January and July regional climate simulation over South America

This work presents results, over the South American region, from the CSIRO Division of Atmospheric Research limited area model (DARLAM) and from the ninelevel general circulation model (GCM) of CSIRO (CSIRO Mk 2), within which it was nested in a one-way mode. Ten separate 30-day DARLAM simulations were performed for both January and July with a resolution of 125 km and were averaged to obtain a climatology for those months. This paper presents for the first time simulations of the January South American climate using a limited area model; previous similar studies simulated only the July climate. The goal of this study was to examine the capability of the CSIRO Mk 2 - DARLAM nested modeling system for simulating the climate in the South American region. Further, it was desired to investigate whether the higher resolution of DARLAM improves the simulated climate over various subregions, compared with the GCM and observations. With this purpose, a representative set of variables was analyzed and statistically compared. Overall, the fields simulated by the nesting system provide a better representation of the South American climate than the GCM. In particular, significant improvements are found in the nested model climatology for near-surface temperature and mean sea level pressure. Comparison of the January and July simulations shows a better wintertime performance. Some significant summertime features, like the Bolivian High, are reasonably well simulated by DARLAM, but not by the GCM. Copyright 2002 by the American Geophysical Union.Fil: Nicolini, Matilde. 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: Katzfey, J. J.. Csiro Oceans and Atmosphere; AustraliaFil: McGregor, J. L.. Csiro Oceans and Atmosphere; AustraliaFil: Salio, Paola Veronica. 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; Argentin

Baixa do Noroeste Argentino e Baixa do Chaco: caracterísitcas, diferenças e semelhanças The Northewestern Argentinean Low and The Chaco Low: their characteristics, differences and similarities

A Baixa do Chaco e a Baixa do Noroeste Argentino são frequentemente confundidas ou tratadas como um único sistema. Isso se deve a vários fatores: o pouco conhecimento que se tem sobre elas, especialmente sobre a Baixa do Chaco, a baixa resolução das reanálises globais que as mostram como um único sistema e a relativamente escassa cobertura de dados sobre a região que ocupam. Este trabalho tenta contribuir para o melhor entendimento das diferenças e semelhanças entre ambos os sistemas, analisando algumas características dinâmicas e termodinâmicas da região em que elas atuam, com a finalidade de aprofundar seu conhecimento e de possibilitar a sua melhor identificação e diferenciação. O estudo utiliza as reanálises do modelo regional Eta/CPTEC do período (2000-2004) e considera os meses de verão, período no qual as duas baixas estão ativas. Os resultados mostraram que a Baixa do Noroeste Argentino está mais relacionada com a atividade transiente, o que pode ser comprovado através da influência do jato subtropical e da variabilidade temporal de algumas variáveis, como a pressão e a temperatura potencial equivalente. A Baixa do Chaco se desenvolve numa atmosfera mais instável do ponto de vista termodinâmico, porém menos afetada pela dinâmica das latitudes médias.<br>The Chaco Low and the Northwestern Argentinean Low are frequently confounded or treated as a single system, due to our limited knowledge about them (especially concerning the Chaco Low), the low resolution of global analyses -that show them as a single low pressure system-, and the relatively poor data coverage over the region where they are usually located. This article aims to contribute to a better understanding of the differences and similarities between them, as well as to analyze the atmospheric dynamical and thermo-dynamical conditions where they evolve. It is considered that this study will aid to a better recognition of both systems. With this purpose, regional reanalyses from the Eta/CPTEC model for the 2000-2004 period has been used. The article focuses in summer months, since both low-pressure systems are more active during this season. Results show that the Northwestern Argentinean Low is more related to transient activity, as can be deducted from the subtropical jet influence on this system and also from the temporal variability of some key variables -such as the sea level pressure and the equivalent potential temperature-. From a thermo-dynamic point of view, the Chaco Low develops in a more unstable environment and is less influenced by middle latitude dynamics

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