The Mediterranean region in central Chile is experiencing a significant decrease in precipitation due to climate change and the dynamics of the El Nino Southern Oscillation(ENSO).Droughts have increased in recent deca...The Mediterranean region in central Chile is experiencing a significant decrease in precipitation due to climate change and the dynamics of the El Nino Southern Oscillation(ENSO).Droughts have increased in recent decades,~with the most severe and longest drought of the last millennium occurring since 2010 in central Chile.The impact of ongoing water scarcity is leading to significant drought-related declines in tree growth and forest dieback in the Mediterranean region.A deep understanding of how tree species respond to climate is crucial to accurately predict how forests will respond to climate change.We examined the growth responses to climate of three endemic and threatened tree species of the Mediterranean forests of central Chile,Nothofagus macrocarpa,Cryptocarya alba and Persea lingue,in a protected area.We observed that the growth of all three species was highly dependent on water availability and ENSO,and that the evergreen species C.alba and P.lingue increased their sensitivity to hydroclimate more than the deciduous species N.macrocarpa.These relationships were consistent across much of southern South America,highlighting the dependence of these species on water availability at large geographic scales.We found that there is a relationship between local water availability and ENSO that has intensified temporally and expanded geographically in recent decades.The xerophyllous species C.alba showed greater resistance and increasing resilience to severe droughts,while P.lingue and N.macrocarpa showed greater growth decline during droughts,possibly due to their preference for wetter environments.Our results highlight the crucial role of ENSO-driven water availability and drought in limiting tree growth and threatening the conservation of Mediterranean forests in central Chile.展开更多
Clouds play a major role in modulating the biometeorological processes. We studied the influence of cloudiness on four biometeorological variables:daily air temperature(Tair), relative humidity(RH),reference evapotran...Clouds play a major role in modulating the biometeorological processes. We studied the influence of cloudiness on four biometeorological variables:daily air temperature(Tair), relative humidity(RH),reference evapotranspiration(ETr),and photosynthetic active radiation(PAR), recorded at four sites of Andean Páramos in southern Ecuador during 2.5 to 5.5 years. First, we quantified both the cloud cover percentage(Cloud%) creating cloud masks over the visible bands of Landsat 7 images and the sky condition(K_(T)) using the records of solar and extraterrestrial radiation. Second, we estimated KTfrom Cloud%. Finally, we quantified T_(air), RH, ET_(r), and PAR under clear, cloudy, and overcast K_(T) and their dependence on KT. The average Cloud% ranged between 65%–76%, and KTcorroborated the prevailing overcast sky(between 55% and 72.5% of the days) over the páramos. The proposed model performed well in the sites of calibration(R^(2)= 0.80;MBE = 0.00;RMSE = 0.05) and validation(R^(2)= 0.74;MBE =-0.07;RMSE = 0.11). The overcast sky diminished T_(air)(≤ 10℃), ET_(r)(≤ 1.6 mm day-1), and PAR(4 MJ m^(-2)day^(-1)) and increased RH(≥ 88%),while the variables showed the opposite behavior during the uncommon clear sky(≤ 5.5% of the days).Thus, mostly the dynamic of RH(R^(2)≥ 0.62), ETr(R^(2)≥ 0.85), and PAR(R2≥ 0.77) depended on K_(T). Hence,the prevailing overcast sky influenced the biometeorology of the páramos.展开更多
The understanding of unsaturated flow in heterogeneous formations is a prerequisite to the understanding of pollutant transfer in the vadose zone and the proper management of infiltration basins settled over such hete...The understanding of unsaturated flow in heterogeneous formations is a prerequisite to the understanding of pollutant transfer in the vadose zone and the proper management of infiltration basins settled over such heterogeneous formations. This study addresses the effect of lithological heterogeneity of a glaciofluvial deposit on flow in the vadose zone underneath an infiltration basin settled in the Lyon suburbs. The basin had already been the subject of several previous studies, some of which demonstrated the impact of soil heterogeneity. But all of them were only based on the sedimentological study of a trench and no study addressed the potential spatial variability of results due to the spatial variability of soil heterogeneity. In this study, we model flow in the vadose zone for several case studies, including drainage, water infiltration during a rainfall event, and a complete meteorological chronic. These calculations were conducted for several sections, previously characterized in the basin using GPR and sedimentological study and compared with a blank (homogeneous section). The results clearly show that heterogeneity impacts unsaturated flow and that these impacts depend upon the section considered. Some geometrical architectural and textural parameters were proposed to explain the spatial variability and effect of the soil heterogeneity on unsaturated flow, thus establishing the first step towards modeling unsaturated flow in the basin at the meso-scale.展开更多
Many parameters are usually used as gauges to describe water quality worldwide, such as the concentrations of phosphorus, forms of nitrogen, dissolved oxygen (DO), among others. Though legislative limits for the conce...Many parameters are usually used as gauges to describe water quality worldwide, such as the concentrations of phosphorus, forms of nitrogen, dissolved oxygen (DO), among others. Though legislative limits for the concentrations of these substances are in place, such is not the case for caffeine. Caffeine is a pharmacologically active alkaloid, from the xanthine group, which can be used as a chemical tracer for anthropic influence over water resources. The objective of this study was to analyze the pollution indicators over the Igua?u River, one of the main rivers in Southern Brazil, through the examination of nutrients, DO and their correlations to caffeine. The water samples were collected from 10 sampling sites along the river course, unevenly spaced to better represent the different environmental scenarios present in its basin, extracted from 2014 to 2017. Caffeine was detected and quantified through high-efficiency liquid state chromatography. Results show that both nutrient and caffeine concentrations increased in intensely urbanized areas, specially from IG2 to IG5 sampling sites. Downstream from IG6 the contaminant concentrations decreased mainly due to higher river flows and lower population density. Caffeine was detected in 82% of the samples, indicating that most of the sampling sites were under anthropic influence.展开更多
The city of S?o Paulo, state of S?o Paulo/Brazil, with about 12 million inhabitants is considered the largest city in Latin America. Just as in other large metropolises it is devoid of green areas, in this way it is o...The city of S?o Paulo, state of S?o Paulo/Brazil, with about 12 million inhabitants is considered the largest city in Latin America. Just as in other large metropolises it is devoid of green areas, in this way it is of great socio-environmental importance of the preservation and maintenance of parks and green areas of the municipality. The Fernando Costa Park, known as the Parque da água Branca, is an urban park located in the central region of the Municipality of S?o Paulo, and has more than 79 thousand m2 of green area, in a total area of 137 thousand m2. Two lakes, populated predominantly with carp, are inserted in the Park, and are important components of the urban landscape and the patrimony of the city, present landscape function (scenic beauty) and are used to contemplate the environment and leisure of the population. The lakes due to the intense eutrophication process with uncontrolled growth of the phytoplankton presented blue-green coloration, with formations of lumps and foams, low transparency, bad smell and unpleasant visual aspect impairing the visitation of this place. In the first stage of the present research, an environmental diagnosis was carried out and the second stage involved elaboration and implementation of mitigating measures aiming at its restoration. The recovery proposal included the implementation of Artificial Floating Islands (IFAs) aiming at pollution control. After 60 days, it was possible to observe the efficiency of the Eichhornia crassipes populated islands showing that the methodology of phytoremediation was efficient in controlling the eutrophication of urban lakes, guaranteeing the recovery and conservation of the scenic beauty of these places.展开更多
A set of 15 combinations of microphysics and cumulus parameterizations for the WRF numerical model were tested in the forecast of a rain event on January 16 2018 over Panama. GPM satellite, upper air soundings and gro...A set of 15 combinations of microphysics and cumulus parameterizations for the WRF numerical model were tested in the forecast of a rain event on January 16 2018 over Panama. GPM satellite, upper air soundings and ground weather stations were used to evaluate the performance of each configuration. Different metrics were used to obtain the configurations that produced the best forecasts. The analysis showed a strong fluctuation of the diurnal precipitation cycle from one region to another. From the set of tests carried, BMJ with Morrison performed slightly above the other combinations in representing well the diurnal cycle for some domain areas, followed by Thom-Gr, WSM6-BMJ and WSM6-KF. While the experiments had a better performance forecasting over sea, they were not able to match the highest values of total precipitation. Regarding spatial rain distribution, all BMJ cumulus combinations showed the best skills mainly over the area comprising the Panama Canal while the others tended to overestimate the rain. Finally, most BMJ experiments showed the highest correlation factor and performed quite well representing the vertical profiles of relative humidity, temperature and wind.展开更多
Brazil is responsible for 27% of the world production of soybeans and 7% of maize. Mato Grosso and Para states in Brazil are among the largest producer. The viability to the cultivation of maize (Zea mays) and soybean...Brazil is responsible for 27% of the world production of soybeans and 7% of maize. Mato Grosso and Para states in Brazil are among the largest producer. The viability to the cultivation of maize (Zea mays) and soybeans (Glycine max), for future climate scenarios (2070-2100, GHG) is evaluated based on crop modeling (DSSAT) forced by observational data and regional climate simulations (HadRM3). The results demonstrated that a substantial reduction in the yield in particular for maize may be expected for the end of the 21st century. Distinct results are found for soybeans. By applying the A2 climate changes scenario, soybean yield rises by up top 60% assuming optimum soil treatment and no water stress. However, by analyzing the inter-annual variability of crop yields for both maize and soybean, could be demonstrated larger year-to-year fluctuations under greenhouse warming conditions as compared to current conditions, leading to very low productivity by the end of the 21st century. Therefore, these Brazilian states do not appear to be economically suitable for a future cultivation of maize and soybeans. Improved adaptation measures and soil management may however partially alleviate the negative climate change effect.展开更多
This paper addresses the modeling of fracture in quasi-brittle materials using a phase-field approach to the description of crack topol-ogy.Within the computational mechanics community,several studies have treated the...This paper addresses the modeling of fracture in quasi-brittle materials using a phase-field approach to the description of crack topol-ogy.Within the computational mechanics community,several studies have treated the issue of modeling fracture using phase fields.Most of these studies have used an approach that implies the lack of a damage threshold.We herein explore an alternative model that includes a damage threshold and study how it compares with the most popular approach.The formulation is systematically explained within a rigorous variational framework.Subsequently,we present the corresponding three-dimensional finite element discretization that leads to a straightforward numerical implementation.Benchmark simulations in two dimensions and three dimensions are then presented.The results show that while an elastic stage and a damage threshold are ensured by the present model,good agreement with the results reported in the literature can be obtained,where such features are generally absent.展开更多
基金funded by Gobierno de Chile with the project“An atlas of droughts for Chile:1000 years of space-time changes and variations throughout the territory”(grant number FONDECYT 1181956).
文摘The Mediterranean region in central Chile is experiencing a significant decrease in precipitation due to climate change and the dynamics of the El Nino Southern Oscillation(ENSO).Droughts have increased in recent decades,~with the most severe and longest drought of the last millennium occurring since 2010 in central Chile.The impact of ongoing water scarcity is leading to significant drought-related declines in tree growth and forest dieback in the Mediterranean region.A deep understanding of how tree species respond to climate is crucial to accurately predict how forests will respond to climate change.We examined the growth responses to climate of three endemic and threatened tree species of the Mediterranean forests of central Chile,Nothofagus macrocarpa,Cryptocarya alba and Persea lingue,in a protected area.We observed that the growth of all three species was highly dependent on water availability and ENSO,and that the evergreen species C.alba and P.lingue increased their sensitivity to hydroclimate more than the deciduous species N.macrocarpa.These relationships were consistent across much of southern South America,highlighting the dependence of these species on water availability at large geographic scales.We found that there is a relationship between local water availability and ENSO that has intensified temporally and expanded geographically in recent decades.The xerophyllous species C.alba showed greater resistance and increasing resilience to severe droughts,while P.lingue and N.macrocarpa showed greater growth decline during droughts,possibly due to their preference for wetter environments.Our results highlight the crucial role of ENSO-driven water availability and drought in limiting tree growth and threatening the conservation of Mediterranean forests in central Chile.
基金National Science Foundation of the United States of America through“A research network for the resilience of headwater systems and water availability for downstream communities across the Americas”funded by the Vice-rectorate for Research of the University of Cuenca。
文摘Clouds play a major role in modulating the biometeorological processes. We studied the influence of cloudiness on four biometeorological variables:daily air temperature(Tair), relative humidity(RH),reference evapotranspiration(ETr),and photosynthetic active radiation(PAR), recorded at four sites of Andean Páramos in southern Ecuador during 2.5 to 5.5 years. First, we quantified both the cloud cover percentage(Cloud%) creating cloud masks over the visible bands of Landsat 7 images and the sky condition(K_(T)) using the records of solar and extraterrestrial radiation. Second, we estimated KTfrom Cloud%. Finally, we quantified T_(air), RH, ET_(r), and PAR under clear, cloudy, and overcast K_(T) and their dependence on KT. The average Cloud% ranged between 65%–76%, and KTcorroborated the prevailing overcast sky(between 55% and 72.5% of the days) over the páramos. The proposed model performed well in the sites of calibration(R^(2)= 0.80;MBE = 0.00;RMSE = 0.05) and validation(R^(2)= 0.74;MBE =-0.07;RMSE = 0.11). The overcast sky diminished T_(air)(≤ 10℃), ET_(r)(≤ 1.6 mm day-1), and PAR(4 MJ m^(-2)day^(-1)) and increased RH(≥ 88%),while the variables showed the opposite behavior during the uncommon clear sky(≤ 5.5% of the days).Thus, mostly the dynamic of RH(R^(2)≥ 0.62), ETr(R^(2)≥ 0.85), and PAR(R2≥ 0.77) depended on K_(T). Hence,the prevailing overcast sky influenced the biometeorology of the páramos.
文摘The understanding of unsaturated flow in heterogeneous formations is a prerequisite to the understanding of pollutant transfer in the vadose zone and the proper management of infiltration basins settled over such heterogeneous formations. This study addresses the effect of lithological heterogeneity of a glaciofluvial deposit on flow in the vadose zone underneath an infiltration basin settled in the Lyon suburbs. The basin had already been the subject of several previous studies, some of which demonstrated the impact of soil heterogeneity. But all of them were only based on the sedimentological study of a trench and no study addressed the potential spatial variability of results due to the spatial variability of soil heterogeneity. In this study, we model flow in the vadose zone for several case studies, including drainage, water infiltration during a rainfall event, and a complete meteorological chronic. These calculations were conducted for several sections, previously characterized in the basin using GPR and sedimentological study and compared with a blank (homogeneous section). The results clearly show that heterogeneity impacts unsaturated flow and that these impacts depend upon the section considered. Some geometrical architectural and textural parameters were proposed to explain the spatial variability and effect of the soil heterogeneity on unsaturated flow, thus establishing the first step towards modeling unsaturated flow in the basin at the meso-scale.
文摘Many parameters are usually used as gauges to describe water quality worldwide, such as the concentrations of phosphorus, forms of nitrogen, dissolved oxygen (DO), among others. Though legislative limits for the concentrations of these substances are in place, such is not the case for caffeine. Caffeine is a pharmacologically active alkaloid, from the xanthine group, which can be used as a chemical tracer for anthropic influence over water resources. The objective of this study was to analyze the pollution indicators over the Igua?u River, one of the main rivers in Southern Brazil, through the examination of nutrients, DO and their correlations to caffeine. The water samples were collected from 10 sampling sites along the river course, unevenly spaced to better represent the different environmental scenarios present in its basin, extracted from 2014 to 2017. Caffeine was detected and quantified through high-efficiency liquid state chromatography. Results show that both nutrient and caffeine concentrations increased in intensely urbanized areas, specially from IG2 to IG5 sampling sites. Downstream from IG6 the contaminant concentrations decreased mainly due to higher river flows and lower population density. Caffeine was detected in 82% of the samples, indicating that most of the sampling sites were under anthropic influence.
文摘The city of S?o Paulo, state of S?o Paulo/Brazil, with about 12 million inhabitants is considered the largest city in Latin America. Just as in other large metropolises it is devoid of green areas, in this way it is of great socio-environmental importance of the preservation and maintenance of parks and green areas of the municipality. The Fernando Costa Park, known as the Parque da água Branca, is an urban park located in the central region of the Municipality of S?o Paulo, and has more than 79 thousand m2 of green area, in a total area of 137 thousand m2. Two lakes, populated predominantly with carp, are inserted in the Park, and are important components of the urban landscape and the patrimony of the city, present landscape function (scenic beauty) and are used to contemplate the environment and leisure of the population. The lakes due to the intense eutrophication process with uncontrolled growth of the phytoplankton presented blue-green coloration, with formations of lumps and foams, low transparency, bad smell and unpleasant visual aspect impairing the visitation of this place. In the first stage of the present research, an environmental diagnosis was carried out and the second stage involved elaboration and implementation of mitigating measures aiming at its restoration. The recovery proposal included the implementation of Artificial Floating Islands (IFAs) aiming at pollution control. After 60 days, it was possible to observe the efficiency of the Eichhornia crassipes populated islands showing that the methodology of phytoremediation was efficient in controlling the eutrophication of urban lakes, guaranteeing the recovery and conservation of the scenic beauty of these places.
文摘A set of 15 combinations of microphysics and cumulus parameterizations for the WRF numerical model were tested in the forecast of a rain event on January 16 2018 over Panama. GPM satellite, upper air soundings and ground weather stations were used to evaluate the performance of each configuration. Different metrics were used to obtain the configurations that produced the best forecasts. The analysis showed a strong fluctuation of the diurnal precipitation cycle from one region to another. From the set of tests carried, BMJ with Morrison performed slightly above the other combinations in representing well the diurnal cycle for some domain areas, followed by Thom-Gr, WSM6-BMJ and WSM6-KF. While the experiments had a better performance forecasting over sea, they were not able to match the highest values of total precipitation. Regarding spatial rain distribution, all BMJ cumulus combinations showed the best skills mainly over the area comprising the Panama Canal while the others tended to overestimate the rain. Finally, most BMJ experiments showed the highest correlation factor and performed quite well representing the vertical profiles of relative humidity, temperature and wind.
基金This study has been sponsored by the National Institute of Science and Technology Climate Change and by the SoCoCA project funded by the Research Council of Norway(contract 190159)Moreover support has been provided by the sub-rede Agricultura do MCTI and by the INCT-Mudanças Climáticas.
文摘Brazil is responsible for 27% of the world production of soybeans and 7% of maize. Mato Grosso and Para states in Brazil are among the largest producer. The viability to the cultivation of maize (Zea mays) and soybeans (Glycine max), for future climate scenarios (2070-2100, GHG) is evaluated based on crop modeling (DSSAT) forced by observational data and regional climate simulations (HadRM3). The results demonstrated that a substantial reduction in the yield in particular for maize may be expected for the end of the 21st century. Distinct results are found for soybeans. By applying the A2 climate changes scenario, soybean yield rises by up top 60% assuming optimum soil treatment and no water stress. However, by analyzing the inter-annual variability of crop yields for both maize and soybean, could be demonstrated larger year-to-year fluctuations under greenhouse warming conditions as compared to current conditions, leading to very low productivity by the end of the 21st century. Therefore, these Brazilian states do not appear to be economically suitable for a future cultivation of maize and soybeans. Improved adaptation measures and soil management may however partially alleviate the negative climate change effect.
文摘This paper addresses the modeling of fracture in quasi-brittle materials using a phase-field approach to the description of crack topol-ogy.Within the computational mechanics community,several studies have treated the issue of modeling fracture using phase fields.Most of these studies have used an approach that implies the lack of a damage threshold.We herein explore an alternative model that includes a damage threshold and study how it compares with the most popular approach.The formulation is systematically explained within a rigorous variational framework.Subsequently,we present the corresponding three-dimensional finite element discretization that leads to a straightforward numerical implementation.Benchmark simulations in two dimensions and three dimensions are then presented.The results show that while an elastic stage and a damage threshold are ensured by the present model,good agreement with the results reported in the literature can be obtained,where such features are generally absent.
