Descripción: This paper evaluates a present climate simulation over southern South America performed with the Meteorological Research Institute/Japanese Meteorological Agency (MRI/JMA) high resolution global model. Main patterns of low and upper-level atmospheric circulation were analysed in a 25-year simulation as well as climate means, interannual variability, trends and bias of temperature and precipitation. The model is able to reproduce the main atmospheric circulation patterns and mean surface variables, although some deficiencies were found such as an overestimation of temperature over central Argentina in most of seasons, an overestimation of austral winter precipitation over northeastern and central Argentina, an underestimation of precipitation in all the seasons over southeast of Brazil, an underestimation of the amplitude of the annual cycle temperature in some regions and an overestimation of the amplitude of the annual cycle of precipitation over mountainous areas. Model interannual variability was also assessed. In general, temperature variability is overestimated, whereas precipitation is underestimated. The spatial structure of the year-to-year variability of precipitation is correctly simulated by the model, although some patterns were misplaced. Most of regions present a cold seasonal bias reaching values of - 2 °C in some regions. It was found that precipitation biases are between 3 and - 1 mm day-1. In some regions and seasons observed and simulated temperature trends coincide, as in austral summer or spring, where the model and the observations show positive trends in most of regions. However, there is no agreement between observed and simulated precipitation trends in almost all the regions and seasons. © 2012 Royal Meteorological Society.

Descripción: 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.

Descripción: Monthly lower stratosphere temperature anomalies in a layer centred about 70 hPa, from the MSU data set are analysed for the period 1979-1997. T-mode approach principal component analysis (PCA) is used in order to obtain the leading spatial anomaly patterns and their sequences of occurrence throughout the period under study. Five principal components (PCs) are significantly different from the spatial distribution of noisy data. The patterns given by the PC scores represent ten typical spatial anomaly patterns: five correspond to the direct mode, that is to say anomaly fields with the same sign as the PC score patterns, and five have the opposite sign. The first three PCs represent simple spatial temperature anomaly distributions, with zonal wave 0 to wave 2 wave structures. The following significant PCs, orders four and five, display a more complex spatial behaviour, with wave 3 wave structures. The first two PC's frequency distribution in time, given by the PC loadings time series, do not show noticeable changes throughout the period analysed. The remaining three PCs show changes in their frequency of occurrence that might be associated with the negative trends in the lower stratosphere temperature, as well as to the other different features observed in the real temperature anomaly time series for the grid points in the Southern Hemisphere. The latter are studied with the PCA in the S-mode approach in the companion paper (Compagnucci et al., 2001. International Journal of Climatology 21: 419-437). Copyright © 2001 Royal Meteorological Society.

Descripción: A Singular Value Decomposition (SVD) analysis was performed jointly on extreme temperature events in Argentina and sea surface temperature (SST) in the South Atlantic and South Pacific. Sea level pressure (SLP) patterns associated with the first SVD coupled mode were also analyzed. Winter is the season of the year that is best represented by the first mode, accounting for up to 70% of the winter covariance between temperature events and SST. The warm and cold events in Argentina are essentially a consequence of the creation of meridional atmospheric circulations over the continent. Such atmospheric patterns result from displacements and intensity changes of the subtropical anticyclones over the oceans and of the continental low-pressure center in northwestern Argentina. The temperature events in southern Argentina are also closely related to the warming and cooling of the coastal waters in the South Atlantic and South Pacific. The analysis suggests that in summer and winter, high (low) occurrence of warm events and low (high) occurrence of cold events are related to similar oceanic and atmospheric circulation situations. The temperature events in Argentina show higher correlation with the Atlantic than with the Pacific, which reflects the importance of the "orographic barrier" of the Andes Mountains in driving the atmospheric circulation. The only exception to this rule concerns the warm events in spring, for which the warming of the equatorial Pacific (the ENSO pattern) appears as the dominant mode. The temporal patterns of the temperature events in Argentina exhibit significant interannual variability in fall, winter, and spring, with periods of 3 to 5 years. The summer patterns suggest a very low-frequency variation with a period longer than 20 years. Copyright 2003 by the American Geophysical Union.

Descripción: A Singular value decomposition (SVD) analysis was performed jointly on the daily intensity of extreme rainfall (DIER) over Argentina and the sea surface temperature (SST) of all the oceans from 17.5°N to 90°S in order to identify the large-scale variability of the SSTs related to extreme rainfall, in the period 1962-2005. The main objective of the article is to objectively recognize regions of the tropical and subtropical oceans that could be related with the extreme rainfall over Argentina. Spring is the season that is best represented by the first mode, accounting for up to 45% of the covariance between the DIER and SST. The first SVD mode of spring, summer and autumn presents a pattern of SST relating to the El Niño-Southern Oscillations (ENSO) phenomena with an enhanced DIER in different zones of centre and east of Argentina. In the second SVD mode of spring and summer, the SST patterns show cold conditions in the tropical and subtropical Atlantic and near Indonesia with an enhancement of the DIER in the centre and east of Argentina. These modes show a significant decadal variability. In the third SVD mode of spring and summer, the SST patterns present warm and cold conditions in the Indian Ocean and the centre and western Pacific Ocean (PO) with decreased rainfall in the northern and eastern portion of Argentina, respectively. This mode shows a significant period of temporal variability of around 14 years. The third mode of autumn presents warm conditions in the tropical Atlantic and the southwest PO with a low DIER in the centre and east of Argentina. This mode also presents temporal variability of around 14 years. The correlation between each mode derived from analysis of SVD and climate indices related with SST were computed. © 2012 Royal Meteorological Society.

Descripción: Phytotelmata, or plant-held waters, are considered to be good model systems for the study of community ecology. The fauna of these natural container habitats, particularly the mosquitoes, have been extensively investigated in tropical regions, but there is little known about them in temperate South America. We assessed the structure of immature mosquito communities in leaf axils, tree holes, and bamboo stumps from a temperate wetland of Argentina. A total of 4,330 immature mosquitoes were collected among the 2,606 phytotelmata inspected. Leaf axils of eight plant species and tree holes were larval habitats for nine mosquito species belonging to the genus Culex, Wyeomyia, Isostomyia, and Toxorhynchites. The mosquito communities showed richness ranging from one to four species. Marked differences were detected in the plant specificity for the species collected. Some of them were exclusively found in one plant species (Isostomyia paranensis in Scirpus giganteus), whereas others were collected in up to five plant species but belonging to the same phytotelm class, the leaf axils. Those from tree holes are well-known dwellers of artificial containers and ground water habitats, such as Culex pipiens. Our results support the idea of low mosquito richness in phytotelmata from temperate regions in comparison with tropical areas, but the observed specificity patterns echo the findings of tropical forests. © 2011 The Society for Vector Ecology.

Descripción: The inversion polymorphisms of the cactophilic Drosophila buzzatti Patterson and Wheeler (Diptera: Drosophilidae) were studied in new areas of its distribution in Argentina. A total of thirty-eight natural populations, including 29 from previous studies, were analyzed using multiple regression analyses. The results showed that about 23% of total variation was accounted for by a multiple regression model in which only altitude contributed significantly to population variation, despite the fact that latitude and longitude were also included in the model. Also, inversion frequencies exhibited significant associations with mean annual temperature, precipitation, and atmospheric pressure. In addition, expected heterozygosity exhibited a negative association with temperature and precipitation and a positive association with atmospheric pressure. The close similarity of the patterns detected in this larger dataset to previous reports is an indication of the stability of the clines. Also, the concurrence of the clines detected in Argentina with those reported for colonizing populations of Australia suggests the involvement of natural selection as the main mechanism shaping inversion frequencies in D. buzzatii.

Descripción: Meteorological phenomena are closely linked to the presence of water vapor. They mainly originate and develop in the troposphere, where almost all the atmospheric water is concentrated. The Global Positioning System radio occultation (GPS RO) technique provides vertical profiles of refractivity from which other properties such as temperature and water vapor can be derived. The GPS RO capability to reproduce global, synoptic, and regional climatological patterns over South America, which is a mostly oceanic continent, is tested. From FORMOSAT-3/COSMIC mission data (2006-2010), our previous knowledge regarding global and synoptic/regional patterns of temperature, equivalent potential temperature, specific humidity, and pressure is verified. Special cases such as baroclinic disturbances arriving at South American midlatitudes and storm events over a mountain region near the Andes are analyzed. The temporal evolution and the latitude-longitude distribution in several layers of the variables listed above are well described with this technique. Copyright 2012 by the American Geophysical Union.

Descripción: Many grasshopper species are considered of agronomical importance because they cause damage to pastures and crops. Comprehension of pest population dynamics requires a clear understanding of the genetic diversity and spatial structure of populations. In this study we report on patterns of genetic variation in the South American grasshopper Dichroplus elongatus which is an agricultural pest of crops and forage grasses of great economic significance in Argentina. We use Direct Amplification of Minisatellite Regions (DAMD) and partial sequences of the cytochrome oxydase 1 (COI) mitochondrial gene to investigate intraspecific structure, demographic history and gene flow patterns in twenty Argentinean populations of this species belonging to different geographic and biogeographic regions. DAMD data suggest that, although genetic drift and migration occur within and between populations, measurable relatedness among neighbouring populations declines with distance and dispersal over distances greater than 200 km is not typical, whereas effective gene flow may occur for populations separated by less than 100 km. Landscape analysis was useful to detect genetic discontinuities associated with environmental heterogeneity reflecting the changing agroecosystem. The COI results indicate the existence of strong genetic differentiation between two groups of populations located at both margins of the Paraná River which became separated during climate oscillations of the Middle Pleistocene, suggesting a significant restriction in effective dispersion mediated by females and large scale geographic differentiation. The number of migrants between populations estimated through mitochondrial and DAMD markers suggest that gene flow is low prompting a non-homogeneous spatial structure and justifying the variation through space. Moreover, the genetic analysis of both markers allows us to conclude that males appear to disperse more than females, reducing the chance of the genetic loss associated with recent anthropogenic fragmentation of the D. elongatus studied range. © 2012 Rosetti, Remis.

Descripción: The variability of atmospheric midlatitudinal ozone between 1980 and 2000 over the Southern Hemisphere is discussed. The distribution of ozone and ozone change during the seasonal cycle is discussed using Total Ozone Mapping Spectrometer Nimbus and Earth Probe data binned at 72 (30° longitude by 5° latitude) bins, between 60° and 30°S. Rather than using a standard trend approach, the annual mean time series for each bin were fitted with a cubic polynomial. The results show that in the zonal mean sense there is a sizable, latitude-dependent slowdown of the ozone loss from the early 1990s onward, but when individual bins are considered, significant longitudinal patterns of ozone change appear, with both positive (enhancement) and negative (depletion) changes in total ozone. Thus regional evolution remains important as an indicator both of chemical depletion evolution and the relation with climate. Such longitudinal behavior is limited in the subtropics and grows toward the subpolar edge of the sampled region. For example, a large decrease was observed over southern South America in the 1990s, but during the 1990s there was only a limited change. The analysis for January, June, and October over the 20-year period shows changes in the evolution along the year, both in time and space. Furthermore, such seasonally dependent changes reach a peak in October, as would be expected. The October pattern of interannual variability could be linked to Southern Annular Mode, though there probably are some other processes driving it. Copyright 2005 by the American Geophysical Union.