Hydrogeology and sustainable future groundwater abstraction from the Agua Verde aquifer in the Atacama Desert,northern Chile

The hyper-arid conditions prevailing in Agua Verde aquifer in northern Chile make this system the most important water source for nearby towns and mining industries. Due to the growing demand for water in this region, recharge is investigated along with the impact of intense pumping activity in this aquifer. A conceptual model of the hydrogeological system is developed and implemented into a two-dimensional groundwater-flow numerical model. To assess the impact of climate change and groundwater extraction, several scenarios are simulated considering variations in both aquifer recharge and withdrawals. The estimated average groundwater lateral recharge from Precordillera (pre-mountain range) is about 4,482 m³/day. The scenarios that consider an increase of water withdrawal show a non-sustainable groundwater consumption leading to an over-exploitation of the resource, because the outflows surpasses inflows, causing storage depletion. The greater the depletion, the larger the impact of recharge reduction caused by the considered future climate change. This result indicates that the combined effects of such factors may have a severe impact on groundwater availability as found in other groundwater-dependent regions located in arid environments. Furthermore, the scenarios that consider a reduction of the extraction flow rate show that it may be possible to partially alleviate the damage already caused to the aquifer by the continuous extractions since 1974, and it can partially counteract climate change impacts on future groundwater availability caused by a decrease in precipitation (and so in recharge), if the desalination plant in Taltal increases its capacity.     

Pyrite formation driven by MSW landfill leachate in the Madrid Basin, Spain

The role of municipal solid waste (MSW) landfill leachate on the genesis of minor amounts of pyrite associated with gypsum in an otherwise predominantly evaporitic sequence was studied in geological and geochemical terms. The potential association between landfill leachate and the conditions required for bacterial reduction of sulfate and fixation of H₂S as pyrite were examined. The lithological column was generally found to contain little or no Fe. The δ³⁴S values for sulfates were consistent with previously reported data; however, the measured δ¹⁸O values were slightly higher. Sulfides disseminated in the marl/lutite exhibited higher δ³⁴S values (≈−8‰) than gypsum-coating pyrite crystals (δ³⁴S < −30‰). Dissolution of gypsum to sulfate and the supply of metabolizable organic matter and Fe required for H₂S fixation as sulfides may have originated from landfill leachate. Intermittent availability of leachate, a result of the precipitation regime, can facilitate sulfur disproportionation and lead to fractionations as high as      

The Removal of Dissolved Metals by Hydroxysulphate Precipitates during Oxidation and Neutralization of Acid Mine Waters, Iberian Pyrite Belt

This study examines the removal of dissolved metals during the oxidation and neutralization of five acid mine drainage (AMD) waters from La Zarza, Lomero, Esperanza, Corta Atalaya and Poderosa mines (Iberian Pyrite Belt, Huelva, Spain). These waters were selected to cover the spectrum of pH (2.2–3.5) and chemical composition (e.g., 319–2,103 mg/L Fe; 2.85–33.3 g/L SO₄⁼) of the IPB mine waters. The experiments were conducted in the laboratory to simulate the geochemical evolution previously recognized in the field. This evolution includes two stages: (1) oxidation of dissolved Fe(II) followed by hydrolysis and precipitation of Fe(III), and (2) progressive pH increase during mixing with fresh waters. Fe(III) precipitates at pH < 3.5 (stages 1 and 2) in the form of schwertmannite, whereas Al precipitates during stage 2 at pH 5.0 in the form of several hydroxysulphates of variable composition (hydrobasaluminite, basaluminite, aluminite). During these stages, trace elements are totally or partially sorbed and/or coprecipitated at different rates depending basically on pH, as well as on the activity of the SO₄⁼ anion (which determines the speciation of metals). The general trend for the metals which are chiefly present as aqueous free cations (Pb²⁺, Zn²⁺, Cu²⁺, Cd²⁺, Mn²⁺, Co²⁺, Ni²⁺) is a progressive sorption at increasing pH. On the other hand, As and V (mainly present as anionic species) are completely scavenged during the oxidation stage at pH < 3.5. In waters with high activities (> 10⁻¹) of the SO ₄⁼ ion, some elements like Al, Zn, Cd, Pb and U can also form anionic bisulphate complexes and be significantly sorbed at pH < 5. The removal rates at pH 7.0 range from around 100% for As, V, Cu and U, and 60–80% for Pb, to less than 20% for Zn, Co, Ni and Mn. These processes of metal removal represent a significant mechanism of natural attenuation in the IPB.     

The intracloud/cloud-to-ground lightning ratio in Southeastern Brazil

The intracloud to cloud-to-ground lightning flash ratio (Z) has been estimated for the first time in Southeastern Brazil and in the tropical region using the Lightning Imaging Sensor (LIS) and Brazilian lightning detection network (BrasilDat) lightning data obtained from 1999 to 2005. Geographical variations of Z and their relation to elevation, latitude, precipitation, total lightning density and percentage of positive CG lightning will be discussed. Daily variations of Z will also be presented. The results suggest that Z values are similar to studies outside the tropics and that are influenced by orographic features.     

Investigation about the dependence of spectral diffuse-to-direct-beam irradiance ratio on atmospheric turbidity and solar zenith angle

Summary The modifications of the solar spectral diffuse and direct-beam irradiances as well as the diffuse-to-direct-beam ratio, E_dλ/E_bλ, as a function of the aerosol optical depth, AOD, and solar zenith angle, SZA, is investigated. The E_dλ/E_bλ ratios decrease rapidly with wavelength and exponential curves in the form E_dλ/E_bλ = aλ^−b can be fitted with a great accuracy. These curves are strongly modified by the solar spectrum distribution, which is affected by the aerosol loading, aerosol optical properties and SZA. The spectral dependence of the above E_dλ/E_bλ ratios in logarithmic coordinates does not yield a straight line, while a significant departure from the linearity is revealed. The reasons for this departure are investigated in detail and it is established that the aerosol physical properties such as single scattering albedo and size distribution along with the effect of SZA are responsible. These parameters strongly affect the scattering processes in the atmosphere and as a consequence the diffuse spectral distribution. The E_dλ/E_bλ ratio, which is an indicator of the atmospheric transmittance (King, 1979), exhibits a strong wavelength and aerosol-loading dependence. The observed differences between turbid and clear atmospheres constitute a manifestation of contrasting air properties and influence solar irradiance spectra. The present work aims at investigating the effect of atmospheric turbidity and SZA on the E_dλ/E_bλ ratio. For this reason, two distinct cases are examined: one having different atmospheric turbidity conditions but same SZA and a second having different SZAs and same atmospheric turbidity levels.     

Climate change and summer mass tourism: the case of Spanish domestic tourism

This paper investigates the impact of climate change on destination choice decisions in a context of domestic coastal tourism in Spain. Destinations are characterized in terms of travel cost and coastal ‘attractors’, such as temperature and beach-related attributes. By means of a discrete choice model based on the random utility theory, these variables are used to explain the observed pattern of interprovincial domestic trips, showing trade-offs between temperature and attractiveness in the probability of a particular destination being chosen. The model is used to investigate the impact of two climate change scenarios on the allocation of domestic tourism within Spain. The findings show that while Spain’s northern colder provinces would benefit from rising temperatures, provinces in the south would experience a decrease in the frequency of trips.     

Some Insights into Topographic,Elastic and Self-gravitation Interaction in Modelling Ground Deformation and Gravity Changes in Active Volcanic Areas

Surface displacements and gravity changes due to volcanic sources are influenced by medium properties. We investigate topographic, elastic and self-gravitation interaction in order to outline the major factors that are significant in data modelling. While elastic-gravitational models can provide a suitable approximation to problems of volcanic loading in areas where topographic relief is negligible, for prominent volcanoes the rough topography could affect deformation and gravity changes to a greater extent than self-gravitation. This fact requires the selection, depending on local relief, of a suitable model for use in the interpretation of surface precursors of volcanic activity. We use the three-dimensional Indirect Boundary Element Method to examine the effects of topography on deformation and gravity changes in models of magma chamber inflation/deflation. Topography has a significant effect on predicted surface deformation and gravity changes. Both the magnitude and pattern of the geodetic signals are significantly different compared to half-space solutions. Thus, failure to account for topographic effects in areas of prominent relief can bias the estimate of volcanic source parameters, since the magnitude and pattern of deformation and gravity changes depend on such effects.     

Top-down and bottom-up modelling to support low-carbon scenarios: climate policy implications

Bottom-up and top-down models are used to support climate policies, to identify the options required to meet GHG abatement targets and to evaluate their economic impact. Some studies have shown that the GHG mitigation options provided by economic top-down and technological bottom-up models tend to vary. One reason for this is that these models tend to use different baseline scenarios. The bottom-up TIMES_PT and the top-down computable general equilibrium GEM-E3_PT models are examined using a common baseline scenario to calibrate them, and the extend of their different mitigation options and its relevant to domestic policy making are assessed. Three low-carbon scenarios for Portugal until 2050 are generated, each with different GHG reduction targets. Both models suggest close mitigation options and locate the largest mitigation potential to energy supply. However, the models suggest different mitigation options for the end-use sectors: GEM-E3_PT focuses more on energy efficiency, while TIMES_PT relies on decrease carbon intensity due to a shift to electricity. Although a common baseline scenario cannot be ignored, the models’ inherent characteristics are the main factor for the different outcomes, thereby highlighting different mitigation options.

Policy relevance

The relevance of modelling tools used to support the design of domestic climate policies is assessed by evaluating the mitigation options suggested by a bottom-up and a top-down model. The different outcomes of each model are significant for climate policy design since each suggest different mitigation options like end-use energy efficiency and the promotion of low-carbon technologies. Policy makers should carefully select the modelling tool used to support their policies. The specific modelling structures of each model make them more appropriate to address certain policy questions than others. Using both modelling approaches for policy support can therefore bring added value and result in more robust climate policy design. Although the results are specific for Portugal, the insights provided by the analysis of both models can be extended to, and used in the climate policy decisions of, other countries.     

气象卫星云图的多分辨小波分解及人工神经网络降水估计研究

采用多分辨小波分析对卫星图象进行预处理 ,在保留其特征信息的同时 ,减小了数据量 ,改善了神经网络训练过程的收敛性能 ,提高了处理速度。采用这一方法根据 GOES- 8的红外亮温图象和气象雷达资料对巴西圣保罗州中部的降水量估计进行了试验 ,取得了良好的效果。     

Adaptation of Pressure Based CFD Solvers for Mesoscale Atmospheric Problems

General purpose Computational Fluid Dynamics (CFD) solvers are frequently used in small-scale urban pollution dispersion simulations without a large extent of ver- tical flow. Vertical flow, however, plays an important role in the formation of local breezes, such as urban heat island induced breezes that have great significance in the ventilation of large cities. The effects of atmospheric stratification, anelasticity and Coriolis force must be taken into account in such simulations. We introduce a general method for adapting pressure based CFD solvers to atmospheric flow simulations in order to take advantage of their high flexibility in geometrical modelling and meshing. Compressibility and thermal stratification effects are taken into account by utilizing a novel system of transformations of the field variables and by adding consequential source terms to the model equations of incompressible flow. Phenomena involving mesoscale to microscale coupled effects can be analyzed without model nesting, applying only local grid refinement of an arbitrary level. Elements of the method are validated against an analytical solution, results of a reference calculation, and a laboratory scale urban heat island circulation experiment. The new approach can be applied with benefits to several areas of application. Inclusion of the moisture transport phenomena and the surface energy balance are important further steps towards the practical application of the method.