Above ground biomass estimation in Mediterranean multiple use systems with high spatial resolution satellite images

Forest biomass has been having an increasing importance in the world economy and in the evaluation of the forests development and monitoring. It was identified as a global strategic reserve, due to its applications in bioenergy, bioproduct development and issues related to reducing greenhouse gas emissions. The estimation of above ground biomass is frequently done with allometric functions per species with plot inventory data. An adequate sampling design and intensity for an error threshold is required. The estimation per unit area is done using an extrapolation method. This procedure is labour demanding and costly. The mail goal of this study is the development of allometric functions for the estimation of above ground biomass with ground cover as independent variable, for forest areas of holm aok (Quercus rotundifolia), cork oak (Quercus suber) and umbrella pine (Pinus pinea) in multiple use systems. Ground cover per species was derived from crown horizontal projection obtained by processing high resolution satellite images, orthorectified, geometrically and atmospheric corrected, with multi-resolution segmentation method and object oriented classification. Forest inventory data were used to estimate plot above ground biomass with published allometric functions at tree level. The developed functions were fitted for monospecies stands and for multispecies stands of Quercus rotundifolia and Quercus suber, and Quercus suber and Pinus pinea. The stand composition was considered adding dummy variables to distinguish monospecies from multispecies stands. The models showed a good performance. Noteworthy is that the dummy variables, reflecting the differences between species, originated improvements in the models. Significant differences were found for above ground biomass estimation with the functions with and without the dummy variables. An error threshold of 10% corresponds to stand areas of about 40 ha. This method enables the overall area evaluation, not requiring extrapolation procedures, for the three species, which occur frequently in multispecies stands.

Large scale underground energy storage for renewables integration: general criteria for reservoir identification and viable technologies.

The increasing integration of renewable energies in the electricity grid contributes considerably to achieve the European Union goals on energy and Greenhouse Gases (GHG) emissions reduction. However, it also brings problems to grid management. Large scale energy storage can provide the means for a better integration of the renewable energy sources, for balancing supply and demand, to increase energy security, to enhance a better management of the grid and also to converge towards a low carbon economy. Geological formations have the potential to store large volumes of fluids with minimal impact to environment and society. One of the ways to ensure a large scale energy storage is to use the storage capacity in geological reservoir. In fact, there are several viable technologies for underground energy storage, as well as several types of underground reservoirs that can be considered. The geological energy storage technologies considered in this research were: Underground Gas Storage (UGS), Hydrogen Storage (HS), Compressed Air Energy Storage (CAES), Underground Pumped Hydro Storage (UPHS) and Thermal Energy Storage (TES). For these different types of underground energy storage technologies there are several types of geological reservoirs that can be suitable, namely: depleted hydrocarbon reservoirs, aquifers, salt formations and caverns, engineered rock caverns and abandoned mines. Specific site screening criteria are applicable to each of these reservoir types and technologies, which determines the viability of the reservoir itself, and of the technology for any particular site. This paper presents a review of the criteria applied in the scope of the Portuguese contribution to the EU funded project ESTMAP – Energy Storage Mapping and Planning.

Contribuição para o ensino da meteorologia e do clima

Numa época em que tanto se fala e escreve sobre Alterações Climáticas torna­ se pertinente elaborar um documento de apoio ao ensino que ajude os professores e alunos a explicar/perceber as complexas interacções do sistema climático. O presente trabalho tem o objectivo de contribuir para uma melhor compreensão dos aspectos físicos elementares que afectam a variabilidade climática e a forma como as diversas actividades desenvolvidas pelo Homem podem desequilibrar o sistema climático. O texto encontra-se amplamente ilustrado, facilitando a sua compreensão, e foram desenvolvidas ferramentas de cálculo em Excel que permitem utilizar as observações recolhidas nas Estações Meteorológicas Automáticas, instaladas nas escolas secundárias aderentes ao projecto PROCURA, para avaliar a difusão e dispersão de uma pluma de poluentes ou para simular o efeito de alterações na concentração de Gases com Efeito de Estufa na temperatura média à superfície. ABSTRACT: At a time when so much is said and written about Climate Changes it becomes relevant to draw up a document to support teaching, helping teachers and students to explain/understand the complex interactions of the climate system. This document aims to contribute to a better understanding of the physical elements that affect climate variability and how the various activities undertaken by humans can disrupt the climate system. The text is amply illustrated, facilitating its understanding, and calculating tools have been developed in Excel to allow the use of observations collected from Automatic Weather Stations, installed in the high schools which joined the project PROCURA, to evaluate the diffusion and dispersion of a plume of pollutants or to simulate the effect of changes in the concentration of Greenhouse Gases on the average temperature at the surface.