Temperature and precipitation extremes in the United States: Quantifying the responses to anthropogenic aerosols and greenhouse gases

Changes in extreme temperatures, heat waves, heavy rainfall events, and precipitation frequency can have adverse impacts on human health, air quality, agricultural productivity, and water resources. Using the aerosol only (AER) and greenhouse gas only (GHG) "single forcing" simulations (3 ensemble members each) from the GFDL CM3 chemistry-climate model, we investigate aerosol- versus greenhouse gas-induced changes in high temperature and precipitation extremes over the United States. We identify changes in these events from 1860 to 2005 and the associated large-scale dynamical conditions. Small changes in these extremes in the "all forcing" simulations reflect cancellations between the individual, opposite-signed effects of increasing anthropogenic aerosols and greenhouse gases. In AER, aerosols lead to lower extreme high temperatures and fewer warm spells over the western US (-2.1 K regional average; -20 days/year) and over the central and northeast US (-1.5 K; -12 days/year). In GHG, a similar but opposite-signed response pattern occurs (+2.7 K and +14 days/year over the western US; +2.5 K and +10 days/year in the central and northeast US). The similar spatial response patterns in AER versus GHG suggest a preferred regional mode of response that is largely independent of the regional distribution of the forcing agent. The influence of both greenhouse gases and aerosols on extreme high temperature is weakest in the southeast US, collocated with the observed "warming hole". No statistically significant change occurs in AER, and a warming of only +1.8 K occurs in GHG. Warming in this region continues to be muted over the 21st century under the RCP 8.5 scenario, with increases in extreme temperatures more than 1 K smaller than elsewhere. Aerosols induce decreases in the number of days per year with at least 10mm of precipitation (R10mm) over the eastern US in summer and winter and over the southern US in spring of roughly 1 day/year. In contrast, greenhouse gases induce increases in R10mm over the eastern US in winter (+0.8 days/year), the northern and central US during spring (+1 day/year), and the southeast US during summer (+0.5 days/year), but decreases over the northeast US in summer (-0.2 days/year). In RCP 8.5, the patterns of extreme temperature and precipitation associated with greenhouse gas forcing dominate

Stratospheric ozone depletion: a key driver of recent precipitation trends in South Eastern South America

On a hemispheric scale, it is now well established that stratospheric ozone depletion has been the principal driver of externally forced atmospheric circulation changes south of the Equator in the last decades of the 20th Century. The impact of ozone depletion has been felt over the entire hemisphere, as reflected in the poleward drift of the midlatitude jet, the southward expansion of the summertime Hadley cell and accompanying precipitation trends deep into the subtropics. On a regional scale, however, surface impacts directly attributable to ozone depletion have yet to be identified. In this paper we focus on South Eastern South America (SESA), a region that has exhibited one of the largest wetting trends during the 20th Century. We study the impact of ozone depletion on SESA precipitation using output from 6 different climate models, spanning a wide range of complexity. In all cases we contrast pairs of model integrations with and without ozone depletion, but with all other forcings identically specified. This allows for unambiguous attribution of the computed precipitation trends. All 6 climate models consistently reveal that stratospheric ozone depletion results in a significant wetting of SESA over the period 1960–1999. Taken as a whole, these model results strongly suggest that the impact of ozone depletion on SESA precipitation has been as large as, and quite possibly larger than, the one caused by increasing greenhouse gases over the same period

Stratospheric Ozone Depletion: The Main Driver of Twentieth-Century Atmospheric Circulation Changes in the Southern Hemisphere

The importance of stratospheric ozone depletion on the atmospheric circulation of the troposphere is studied with an atmospheric general circulation model, the Community Atmospheric Model, version 3 (CAM3), for the second half of the twentieth century. In particular, the relative importance of ozone depletion is contrasted with that of increased greenhouse gases and accompanying sea surface temperature changes. By specifying ozone and greenhouse gas forcings independently, and performing long, time-slice integrations, it is shown that the impacts of ozone depletion are roughly 2–3 times larger than those associated with increased greenhouse gases, for the Southern Hemisphere tropospheric summer circulation. The formation of the ozone hole is shown to affect not only the polar tropopause and the latitudinal position of the midlatitude jet; it extends to the entire hemisphere, resulting in a broadening of the Hadley cell and a poleward extension of the subtropical dry zones. The CAM3 results are compared to and found to be in excellent agreement with those of the multimodel means of the recent Coupled Model Intercomparison Project (CMIP3) and Chemistry–Climate Model Validation (CCMVal2) simulations. This study, therefore, strongly suggests that most Southern Hemisphere tropospheric circulation changes, in austral summer over the second half of the twentieth century, have been caused by polar stratospheric ozone depletion

Modeling Evidence that Ozone Depletion Has Impacted Extreme Precipitation in the Austral Summer

The impacts of stratospheric ozone depletion on the extremes of daily precipitation in the austral summer are explored using two global climate models. Both models indicate that stratospheric ozone losses since the late 1970s may have increased the frequency and intensity of very heavy precipitation in austral summer over southern high and subtropical latitudes, and may have decreased the frequency and intensity over southern midlatitudes. This hemispheric wide pattern of extreme precipitation response projects strongly onto a previously identified pattern of seasonal mean precipitation response, both of which are shown to be likely of dynamic rather than thermodynamic origin

INTERVENCIONES URBANAS: EXPERIENCIA ACADÉMICA EN EL DESARROLLO DE PROYECTOS ESTRATÉGICOS

El desarrollo de ejercicios de intervención urbano arquitectónica desarrollado por alumnos y docentes de Taller IX durante el primer semestre de 2007 en ciertos sectores de la ciudad de Medellín, con motivo de la convocatoria realizada por la Alcaldía Municipal y la Empresa de Desarrollo Urbano – EDU, se ha constituido en la base para el establecimiento de puntos de contacto entre la rigurosidad de la interpretación y reflexión académica, con los reales procesos de intervención en la ciudad, se abre un espacio de reconocimiento de la actividad académica desarrollada en el ámbito regional y proyectada en el contexto nacional, y experimenta una forma de acercamiento a la realidad cotidiana de la ciudad y a las más recientes formas de gestión y planificación territorial desarrolladas en el país.ABSTRACTThe Academy has been leading a debate about urban interventions in the most affected areas and also the areas with a potential re-development and those with a possibility to become part of the urban fabric. The debate has been constituted as a assessment between a radical interpretation and an academic analysis taking actual urban intervention processes leaded by architectural students, the community and the strategic projects which started the urban transformation processes

Mid-21st century ozone air quality and health burden in China under emissions scenarios and climate change

Despite modest emissions reductions of air pollutants in recent years, China still suffers from poor air quality, and the outlook for future air quality in China is uncertain. We explore the impact of two disparate 2050 emissions scenarios relative to 2015 in the context of a changing climate with the Geophysical Fluid Dynamics Laboratory Atmospheric Model version 3 (GFDL-AM3) chemistry-climate model. We impose the same near-term climate change for both emission scenarios by setting global sea surface temperature (SST) and sea ice cover (SIC) to the average over 2010–2019 and 2046–2055, respectively, from a three-member ensemble of GFDL coupled climate model simulations under the RCP8.5 (Representative Concentration Pathway) scenario. By the 2050s, annual mean surface ozone increases throughout China by up to 8 ppbv from climate change alone (estimated by holding air pollutants at 2015 levels while setting SIC and SST to 2050 conditions in the model) and by 8–12 ppbv in a scenario in which emissions of ozone precursors nitrogen oxides (NO x ) and anthropogenic volatile organic compounds (VOCs) increase by ~10%. In a scenario in which NO x and anthropogenic VOC emissions decline by 60%, annual mean surface ozone over China decreases by 16–20 ppbv in the 2050s relative to the 2010s. The ozone increase from climate change alone results in an additional 62 000 premature deaths in China as compared to 330 000 fewer premature deaths by the 2050s under a strong emissions mitigation scenario. In springtime over Southwestern China in the 2050s, the model projects 9–12 ppbv enhancements to surface ozone from the stratosphere (diagnosed with a model tracer) and from international anthropogenic emissions (diagnosed by differencing AM3 simulations with the same emissions within China but higher versus lower emissions in the rest of the world). Our findings highlight the effectiveness of emissions controls in reducing the health burden in China due to air pollution, and also the potential for climate change and rising global emissions to offset, at least partially, some of the ozone decreases attained with regional emission reductions in China

Caracterización de películas de mezclas de polihidroxibutirato con policaprolactona reforzadas con organomontmorillonitas con distinto espaciado interlaminar

Continuando con investigaciones anteriores, en este trabajo se realiza el análisis de las variaciones inducidas por la modificación en la cantidades relativas de los polímeros biodegradables: policaprolactona (PCL) y polihidroxibutirato (PHB) en las características mecánicas, térmicas y dieléctricas de películas producidas a partir de mezclas de ambos polímeros reforzadas con organoarcillas (OMMT) que presentan distinto espaciado interlaminar. En trabajos previos hemos determinado que: la inclusión de las OMMT comerciales Cloisite 30B® (CB30), Cloisite15A® (C15A) y Cloisite93A® (C93A) en películas de mezclas 50/50 de estos polímeros modifica la morfología de la mezcla, mejora la resistencia a la tracción, aumenta la elasticidad y disminuye la permeabilidad del oxígeno. En este trabajo hemos encarado la caracterización de películas obtenidas a partir de mezclas de los mismos polímeros pero en distinta proporción PHB 20% y PCL 80%, en adelante 20/80, pura y reforzadas mediante la inclusión de las OMMT mencionadas. Las muestras producidas fueron analizadas mediante dispersión de rayos X de alto (WAXS) y bajo (SAXS) ángulo y microscopia electrónica de barrido (SEM). Se estudiaron además sus propiedades mecánicas y dieléctricas. Se presentan los resultados y se comparan con los obtenidos previamente para las muestras 50/50.Sección: Ciencias Básicas.Facultad de Ingenierí

Obtención y caracterización de nanocompuestos basados en mezclas de polímeros biodegradables y arcillas orgánicamente modificadas

Se desarrollaron compuestos de matriz polimérica biodegradable mediante mezclado en fundido de mezclas Polihidroxibutirato (PHB)/Policaprolactona (PCL) en porcentaje 50/50 p/p y montmorillonitas comerciales Cloisite ® modificadas con diversos modificadores orgánicos (órgano-arcillas C15A, 93A y 30B) al 5% p/p. A partir de estos compuestos se obtuvieron películas por termo-compresión (165 ºC, 100 bar de presión). Las respuestas SAXS y WAXS de todas las películas muestran expansión de la distancia interlaminar de las órganoarcillas (OMMT) indicando ingreso de cadenas poliméricas en las galerías de las arcillas, y también permiten suponer un grado importante de exfoliación o intercalación en las OMMT cuyo potencial Zeta es más elevado. Los ensayos de tracción muestran que la adición de arcillas produjo un efecto rigidizante en todas las matrices dado por el incremento en el módulo de young (E) de los compuestos comparado con las matrices sin arcillas. Medidas dieléctricas mostraron un incremento de hasta aproximadamente 8 unidades en la constante dieléctrica para frecuencias inferiores a 1 Hz respecto del valor observado a altas frecuencias, en las muestras con inclusión de 30B y 15A.Publicado en Terceras Jornadas de Investigación, Transferencia y Extensión. La Plata : Universidad Nacional de La Plata, 2015.Facultad de Ingenierí

Obtención y caracterización de nanocompuestos basados en mezclas de polímeros biodegradables y arcillas orgánicamente modificadas

Se desarrollaron compuestos de matriz polimérica biodegradable mediante mezclado en fundido de mezclas Polihidroxibutirato (PHB)/Policaprolactona (PCL) en porcentaje 50/50 p/p y montmorillonitas comerciales Cloisite ® modificadas con diversos modificadores orgánicos (órgano-arcillas C15A, 93A y 30B) al 5% p/p. A partir de estos compuestos se obtuvieron películas por termo-compresión (165 ºC, 100 bar de presión). Las respuestas SAXS y WAXS de todas las películas muestran expansión de la distancia interlaminar de las órganoarcillas (OMMT) indicando ingreso de cadenas poliméricas en las galerías de las arcillas, y también permiten suponer un grado importante de exfoliación o intercalación en las OMMT cuyo potencial Zeta es más elevado. Los ensayos de tracción muestran que la adición de arcillas produjo un efecto rigidizante en todas las matrices dado por el incremento en el módulo de young (E) de los compuestos comparado con las matrices sin arcillas. Medidas dieléctricas mostraron un incremento de hasta aproximadamente 8 unidades en la constante dieléctrica para frecuencias inferiores a 1 Hz respecto del valor observado a altas frecuencias, en las muestras con inclusión de 30B y 15A.Publicado en Terceras Jornadas de Investigación, Transferencia y Extensión. La Plata : Universidad Nacional de La Plata, 2015.Facultad de Ingenierí