Efectos remotos del cambio de uso de suelo en el clima del sudeste de Sudamérica

Grandes áreas de Sudamérica están sufriendo cambios en el uso del suelo, en general, de origen antropogénico. El aumento de la precipitación en regiones áridas combinado con los avances tecnológicos incrementó la disponibilidad de tierras productivas. Esto derivó en un proceso de expansión de la frontera agrícola sobre zonas con vegetación natural. Desde el punto de vista hidroclimático, el reemplazo de vegetación natural por cultivos altera la partición de agua y energía en superficie. Al cambiar la vegetación se modifican propiedades biofísicas relacionadas a la misma tales como albedo, resistencia estomática o rugosidad de superficie. Este cambio en las propiedades produce efectos sobre las variables hidroclimáticas tanto locales como remotos. Este trabajo tiene por objetivo evaluar los efectos remotos de los cambios de cobertura del suelo mediante simulaciones con el modelo climático WRF (Weather Research and Forecasting). Se realizaron simulaciones asumiendo dos escenarios de cobertura/uso de suelo. Una simulación de control donde se simula el comportamiento del clima sin alterar la cobertura vegetal y una simulación donde se reemplaza bosques, pasturas y sabana por cultivos, ambas durante la primavera de 2002. Para evaluar los efectos remotos, se analiza el comportamiento de diferentes variables hidroclimáticas en diferentes regiones de Argentina y de Sudamérica donde no se realizaron cambios de cobertura. Los resultados indican que la expansión de cultivos sobre vegetación nativa modifica las propiedades biofísicas alterando en tiempo y espacio el comportamiento de variables hidroclimáticas. En particular, se observan cambios en los balances hidrológicos de diferentes regiones y también, cambios importantes en la circulación de los vientos.Eje: Ciencias Hidrológicas y Criósfera.Facultad de Ciencias Astronómicas y Geofísica

Efectos remotos del cambio de uso de suelo en el clima del sudeste de Sudamérica

Grandes áreas de Sudamérica están sufriendo cambios en el uso del suelo, en general, de origen antropogénico. El aumento de la precipitación en regiones áridas combinado con los avances tecnológicos incrementó la disponibilidad de tierras productivas. Esto derivó en un proceso de expansión de la frontera agrícola sobre zonas con vegetación natural. Desde el punto de vista hidroclimático, el reemplazo de vegetación natural por cultivos altera la partición de agua y energía en superficie. Al cambiar la vegetación se modifican propiedades biofísicas relacionadas a la misma tales como albedo, resistencia estomática o rugosidad de superficie. Este cambio en las propiedades produce efectos sobre las variables hidroclimáticas tanto locales como remotos. Este trabajo tiene por objetivo evaluar los efectos remotos de los cambios de cobertura del suelo mediante simulaciones con el modelo climático WRF (Weather Research and Forecasting). Se realizaron simulaciones asumiendo dos escenarios de cobertura/uso de suelo. Una simulación de control donde se simula el comportamiento del clima sin alterar la cobertura vegetal y una simulación donde se reemplaza bosques, pasturas y sabana por cultivos, ambas durante la primavera de 2002. Para evaluar los efectos remotos, se analiza el comportamiento de diferentes variables hidroclimáticas en diferentes regiones de Argentina y de Sudamérica donde no se realizaron cambios de cobertura. Los resultados indican que la expansión de cultivos sobre vegetación nativa modifica las propiedades biofísicas alterando en tiempo y espacio el comportamiento de variables hidroclimáticas. En particular, se observan cambios en los balances hidrológicos de diferentes regiones y también, cambios importantes en la circulación de los vientos.Eje: Ciencias Hidrológicas y Criósfera.Facultad de Ciencias Astronómicas y Geofísica

Efectos remotos del cambio de uso de suelo en el clima del sudeste de Sudamérica

Grandes áreas de Sudamérica están sufriendo cambios en el uso del suelo, en general, de origen antropogénico. El aumento de la precipitación en regiones áridas combinado con los avances tecnológicos incrementó la disponibilidad de tierras productivas. Esto derivó en un proceso de expansión de la frontera agrícola sobre zonas con vegetación natural. Desde el punto de vista hidroclimático, el reemplazo de vegetación natural por cultivos altera la partición de agua y energía en superficie. Al cambiar la vegetación se modifican propiedades biofísicas relacionadas a la misma tales como albedo, resistencia estomática o rugosidad de superficie. Este cambio en las propiedades produce efectos sobre las variables hidroclimáticas tanto locales como remotos. Este trabajo tiene por objetivo evaluar los efectos remotos de los cambios de cobertura del suelo mediante simulaciones con el modelo climático WRF (Weather Research and Forecasting). Se realizaron simulaciones asumiendo dos escenarios de cobertura/uso de suelo. Una simulación de control donde se simula el comportamiento del clima sin alterar la cobertura vegetal y una simulación donde se reemplaza bosques, pasturas y sabana por cultivos, ambas durante la primavera de 2002. Para evaluar los efectos remotos, se analiza el comportamiento de diferentes variables hidroclimáticas en diferentes regiones de Argentina y de Sudamérica donde no se realizaron cambios de cobertura. Los resultados indican que la expansión de cultivos sobre vegetación nativa modifica las propiedades biofísicas alterando en tiempo y espacio el comportamiento de variables hidroclimáticas. En particular, se observan cambios en los balances hidrológicos de diferentes regiones y también, cambios importantes en la circulación de los vientos.Eje: Ciencias Hidrológicas y Criósfera.Facultad de Ciencias Astronómicas y Geofísica

The imprint of strong-storm tracks on winter weather in North America

Northern Hemisphere winter storm tracks and their relation to winter weather are investigated using CFSR data. Storm tracks are described by isentropic PV maxima within a Lagrangian framework; these correspond well with those described in previous studies. Our diagnostics focus on strong-storm tracks, which are comprised of storms that achieve a maximum PV exceeding the mean value by one standard deviation. Large increases in diabatic heating related to deep convection occur where the storm tracks are most intense. The cyclogenesis pattern shows that strong storms generally develop on the upstream sectors of the tracks. Intensification happens towards the eastern North Pacific and all across the North Atlantic Ocean, where enhanced storm track-related weather is found. In this study, the relation of storm tracks to near-surface winds and precipitation is evaluated. The largest increases in storm track-related winds are found where strong storms tend to develop and intensify, while storm precipitation is enhanced in areas where the storm tracks have the highest intensity. Strong storms represent about 16% of all storms but contribute 30-50% of the storm precipitation in the storm track regions. Both strong-storm related winds and precipitation are prone to cause storm-related losses in the eastern US and North American coasts. Over the oceans, maritime operations are expected to be most vulnerable to damage offshore of the US coasts. Despite making up a small fraction of all storms, the strong-storm tracks have a significant imprint on winter weather in North America potentially leading to structural and economic loss

GCIP water and energy budget synthesis (WEBS)

As part of the World Climate Research Program\u27s (WCRPs) Global Energy and Water-Cycle Experiment (GEWEX) Continental-scale International Project (GCIP), a preliminary water and energy budget synthesis (WEBS) was developed for the period 1996–1999 from the “best available” observations and models. Besides this summary paper, a companion CD-ROM with more extensive discussion, figures, tables, and raw data is available to the interested researcher from the GEWEX project office, the GAPP project office, or the first author. An updated online version of the CD-ROM is also available at http://ecpc.ucsd.edu/gcip/webs.htm/. Observations cannot adequately characterize or “close” budgets since too many fundamental processes are missing. Models that properly represent the many complicated atmospheric and near-surface interactions are also required. This preliminary synthesis therefore included a representative global general circulation model, regional climate model, and a macroscale hydrologic model as well as a global reanalysis and a regional analysis. By the qualitative agreement among the models and available observations, it did appear that we now qualitatively understand water and energy budgets of the Mississippi River Basin. However, there is still much quantitative uncertainty. In that regard, there did appear to be a clear advantage to using a regional analysis over a global analysis or a regional simulation over a global simulation to describe the Mississippi River Basin water and energy budgets. There also appeared to be some advantage to using a macroscale hydrologic model for at least the surface water budgets

Recent developments on the South American monsoon system

This paper reviews recent progress made in our understanding of the functioning and variability of the South American Monsoon System (SAMS) on time scales varying from synoptic to long-term variability and climate change. The SAMS contains one of the most prominent summertime climate patterns in South America, featuring a strong seasonal variability in a region lying between the Amazon and the La Plata Basin. Much of the recent progress is derived from complementary international programs, such as the Monsoon Experiment South America (MESA), as well as from ongoing international programs such as the Large Scale Biosphere Atmosphere Experiment in the Amazon Basin (LBA) and the La Plata Basin (LPB) Regional Hydroclimate Project, which includes the CLARIS LPB Europe-South America Network for Climate Change Assessment and Impact Studies in La Plata Basin Project. The latter assesses atmosphere-land surface interactions, the role of land use changes and aerosols from biomass burning considered as sources of variability and change in the SAMS functioning, characteristics and behaviour. The SAMS region is particularly susceptible to variations of climate due to the importance of hydroelectricity generation and the agricultural base of local economies. Also addressed in this report are projections of climate change and extremes, which are important for impact and vulnerability assessments. This discussion includes the need to identify and understand important processes that control the monsoonal climate, how these processes may vary and change, and how they may interact with key societal sectors, including water resource management, hydroelectric generation, agriculture, and agribusiness. This paper reports on the major contributions of MESA to the knowledge of characteristics, functioning and variability of the SAMS, and is based on recent studies and publications, and can be considered as an update of a previous review by C. S. Vera et al. (2006a). © 2010 Royal Meteorological Society.Fil:Berbery, E.H. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Vera, C.S. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Saulo, A.C. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

The agricultural expansion in South America's Dry Chaco: regional hydroclimate effects

The Gran Chaco ecoregion is South America's largest remaining continuous stretch of dry forest. It has experienced intensive deforestation, mainly in the western part known as the Dry Chaco, resulting in the highest rate of dry-forest loss globally between 2000 and 2012. The replacement of natural vegetation with other land uses modifies the surface's biophysical properties, affecting heat and water fluxes and modifying the regional climate. This study examines land use and land cover changes (LULCCs) in the Dry Chaco from 2001 to 2015 and their effects on local and non-local climate and explores the potential impacts of future agricultural expansion in the region. To this end, Weather Research and Forecasting (WRF) model simulations are performed for two scenarios: the first one evaluates the observed land cover changes between 2001 and 2015 that covered 8 % of the total area of the Dry Chaco; the second scenario assumes an intensive agricultural expansion within the Dry Chaco. In both scenarios, deforestation processes lead to decreases in leaf area index (LAI), reductions in stomatal resistance, and increases in albedo, thus reducing the net surface radiation and, correspondingly, decreasing the turbulent fluxes, suggesting a decline in available energy in the boundary layer. The result is an overall weakening of the water cycle in the Dry Chaco and, most prominently, implying a reduction in precipitation. A feedback loop develops since dry soil absorbs significantly less solar radiation than moist soil. Finally, the simulations suggest that the Dry Chaco will intensify its aridity, extending drier and hotter conditions into the Humid Chaco.</p

Global Meteorological Drought: A Synthesis of Current Understanding with a Focus on SST Drivers of Precipitation Deficits

Drought affects virtually every region of the world, and potential shifts in its character in a changing climate are a major concern. This article presents a synthesis of current understanding of meteorological drought, with a focus on the large-scale controls on precipitation afforded by sea surface temperature (SST) anomalies, land surface feedbacks, and radiative forcings. The synthesis is primarily based on regionally focused articles submitted to the Global Drought Information System (GDIS) collection together with new results from a suite of atmospheric general circulation model experiments intended to integrate those studies into a coherent view of drought worldwide. On interannual time scales, the preeminence of ENSO as a driver of meteorological drought throughout much of the Americas, eastern Asia, Australia, and theMaritime Continent is now well established, whereas in other regions (e.g., Europe, Africa, and India), the response to ENSO is more ephemeral or nonexistent. Northern Eurasia, central Europe, and central and eastern Canada stand out as regions with few SST-forcedimpacts on precipitation oninterannual time scales.Decadal changesin SST appear to be a major factor in the occurrence of long-term drought, as highlighted by apparent impacts on precipitation of the late 1990s ‘‘climate shifts’’ in the Pacific and Atlantic SST. Key remaining research challenges include (i) better quantification of unforced and forced atmospheric variability as well as land–atmosphere feedbacks, (ii) better understanding of the physical basis for the leading modes of climate variability and their predictability, and (iii) quantification of the relative contributions of internal decadal SST variability and forced climate change to long-term drought

Domain choice in an experimental nested modeling prediction system for South America

The purposes of this paper are to evaluate the new version of the regional model, RegCM3, over South America for two test seasons, and to select a domain for use in an experimental nested prediction system, which incorporates RegCM3 and the European Community-Hamburg (ECHAM) general circulation model (GCM). To evaluate RegCM3, control experiments were completed with RegCM3 driven by both the NCEP/NCAR Reanalysis (NNRP) and ECHAM, using a small control domain (D-CTRL) and integration periods of January–March 1983 (El Niño) and January–March 1985 (La Niña). The new version of the regional model captures the primary circulation and rainfall differences between the two years over tropical and subtropical South America. Both the NNRP-driven and ECHAM-driven RegCM3 improve the simulation of the Atlantic intertropical convergence zone (ITCZ) compared to the GCM. However, there are some simulation errors. Irrespective of the driving fields, weak northeasterlies associated with reduced precipitation are observed over the Amazon. The simulation of the South Atlantic convergence zone is poor due to errors in the boundary condition forcing which appear to be amplified by the regional model. To select a domain for use in an experimental prediction system, sensitivity tests were performed for three domains, each of which includes important regional features and processes of the climate system. The domain sensitivity experiments were designed to determine how domain size and the location of the GCM boundary forcing affect the regional circulation, moisture transport, and rainfall in two years with different large scale conditions. First, the control domain was extended southward to include the exit region of the Andes low level jet (D-LLJ), then eastward to include the South Atlantic subtropical high (D-ATL), and finally westward to include the subsidence region of the South Pacific subtropical high and to permit the regional model more freedom to respond to the increased resolution of the Andes Mountains (D-PAC). In order to quantify differences between the domain experiments, measures of bias, root mean square error, and the spatial correlation pattern were calculated between the model results and the observed data for the seasonal average fields. The results show the GCM driving fields have remarkable control over the RegCM3 simulations. Although no single domain clearly outperforms the others in both seasons, the control domain, D-CTRL, compares most favorably with observations. Over the ITCZ region, the simulations were improved by including a large portion of the South Atlantic subtropical high (D-ATL). The methodology presented here provides a quantitative basis for evaluating domain choice in future studies