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Publications (54)
This chapter includes a general characterization of the atmospheric boundary layer with an analysis of micro, macro, and synoptic atmospheric scales in the troposphere. The dimensional scales and frequencies of average flow, turbulence, and atmospheric waves are discussed in relation to the transport of scalar and vector variables. The conditions o...
This chapter presents 13 exercises solved on the topics of Chaps. 1– 6, aiming at consolidating the physical principles to solve applied problems. Exercises 1 and 2 provide the calculation of the energy of one mole of photons and the modeling of continuous solar radiation in the eventual absence of measured data. Exercise 3 shows the calculation of...
This chapter aimed to characterize the aerodynamic mass and energy fluxes over forest canopies. These canopies are rough surfaces wherein flow-gradient assumptions may not be valid, leading to exponential wind profiles in trunk spaces and understory, superimposed by logarithmic profiles above the top of canopies. This leads to airflow regimes where...
In this chapter, an assessment of airflow over modified surfaces was made, mainly corresponding to urban areas, hills, or of transition between surfaces with different roughness, different land uses, and ambient temperatures. This surface heterogeneity that leads to a development of an internal boundary layer, including sublayers, with a determined...
In this chapter, an assessment was carried out on aerodynamic boundary surface layer characterization, where vertical vector fluxes of scalar quantities, e.g., momentum or sensible heat, are considered constant. This approach is grounded on the Prandtl mixed layer empirical theory based on the analogy between eddies in turbulent flow and molecules...
This chapter aimed to make a characterization of turbulent airflow in the surface boundary layer, following qualitative and quantitative approaches. The former is based on a generalization of Navier–Stokes equations, applied to flow mean and fluctuation components, for obtaining budgets of vectorial and scalar quantities. The latter is based on sim...
Global climate grid.9983.b change and GHG emissions are essential topics for understanding physical processes ongoing in the atmospheric boundary layer, within a control volume extending from the top ground to the troposphere. This chapter aimed therefore to deliver a qualitative and quantitative approach to climate change processes and carbon bala...
Heat and mass transfer principles, coupled with the modulation of energy and mass budgets, were covered in this chapter. Transfer processes regulate a spectrum of phenomena, such as variations of carbon and water exchanges or sediment transport. The main topics related to heat conduction were Fourier’s law and the thermal exchanges in the upper lay...
This book is an interdisciplinary and accessible guide to environmental physics. It allows readers to gain a more complete understanding of physical process and their interaction with ecological ones underpin important environmental issues.
The book covers a wide range of topics within environmental physics, including:
• natural and anthropogenic...
The impact of atmospheric reactive nitrogen (Nr) deposition on carbon (C) sequestration in soils and biomass of unfertilized, natural, semi-natural and forest ecosystems has been much debated. Many previous results of this dC/dN response were based on changes in carbon stocks from periodical soil and ecosystem inventories, associated with estimates...
The impact of atmospheric reactive nitrogen (Nr) deposition on carbon (C) sequestration in soils and biomass of unfertilised, natural, semi-natural and forest ecosystems has been much debated. Many previous results of this dC / dN response were based on changes in carbon stocks from periodical soil and ecosystem inventories, associated with estimat...
Abstract
Accurate predictions of net ecosystem productivity (NEPc) of forest ecosystems are essential for climate change decisions and requirements in the context of national forest growth and greenhouse gas inventories. However, drivers and underlying mechanisms determining NEPc (e.g. climate, nutrients) are not entirely understood yet, particula...
The inter- and seasonal patterns of water vapor and canopy carbon fluxes were compared for four forest ecosystems in two contrasting climatic zones in Europe. The eddy covariance and ancillary data were taken from the Carboeurope and FLUXNET databases and a linear modeling statistical analysis was made. The four sites were a high-density poplar (Po...
The increase in global average temperature, linked to climate change, at the surface of the globe in the twentieth century was 0.4 to 0.8 °C (IPCC, 2001). Particularly in Mediterranean regions the frequency and severity of droughts, worsened since the 70s due to the increase in atmospheric temperature and decreased precipitation. The drought of 200...
In Portugal, eucalypt (Eucalyptus globulus Labill.) stands aimed mainly for pulp production, occupy an area of 739,515ha, corresponding to 23% of total forest area. The main objective of this work was to report the recovery of seasonal pattern of GPP in a eucalypt site in Pegões (Southern Portugal) after a felling carried out in October - November...
This paper summarizes results between 2002 and 2010 from eddy covariance measurements of carbon uptake in the 12 month annual growing period eucalypt site of Espirra in Southern Portugal (38 degrees 38' N, 8 degrees 36' W). This site, aimed for pulp production is part of an intensively 300 ha eucalypt coppice, with about 1100 trees ha. The climate...
Basal ecosystem respiration rate (BR), the ecosystem respiration rate at a given
temperature, is a common and important parameter in empirical models for quantifying
ecosystem respiration (ER) globally. Numerous studies have indicated that BR varies in
space. However, many empirical ER models still use a global constant BR largely due to
the lack o...
This paper reports on results from eddy covariance measurements of carbon uptake and evapotranspiration in the eucalypt site of Espirra in Southern Portugal (38 degrees 38'N, 8 degrees 36'W). This site was included in the "Carboeurope" European network and is part of a 300 ha eucalypt forest, with about 1100 trees ha(-1), intensively managed as a c...
The main objective of this work was to report the recovery of seasonal pattern of GPP obtained by eddy covariance measurements in a eucalypt (Eucalyptus globulus Labill.) site in Pegões (Southern Portugal) after a felling processed in October and November of 2006. This was made in a wider context of a general description of the evolution of carbon...
Understanding the relationships between climate and carbon exchange by terrestrial ecosystems is critical to predict future levels of atmospheric carbon dioxide because of the potential accelerating effects of positive climate–carbon cycle feedbacks. However, directly observed relationships between climate and terrestrial CO2 exchange with the atmo...
Espirra site (38°38'N,8°36'W) is located in a 300ha Eucalyptus globulus plantation, with a Mediterranean type climate with a mean annual precipitation of 709mm and a mean annual air temperature of 15.9°C. The plantation was established in 1986 with about 1100 trees ha-1. A 33m observation tower was installed in 2002, with an eddy covariance system....
As climate changes, the main changes in precipitation will likely be in
the intensity, frequency and duration of events. It has been suggested
that these changes will be more important for ecosystems biogeochemical
cycles than the effects of changes in average precipitation, atmospheric
warming or increased CO2 concentration. Although more extreme...
Espirra site (38°38'N,8°36'W) is located in a 300ha Eucalyptus globulus plantation, with a Mediterranean type climate with a mean annual precipitation of 709mm and a mean annual air temperature of 15.9°C. The plantation was established in 1986 with about 1100 trees ha-1. A 33m observation tower was installed in 2002, with an ultrasonic Gill anemome...
We applied a site evaluation approach combining Lagrangian Stochastic footprint modeling with a quality assessment approach for eddy-covariance data to 25 forested sites of the CarboEurope-IP network. The analysis addresses the spatial representativeness of the flux measurements, instrumental effects on data quality, spatial patterns in the data qu...
We applied a site evaluation approach combining Lagrangian Stochastic footprint modeling with a quality assessment approach for eddy-covariance data to 25 forested sites of the CarboEurope-IP network. The analysis addresses the spatial representativeness of the flux measurements, instrumental effects on data quality, spatial patterns in the data qu...
Terrestrial ecosystems sequester 2.1 Pg of atmospheric carbon annually. A large amount of the terrestrial sink is realized by forests. However, considerable uncertainties remain regarding the fate of this carbon over both short and long timescales. Relevant data to address these uncertainties are being collected at many sites around the world, but...
We applied a site evaluation approach combining Lagrangian Stochastic footprint modelling with a quality assessment approach for eddy-covariance data to 25 forested sites of the CarboEurope-IP network. The analysis addresses the spatial representativeness of the flux measurements, instrumental effects on data quality, spatial patterns in the data q...
Droughts reduce gross primary production (GPP) and ecosystem respiration (Reco), contributing to most of the inter-annual variability in terrestrial carbon sequestration. In seasonally dry climates (Mediterranean), droughts result from reductions in annual rainfall and changes in rain seasonality. We compared carbon fluxes measured by the eddy cova...
Droughts cause reductions in gross primary production (GPP) and also in net ecosystem exchange (NEE), contributing to most of the inter-annual variability in terrestrial carbon sequestration. In seasonally dry climates (Mediterranean) droughts result from reductions in annual rainfall and from changes in rain seasonality. In western Iberia, the hyd...
The drought of 2003 was exceptionally severe in many regions of Europe, both in duration and in intensity. In some areas, especially in Germany and France, it was the strongest drought for the last 50 years, lasting for more than 6 months.We used continuous carbon and water flux measurements at 12 European monitoring sites covering various forest e...
Terrestrial ecosystems sequester 2.1 Pg of atmospheric carbon annually. A large amount of the terrestrial sink is realized by forests. However, considerable uncertainties remain regarding the fate of this carbon over both short and long timescales. Relevant data to address these uncertainties are being collected at many sites around the world, but...
Terrestrial ecosystems sequester 2.1 Pg of atmospheric carbon annually. A large amount of the terrestrial sink is realized by forests. However, considerable uncertainties remain regarding the fate of this carbon over both short and long timescales. Relevant data to address these uncertainties are being collected at many sites around the world, but...
Seasonal patterns of carbon assimilation and evapotranspiration of 2004 in Eucalyptus globulus plantation of the CarboEurope-IP Portuguese site of Herdade da Espirra are discussed. The atmospheric fluxes were obtained by the eddy covariance method. A separation of atmospheric carbon flux, or net ecosystem exchange (NEE), in gross primary production...
Eddy covariance flux data from the Portuguese CarboEurope forest site 'Herdade da Espirra' obtained from 2003 to 2005 is analysed. A 32m tower contains at its top the eddy covariance unit, as well as an automatic weather station. The site (38º38'N, 8º36'W) is an Eucalyptus Globulus 300 hectare plantation, 11 years aged forest with 20m mean canopy h...
A twenty-two month campaign of turbulent flux measurements of CO 2 and water vapour was made, in order to contribute to the evaluation of the role of Eucalyptus globulus plantations in carbon sequestration. In this paper results of the fluxes are presented, considering its seasonal and daily variability. The mean yearly net ecosystem exchange was 8...
A twenty-two month campaign of turbulent flux measurements of CO2 and water vapour was made, in order to contribute to the evaluation of the role of Eucalyptus globulus plantations in carbon sequestration. In this paper results of the fluxes are presented, considering its seasonal and daily variability. The mean yearly net ecosystem exchange was 8....
The energy balance of a Mediterranean greenhouse has been evaluated, measuring the different energy fluxes between the greenhouse and the surroundings. The experiments were conducted in a chapel type greenhouse, with wooden structure, 17m wide and 30 m long, 5.5 m height in the center and 2.2 m height laterally. The greenhouse was cladded with a si...
Passive control methods were used to suppress combustion instability in a combustor with a bluff-body stabilizer. The instabilities in this combustor are excited by interaction between vortices shed downstream of the stabilizer and the combustion chamber acoustic modes. The passive control methodology was to change the geometrical design of the sta...
The evaluation of instantaneous temperature in a premixed flame
using fine-wire Pt/Pt-13%Rh thermocouples was found to be subject to
significant errors due to catalytic effects. An experimental study was
undertaken to assess the influence of local fuel/air ratio, thermocouple
wire diameter, and gas velocity on the thermocouple reading errors
induce...
A technique was developed to enable the evaluation of the correlation between velocity and temperature, with laser Doppler anemometer (LDA) as the source of velocity signals and fine wire thermocouple as that of flow temperature. The discontinuous nature of LDA signals requires a special technique for correlation, in particular when few seeding par...
Measurements of axial and radial velocities obtained with laser anemometry in the transitional region of a hot round jet are reported. The temperature has been measured with 15 m-diameter thermocouples. The results include distributions of probability and power spectra of velocity and temperature. Velocity-temperature correlations were obtained sho...
Thermocouples with three different wire diameters (15, 40 and 50 microns) were used in association with an analog compensation circuit connected to a data acquisition system. Measurements of the time constant were performed using two different heating techniques; Joule effect and external heating by laser beam. The thermocouples were used to quanti...
The present paper reports measurements of axial and radial velocities obtained with laser-Doppler anemometry in the transitional region of a round jet. The predominant frequencies of the coherent structures detected in the non-artificially excited jet, correspond to Strouhal numbers, around 0.33 and 0.55 and an interpretation of these observations...
The results of three dynamic flow experiments using laser-Doppler
velocimetry confirm that velocity bias is present except when the time
scale of sampling is larger than both the time scale corresponding to
the particle arrival rate and to that of the integral turbulence time
scale. Firstly, measurements using a 2 W argon laser were obtained on
the...
Laser Doppler anemometry has been used to measure the mean and rms values of the axial and radial velocity components in jets with Reynolds numbers of up to 28,700. It is shown that even in flows that are not excited externally, coherent structures with Strouhal numbers of about 0.33 and 0.55 can be detected. The coherent structures associated with...
A water spray, from a twin-fluid atomizer, was studied at different air temperature and at atmospheric pressure. The Sauter Mean Diameter, D32, and the droplet volume distribution were measured at four different distances from the injector. An optical method was used to measure droplet sizes. Predictions of the Sauter Mean Diameter, liquid volume c...