Cambio climático : mito o realidad

Fil: Solman, Silvina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Dpto. de Ciencias de la Atmósfera y los Océanos; Argentina.En los últimos dos siglos, a partir de la revolución industrial, la utilización de los combustibles fósiles\ncomo la principal fuente de energía de la humanidad ha provocado un notable incremento en la\nconcentración de dióxido de carbono en la atmósfera. Este aumento está provocando cambios en el\nclima en el orden global. Las consecuencias de estas transformaciones, provocadas por la actividad\ndel hombre, pueden ser muy graves ya que afectan la producción mundial de alimentos, la salud y\nhasta la propia existencia de algunos Estados. ¿Qué puede pasar con el clima del planeta en los\npróximos 100 años?

Actividad humana y cambio climático

Síntesis de la opinión aceptada por la mayoría de los científicos que estudiaron el cambio del clima de la Tierra en el último siglo y medio.Fil: Solman, Silvina Alicia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmosfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmosfera; Argentin

Systematic temperature and precipitation biases in the CLARIS-LPB ensemble simulations over South America and possible implications for climate projections

Within the framework of the CLARIS-LPB EU Project, a suite of 7 coordinated Regional Climate Model (RCM) simulations over South America driven by both the ERA-Interim reanalysis and a set of Global Climate Models (GCMs) were evaluated. The systematic biases in simulating monthly mean temperature and precipitation from the 2 sets of RCM simulations were identified. The Climate Research Unit dataset was used as a reference. The systematic model errors were more dependent on the RCMs than on the driving GCMs. Most RCMs showed a systematic temperature overestimation and precipitation underestimation over the La Plata Basin region. Model biases were not invariant, but a temperature-dependent temperature bias and a precipitation-dependent precipitation bias were apparent for the region, with the warm bias amplified for warm months and the dry bias amplified for wet months. In a climate change scenario, the relationship between model bias behaviour and the projected climate change for each individual model revealed that the models with the largest temperature bias amplification projected the largest warming and the models with the largest dry bias amplification projected the smallest precipitation increase, suggesting that models’ bias behaviour may affect the future climate projections. After correcting model biases by means of a quantile-based mapping bias correction method, projected temperature changes were systematically reduced, and projected precipitation changes were systematically increased. Though applying bias correction methodologies to projected climate conditions is controversial, this study demonstrates that bias correction methodologies should be considered in order to better interpret climate change signals.Fil: Solman, Silvina Alicia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmosfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmosfera; Argentin

Regional Climate Modeling over South America: A Review

This review summarizes the progress achieved on regional climate modeling activities over South America since the early efforts at the beginning of the 2000s until now. During the last 10 years, simulations with regional climate models (RCMs) have been performed for several purposes over the region. Early effortsweremainly focused on sensitivity studies to both physicalmechanisms and technical aspects of RCMs. The last developments were focused mainly on providing   high-resolution information on regional climate change. This paper describes the most outstanding contributions fromthe isolated efforts to  the ongoing coordinated RCM activities in the framework of the CORDEX initiative, which represents a major endeavor to produce ensemble climate change projections at regional scales and allows exploring the associated range of uncertainties. The remaining challenges in modeling South American climate features are also discussed.Fil: Solman, Silvina Alicia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera; Argentin

Subpolar High Anomaly Preconditioning Precipitation over South America

The mechanisms associated with the intraseasonal variability of precipitation over South America during the spring season are investigated with emphasis on the influence of a quasi-stationary anomalous circulation over the southeastern South Pacific Ocean (SEP). A spectral analysis performed to the bandpass- filtered time series of daily precipitation anomalies for the La Plata Basin (LPB) and the South Atlantic convergence zone (SACZ) regions revealed several statistically relevant peaks corresponding to periods of roughly 23 days and 14–16 days—the lower (higher) frequency peaks more prevalent for the SACZ (LPB). The large-scale circulation patterns preconditioning precipitation variability over both regions were explored by means of a regression analysis performed on the daily 500-hPa geopotential anomaly field provided by the NCEP–NCAR reanalysis dataset. The most prominent feature of the regression fields is the presence of a quasi-stationary anomalous anticyclonic (cyclonic) circulation over the southeastern South Pacific Ocean associated with positive rainfall anomalies over the LPB (SACZ) and, emanating from that high (low), an external Rossby wave propagating northeastward toward the South American continent. The synoptic-scale activity, quantified in terms of a frontal activity index, showed a strong influence on precipitation over the LPB and to a lesser extent over the SACZ. Moreover, the frontal activity is actually modulated by the anomalous high circulation over the SEP region. The behavior of this anomalous circulation may be supported by a positive feedback mechanism that can enhance the response of the high anomaly itself, which in turns reinforces the Rossby wave train propagating toward the South American continent.Fil: Solman, Silvina Alicia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmosfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmosfera; ArgentinaFil: Orlanski, Isidoro. University of Princeton; Estados Unido

Impacts of land use changes over southern South American climate: a modeling study using the MM5 regional model

La Plata Basin (LPB) and the Argentinean Pampas are two of the most important agricultural regions in the world. In the last decades the areas devoted to agriculture over these regions have been extended at the expense of deforestation and replacement of natural pastures. Land use/land cover changes (hereafter LULCC) may modify the exchanges of energy and moisture between the land surface and the atmosphere due to the control that land surface exerts on the partitioning of available energy at the surface between sensible and latent heat fluxes and the available water between evaporation and runoff. Besides that, the surface heterogeneity not only determines the microclimate but also affects mesoscale atmospheric circulations (Hartmann, 1994; Weaver and Avissar, 2001; Yang, 2004; Sertel et al., 2010).Fil: Pessacg, Natalia Liz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmosfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmosfera; ArgentinaFil: Solman, Silvina Alicia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmosfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmosfera; Argentin

Ciclo energético de ondas planetarias en el Hemisferio Sur

Con el fin de analizar los procesos que se llevan a cabo durante el desarrollo de la inestabilidad barocllnica, se estudid la evolución no lineal de perturbaciones baroclinicas que se desarrollan en el seno de un flujo zonal baroclinicamente inestable. El ciclo energético asociado a las perturbaciones puso de manifiesto el desarrollo de un ciclo principal y ciclos secundarios. El ciclo principal estd caracterizado por la conversión de energía potencial a energía cinética, amortiguado por procesos barotrópicos, cuyo efecto se incrementa durante la etapa de decaimiento de la perturbación. Durante el desarrollo del sistema se produce el desdoblamiento de la zona baroclínica inicial en dos bandas baroclínicas, asociadas a dos jets, o corrientes en chorro, baroclínicos. La banda subtropical mantiene un gradiente térmico meridional intenso y, en consecuencia, una cortante vertical del flujo zonal intensa. La banda polar está asociada a la parte ocluida del sistema frontal y presenta una estructura barotrópica. El jet asociado, el jet Polar, es muy intenso y tiene asociada una cortante meridional importante. El transporte meridional de cantidad de movimiento que se establece durante el desarrollo de la inestabilidad baroclínica es hacia el Polo con un máximo en capas altas y un máximo secundario cercano a superficie, centrado en la latitud donde se ubica el corazón del jet inicial. Esta configuración induce una aceleración del flujo zonal hacia el Polo, por convergencia de flujo de cantidad de movimiento y una desaceleración hacia el Ecuador, por divergencia de flujo de cantidad de movimiento, que contribuye a la formación de estes en capas bajas. Durante el desarrollo de los ciclos secundarios las perturbaciones crecen barotrópicamente. Este comportamiento está asociado con el desarrollo de cortantes meridionales inestables en el flanco polar de los jets. Se evaluó la sensibilidad del desarrollo del sistema baroclínico a factores tales como la fricción superficial y la presencia de una componente barotrópica superpuesta al flujo zonal inicial. Los resultados obtenidos mostraron que durante la etapa de evolución no lineal del sistema baroclínico, la fricción superficial tiende a inhibir el desarrollo de la componente barotrópica, con lo cual, inhibe el desarrollo de la inestabilidad barotrópica durante los ciclos secundarios. Tanto la fricción superficial como la presencia de la componente barotrópica actúan como factores estabilizadores del desarrollo baroclínico.Fil:Solman, Silvina Alicia. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Temperature and precipitation biases in CORDEX RCM simulations over South America: possible origin and impacts on the regional climate change signal

Precipitation and temperature biases from a set of Regional Climate Models from the CORDEX initiative have been analysed to assess the extent to which the biases may impact the climate change signal. The analysis has been performed for the South American CORDEX domain. A large warm bias was found over central Argentina (CARG) for most models, mainly in the summer season. Results indicate that the possible origin of this bias is an overestimation of the incoming shortwave radiation, in agreement with an underestimation of the relative humidity at 850 hPa, a variable that could be used to diagnose cloudiness. Regarding precipitation, the largest biases were found during summertime over northeast of Brazil (NEB), where most models overestimate the precipitation, leading to wet biases over that region. This bias agrees with models’ underestimationof both the moisture flux convergence and the relative humidity at lower levels of the atmosphere. This outcome suggests that the generation of more clouds in the models may drive the wet bias over NEB. These systematic errors could affect the climate change signal, considering that these biases may not be stationary. For both CARG and NEB regions, models with higher warm biases project higher warming levels, mainly in the summer season. In addition, it was found that theserelationships are statistically significant with a confidence level of 95%, pointing out that biases are linearly linked with the climate change signal. For precipitation, the relationship between the biases and the projected precipitation changes is only statistically significant for the NEB region, where models with the largest wet biases present the greatest positive precipitation changes during the warm season. As in the case of biases, the analysis of the temperature and precipitation projections over some regions of South America suggests that clouds could affect them. The results found in this study point out that the analysis of the bias behaviour could help in a better interpretation of the climate change signal.Facultad de Ciencias Astronómicas y GeofísicasConsejo Nacional de Investigaciones Científicas y Técnica

Regional climate change scenarios over southern South America for future climate (2080-2099) using the MM5 Model. Mean, interannual variability and uncertainties

is work focuses on evaluating the climate change projected by the end of the 21st century under the SRES A2 emission scenario over southern South America using the regional model MM5. e model projects: (i) an increase of precipitation over central Argentina, Uruguay and southern Brazil during summer and fall; (ii) a decrease in precipitation over most of the study domain during winter and spring; (iii) an important decrease in precipitation over central and southern Chile, through the year. In general, the projected temperature increase depends on the season and the examined area; particularly, it is highest over tropical and subtropical latitudes in spring and over high latitudes in summer. e MM5 model projects: (i) an increase of the interanual precipitation variability of precipitation over central Argentina and Uruguay regardless the season; (ii) a slight decrease in interannual temperature variability over large extents of Argentina for summer and winter; (iii) a slight increase in interannual temperature variability at transition seasons; with highest values over central Chile in autumn and over north central Argentina in spring. From the reliability assessment of regional climate projections, it can be concluded that signal-to-noise ratio is high for temperature and low for precipitation. erefore, the MM5 model is a useful tool in the generation of regional climate change scenarios of high resolution over southern South America, particularly for temperature, and is a starting point to perform studies related to impacts of climate change.Este trabajo evalúa las proyecciones de cambio climático del modelo regional MM5 para fines del siglo veintiuno en el escenario de emisión SRES A2 en el sur de Sudamérica. El modelo proyecta: (i) aumento de la precipitación en el centro de Argentina, Uruguay y sur de Brasil en verano y otoño; (ii) disminución de la precipitación en la mayor parte de la región de estudio en invierno y primavera; (iii) marcada reducción de la precipitación en el centro y sur de Chile durante todo el año. En general, el aumento de temperatura proyectado depende de la época y la región examinada; particularmente es máximo en latitudes tropicales y subtropicales en primavera y en altas latitudes en verano. El modelo MM5 proyecta: (i) aumento de la variabilidad interanual de la precipitación en el centro de Argentina y Uruguay independientemente de la época del año; (ii) una leve disminución de la variabilidad interanual de la temperatura en la mayor parte de territorio argentino para verano e invierno; (iii) un leve aumento de la variabilidad interanual de la temperatura en las estaciones intermedias; con valores mayores en el centro de Chile en otoño y en el centro norte de Argentina en primavera. De la evaluación de cuán robustas son las proyecciones climáticas regionales, puede concluirse que la relación señal-ruido es alta para la temperatura y baja para la precipitación. Por lo tanto, el modelo MM5 es una herramienta de mucha utilidad para la generación y evaluación de escenarios regionales de cambio climático en el sur de Sudamérica, en especial para la temperatura. Esto constituye un punto de partida para realizar estudios relacionados con el impacto del cambio climático.Fil: Cabre, Maria Fernanda. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; Argentina. Centre National de la Recherche Scientifique; FranciaFil: Solman, Silvina Alicia. Centre National de la Recherche Scientifique; Francia. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; ArgentinaFil: Nuñez, Mario Nestor. Centre National de la Recherche Scientifique; Francia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; Argentin

Relationship between frontal systems and extreme precipitation over southern South America

The relationship between frontal systems and extreme precipitation events over southern South America is analyzed for the austral winter (May--August) and spring (September-December), on a 39-year period spanning from 1979 to 2017. Daily gridded data from the CPC Global Unified Precipitation dataset and the ERA5 reanalysis is employed. Fronts are identified by means of an objective front index (FI) that takes into account both dynamic (cyclonic vorticity) and thermodynamic (thermal contrast) characteristics. Extreme precipitation is characterized by the seasonal 95th percentile.Fronts occur in midlatitudes in about 10% of the days but there is a seasonal shift with larger occurrence frequencies located at southern latitudes in spring compared to winter. Front intensity-calculated as the seasonal mean of FI-is stronger in winter than in spring but the spatial pattern is similar on both seasons. Fronts explain about 50% of extreme precipitation on winter and 40% on spring; the percentage of total precipitation explained by fronts is lower but the spatial distribution is similar.Comparison between fronts that produce precipitation and the ones associated with extreme precipitation revealed that the latter are more intense on average. Fronts that produce extreme precipitation have a stronger dynamic forcing (i.e. higher cyclonic vorticity values) and a higher moisture availability (higher specific humidity anomaly). These two characteristics are the most promising for enhancing extreme precipitation events forecast.Facultad de Ciencias Astronómicas y GeofísicasConsejo Nacional de Investigaciones Científicas y Técnica