Sensitivity of a distributed temperature-radiation index melt model based on AWS observations and surface energy balance fluxes, Hurd Peninsula glaciers, Livingston Island, Antarctica

We use an automatic weather station and surface mass balance dataset spanning four melt seasons collected on Hurd Peninsula Glaciers, South Shetland Islands, to investigate the point surface energy balance, to determine the absolute and relative contribution of the various energy fluxes acting on the glacier surface and to estimate the sensitivity of melt to ambient temperature changes. Long-wave incoming radiation is the main energy source for melt, while short-wave radiation is the most important flux controlling the variation of both seasonal and daily mean surface energy balance. Short-wave and long-wave radiation fluxes do, in general, balance each other, resulting in a high correspondence between daily mean net radiation flux and available melt energy flux. We calibrate a distributed melt model driven by air temperature and an expression for the incoming short-wave radiation. The model is calibrated with the data from one of the melt seasons and validated with the data of the three remaining seasons. The model results deviate at most 140 mm w.e. from the corresponding observations using the glaciological method. The model is very sensitive to changes in ambient temperature: a 0.5 ◦ C increase results in 56 % higher melt rates.

Towards a dynamic model for the Urban Heat Island of Madrid

Present research is framed within the project MODIFICA (MODelo predictivo - edIFIcios - Isla de Calor urbanA) aimed at developing a predictive model for dwelling energy performance under the urban heat island effect in order to implement it in the evaluation of real energy demand and consumption of dwellings as well as in the selection of energy retrofitting strategies. It is funded by Programa de I+D+i orientada a los retos de la sociedad 'Retos Investigación' 2013. Despite great advances on building energy performance have been achieved during the last years, available climate data is derived from weather stations placed in the outskirts of the city. Hence, urban heat island effect is not considered in energy simulations, which implies an important lack of accuracy. Since 1980's several international studies have been conducted on the urban heat island (UHI) phenomena, which modifies the atmospheric conditions of the urban centres due to urban agglomeration [1][2][3][4]. In the particular case of Madrid, multiple maps haven been generated using different methodologies during the last two decades [5][6][7]. These maps allow us to study the UHI phenomena from a wide perspective, offering however an static representation of it. Consequently a dynamic model for Madrid UHI is proposed, in order to evaluate it in a continuous way, and to be able to integrate it in building energy simulations.

Hacia un modelo dinámico para la isla de calor urbana de Madrid = Towards a Dynamic Model for the Urban Heat Island of Madrid

Esta investigación se enmarca dentro del proyecto MODIFICA (modelo predictivo - Edificios - Isla de Calor Urbano), financiado por el Programa de I + D + i Orientada a los Retos de la sociedad 'Retos Investigación' de 2013. Está dirigido a desarrollar un modelo predictivo de eficiencia energética para viviendas, bajo el efecto de isla de calor urbano (AUS) con el fin de ponerla en práctica en la evaluación de la demanda de energía real y el consumo en las viviendas. A pesar de los grandes avances que se han logrado durante los últimos años en el rendimiento energético de edificios, los archivos de tiempo utilizados en la construcción de simulaciones de energía se derivan generalmente de estaciones meteorológicas situadas en las afueras de la ciudad. Por lo tanto, el efecto de la Isla de Calor Urbano (ICU) no se considera en estos cálculos, lo que implica una importante falta de precisión. Centrado en explorar cómo incluir los fenómenos ICU, el presente trabajo recopila y analiza la dinámica por hora de la temperatura en diferentes lugares dentro de la ciudad de Madrid. Abstract This research is framed within the project MODIFICA (Predictive model - Buildings - Urban Heat Island), funded by Programa de I+D+i orientada a los retos de la sociedad 'Retos Investigación' 2013. It is aimed at developing a predictive model for dwelling energy performance under the Urban Heat Island (UHI) effect in order to implement it in the evaluation of real energy demand and consumption in dwellings. Despite great advances on building energy performance have been achieved during the last years, weather files used in building energy simulations are usually derived from weather stations placed in the outskirts of the city. Hence, Urban Heat Island (UHI) effect is not considered in this calculations, which implies an important lack of accuracy. Focused on exploring how to include the UHI phenomena, the present paper compiles and analyses the hourly dynamics of temperature in different locations within the city of Madrid.

Pressure measurements of the detachment bubble on the Bolund Island

Pressure measurements on the surface of a 1:230 scale model of Bolund Island are presented. The model is smooth and no boundary layer generation has been considered since the experiment is designed as the simplest possible reference case. Measurement have been taken for a range of Reynolds numbers based on the average undisturbed wind speed U∞ and the maximum height of the island, h [1.7×104, 8.5×104], and for a range of wind directions. Four minutes time series of pressure in more than 400 points have been acquired and analysed to obtain the spatial distribution of both the time average and the variance of the pressure signal. The horizontal extension of the detachment bubble for the different Reynolds numbers and wind directions is identified by isobars and curves of constant value of pressure variance. The applicability of this technique for evaluating the horizontal topology of high turbulence regions associated to detachment bubbles after escarpments in potential wind farm sites is analysed. The results obtained shows that the behaviour of the mean pressure coefficient, Cp, the std. pressure coefficient, Cp, and the skewness of the pressure, Sp can be used to study the bubble over the island to a certain extent. This experiment is part of the set of different analysis on the Bolund test case that is being undertaken within WAUDIT project by the different scientific groups.

Critical Role of Two-Dimensional Island-Mediated Growth on the Formation of Semiconductor Heterointerfaces

We experimentally demonstrate a sigmoidal variation of the composition profile across semiconductor heterointerfaces. The wide range of material systems (III-arsenides, III-antimonides, III-V quaternary compounds, III-nitrides) exhibiting such a profile suggests a universal behavior. We show that sigmoidal profiles emerge from a simple model of cooperative growth mediated by twodimensional island formation, wherein cooperative effects are described by a specific functional dependence of the sticking coefficient on the surface coverage. Experimental results confirm that, except in the very early stages, island growth prevails over nucleation as the mechanism governing the interface development and ultimately determines the sigmoidal shape of the chemical profile in these two-dimensional grown layers. In agreement with our experimental findings, the model also predicts a minimum value of the interfacial width, with the minimum attainable value depending on the chemical identity of the species.

Pressure measurements of the detachment bubble on the Bolund Island

Pressure measurements on the surface of a 1:230 scale model of Bolund Island are presented. The model is smooth and no boundary layer generation has been considered since the experiment is designed as the simplest possible reference case. Measurement have been taken for a range of Reynolds numbers based on the average undisturbed wind speed U? and the maximum height of the island, h [1.7×104 , 8.5×104], and for a range of wind directions. Four minutes time series of pressure in more than 400 points have been acquired and analysed to obtain the spatial distribution of both the time average and the variance of the pressure signal. The horizontal extension of the detachment bubble for the different Reynolds numbers and wind directions is identified by isobars and curves of constant value of pressure variance. The applicability of this technique for evaluating the horizontal topology of high turbulence regions associated to detachment bubbles after escarpments in potential wind farm sites is analysed. The results obtained shows that the behaviour of the mean pressure coefficient, Cp, the std. pressure coefficient, C?p, and the skewness of the pressure, Sp can be used to study the bubble over the island to a certain extent. This experiment is part of the set of different analysis on the Bolund test case that is being undertaken within WAUDIT project by the different scientific groups.

Assessing the impact of adaptive accessibility on the optimal transport policy implementation by using an integrated land-use/transport model for Madrid

Accessibility is an essential concept widely used to evaluate the impact of land-use and transport strategies in transport and urban planning. Accessibility is typically evaluated by using a transport model or a land-use model independently or successively without a feedback loop, thus neglecting the interaction effects between the two systems and the induced competition effects among opportunities due to accessibility improvements. More than a mere methodological curiosity, failure to account for land- use/transport interactions and the competition effect may result in large underestimation of the policy effects. With the recent development of land-use and transport interaction (LUTI) models, there is a growing interest in using these models to adequately measure accessibility and evaluate its impact. The current study joins this research stream by embedding an accessibility measure in a LUTI model with two main aims. The first aim is to account for adaptive accessibility, namely the adjustment of the potential accessibility due to the effect of competition among opportunities (e.g., workplaces) as a result of improved accessibility. LUTI models are particularly suitable for assessing adaptive accessibility because the competition factor is a function of the number of jobs, which is related to land-use attractiveness and the number of workers which is related, among other factors, to the transport demand. The second aim is to identify the optimal implementation scenario of policy measures on the basis of the potential and adaptive accessibility and analyse the results in terms of social welfare and accessibility. The metropolitan area of Madrid is used as a case-study and two transport policy instruments, namely a cordon toll and bus frequency increase, have been chosen for the simulation study in order to present the usefulness of the approach to urban planners and policy makers. The MARS model (Metropolitan Activity Relocation Simulator) calibrated for Madrid was employed as the analysis tool. The impact of accessibility is embedded in the model through a social welfare function that includes not only costs and benefits to both road users and transport operators, but also costs and benefits for the government and society in general (external costs). An optimisation procedure is performed by the MARS model for maximizing the value of objective function in order to find the best (optimal) policy imp lementations intensity (i.e., price, frequency). Last, the two policy strategies are evaluated in terms of their accessibility. Results show that the accessibility with competition factor influences the optimal policy implementation level and also generates different results in terms of social welfare. In addition, mapping the difference between the potential and the adaptive accessibility indicators shows that the main changes occur in areas where there is a strong competition among land-use opportunities.

Thermal characterization of urban heat island (UHI) according to urban morphology of Madrid

Present research is framed within the project MODIFICA (MODelo predictivo - edIFIcios - Isla de Calor Urbana) aimed at developing a predictive model for dwelling energy performance under the urban heat island effect in order to implement it in the evaluation of real energy demand and consumption of dwellings as well as in the selection of energy retrofitting strategies. It is funded by Programa de I+D+i orientada a los retos de la sociedad 'Retos Investigación' 2013. The scope of our predictive model is defined by the heat island effect (UHI) of urban structures that compose the city of Madrid. In particular, we focus on the homogeneous areas for urban structures with the same urban and building characteristics. Data sources for the definition of such homogeneous areas were provided by previous research on the UHI of Madrid. The objective is to establish a critical analysis of climate records used for energy simulation tools, which data come from weather stations placed in decontextualized areas from the usual urban reality, where the thermal conditions differs by up to 6ºC. In this way, we intend to develop a new predictive model for the consumption and demand in buildings depending on their location, the urban structure and the associated UHI, improving the future energy rehabilitation interventions