista exercem um efeito regulador importante na variabilidade inter-anual de incêndios florestais. Mostra-se que o feedback existente entre a ocorrência destes padrões atmosféricos, a ocorrência de secas, e os incêndios florestais, acontece a diferentes escalas temporais. Nos meses antecedentes à época de incêndios, uma frequência superior ao normal de cristas (bloqueios) é responsável por valores de precipitação abaixo (acima) da média no sul da Europa, aumentando a vulnerabilidade da vegetação. Durante a própria época de incêndios, este padrão atmosférico está associado a condições anomalamente quentes e secas que promovem a ignição e fácil propagação do fogo. Finalmente, no contexto das alterações climáticas, verificou-se que nas últimas décadas a frequência de cristas sub-tropicais aumentou bastante no sul da Europa. As projeções futuras dos Modelos de Circulação Geral sugerem uma expansão para norte das altas pressões subtropicais (associadas à expansão da célula de Hadley). Por outro lado, não existem sinais dinâmicos de alterações muito significativas na frequência e localização dos bloqueios de alta latitude no sector Euro-Atlântico, exceto uma ligeira tendência de deslocamento para nordeste na sua região preferencial de ocorrência. Pretende-se como trabalho futuro utilizar também uma abordagem dinâmica (não apenas baseada em campos de anomalia) para o algoritmo de deteção de cristas, que permitirá uma maior confiança na extrapolação para cenários futuros. Blocking high pressure systems are large-scale atmospheric circulation patterns with meteorological impacts that vary across regions and seasons, depending on the blocking location, spatial characteristics and temporal length. While blocking episodes are an important component of intra-seasonal and inter-annual variability at mid-latitudes, particularly in Europe, previous studies have mostly focused on characterizing European blocking impacts on either winter or summer seasons. In this thesis, a thorough characterization of Euro-Atlantic blocking occurrence within different longitudinal sectors (Atlantic, European and Russian) was performed, followed by a comprehensive analysis of their seasonal impacts on temperature and on the precipitation regimes of the European continent and specific sub-regions, with particular emphasis on Iberia, and on extreme events. In order to distinguish high-latitude blocking from other common high pressure systems affecting Europe, namely sub-tropical ridges, a novel ridge detection scheme was developed. Ridges do not require a wave-breaking occurrence as blockings do, although they are frequent precursors of wave-breaking, which may lead to blocking. Thus, as an additional novelty, this thesis also characterizes the distinctive seasonal impacts associated with sub-tropical ridges occurring at different longitudinal sectors of the Euro-Atlantic region. Finally, an assessment of the involved mechanisms behind the temperature and precipitation responses to blocking is also carried out. This included for precipitation the role of cyclonic activity (storm-tracks and cut-off lows), moisture transport, and large-scale atmospheric instability, while for temperature the focus was on the role played by horizontal advection, subsidence and imbalances in various radiation budgets. This distinction clarifies that most extreme heat episodes in southern Europe and Mediterranean areas should not be attributed to blockings, but rather to ridges. In central and northern areas of the continent, both regimes are responsible for warm conditions in summer, due to enhanced radiative heating and increased subsidence. During winter, blocking and ridges lead to opposite temperature responses. Blocking reinforces cold northerly advection in its eastern flank, thus promoting European cold winter spells, especially those located in the eastern Atlantic and western Europe, while mild Atlantic flows associated to ridge patterns result in warmer conditions. Regarding the impacts on precipitation, blocking and ridges are associated with a marked northsouth dipole for the three considered longitudinal sectors of occurrence. While blocking patterns force a split of the storm-track, ridges are associated with a stronger zonal flow at higher latitudes. Thus, negative (positive) precipitation anomalies during blocks occur at higher (lower) latitudes. Enhanced atmospheric instability and cyclonic activity south of blocking centers relate very well with increased rainfall in southern Europe, including Iberia, where torrential regimes are more relevant in the precipitation totals. This dipole is reversed during ridges, which lead to dry conditions in southern Europe. The seasonal analysis further reveals that winters characterized by high frequencies of blocking (ridge) occurrence present above (below) average snow covered soils. Blocking/ridge impacts on temperature and precipitation have also additional effects on meteorological and climate extreme events with large socio economic impacts. Thus, the results show a blocking/ridge role at different time-scales in controlling a significant part of wildfire inter annual variability in Mediterranean areas. Meteorological pre-conditioning raises vegetation stress during dry winters, while increased ridge and blocking occurrence in summer fosters meteorological conditions which are prone to fire ignition and spread. Finally, outputs from state-of-the-art General Circulation Models raise the challenge to develop further these automated schemes for blocking/ridges detection, as their representation in climate models is crucial to understand impacts towards the later decades of the 21st century. Summing up, the main novelties and achievements of this thesis are: 1) the clear disentanglement between blocks and ridges; 2) the seasonal analyses of specific regional impacts resulting from different locations of blocking/ridge structures; 3) the detailed analysis of dynamical/physical forcing mechanisms associated to each considered weather pattern. Tese de doutoramento, Ciências Geofísicas e da Geoinformação (Meteorologia), Universidade de Lisboa, Faculdade de Ciências, 2017

Social competence, the ability of individuals to regulate the expression of their social behaviour in order to optimize their social relationships in a group, is especially benefic for individuals living in complex social environments, and implies the ability to perceive social cues and produce appropriate behavioural output responses (Social Plasticity). Numerous examples of social competence can be found in nature, where individuals extract social information from the environment, and change their behavioural response based on the collected information. At the neuronal level, two major plasticity mechanisms have been proposed to underlie social plasticity, structural reorganization and biochemical switching of the neuronal networks underlying behaviour. The neural substrate for behavioural plasticity has been identified as the social decision-making (SDM) network, such that the same neural circuitry may underlie the expression of different behaviours depending on social context. The goal of this work is to study the proximate mechanism underlying behavioural flexibility in the context of experience-dependent behavioural shifts, in an integrative framework. For this purpose we exposed male zebrafish to two types of social interactions: (1) real-opponent interactions, from which a Winner and Loser emerged; and (2) Mirror-elicited interactions, that produced individuals that did not experience a change in social status, despite expressing similar levels of aggressive behaviour to those participating in real-opponent fights. In a first set of experiments, we studied the influence of neuromodulators on social plasticity mechanisms, by characterizing the endocrine response to social challenges, as well as the social modulation of brain monoamines and nonapeptides. Next we tested the SDM network hypothesis by contrasting changes in functional localization vs. connectivity across this network. Finally we characterized changes in expression of key genes for different neuroplasticity mechanisms in response to changes in social status. Our research suggests different social plasticity mechanisms underlying Winners and Losers both at physiological and molecular levels, for Mirror-fighters, where the experience of winning or losing was decoupled for the fighting experience, few changes were detected. This, by itself suggests a pivotal role of social perception in triggering shifts between socially driven behavioural states. Tese de doutoramento, Biologia (Etologia), Universidade de Lisboa, Faculdade de Ciências, 2015