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The seasonal variability of surface layer salinity (SLS), evaporation (E), precipitation (P ) and E -P over the global ocean is examined using in situ salinity data and the National Center for Environmental Prediction's Climate System Forecast Reanalysis. Sea- 5 sonal amplitudes and phases are calculated using harmonic analysis and presented in all areas of the open ocean between 60° S and 60° N. Areas with large amplitude SLS seasonal variations include: the intertropical convergence zone in the Atlantic, Pacific and Indian Oceans; western marginal seas of the Pacific; and the Arabian Sea. The median value in areas that have statistically significant seasonal cycles of SLS 10 is 0.19. Between about 60° S and 60° N, 37% of the ocean surface has a significant seasonal cycle of SLS and 75% a seasonal cycle of E -P . Phases of SLS have a bimodal distribution, with most areas of the ocean peaking in SLS in either March/April or September/October. The same calculation is done with surface freshwater flux using a mixed-layer depth 15 climatology. With the exception of an area near the western boundaries of the North Atlantic and North Pacific, seasonal variability is dominated by precipitation. Surface freshwater fluxes also have a bimodal distribution, with peaks in January and July, 1-2 months before the peaks of SLS. The amplitudes and phases of SLS and surface fluxes compare well in a qualitative 20 sense, suggesting that much of the variability in SLS is due to E -P forcing. However, the amplitudes of SLS are somewhat larger than would be expected and the peak of SLS comes typically about one month earlier than expected. The differences of the amplitudes of the two quantities is largest in such areas as the Amazon River plume, the Arabian Sea, the ITCZ and the eastern equatorial Pacific and Atlantic, indicating 25 that other processes such as ocean mixing and lateral transport must be important, especially in the tropics. [ABSTRACT FROM AUTHOR]

This paper aims to describe the spatial-temporal variability in catch of the main fishery resources of the Amazon River and floodplain lakes of the Lower Amazon, as well as relating the Catch per Unit of Effort with anomalies of some of the Amazon River, atmosphere and Atlantic Ocean system variables, determining the influence of the environment on the Amazonian fishery resources. Finfish landings data from the towns and villages of the Lower Amazon for the fisheries of three sites (Óbidos, Santarém and Monte Alegre), were obtained for the period between January 1993 and December 2004. Analysis of variance, detrended correspondence analysis, redundancy analysis and multiple regression techniques were used for the statistical analysis of the distinct time series. Fisheries production in the Lower Amazon presents differences between the Amazon River and the floodplain lakes. Production in the Amazon River is approximately half of the one of the floodplain lakes. This variability occurs both along the Lower Amazon River region (longitudinal gradient) and laterally (latitudinal gradient) for every fishing ground studied here. The distinct environmental variables alone or in association act differently on the fishery stocks and the success of catches in each fishery group studied here. Important variables are the flooding events; the soil the sea surface temperatures; the humidity; the wind and the occurence of El Niño-Southern Oscillation events. Fishery productivity presents a large difference in quantity and distribution patterns between the river and floodplain lakes. This variability occurs in the region of the Lower Amazon as well as laterally for each fishery group studied, being dependent on the ecological characteristics and life strategies of each fish group considered here. [ABSTRACT FROM AUTHOR]

The article presents a study on the light reaching the ground vegetation in the high forest phase and its relation on the differences in forest structure of two selected sites, where one is on the slopes of Mount Andes and the other is at the extreme western edge of the Amazon basin. The authors state that their observations and analysis have enabled them to associated some of the differences between the two forests with differences in light climate. They mention that the interactions between light and other factors, specially root competition, may be very important. They believe that future studies on light as an ecological factor in tropical forests will most productively be aimed to the reaction of individual species to light at various stages of growth.

In the central Amazon, surrounding Manaus City, Brazil, the landscape dominated by forest and water bodies supports development of river breezes. Seasonal inundations modify this local scenery affecting, consequently, the local circulations. However, this effect has not properly been investigated yet. Thus, we carried out numerical experiments for a river breeze case to investigate the seasonal flooding effect on the river breeze and detail the processes involved in the river breeze development. In the numerical experiments, we ran the Catchment‐Based Macro‐scale Floodplain (CaMa‐Flood) model to simulate flooding depth and extent and used the CaMa‐Flood outputs to force the Ocean‐Land‐Atmosphere Model. The seasonal flooding alters the surface energy partitioning causing a temperature decrease over the river region and intensification of the river breezes in the daytime. The intensified river breezes propagate more rapidly through the upland region, take longer to dissipate and promote stronger upward vertical motion altering the heat and mass transport. These novel findings are fundamentally important to the understanding of the local climate variability of the central Amazon. We can infer that river breezes and its consequence to local climate are less (more) pronounced in drought (wet) years. Key Points: Different energy partitioning of the water and land surface triggers the river breezes in the central AmazonSeasonal flooding intensifies the river breezes by altering the surface energy partitioningThe roughness variation between the floodplain and the upland regions has no clear influence on the displacement of the river breeze fronts [ABSTRACT FROM AUTHOR]

The archaeological sites near Monte Alegre, along Brazil's lower Amazon River, provide new information on the little-known activities and symbolism of South American Paleoindians toward the end of the Ice Age. While paleoindian sites like Monte Verde in Chile, or Guitarrero Cave in Peru, are located near the pacific coast, Monte Alegre lies much further inland, 680 km upriver from the mouth of the Amazon River and the Atlantic Coast. With excavated wood charcoal radiocarbon dated as early as 13,200 calibrated years ago, the hill—as a source of sandstone and quartz lithics—supplied early pioneers with adequate tools needed for colonizing the interior of the continent. Once there, they painted rock art on the landscape, which bears a record of the sun's horizon positions throughout the year. At just 2° south of the equator, Monte Alegre shows no overt seasonal changes beyond fluctuating rainfall amounts, unlike at higher latitudes where temperature, amount of daylight, foliage, and forms of precipitation markedly change. Near the equator, solar and stellar horizon sightings most visibly track the passage of time and seasonal cycles. However, horizons are often hidden behind high forest canopy throughout much of the Amazon Rainforest; but in the Monte Alegre hill ridges looming above the river, paleoindians could hike above the canopy to peer at the horizon, more effectively synchronizing their activities to ecological cycles. This research suggests that Monte Alegre paleoindians delimited the azimuthal range of the sun in a solar year with notational pictographs aligned to horizon sightings at Painel do Pilão, and leaving a painted grid of tally marks that might have served as a rudimentary early calendar. The broad-reaching implication for early Americans is that through the strategic placement of rock art, these ancient artists fostered predictive archaeorecording from which resources could be optimally extracted, ceremonial activities could be consistently scheduled, and gatherings for social and economic exchange could be more efficiently coordinated. [ABSTRACT FROM AUTHOR]

This study used an atmospheric general circulation model (AGCM) with a 20-km grid spacing and a global river routing model with 0.5° grid resolution to project climatological mean river discharges in the late 21st century under a changing climate. We also performed an ensemble simulation with the same AGCM except with a resolution of 60 km and forced with different lower boundary conditions to quantify the level of confidence in the projections. By the late 21st century, projected annual mean river discharges increased in the high latitudes and in India and the southeastern United States but decreased in broad regions of Europe, western Asia, the western United States, Central America, and the southern half of the Amazon River basin. Projected future changes in monthly river discharges include unique seasonal details not present in the annual discharge projections: in the Amazon River, for example, river discharges were projected to increase in the high-water season but decrease in the low-water season. These seasonal changes suggest that monthly river discharge projections should be useful for assessing the human impacts and risks in future planning of water resources and flood control. We devised a way to measure the consistency between the various projections made by our 60-km ensemble simulations and our standard 20-km high-resolution model. Wherever the projected changes were consistent, the future changes also tended to be statistically significant in our high-resolution model. These results encourage a future projection of discharge for a specific river basin in the world. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The evolution of monsoon onset across South America has complex temporal and regional variability that are controlled by local and remote land-ocean-atmosphere processes. In this study, a three-stage conceptual model for the onset of the South American monsoon season is proposed based on a rain threshold analysis and a rotated empirical orthogonal function (REOF) analysis of the Global Precipitation Climatology Project version 2 (GPCP-v2) dataset. This two-pronged approach allowed the identification of regions of South America that share a common seasonal cycle of rainfall variability and likely have a common mechanism for monsoon onset. According to this model, the first stage of onset starts around pentad 59 (October 18-22) when precipitation begins in the northwestern part of the continent and gradually progresses towards the south and southeast. The second stage is marked by the abrupt establishment of the South Atlantic Convergence Zone (SACZ). This stage occurs on average around pentad 61 (October 28-November 1). The third stage of monsoon onset involves the late arrival of the monsoon to the mouth of the Amazon River, associated with the slow migration of the Atlantic Intertropical Convergence Zone (ITCZ). This final stage of onset occurs on average by pentad 73 (December 27-31). This three-stage model of onset provides a useful framework for the study of regional differences in monsoon onset mechanisms, a subject that is further explored in two companion studies. Copyright © 2010 Royal Meteorological Society [ABSTRACT FROM AUTHOR]